Category : LESSONS
CELL – The fundamental unit of life
“Cell is the structural and functional unit of life”
Discovery of cell: – Robert Hooke (1665) is credited with the discovery of cell. He made microscope with visualizing power 100x. He observed very thin slice of cork under microscope and saw that the ork resembled the structure of a honey comb containing many tiny compartments; he called them “cellula” now termed cells. He saw only cell wall not organelles. He published his work in ‘ Micrographia’. Some organisms such as most bacteria are unicellular (consists of a single cell) Other organisms such as humans are multicellular. All cells are derived from other cells by cell division. Later on Anton Van Leewenhoek (1683) merchant of lenses made microscope of 300x . He was the first person to observe free cells like bacteria, protozoa, red blood cells, and sperms etc. He is known as Father of microscopy. He observed his own blood & found cells in it, he called it RBC‟s. Small microorganisms he called animalcules, actually bacteria.
Contribution of some scientists in the field of Cell Biology:
1. Swanson is called ‘ Father of Modern Biology’
2. Term bacteria by Ehvein Berg. Nehmiah Grew in 1682 proposed that all plant tissues are made up of small structures called cells. (Cell concept)
3. Alfonso Corti (1772) observed living substances in the cells.
4. Nucleus was first observed by Robert Brown (1831) within the cells of orchid roots.
5. Johannes Purkinje (1839) called the jelly like substance Protoplasm
6. Hugo Von Mohl (1846) also suggested the name ‘ protoplasm, for similar substance found in plants.
7. Protoplasm is ‘physical basis of life’ has been stated by Huxley.
8. In 1932, two German Scientists, Ruska and Knoll, invented the electron microscope
9. In the year 1838, Matthias Schleiden, a German botanist, first proposed the idea that all plants consist of cells.
10. In 1839, Theodar Schwann, another German botanist, asserted that all plants and animals are made up of cells
11. In 1824: Rene Dutroche proposed that all plant and animal tissue are made up of globular cells, which are binded with each other by cohession forces.)
12. In 1885, Rudolf Virchow expressed that all cells arise from pre-existing cells.
13. Man is estimated to have about 100 trillion (1014) cells in number.
Scientists Who Contributed To The Cell Theory
1665 -English scientist that cut a thin slice of cork and looked at it under his microscope. To him, the cork seemed to be made up of empty little boxes, which he named cells.
Anton Van Leewenhoek
1673 Dutch naturalist who created a very powerful (for the time period) single lens microscope, He observed pond water. In pond scum he discovered small animals he called animalcules, or little animals (protists), and also discovered bacteria while examining scraping of crud from his teeth.
1838 German botanist who determined plants are composed of cells.
German physiologist and histologist who in 1838 and 1839 identified the cell as the basic structure of plant and animal tissue (1810-1882)
1858 – A doctor who stated that all living cells come from other living cells (part 3 of the cell theory) The Cell Theory:
Three parts – 1. All organisms are made up of one or more cells.
2 Cells are the basic unit of life.
3. All cells arise from pre-existing cells
(Italy 1668) Tested the hypothesis of spontaneous generation with flies on meat, and disproved it Louis Pasteur
(1861) pasteurized wine, milk, disproved spontaneous generation of microbes, discovered several bacterial pathogens
Schleiden and Schwann’s Cell Theory:
1) Cell is the basic unit of life.
2) Each cell is bounded by a thin membrane called Plasma membrane which in turn surrounds protoplasm, which contains nucleus. In plants cell wall surrounds the plasma membrane. 3) All cells are alike in structure and metabolic activities.
4) All cells can maintain their vitality independently.
5) The function of organism is the total sum of activities & interactions of constituent cells
Modern cell theory (Nageli (1846) and Rudolf Virchow (1855))
The new cell theory states the following points.
1. The cell is the structural and functional unit of life.
2. The new cells arise from the preexisting cell only.
3. The Cells contains nucleus which has hereditary information (DNA) in it which is passed from cell to cell.
4. Energy flow occurs within cells.
5. All cells are basically same in chemical composition in organisms of similar species.
6. All known living things are made up of one or more cells.
7. All the activities of an organism are the outcome of the activities of its constituent cells.
Q. Give the differences between an eukaryotic cell and a prokaryotic cell.
Prokaryotic cell Eukaryotic cell
1. These are generally small in size (1-10m). 1. These are generally larger in size (5-100m) 2. Distinct nucleus is absent.i.e: genetic material 2. Distinct nucleus is present and is surrounded is not surrounded by a nuclear membrane and by a nuclear m embrane and is not in direct is in direct contact with cytoplasm. contact with cytoplasm.
3. Single chromosome present. 3. Contains more than one chromosomes.
4. Membrane bounded cell organelles are 4. Membrane bound cell organelles are present. absent.
5. Cell division occurs by binary fission or 5. Cell division occurs by mitosis or meiosis Budding. Mitosis does not occur
6. Reserve food material is in the form of glycogen. 6. Reserve food material is in the form of starch.
(iii) Pectins :- These are water soluble heterogeneous branched polysaccharides which are negatively charged. When Ca++ ions are added to solution of pectin molecules it cross links them to produce a semi rigid gel. This helps to link the cell wall components together.
(2) Origin:-The cell wall is a non living substance which is secreted by the living protoplast of the cell.
Every living cell in higher plants is connected to its living neighbours by fine cytoplasmic channels called plasmodesmata. The plasma membrane of one cell is continuous with the plasma membrane of other cell at plasmadesmata.
(4) Functions:-Cell wall provides mechanical support to the cell.
There are few points regarding plasma membrane, which are as follows:
1) Plasma membrane is a biomembrane that only surrounds cytoplasm of cell.
2) The bio-membranes are present both inside and outside cell, therefore a term plasma membrane was introduced.
3) It was first of all seen under microscope by Schwann and the term cell membrane or bio-membrane was coined by Naegali.
4) It is dynamic in nature, i.e. it can be removed, extended, renewed, moved and folded.
4) It is a thin lining selectively permeable membrane that surrounds all the prokaryotic as well as eukaryotic cells. It also surrounds the most cells organelles in eukaryotic cells .
5) It is living, elastic and made of proteins and lipids (fats).It has the same structure every where hence it is also called unit membrane.
Function: Its function is to provide a mechanical barrier for the protection of the inner cell contents and to regulate the movement of molecules in and out of the cell.
Molecular structure of plasma membrane
Fluid Mosaic Model given by Nicolson and Singer in 1972, fully explains the molecular structure of plasma membrane. According to this model, the plasma membrane is a bilamellar structure i.e. it is made of two layers of Phospholipids in which proteins molecules are embedded, The protein molecules in the plasma membrane have been compared to the “ ice bergs floating in the sea of lipids”. The proteins present inside the membrane between the Phospholipids molecules are known as intrinsic proteins and those on the outer surface of the membrane are known as extrinsic proteins. There are some intrinsic proteins seen through out the phospholipid layer, these are known as channel proteins. On the outer surface of membrane there are present Glycogen molecules, if these molecules are attached with lipid molecules they form Glycolipid complex and if to the proteins they form Glycoprotein complex. Each phospholipid molecule has a hydrophobic tail directed inwards and hydrophilic head directed outer wards, that is why Phospholipids are amphiphatic in nature.
The term protoplasm was coined by Purkunjee for whatever is contained in the cell. It is divided in to two parts namely cytoplasm and Nucleoplasm. The Nucleoplasm is present in Nucleus and is confined to the boundries of Nuclear membrane.
The part of the cell between the cell membrane and the nuclear membrane is called the cytoplasm. The cytoplasm consists of the matrix and the organelles. The matrix is a transparent semi fluid substance. When active, it is always in a state of movement. The organelles are found embedded in the cytoplasm. They have definite shape, structure and function. All the metabolic activities of the cell such as synthesis, secretion, digestion and energy generation, are performed by the different cell organelles.
Cell organelles can be seen only with the help of an electron microscope.
The Cytoplasm is having following components
1. Cytosol 2) Cell organelles and 3) Cell inclusions
1) Cytosol:- It is an aqeous transparent ground substance also called Cytoplasmic matrix or hylaloplasm. It contains 90% water, Biomolecules such as minerals, sugars , Aminoacids, Nucleotides, Enzymes Vitamines, dissolved gases etc are necessary for the cell..
Cytoplasmic matrix exists in Sol-Gel state which are inter changeable. The gel state remains at periphery and is called as plasmagel or ectoplasm. While as Sol mainly remains in the centre & is called as plasmasol or endoplasm.
2) Cell organelles:-Cell organelles are sub cellular membrane bound compartments lying within the cell. Each of the cell organelles perform a specific function for the cell and also posses the property to survive independently outside the cell if they are put in a nutrient media which supplies the nutrient that are supplied by cell. Organelles are also sometimes called as organoids & they are of two types : Cytoplasmic and extra cytoplasmic orgenneles.
i) Cytoplasmic: Cytoplasmic organelles are those which are considered as part of cytoplasm. E.g. Mitochondria, Plastids, Endoplasmic Reticulum, Golgi complex, Lysosomes etc.
1) MITOCHONDRIA discovered by Kolliker (1880) in striated muscles of insects.
Mitochondria are double membrane bound cell organelles found within almost all eukaryotic cells. These are the sites for cellular respiration.
Ultra structure:-The mitochondria are double membrane bound structures containing an outer membrane and an inner membrane, the space between the two membranes is called perichondrial space or inter membrane space. It is filled with watery fluid. The space bound by the inner membrane is called the inner Chamber. The inner chamber is filed with matrix called mitochondrial matrix containing Mg++, Ca++ ions, Circular DNA Molecule and Ribosomes. The outer membrane is smooth while as the inner membrane is folded into a series of folds called Cristae. On the inner surface of cristae there is Knob like particles called Elementary particles or F0- F1 particles or oxysoms . The Elementary particle contains an enzyme called ATP synthetase which is an important for formation of ATP during cellular respiration. That is why they are also called the power house of cell.
Mitochondria are capable of self duplication (Replication). They are also able to synthesize some of their own proteins. Hence they are regarded as semiautonomous organelles. The highest no of mitochondria is found in flight muscles of insects.
Functions:-The mitochondria performs the following functions:-
Cell Respiration: – Mitochondria are the respiratory centers of the cell. They bring about oxidation of various stuffs such as carbohydrates, fats, proteins etc.
Thermo genesis:-In young mammals and hibernating mammals such as bats. There is a special tissue in the chest region called brown fat, which consists of numerous mitochondria which functions as a automatic furnace and generates enormous heat.
They are semi- autonomous, double cytoplasmic organelles. Plastid is 2nd largest organelle in plant after nucleus. The different types of plastids were discovered by Schimper 1885. All plastids are develop from proplastids. The different types of plastids classified by Hackel are:
(a) Leucoplasts are the colourless plastids which act as storage organelles for nutrients and are classified on the basis of the material stored in them e.g. Amyloplasts store carbohydrates in the form of starch. Aleuroplasts or Proteinoplasts store proteins , whereas Elaioplasts ( Oleosomes) store oil or fats. Leucoplasts are the largest plastids.
(b) Chromoplasts: They are the 2nd largest plastids. Chromoplasts are those plastids which contain pigments other than chlorophyll, therefore they don‟t perform photosynthesis. They mainly contain yellowish brown pigment called caretenoids. They impart colour to fruits and flowers, which is important for entomophilly (pollination by insects). The colour of tomato & Red chillies is due to presence of lycopene in their chromoplast. Chromoplast also helps in formation of Abssicic acid, which is important for opening and closing of stomata & seed dormancy. During ripening chromoplasts develop from chloroplasts ( chlorophyll & thyllakoid membrane break down.)
(c) Chloroplasts: chloroplast was discovered by Sachs & the term chloroplast was coined by Schimper. Chloroplast is the smallest plastid but it is considered as the 2nd largest organelle in plants after Nucleus. Chloroplasts are also semi- autonomous double membrane plastids containing green pigment called chlorophyll, which helps in photosynthesis. They also contain DNA, RNA and ribosome(70S).
Number: In green algae Chlorella, Ulothrix & Chlymadomonas, only one chloroplast is present in cell. In leaf cell of plant, 20-40 chloroplasts are present.
Shape: Normally, chloroplast is discoidal in shape but in some green algae, chloroplasts posses unique shapes. In spirogyra, it is ribbon shaped. In Ulothrix, it is collar shaped & in chlymadomonas it is cup shaped.
Size: it‟s size varies from 4-10 microns.
The chloroplast has circular DNA like mitochondria, which encodes both RNA & PROTEINS.
Ribulose bisphosphate carboxylase ( Rubisco ) is encoded by its DNA.
Ultrastructure: chloroplast under e- microscope reveals these structures:
1) Envelope 2) Matrix
1) Envelope: it is made up of 2 membranes, outer membrane & inner membrane. Each membrane posses the thickness of 75-100Å. The 2nd membrane bound a space called periplastidial space & its width is 100-120Å. Outer membrane is highly permeable of phorins while as inner membrane is selectively permeable because of presence of carrier proteins.
2) Matrix: The matrix of the chloroplast contains Rubisco ( i.e. Ribulose biphosphate carboxylase, RuBP or RuDP) which is the most abundant enzyme or protein of the biological world. The matrix of the chloroplast is differentiated into Granna and stroma.
i) Granna: In a typical chloroplast they are 40-60 in number and each grana may have 2-100 small flattened thylakoids. The thalakoids are structural and functional unit of chloroplasts. They are sac like structures enclosed by membrane. These thylakoids are piled one upon the other to form a granum. They are also referred to as ‘ Baggy Trousers’. The space present in stromal thylakoids is termed a fret channel. The thalakoids are arranged on one above the other just like stalk of coins & this type of chloroplast is called Grannal chloroplast. The thylakoids perform every function what the inner membrane of mitochondria performs.
Grana are absent in chloroplast of algae and bundle sheath chloroplast of C4 plants. In Red algae, only one thalakoid is present in chromatophore. In green algae, many thalakoids are present in chloroplast but they are not arranged on one above the other & such type of chloroplast is called as Agranal chloroplast.
Photosynthetic pigments are located in the membranes of thylakoides in specific areas called as Quantasomes, discovered by Park and Biggins. The Quantasomes act as transducers & convert solar energy into chemical energy(ATP).
ii) Stroma: it is the ground substance that is present in the chloroplast. It is semi-autonomous in nature.
1) Chloroplasts are seat of photosynthesis i.e. it converts simple raw material ( CO2 & H2O ) into organic food.
2) Chloroplast helps in photophosphorylation i.e. it converts radiant energy(solar energy) into chemical energy(ATP).
3) Chloroplast helps in storage of starch, vitamin E, K & Quinones. 4) Chloroplast helps in synthesis of Amino Acids.
3) ENDOPLASMIC RETICULUM Discovered by Thomson and porter
Definition:- The term endoplasmic reticulum was used by Keith Porter (1953) in liver cells. It is an inter connected system of membrane bound channels in the cytoplasm arising from outer membrane of nucleus up to plasma membrane.
Occurrence:- Endoplasmic Reticulum is present in all eukaryotic cells except mature R.B.C‟s egg and embryonic cells. The Endoplasmic Reticulum is highly developed in the cells which are actively engaged in the synthesis of proteins eg. Gland cells.
Morphology:- The Endoplasmic Reticulum occur in the following three forms.(1) Lamellar form or cisternae (2).Vesicular form or Vesicles and (3) Tubular form or tubules.
4) GOLGI COMPLEX
Definition :- Golgi complex are boat like, membrane bound cell organelles having lace like margins present in all animal and plant cells. In plant cells Golgi apparatus is called as Dictyosomes.
Occurrence:- Golgi Complex (Golgi apparatus) occur in almost all eukaryotic cells. Their number varies in different types of cells.
Position or Distribution :- The Golgi bodies are usually found scattered through out the cytoplasm and their distribution do not seen ordered or localized in any particular manner.
Golgi complex is made of cisternae, vesicles and tubules
(1) Cisternae :- Cisternae are central flattened plate like or saucer like closed compartments which are held in parallel bundles or stacks one above the other. The ends of cisternae are curved due to this the entire dictyosome takes the shape of a boat. It has two faces, one is “cis face or conves face” which is directed towards SER. Another is “trans face or maturing face” which is faced towards plasma membrane.
(2) Vesicles:- The vesicles are oval membrane bound vacuolar structure oftenly remain suspended in the cytoplasm. Vesicles are of 3 types: Transitional vesicles, Secretory Vesicles and Clathrin Coated Vesicles.
(3)Tubules :- They are the tube like structures having a diameter of 20-80 nm & are present at the periphery of cisternae .
In adddition to this it contains Golgian vacoules which arise from cisternae at the maturing face. They latter on give rise to lysosomes because they contain lytic enzymes.
Functions:- (1) Golgi Complex helps in biosynthesis of polysaccharide .
(2) Golgi complex helps in packaging of cellular synthetic products and differentiation of cellular membranes .
(3) It forms the acrosome of the sperm.
Definition :- Lysosomes are membrane bound vesicles found mostly in animal cells containing various hydrolytic enzymes in them.
Ultrastructure :- The lysosomes are bounded by a single unit membrane. There are various hydrolytic enzymes inside the membrane which can cause digestion of various membranes with in the cell.
If some times lysosomes in the cells get ruptured, the enzymes present in it can destroy the whole cell, that is why these are also called suicidal bags. The lysosome number is high in phagocytes. The enzymes present in the lysosome do not digest the lysosomal membrane because the proteins present in the membrane are glycosylated i.e. their inner surface contains glycogen molecules which prevent it from being digested by the enzymes present in the lysosome.
Fuctions of lysosomes :- Lysosomes perform the following functions
(1).Digestion of large extracellular particles :- The lysosomes present in the W.B.C‟ (leucocytes ) enable them to devour foreign proteins, bacteria and virus
(2) Digestion of intracellular substances :- During starvation the lysosomes digest the reserve food material such as proteins, lipids and glycogen and supply the necessary amount of energy to the cell .
(4) Autolysis :- In certain conditions the lysosomes digest the various cell organelles and the digested material is utilized by other cells of the body. e.g. In metamorphosis of amphibians there are various body parts in the embryonic stage which are lost in the adults eg. Gills, fins and tail all these parts are digested by lysosomes and the digested material is used by other cells.
Definition: – The vacuoles are membrane bound large fluid filled vesicles mostly found in plant cells Number:-There may be several vacuoles in a single cell .Generally they occupy about 30% of total volume of the cell.
Structure: – Vacuoles are bounded by a single unit membrane called Tonoplast. In immature and actively dividing cells the vacuoles are very small. The vacuoles arise initially in young dividing cells probably by the fusion of vesicles derived from the Golgi apparatus. The vacuoles are structurally and functionally related to lysosomes in animal cells and may contain a variety of hydrolytic enzymes contain sugars, salts, acids and nitrogeneous compounds such as Alkaloids and anthocyanin pigments. Functions:- (1) A vacuole has a variety of functions. It can act as a storage organelle for both nutrients and waste products.
(2) Vacuoles present in the petal cells of flowers contains anthocyanin pigment which make the petals colorful for attracting pollinating insects.
(3). Vacuoles maintain the turgidity of cells in plants by removing excess water.
(4) Vacuoles present in some plants contain toxic substances such as alkaloids which protect these plants from grazing animal‟s as these toxins cause indigestion in them.
ii)Extra cytoplasmic: these organelles are those which are not considered as part of cytoplasm. E.g. Nucleus
(1) Definition:- The nucleus is the most conspicuous membrane bound organelle of an eukaryotic cell.
It contains chromatids (chromosomes in it )
(2) Number: – Cell usually has a single nucleus in it and said to be mono nucleate. Some cells of liver or cartilage have two nuclei and are said to be binucleate, cells with many nuclei are called polynucleate.
(3) Location: – In embryonic cells the nucleus occupies a central position but may get displaced. In Adipose tissue the fat globule displaces the nucleus towards the peripheral position and the cell attains ring shape.
(4) Shape:- The shape of the nucleus varies in different cells .it may be disc shaped spherical cubiodal, ovoid, lobed (W.B.C‟s ) C shaped (Vorticella ), Kidney shaped (Paramecium )
(5) Ultrastructure: – The nucleus is double membrane structure containing an outer membrane and an inner membrane in between the two membranes there is a space called perinuclear space. Which is filled with a fluid containing lipid droplets.
The nuclear membrane are perforated by pores called nuclear pores .At the margin of each pore the outer and inner membrane are continuous.
The protoplasm present in the nucleus is called nucleoplasm it contains DNA associated with proteins forming highly condensed thread like structures called chromatids inside the nucleus there is a spheroid body called nucleolus.
(1) Definition: Ribosomes are dense round granular particles present in all cells.
(2) Occurrence and distribution: Ribosomes are present in both prokaryotes and eukaryotic cells. These are also present in cell organelles like mitochondria and chloroplasts. The Ribosomes may lie freely in the cytoplasm or on the surface of endoplasmic reticulum. Ribosomes may remain singly called monosomes or many ribosomes may remain attached with messenger RNA (mRNA) forming a chain like structure called polysome. The cells in which active protein synthesis takes place have high content of ribosomes e.g. Gland cells.
(3) Types:- Ribosomes are of two types namely 70s type and 80s type. 70s type Ribosomes are present in prokaryotic cells and chloroplast and mitochondria. 80s type ribosomes are present in euraryotic cells.
(4) Shape: – The shape of the Ribosome is like telephone receiver. Having an upper smaller unit and lower larger unit. Both the units are Negative charged and these remain held together by Mg++ ions.
(5) Chemical composition: – Both the upper & lower units of Ribosome are made of ribosomal RNA (rRNA) and proteins.
(6) Functions:- Ribosomes are the sites for protein synthesis.
Cell inclusions: The cell inclusions are non living materials present in the cytoplasm. These are also called deutoplasmic substances. The common cell inclusion is stored food materials, secretions and excretions and inorganic crystals.
Mitosis and Meiosis – A Comparison
Having studied the two types of cell divisions, mitosis and meiosis, let us summarize the differences between them.
Mitosis occurs in all somatic cells Meosis only in reproductive (sex) cells
Chromosome number remains same, i.e., diploid (2n), hence it is equational division Chromosome number reduces to half, i.e., haploid (n), hence it is reductional division
Two daughter cells are produced Four daughter cells are produced
One cell division involves four phases Consists of two sub-divisions: Meiosis – I and Meiosis – II each involving four phases. Prophase – I is again subdivided into five sub-stages
No crossing over Crossing over takes place
Daughter cells have identical
chromosomes to parent cell, i.e., genetic material remains constant Daughter cells have chromosomes with combined genetic material from both parents i.e., genetic variability occurs
Lesson No. 2 Tissues
TISSUE:- A Tissue is a group of similar or dissimilar cells having same origin arranged in a characteristic manner which co-operate to perform a specific role in the body of an organism. The term tissue was coined by “Bichat”
HISTOLOGY:- The term Histology was coined by “Mayer” It is the microscopic study of tissue in relation to their function.
HISTOGENESIS:- Histogenesis is the formation of tissues and organs from the undifferentiated cells in the embryo.
CLASSIFICATION OF TISSUE:-
Meristematic Tissues Permanent Tissue
Apical Meristem Interclary meristem Lateral meristem
Simple permanent tissue Complex Permanent Tissue
Parenchyma Collenchyma Schlerenhyma Xylem Phloem
Q.1:- What is Meristematic tissue?
Ans:- These are the tissues which are composed of living cells present in different parts of a plant and are in continuous state of division thus adding new cells to the plant body resulting in growth of the plant.
Depending upon the position, the meristematic tissues are classified in to 3 types.
1. Apical Meristem:- The meristem is located on the apices of roots and shoots. The meristem located on shoot apex is known as shoot apical meristem and the meristem located on apex of root is known as root apical meristem. The apical meristem causes the length of the plant to increase.
2. Lateral meristem:- It is Present on the lateral sides of plant . These meristems help in increasing the girth of plant.
3. Intercalary meristem:- This meristem is present at the base of the nodes, base of the internodes or at the base of the leaf. It helps in increasing the length of branches.
Q.2:- What are permanent tissues?
Ans. The tissues which are composed of living or dead cells formed from meristematic tissues located in different locations in a plant having lost the power of division are called permanent tissues.
Permanent tissues are of two types:- Simple permanent tissue and Complex permanent tissue. Q.3:- What are simple permanent tissues?
Ans. Simple permanent tissues are those tissues which are composed of only one kind of cells. E.g. Parenchyma, Collenchyma, Sclerenchyma.
A)PARENCHYMA:- Parenchyma tissue is composed of thin walled isodiametric cells having intercellular spaces between them (paraenchymatous cells). They vary in shape and may be oval, spherical or cylindrical in shape.
Parenchyma is concerned with photosynthesis called Chlorenchyma. It is also concerned with storage of various materials, wound healing and origin of adventitious structure. Some times in aquatic plant, a special type of parenchyma develops which possess large air spaces among the cells and is known as Aerenchyma.
B)COLLENCHYMA:- The cells of collenchyma have thin walls and possess the deposition of cellulose hemicellulose and lignin at corners only. Due to this deposition the collenchyma tissue has high water absorbing capacity. This tissue is elastic & extensible, thus giving tensile strength to the organs in which they are present. This tissue is present at the margins of some leaves and resist the tearing effect of wind. In the stems of plants they provide mechanical support. The collenchymatous cells are living.
C) SCLERENCHYMA:- It consists of dead cells having very high deposition of lignin. Due to legnin deposition all lumen is greatly reduced or is totally absent.
Sclerenchymatous cells are of two types namely fibres and sclereids:
Fibres: The Fibres are much long thick walled dead cells having pointed ends. These fibres are present in hypodermis of monocot stem e.g jute.
SCLEREIDS:- The sclereids are short and possess extremely thick lamellated lignified walls with long tubular simple pits. These are present in stony fruits such as pyrus (pear)
Q.4:-What is Complex permanent Tissue:- Complex permanent tissues are those tissues which are composed of more than one kinds of cells e.g. Xylem, Phloem.
A) Xylem : Xylem is composed of tracheids, vessels, xylem parenchyma and xylem fibres.
(i) Tracheids: Tracheids are the fundamental cell type in xylem. The tracheid is an elongated tube cell tapering, round or oval in both ends with hard and lignified walls. It is without protoplast and dead at maturity. The tracheids are specially adapted to function of conduction. Due to their firm and rigid walls they also aid in support of plant body.
(ii) Vessels:- The vessels are drum shaped cells placed one above another forming long tubes. The walls between the vessels are perforated or dissolved hence these are (syncytes). The walls of vessels are lignified. The lignifications on the walls may take place in the form of rings (Annular Thickening) springs (spiral thickening), net like (reticulate) scales (scaliform)
(iii) Xylem Parenchyma:- The xylem parenchyma is present outside the vessels and tracheids and it helps in lateral conduction of water and minerals. These are only living cells in xylem tissue . (iv) Xylem fibres:- The xylem fibres are long with highly lignified walls and their lumen is very much reduced.
B)Phloem: Phloem is composed of four types of cells namely seive tubes, companion cells, phloem fibres and phloem parenchyma.
(i)Sieve tubes:- Sievetubes are cylindrical & elongated cells with a thin cellulose wall and are placed end to end forming a continuous tube. The end walls of sievetube elements are called sieve plates. The sieneplates are perforated by numerous pores.
(ii)Companion cells:- Companion cells are associated with sievetubes and which lie side by side with them. Companion cells help the sieve tube cells in the conduction of food.
(iii) Phloem Parenchyma: Phloem parenchymatous cells may be elongated, pointed, cylindrical or sub-spherical in shape. Phloem parenchymatous cells store various types of materials such as oil, starch, mucilage, latex etc.
(iv) Phloem fibres:- Phloem fibres are dead sclerenchymatous fibres. The walls of these cells are lignified and thus provide mechanical strength to the parts of plants. Q.5 Which tissue forms the husk of coconut.
Ans. The sclerenchymatous tissue forms the husk of coconut. Q.6 What is the role of epidermis in plants?
Ans. In Aerial roots the multiple epidermal cells are modified to velamen which absorb water from the atmosphere
In leaf epidermal cells contain big vacuoles containing water, which play an important role in folding and enfolding of leaves.
Q.7 How does the cork act as protective tissue?
Ans. The cork forms the outermost layer of plants. It protects the plants from water loss and attack of pathogens.
Q.8 What are the functions of stomata?
Ans. Stomata are minute pores present in aerial parts of plant such as green stems and mostly leaves. These are guarded by two guard cells Stomata helps in gaseous exchange ( Co2 and O2 ) and transpirations occurs through them.
TISSUE:- A tissue can be defined as a group of cells similar in structure, origin and function. The word “tissue” was given by a French anatomist and physiologist Bichat (1771-1802). But the the term tissue had already been coined by N. Grew (1682) in relation to plant anatomy. Bichat (1771-1802) is considered as “Father of histology”.
An Italian scientist Marcello Malpighi (1628-1694) is founder of histology”. He founded a separate branch for the study of tissues called histology.
Q.No.1:- What is Epithelial Tissue?
Epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body. Cells of the epithelium are set very close to each other, separated by very thin films of extracellular material. Neighbouring cells are held together by cell junctions. The epithelial tissue rests on a non cellular basement membrane , which separates it from the underlying connective tissue. In humans, epithelium is classified as a primary body tissue, the other ones being connective tissue, muscle tissue and nervous tissue.
Blood vessels are absent in the epithelial tissue. Materials are exchanged between epithelial cells and vessels of the connective tissues by diffusion.
Classification of Epithelial Tissue: The Epithelial tissue is broadly classified into two main types:
A) Simple Epithelium
B) Compound Epithelium
A) Simple Epithelium:
It is formed of a single layer of cells , The adjacent cells are held together resting on the basement membrane. Simple epithelium occurs mainly on secretory and absorptive surfaces. It helps in nutrition, excretion, secretion but not for protecting the underlying tissue. It is found in lining of gut, mucous membrane, skin etc. These are of 4 types:
i) Squamous Epithelium: It consists of a layer of thin flat scale like cells with prominent nuclei. The outline of the cells is wavy or irregular. Inter cellular spaces are completely absent. Since the arrangement of the cells resembles that of tiles on a pavement, it is commonly called as “pavement epithelium”. It is found lining the lumen of blood vessels where it is known as endothelium. It also
occurs in the lining of the buccal cavity, in the alveoli of lungs and in the Bowman’s capsule of the nephrons. ii) Cuboidal or Cubical Epithelium: In this type, the cells are Cubical in vertical section and polygonal in surface view. The cells contain granular cytoplasm and a single large nucleus situated in the centre. Cuboidal epithelium is found commonly in glands and their smaller ducts. The cells participate in secretion , excretion and absorption. iii) Columnar epithelium: In columnar epithelium, the cells are tall column or pillar like. The cells are compactly arranged on a basement membrane. However, a few inter cellular spaces are present, filled with a cementing substance. A single large oval nucleus, which is found more towards the basement membrane. Columnar epithelium is found lining the alimentary canal, from esophagus to anus.
(iv) Ciliated Epithelium: They are columnar epithelium characterized by the presence of numerous hair-like outgrowths called cilia on their free surface. The cilia help in transportation and also function as a filtering mechanism. The function of the cilia is to move particles, free cells or mucus in a specific direction over the epithelial surface . It is present in the regions like the nasal passage, the trachea and the fallopian tube bronchioles and small bronchi.
B) Compound Epithelium: They are multi layered where the cells in the lowermost layer is in contact with basement membrane. Being multilayered it does not perform the role of secretion or absorption. It functions as protective layer against mechanical, chemical, thermal & osmotic stress. These are of two types.
1) Stratified Epithelium:
They are multi layered epithelium with varying types of cells. The cells can be- squamous, cuboidal or columnar. It is of the following types:
a) Stratified squamous epithelium: it is found where there is lot of wear & tear. E.g. skin, tongue, buccal cavity and the esophagus.
b)Stratified cubical epithelium: In this more than one layer of cuboidal cells are found arranged on a basement membrane. It occurs in the larger ducts of sweat glands and in the lining of the pharynx, salivary and pancreatic ducts.
c) Stratified columnar epithelium: In this type, the epithelium has several layers of polyhedral cells with columnar cells found only in the superficial layer. It occurs in the male urethra.
2) Transitional Epihelium: They are stretchable epithelium in which cells are large and rounded or conical. They are thin. It lines the inner surface of the urinary bladder and ureters. It allows considerable expansion of these organs to accomodate urine , because stretching considerably flattens and broadens the cells of superficial and middle layers. Q:Write a short note on Glandular epithelium?
Ans: Glandular epithelium forms the covering of all the major glands. It is also present in the intestinal lining. The cells are generally columnar or cuboidal. There are two major types of glands endocrine and exocrine.. Endocrine glands release their secretions directly in the blood stream, from where they
travel to the target organs e.g hormones., whereas exocrine glands reach the target organs through the medium of ducts e.g mucus, sweat etc. Both of these glands produce their secretions through the glandular epithelium tissue which comprises of several specialized cells called goblet cells. Q.No.2:- Explain the structure as well as functions of Muscular tissue?
Muscles cause movement of limbs and internal organs as well as locomotion in some animals.
The cells of muscle tissue can shorten forcefully and then return to the relaxed state.
This property of the muscle is known as contractility. On stimulation the muscle cells respond by contracting. This property of the muscle cell is responsible for various movement in the organism.
The muscle cells are known as muscle fibers since they are very thin and elongated.
Some muscles are associated with the skeleton and some other muscle fibers are associated with the viscera , blood vessels and the heart.
Therefore the muscle tissue can be classified into striated muscle, unstriated muscles and cardiac muscles according to their structure, location and function.
i) Striated Muscle : They are also known as skeletal or Voluntary Muscle. They are attached to the bones by bundle of colagen fibres known as the tendons. It is under the control of the somatic nervous system.
The skeletal muscle is made up of a number of muscle fibres .These muscle fibers are long , cylindrical and multinucleated cells composed of actin and myosin myofibrils repeated as sarcomere which is the basic functional unit of cell and responsible for skeletal muscle’s striated appearance and forming the basic machinery necessary for muscle contraction.
A voluntary muscle is composed of long bundles of striated muscle fibres. Each fiber is long unbranched , cylindrical cell. It shows transverse striations in the form of regular alternate dark (A) and light ( l) bands. The plasma membrane covering the fibre is called Sarcolemma and the cytoplasm inside the fibre is called Sarcoplasm. The sarcoplasm contains many long thin unbranched cross striated cylindrical structures called Myofibrils. A myofibril consists of approximately 10,000 sarcomeres end to end. Muscles are rich in proteins. Most of these proteins occur as two types Actin & Myosin.The thick filaments are made up of protein Myosin. These myosin filaments are located inside the A bands. Thin filaments are more numerous. They are composed of the protein Actin.
ii) Non- Striated or Smooth muscle fibres: They do not show cross striations instead, they look smooth. Smooth muscles can not be moved voluntarily. So they are also called Involuntary Muscles. Such smooth muscles occur on the walls of hollow visceral organs such as the urinary bladder ,gastrointestinal tract.,hair roots, and on the wall of large blood vessels .Smooth muscle fibres are elongated spindle-shaped cells. They are packed parallel to each other in branching bundles. Each fibre contains a single, spindle shaped nucleus at its thick central part. The smooth muscle fibre is generally shorten than a striated muscle fibre. Mitochondria and other organelles are less extensive and protein filaments are not regularly arranged to give rise to striations. Smooth muscle is under the control of autonomic nervous system, whereas skeletal muscle is under the control of the somatic nervous system.
iii) Cardiac muscle: occurs exclusively in the heart. It possesses considerable automatic rhythmicity and generates its own wave of excitation. The excitation can also pass directly from fibre to fibre in the cardiac muscle. It is not under voluntary control. It shows cross-striations, but striations are much fainter than those of striated muscle. Between the cardiac fibres intercalated are present. They are specialized regions of cell membrane of two adjacent fibres. The intercalated discs function as boosters of contraction wave and permit the wave of contraction to be transmitted from one to another. Cardiac
muscle cells are short cylindrical cells joined end to end to form rows. They possess numerous mitochondria and glycogen granules. This is because they need a large amount of energy. Where two cardiac muscle cells meet end to end, dense zig-zig junction is formed between them. It is called an Intercalated Disc.
Q.No.3:- Expain Nerve Tissue briefly?
Nerve tissue is made up of neuron
Neuron: are the basic building blocks of the nervous system. These specialized cells are the information-processing units of the brain responsible for receiving and transmitting information. Each part of the neuron plays a role in the communication of information throughout the body. It consists:
1) Dendrite 2) Cyton 3) Axon.
1) Dendrites: are tree like extensions at the beginning of a neuron. These tiny protrusions receive information from other neurons and transmit electrical stimulation to the cyton. Each Dendron at its upper end divides into branches & these branches are known as dendrites to increase surface area for receiving stimulus.
2)The cell body or cyton: oval, spherical or stellate (star like) in shape. It has a centrally located nucleus, the cytoplasm of cell body is called neuroplasm. Its plasma membrane is called neurolemma.
At cyton, the signals from the dendrites are joined and passed on. The cyton and dendrites have small, conical, angular highly basophilic structure in the cytoplasm which are called as Nissl bodies and they are absent in the axon and axon hillock. These Nissl bodies are made up of ribosomes, ER etc.
3) The axon is the single elongated fiber that extends from the cell body to the terminal endings and transmits the neural signal. The part of cyton from where the axon arises is called as axon hillock.The larger the axon, the faster it transmits information. Some axons are covered with a fatty substance called myelin that acts as an insulator Such an insulated cell process of the neuron is called a nerve fiber. These myelinated axons transmit information much faster than other neurons. Myelin sheath is absent at certain points called as Nodes of Ranvier. In myelinated nerve fibre the impulse jumps from one node of Ranvier to the other , this is called as saltatory conduction of the impulse. The axon divides to form axon ending called terminal arborisations, each with a synaptic knob. The synaptic
knob contain mitochondria and secretory vesicles. The vesicles contain neurotransmitter which is noradrenaline or Acetyl choline.
The terminal buttons are located at the end of the neuron and are responsible for sending the signal on to other neurons. At the end of the terminal button is a gap known as a synapse. Neurotransmitters are used to carry the signal across the synapse to other neurons.
Q.No.4:- Explain Connective Tissue with suitable Examples?
Ans:- Connective tissue is a type of tissue which provides connectivity within the living body. It is further classified into following types:
A) Connective tissue proper B) Supportive connective tissue C) Fluid Connective tissue
iii)Tendon: It is a very dense , strong and fibrous connective tissue with thick parallel bundles of collagen fibres. Tendon forms the strong attachment of a skeletal muscle to a bone.They connect muscle to bone. They are made of special cells called tenocytes, water, and fibrous collagen proteins. Millions of these collagen proteins weave together to form the strong strand of flexible tissue called a tendon. Tendons grow into the bone and form a tough mineralized connection. This connection creates a permanent bond that is extremely tough to break.
Tendon is a modified white fibrous tissue. iv)Ligament: It is a dense fibrous connective tissue . The ligament connects bones at the joints and holds them in position. Ligaments are the fibrous, slightly stretchy connective tissues that hold one bone to another in the body, forming a joint. Ligaments control the range of motion of a joint, preventing the elbow from bending backwards. Ligaments are composed of strands of collagen fibers.
B) Supportive Connective Tissue: E.g. Cartilage & Bone
i)Cartilage: Cartilage is a solid but semi rigid and flexible connective tissue. The entire skeleton is made up of cartilage. In mammal embryos, the skeleton first forms as cartilage tissue. Cartilage acts as a model and is gradually replaced by bone as the embryo grows. The process by which bone tissue follows the cartilage model and slowly replaces it is known as ossification. Cartilage is found in the tip of the nose, in the external ear and in the walls of the trachea (windpipe) and the larynx (voice-box). Cartilage consists of living cells, chondrocytes which contain the protein chondrin.
ii)BONES: Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blodd cells and store minerals.. Bone tissue is a type of dense connective tissue. They are lightweight, yet strong and hard. The bone contains osteocytes, which contain ossein protein. There are 206 bones in the adult human body and 270 in an infant. The largest bone in the human body is the femur.
C) Fluid Connective Tissue: E.g. Blood
Blood: Blood is a fluid connective tissue. The cells are distinctly different from other connective tissue cells both in structure and functions. The extracellular material in blood is a fluid devoid of fibres. Fluids outside the cells are generally called Extracellular fluids ( ECF). This fluid is straw coloured , slightly alkaline ( pH 7.4) aqueous fluid called plasma. The cellular elements of the blood i.e. the white blood corpuscles, red blood corpuscles and platelets are suspended in the plasma. The normal
total circulating blood volume is about 8% of the body weight ( 5600ml in a 70 kg Functions of blood
1) It transports food and oxygen to tissues.
2) It helps in removing waste products from the body tissues.
3) It helps in maintaining body temperature.
4) It helps in fighting against infection.
Lesson No. 3
Q.1 What is bio – diversity?
Ans.: The living organisms exist in different forms. They have different morphological and anatomical characters. This variation in the characters of living organisms is called Bio – diversity. Q.2 What is classification?
Ans.: Classification is the grouping and sub grouping of living organisms on the basis of their similarities, relationship and evolution.
Q.3 What are advantages of classification?
Ans. Classification has the following advantages:
1. It makes the study of wide varieties of living organisms easier.
2. It helps us in the identification of living organisms.
3. It is not possible for man to study all the organisms, but the study of a few representatives of each group help us to know the characteristics of whole group.
4. It helps us to know the relationship between different groups of organisms.
5. It gives us information about the animals which are not present in our own locality. Q.4 Give the history of classification of living organisms?
Ans. (a) Natural system of classification: In natural system of classification many characteristics are taken into account. Practically all aspects of morphology, anatomy, cytology, physiology, development, reproduction, behaviour and biochemistry are taken into account.
(b) Artificial System of classification:- Artificial system of classification is that system of classification in which habit, habitat, or one to two morphological characters are basis for grouping of organisms. The first artificial system of classification was used by Manu in the East and Pliny in the west. Pliny used this classification in his book „Historia naturils‟. He divided animals into two groups (i) Flight animals (ii) Flightless animals. The flight animals included birds, bats and insects. Plants were divided into groups such as herbs, shrubs, vines, trees, succulents etc. Q) Define the following terms:
(a) Systematics:- Systematics is that branch of biology which deals with the classification or arrangement of different kinds of organisms on the basis of existing relationships among them selves.
(b) Classification: Classification is the ordering of plants and animals in to groups on the basis of their relationship.
(c) Phylogeny: The evolutionary history of a particular group of organisms is called phylogeny. Q.5 What is two kingdom system of classification?
Ans. Two kingdom system of classification was established by a Swedish biologist Carolus Linnaeus in 1758. Carolus Linnaeus divided all organisms into two distinct kingdoms. (i) Plant Kingdom and (ii) Animal Kingdom. According to this scheme of classification, plants are the stationary organized bodies having life and no sensation. The animals are the organized bodies having life, sensation and power of locomotion. Carolus Linnaeus published his scheme of classification in the famous book “Systema Natura”
Disadvantages of two – kingdom system of classification:_
(a) Two kingdom system of classification became inadequate with the discovery of a large number of new animals.
(b) The two kingdoms are not clearly defined at the lower level of organization.
(c) Two kingdom system of classification does not depict evolutionary relationship of organisms.
(d) In two – kingdom system of classification all the prokaryotes have been included in plant kingdom.
(e) Euglena having the characteristic property of both plants (Photosynthesis) and animals (locomotion) was a drawback of two kingdom system of classification.
(f) Chlamydomonas is unicellular algae. It is motile like animals but has photosynthetic property like green plants.
Q. 6 What is phylogenetic system of classification?
Ans. Phylogenetic system of classification is that system of classification in which plants and animals are classified into various groups on the basis of their evolutionary sequence (History)
Q.7 What is the scientific name?
Ans. Those names which are used in biological writings and universal applications are called scientific names. It was developed by Carolus Linnaeus.
Q.8 What is five kingdom system of classification?
Ans. The five kingdom system of classification was given by Robert H. Whittaker in 1969 to overcome the drawbacks present in the two kingdom system of classification.
According to five kingdom system of classification all organisms in the world were divided into five kingdoms namely:
(i) Kingdom Monera (ii) Kingdom protista (iii) Kingdom Fungi (iv) Kingdom Plantae and (v) Kingdom Animalia
The five kingdom system of classification is based on (i) Complexity of cell structure (ii) Complexity of organisms body (iii) Mode of nutrition (iv) Phylogenetic relationship.
Q.9 What are the characteristic features of kingdom monera?
Ans. 1.They are all pro-karyotic, unicellular organisms
2.They lack the membrane bound organelles such as mitochondria, chloroplast, nucleus etc.
3.The genetic material i.e. D. N. A lies free in the cytoplasm
4.They include both autotrophic (cynobacteria) and heterotrophic (lactobacillus) organisms.
5.Ribosome‟s are of 70s types, they process a cell wall in their cells.
6.The cell wall may be surrounded by slimy layer.
Q.10 Give the salient features of kingdom protista?
Ans. Following are the salient features of kingdom protista:
(i) The kingdom protista includes the unicellular eukaryotic organisms.
(ii) They have a complete set of cell organelles in them.
(iii) The ribosomes are of 805 types
(iv) Genetic material is enclosed inside the nuclear membrane (v) There are many chromosomes in the cells of protista.
(vi) The genetic material DNA is not naked but is associated with histone proteins.
(vii) Locomotion is performed by Cilia, flagella or pseudopodia.
(viii) They do not possess a cell wall in their cells.
(ix) They are both autotrophic (euglena) and heterotrophic (plasmodium) amoeba, Giardia, Trichchomonas etc.
Q.11 What are the salient features of kingdom fungi?
Ans. The kingdom Fungi includes, yeast, moulds, mushrooms etc.
(i) They are predominantly multi cellular eukaryotes without chlorophyll.
(ii) The body of fungus is filamentous and is called mycelium. The mycelium is formed of filaments called hyphae, which are formed of fungal cells.
(iii) Fungal cells have cell wall composed of chitin.
(iv) They have reserve food material in the form of glycogen.
(v) They reproduce sexually and asexually.
(vi) They have saprophytic mode of nutrition.
(vii) Some fungi remain in symbiotic association with algae forming an entity called lichen.
(viii) Some fungi remain in association with roots of higher plants. This association is called Mycorrhiza. Example, Mushroom, Mould, Aspergillus etc.
(A) Kingdom Animalia
Introduction: Animals make up millions of species and are among the most bountiful living things. They are very diverse in form, ranging from single celled microscopic one to multicellular macroscopic organisms. Q1)
Ans: Grades of Organisation and body plan: Animals though show different shapes & sizes but posses either cellular, tissue, organ or organ system of organization. The cellular grade of organization can be observed in all protozoans (unicellular or acellular) where all the vital activities of the body are performed by a single cell, e.g Amoeba. The next higher level of body organization is observed in multicellular animals, which are called Metazoans. Based on complexity of organization, metazoans are further subdivided into two subkingdoms- Parazoa and Eumetazoa . In Parazoa (e.g; Sponges), the cells are loosely aggregated and do not form tissues or organs. In Eumetazoans, which includes the rest of animals, the cells are organized into structural and functional units called tissues, organs and organ systems. Q.2)
Ans: Diploblastic & Triploblastic organization : In radiate animals , the cells are arranged into two fundamental layers, an external ectoderm & an internal endoderm with an intervening mesoglea. Such animals are therefore called diploblastic. In Bilateria, a third germ layer, mesoderm is present in between ectoderm and endoderm . Hence they are called Triploblastic animals.
Q.3) Segmentation: In some Bilateria the body is of many segments , which show serial repetition of parts(e.g ; Earthworm). This kind of segmentation is called metameric segmentation and the phenomenon is known as Metamerism.
Q.4) Phylum Protozoa & its general characters?
Ans: They are microscopic organisms in which a single cell performs all the vital activities . For this reason , Protozoans are also refered to as acellular organisms . There are about 15,000 species of Protozoans known to exist in the world.
i) They are aquatic (fresh water or marine) and cosmopolitan in distribution.
ii) Some forms are parasitic.
iii) The protozoan cell body is either naked (e.g ; Amoeba) or surrounded by a non rigid pellicle.Cellulose is absent in pellicle. iv) Some Protozoans secrete shells of various inorganic compounds as external covers.
v) Locomotory organs may be flagella (flagellates) or cilia (ciliates) or Psendopodia (Sarcodines). Locomotory organs are absent in parasitic forms (e.g; sporozoa). In them, neurofibrils are present underneath the cell surface. vi) Mode of nutrition is generally holozoic and feed largely on bacteria, microscopic algae and minute animals such as rotifers or on other protozoans including members of their own
species. Some protozoans are holophytic; they contain chlorophyll and prepare their own food by photosynthesis (e.g; Euglena).
vii) Contractile vacuole is found in almost all fresh water protozoans for osmoregulation . It also helps in excretion. viii) Mode of reproduction is also very specialized . Most sarcodines , flagellates and ciliates show asexual reproduction by binary fission, multiple fission or even budding . Some ciliates, e.g; Paramoecium reproduces by sexual means (through conjugation). Examples of Protozoans:
Free living-Euglena, Amoeba, Paramoecium etc.
Parasitic- Monocystis, Entamoeba.Plasmodium, Trypanosoma & Giardia.
Q.5) Phylum Porifera & its general characters?
Ans: Members of this phylum are also called as sponges and are the most primitive group of multicellular animals, with about 5000 known species .
i) Mostly they are marine and remain attached to rocks(sessile).A few in fresh water(e.g; Family spongilladea). ii) They range in size from 1cm to 1m in length. iii) Some forms are radially symmetrical, but the larger ones are asymmetrical. iv) They are multicellular with cellular grade of body organization. v) Body shape is vase or cylindrical like.
vi) The body surface is perforated by numerous pores, the Ostia through which water enters the body & one or more large openings, the Oscula by which water passes out.
vii) They are diploblastic.
viii) The interior body space is either hollow or permeated by numerous canals lined with choanocytes. The interior space of sponge body is called spongocoel. ix) They have a characteristic skelton consisting of either spongin fibres, calcareous spicules or siliceous spicules.
x) They are monoecium & the reproduction is both Sexual or Asexual.
xi) Fertilization is internal & mostly cross fertilization occurs. Q.6) Phylum coelentrata & its characteristics?
Ans: Coelentrata may be defined as diploblastic Metazoa with tissue grade of body organization having nematocysts and a single gastrovascular cavity or Coelenteron.
i) They are Metazoans with tissue grade of organization.
ii) They are aquatic, mostly marine except few fresh water forms like Hydra. iii) They are sedentary or free swimming and solitary or colonial. iv) Individuals are radially or bilaterally symmetrical with a central gastrovascular cavity. v) They are diploblastic & Acoelomatic .
vi) Short and slender tentacles encircle the mouth in one or more whorls.
vii) The tentacles are provided with nematocysts; tentacles serve for food capture, its ingestion and for defence. viii) Skeleton (either endo or ecto) is of common occurrence.
ix) They are usually carnivorous ,digestion is extracellular as well as Intracellular Anus is absent. x) Reproduction is both Sexual & Asexual.
xi) A ciliated planula larva is usually present in the life history.
Examples: Bonganinvillea, Halistemma, Vellela, Porpita, etc.
Q.7) Phylum Platyhelmenthes & their general characters?
Ans: Platyhelmethes are triploblastic , bilaterally symmetrical , dorssoventrally flattened, acoelomate flat worms with organ grade of construction without definite anus, circulatory, skeletal & respiratory but with ptonephridial excretory system & mesenchyme filling the space between the various organs of the body.
Protonephredia: A hallow cell in the excretory system of certain invertebrates including flat-worms & rotifers , containing a tuft of rapidly beating cilia that serve to propel (drive foreward) waste product into excretory tubules.
i) They are small to moderate in size , varying from microscopic to extremely elongated forms. ii) Majority of flatworms are white colourless , some derive colour from the ingested food, while the free living forms are brown , grey, black or brilliantly coloured. iii) Anterior end of the body is differentiated into head.
iv) Ventral surface bearing mouth & genital pores is well marked in turbullarians but is less marked in trematodes & cestodes.
v) Body is covered with a cellular syncytial one layered partly ciliated epidermis, while is parasitic in trematodes & cestodes, epidermis is lacking & the body is covered with cuticle.
vi) Exo & endoskeleton are completely absent .Hence body is generally soft. Hard parts consists of cuticle, spines, hooks, thorns, teeth, etc.
vii) They are acoelomates.
viii) Digestive system is totally absent in Acoela & tapeworms but in other flatworms it consists of mouth , pharynx and blind intestine (anus absent) . ix) Respiratory & circulatory systems are absent.
x) Excretory system consists of single or paired Protonephredia with flame cells or bulbs. xi) Sexes are generally united with a few exceptions.
xii) In majority of forms, eggs are devoid of yolk but provided with special type of yolk cells & are covered by egg shell. xiii) Cross fertilization in trematodes & self fertilization in Cestodes is very common. Fertilization is internal.
Definition: Molluscs are soft-bodied bilaterally symmetrical , unsegmented , coelomate animals; usually shelled having a mantle, ventral foot, anterior head and a dorsal visceral mass.
1. Molluscs are essentially aquatic mostly marine, few freshwater and some terrestrial forms.
2. The body is soft, unsegmented, bilaterally symmetrical and consists of head , foot, mantle and visceral mass.
3. The body is clothed with one layered often ciliated epidermis.
4. Body is commonly protected by an exoskeletal calcareous shell of one or more pieces, secreted by mantle.
5. Head is distinct, bearing the mouth and provided with eyes, tentacles and other sense organs except in Pelecypoda and Scaphopoda.
6. Ventral body wall is modified into a muscular flat or plough-like surface, the foot which is variously modified for creeping, burrowing and swimming.
7. Mantle or pallium is a fold of body wall that leaves between itself and the main body mass , the mantle cavity.
8. Visceral mass contains the vital organs of the body in a compact form taking form of a dorsal hump or dome.
9. Body cavity is haemocoel. The true coelom is generally limited to the pericardial cavity and the lumen of the gonads and nephridia.
10. Digestive tract is simple with an anterior mouth and posterior anus but in gastropods, scaphopods and cephalopods the intestine becomes U-shaped bringing the anus to an anterior position.
11. Pharynx contains a rasping organ the radula except in Pelecypoda.
12. Circularory system is open except in cephalopods which shows some tendency towards a closed system.
13. Respiratory organs consists of numerous gill or ctenidia usually provided with osphradium at the base. Lung is developed in terrestrial forms. Respiratory pigment is usually haemocyanin.
14. Excretory system consists of a pair of metanephridia which are true coelomoducts and communicate from pericardial cavity to the exterior by nephridiopore.
15. Nervous system consists of paired cerebal, pleural, pedal and visceral ganglia joined by longitudinal and transverse connectives and nerves.
16. Sexes usually separate (dioecious) but some are hermaphroditic.
17. Fertilization is external or internal.
18. Development is either direct or with metamorphosis through the trochophore stage called veliger larva.
Definition: Arthropods are bilaterally symmetrical , triploblastic, metamerically segmented animals with coelom which is reduced and modified. Their body is covered externally in a chitinous exoskeleton which moults periodically and their appendages are jointed.
1. Arthopods are triploblastic , bilaterally symmetrical, metamerically segmented animals.
2. Body is covered with a thick chitinous cuticle forming an exoskeleton.
3. Body segments usually bear paired lateral and jointed appendages.
4. Musculature is not continuous but comprises separate striped muscles.
5. Body cavity is haemocoel. The true coelom is reduced to the spaces of the genital and excretory organs.
6. Digestive tract is complete, mouth and anus lie at opposite ends of the body.
7. Circulatory system is open with dorsal heart and arteries but without capillaries.
8. Respiration through general body surface, by gills in aquatic forms, tracheae or book lungs in terrestrial forms.
9. True nephridia are absent, excretion by coelomoducts or Malpighian tubules or green or coxal glands.
10. Cilia are entirely absent from all parts of the body.
11. Sexes are generally separate and sexual dimorphism is often exhibited by several forms.
12. Fertilization is internal.Development is usually indirect through larval stages.
13. Parental care is also often well marked in many arthropods.
14. Most diversified group inhabiting the land, water and air.
Definition: Echinoderms are enterocoelous coelomates with pentamerous radial symmetry, without distinct head or brain having a calcareous endoskeleton of separate plates or pieces and a peculiar water vascular system of coelomic origin with podia or tube-feet projecting out of the body.
1. The echinoderms are exclusively marine and are among the most common and widely distributed of marine animals.
2. They occur in all seats from the intertidal zone to the great depths.
3. Symmetry usually radial, nearly always pentamerous.
4. Body is triploblastic, coelomate with distinct oral and aboral surfaces and without definite head and segmentation.
5. They are of moderate to considerable size but none are microscopic.
6. Body shape rounded to cylindrical or star-like with simple arms radiating from a central disc or branched feathery arms arise from a central body.
7. Surface of the body is rarely smooth ,typically it is covered by five symmetrically spaced radiating grooves called ambulacra with five alternating inter-radii or inter-ambulacra.
8. Body wall consists of an outer epidermis, a middle dermis and an inner lining of peritoneum.
9. Endoskeleton consists of closely fitted plates forming a shell usually called theca or test or may be composed of separate small ossicles.
10. Coelom is spacious lined by peritoneum , occupied mainly by digestive and reproductive systems and develops from embryonic archenteron, i.e. enterocoel.
11. Presence of water vascular or ambulacral system is the most characteristics feature. It consists of tubes filled with a watery fluid.
12. Alimentary tract is usually coiled tube extending from the mouth located on the oral surfaces to the anus on the aboral or oral surface.
13. Circulatory or haemal or blood lacunar system is typically present.
14. Respiration occurs through a variety of structures, i.e., papulae in starfishes, peristomial gills in sea urchins, gential bursae in brittle stars and cloacal respiratory trees in holothurians.
15. Excretory system is wanting.
16. Nervous system is primitive , consisting of networks concentrated into the radial ganglionated nerve cords.
17. Sense organs are poorly developed.
18. Sexes are usually separate(dioecious) with few exceptions. Gonads are simple with or without simple ducts.
19. Reproduction is usually sexual , few reproduce asexually or by regeneration.
20. Fertilization is external, while few echinoderms are viviparous.
21. Development is indeterminate including characteristic larvae which undergo metamorphosis into the radially symmetrical adults. Q) Ancestory of chordates?
Ans: Phylum chordate marks the climax of animal evolution. Its representatives called chordates, are the most familiar, adaptable, successful, and most widely distributed animals with diverse form in their habit and habitats. Approximately 30 animal pluyla have been currently recognized, the last and major among these being pluylum chordata. It was created by Balfour in 1880 Word chordate is derived from two greek words “Chorde” means String/chord and “ata” means bearing. They represent as a group, the background of man himself.
All the chorates possess three outstanding, unique characteristics at some stages of their life history .These three fundamental characters are
1. A dorsal hollow or tubular nerve chord.
2. A longitudinal supporting rod-like motochord/chorda dorsalis.
3. A series of paired pharyngeal gills slits.
i) Dorsal Nerve chord: The central nervous system of chordates consists of a single, tubular, fluid-filled, non ganglionated nerve chord, situated along the mid dorsal line above the notochord above the coelom. The nerve chord or neural plate is derived by sinking in of the median dorsal strip of ectoderm of embryo . Its cavity is called as neurocoel. It persists throughout the life of all chordates and is differentiated into an anterior short, wide brain and a posterior long, slender spinal-cord.
ii) Notochord/Chorda dorsalis: It is a solid , unjointed rod, located in the mid dorsal line between the Gut and the central nervous system outside the coelom.
The phylum derives its name from their structure i.e. in Greek noton= back and in latin chorda= a chord. It develops as a longitudual outfold from the dorsal part of the Gut wall. It orginates from the endodermal roof of the embryonic archaenteron. It consists of large, vacuolated thin epithelial cells called notochordial cells. The epithelium secretes two sheathes- the inner thick sheath of fibrous connective tissue and the outer thin sheath of elastic connective tissue. It serves as an axial endoskeleton, giving support to the body. In some lower chordates, notochord persists throughout the life but in most higher chordates it is partly or wholly replaced in the adult stage by a jointed backbone or vertebral column.
iii) Gill Slits: Gill slits also called visceral or branched clefts , are paired perforations on the lateral sides of the anterior part, leading from pharynx to the exterior of the body. They develop in the embryo as ectodermal invaginations that meet and fuse with corresponding endodermal evaginations from the pharyngeal wall. They persist throughout the life in all lower chordates,(branchiostomes), fishes and some amphibeans. They disappear or become modified in the adult with the acquisition of pulmonary respiration.
iv) Tail: It lies behind anus , contains notochord , nerve chord, blood vessels and muscles but lacks coclan and viscera. It is present in all chordates .In aquatic forms, it serves for locomotion.
Origin and Ancestory of chordates:
The origin of chordates including lower forms remains obscure. Scientists have not succeeded in determining which lower forms have given rise to them. Their early ancestors mostlikely were soft bodied and have no definite fossil remains. The fossil record of known vertebrates have been reported from the late Cambrian strats, so they must have originated prior to Cambrian period.On the basis of resemblance between the lower chordates and some invertebrates, many theories of chordate origin have been formulated .Only tow of these, namely , echinoderm theory and Ascidian theory , deserve serious consideration , others being of only historic importance.
1.Echinoderm theory: The theory is also called as Echinoderm- Hemichordate Ancestory. The theory traces the origin of chordates, hemichordates and echinoderms from a common ancestor. The relationship between these groups is shown by three lines of evidence embryological, biochemical, and serological.
A . Embryological evidence: Both echinoderms and chordates have equipotential and radial cleavage, enterococlous formation of coelom and mesoderm and deuterostomons mouth. The theory is based on the marked resemblance between bipinnaria larva of certain echinoderms and the tornaria larva of hemichordates. Both have a minute, oval transparent body with identical external ciliated bands
(sensory cilia at the anterior end), complete digestive tract having ventral mouth and posterior anus and the same number of coelomic cavities (five). Nervous system develops from dorsal strip of ectoderm in both groups.
B. Biochemical evidence: Both echinoderms and chordates use phosphocreatine in the energy cycle of their muscle contraction. However , phosphoarginine is also used by by some groups for the same purpose. Certain hemichordates and few echinoderms use both phosphocreatine and phosphoarginine thereby indicating that they are the connecting links between chordates and invertebrates.
C. Serological evidence: A closest resemblance exists between the body fluid proteins of chordates and echinoderms than between chordates and Annelids or Arthropods. As the degree of resemblance of the proteins of live animals shows their evolutionary relationship, the chordates are more related to echinoderms.
Besides the above three lines of evidence, adult chordates and echinoderms resemble in having mesodermal endoskeleton.
From the resemblance between echinoderms, hemichordate and chordates, Hyman (1959) and others concluded that all the three have a common ancestory (probably pterobranch like creatures)
Q) What are Reptiles. Mention their important characters?
Ans: Reptiles are cold blooded , air breating vertebrates, a group that includes snakes, lizards, turtles, tortoises, crocodiles and alligators. Many scientists believe that both mammals and birds evolved from this class of animals . In the present world nearly 5000 known species of reptiles are living. They are first true land vertebrates and also first amniotic groups of vertebrate animal.
1. Reptiles are cold blooded vertebrates.
2. They are terrestrial or aquatic animals.
3. The body of reptiles is covered with horny scales of bonyscutes.
4. Their skin is dry and glands are absent in the skin.
5. Four limbs are present.
6. They are pentadactyl(having five fingers).
7. The vertebrae are gastrocentrous and ribs form a true sternum.
8. Respiratory organ is lungs.
9. Heart is divided into two auricles and ventricle , which is divided into two chambers incompletely.
10. RBC‟s are nucleated.
11. Kidneys are metanephric.
12. 12 pairs of cranial nerves are seen.
13. Fertilization is internal and eggs are laid on land.
Q) What are Mammals. Mention their important characters.
Ans: Mammals are warm blooded vertebrates that evolved in the Jurassic period about 175 million years ago. They evolved from reptiles. For over 100 million years , mammals were small and not diverse, but with the extinction of dinosaurs (65 million years ago) , they grew in size and diversified. Common examples include rodents, bats, dogs, bears, cats , deer, sheep,goats and humans. In all there are about 5400 species, distributed in about 1200 genera, 153 families and 29 orders.
1. All mammals bear hair on their body at some point in their lives.
2. The jaws of mammals are made up of a single bone on each side.
3. Mammals have unique heart. Although mammals have foure chambered heart like birds, the main artery turns left, as it leaves the heart. In birds it turns to right, while as in all other vertebrates, there are more than one artery that orginate from the heart.
4. All mammals have two sets of teeth in their life time, i.e. their teeth are replaced only once.
5. All mammals have a sheet of muscles and tendous , known as diaphragm that separated the thoracic cavity from the abdominal cavity.
6. Backbone is present.
7. They are warm blooded.
8. The females of class mammalian have mammary glands that produce milk with which females feed their young ones.
Q) What are Amphibians? Mention their general characters?
Ans: An amphibian is any non-amniotic (lacking eggs with a shell), cold blooded, tetrapod animals that spends least part of its time on land. Living examples include frogs, toads, salamanders, newts, etc. There are only about 6200 living species.
1. They are cold blooded vertebrates which can hue on land and in water.
2. Amphibians show four limbs with which they can swim in water and jump or walk on land(but in Apoda limbs are absent).
3. In Amphibians exoskeleton is absent. But in Apoda animals small cycloid scales are present.
4. In adult Amphibians lungs are present and gills are absent. But in some urodelans the gills are present.
5. Their skin is a respiratory organ.
6. The skull in dicondylic.
7. Ribs are absent.
8. Heart is 3 chambered with two auricles and one ventricle.
9. Kidneys are mesonephric.
10. 10 pairs of cranial nerves are there.
11. In their life history, a larva stage may be present.
(B) Kingdom Plantae
Introduction: The plantae includes all land plants: mosses, ferns, conifers, flowering plants and so on. With more than 250000 species, they are second in size only to the arthopoda. Plants have been appeared in the Ordovician, but did not begin to resemble modern plants until the late Silurian.
Q1) Classification of plants?(An overview)
Ans: Plants were classified on their use , form and structure. Earlier system classified plants on the basis of their habital as- trees , shrubs, under shrubs & herbs. Gradually , the natural affinities in addition to morphological features became the major consideration for grouping plants. Studies on evolution helped in understanding the phylogeny of organisms. Taxanomists then started using the phylogenetic relationship for classification purpose.
Q2) What were some of the basic attempts of classification of plants?
Ans: In a majority of systems , which recognized only two kingdoms of organisms, the plants were included in plant kingdom, where as the animals in Animal kingdom.
For the classification of plants, several systems were proposed from time to time. Some are given below.
a) While using the no. and position of stamens, Linnens divided flowering plants into 23 classes, starting with the class Monandria(with a single stamen) & plants with 20 or more stamens were assigned to class Icosandria . He also included all non flowering plants such as algae, fungi , lichens,mosses and ferns in a separate class called Cryptogamia. His system was labeled as artificial since it was based on a few characters. More over, his system places widely unrelated families of monocotyledons & dicotyledons in one class.
Subsequently several systems were proposed from time to time, and it is difficult to discuss all of them.
Q3) What are cryptogams and phanerogams?
Ans: Simple systems which divides plant kingdom into two sub kingdoms – phanerogamae and cryptogamae, considering the presence or absence of flowers and seeds.
All flowering plants which bear seeds are included in phanerogamae (phaneros=visible; and gamos= Marriage).
While as the cryptogamae (cryptos=concealed; and gamos=Marriage) covers all non- flowering plants such as –alagae , fungi, lichens, mosses and ferns.
The cryptogames are further classified into three divisions – Thallophyta, Bryophyta and Pteridophyta, each bearing classes assigned on the basis of similarities and differences among each group.
Q4) What are the divisions of Phanerogames?
Ans: Phanerogames are also called as spermatophytes (sperma= seed; and phyton=plant).
The phanerogames are divided into two divisions- a) Gymnospermae and b) Angiospermae.
a) Gymnosperms: Gymnosperms (Gymno=naked, and sperma = seed) are represented by those plants which have naked ovules or seeds without any covering e.g; Cycads , pines and Cedars.
b) Angiosperms: Angiosperms (Angios=enclosed, and sperma= seed) include all the flowering plants which possess seeds and have ovules enclosed in an ovary or fruit.
Q5) What are the general character of Thallophytes .What are its sub-divisions?
1. Plants may be unicellular or multicellular . Plant body is thallus type i.e; not differentiated into Root, stem and leaves.
2. Plants do not bear flowers.
3. They may be green or non-green due to presence or absence of chlorophyll respectively. Generally Thallophyta is divided into two subdivisions:-
I) Subdivision Algae:-
i) These are generally found in water or in moist places, but on land as well. Thy are also found on the surfaces of other plants or even animals . ii) Thallus may be unicellular flagellated (e.g; Chalamydomonas) or nonflagellated (e.g; Chlorella), a colonial form (e.g; Volvox) or may even be of filamanentons type (e.g; Ulothrix & Spirogyra). In some forms, the thallus is flattened & leaf like (e.g; Lamanaria), which anchor to rocks with the help of hold fast. iii) A variety of pigments in algae provide different colours. In Green algae , there is presence of chlorophyll a and chlorophyll b along with carotenoids as photosynthetics pigments. iv) Mode of nutrition is autotrophic i.e; they do photosynthesis and store food material in the form of starch.
II) Subdivision Fungi:
It includes non green thallophytes & have the following characters:-
i) Plants usually grow in moist and dark places. They are found on dead and decaying organic matter or on the body of other organisms. ii) Chlorophyll is not present , therefore no photosynthesis occurs and hence mode of nutrition is Heterotrophic. iii) They are white , black and brown in colour. iv) They store their food in the form of glycogen.
v) They may be unicellular or multicellular e.g; Mushroom , yeast, Mucor.
Q6) Write a brief note on Bryophytes?
Ans: Bryophytes are simple & truly land habituating plants, present on moist shady places in tufts. They are small in size and range from few mm‟s to few cm‟s . Their plant body is thalloid and leaf like. Plants are green in colour. Plants represent gametophytic generation which after fusion forms sporophyte, which after meiotic division forms gametophyte, which is called alternation of generation. Plants may be unicellular, multicellular and smooth walled or tuberculated. Internally the plant body doesn‟t show any vascular tissue like xylem & Pholem. Q7) Sexual reproduction in Bryphytes?
Ans: Sexual reproduction in Bryophytes in Oogamous type and take place by Anthredia and Archegonia . Anthredia produce Antherozoids, which are large, motile and bicilliated structures. Archegomium is a multicellular , flask shaped organ having neck canal cells, neutral canal cells and egg. Water medium is essential for fertilization.
Fusion of antherozoids and eggs result in the formation of zygote or Oospore which is diploid (2N) Sporophytic in nature. Oospore develops into Sporophyte which bears foot, seta and capsule. Spores are formed in capsule after reductional division. All spores are alike . Spores on germination give rise to Gametophytic plant body usually through Protonema. Q8) How Bryophytes are different from Tracheophytes?
Ans: Bryophytes are distinguished from Tracheophytes by two important characters;
i) First, in all Bryophytes the ecologically persistent photosynethetic phase of life cycle is haploid(N) gametophyte rather than diploid (2N ) sporophyte. ii) Second no well developed vascular system is found in Bryophytes.
Q9) What are the subdivisions of Phylum Bryphyta?
Ans: At one time Bryophytes were placed in one Phyllum, intermediate in position between algae and vascular plants.
Modern studies of cell ultra structure and molecular biology however, confirm that Bryophytes comprise three separate evolutionary lineages, which are today recognized as Mosses(Phyllum Bryophyta), Liverworts (Phyllum Marchantiophyta) and Hornworts (Phyllum Anthoceratophyta).
Q10) What are pteridophytes. What are their main characteristic features?
Ans: This group of plants derives its name from a fern, pteris, which also represents its silent features.(Pterido=pteris , phyton=plant). Characteristics:-
1. They occur in humid and tropical climates and usually grow on soil , rocks, in ponds and as epiphytes on other plants.
2. A typical pteridophyte as represented by a fern has a body differentiated into distinct underground stem like Rhizome , bearing roots and aerial shots with leaves.
3. Pteriodophytes have primitive vascular system.
4. Some pteriodophytes have simple leaves, while as some have compound leaves.
5. Sporangia are borne on ventral surface of leaves as yellow or brown spots(Sori).
The spores bearing leaves are called Sporophylls. The Sori bear groups of Sporangium full of spores.
6) Plant body of pteridophytes is sporophyte (2N).
7) Spores are haploid(N) , which on germination form a thallus like structure called Prothallus, which is multicellular and represents gametophytic phase . The Arthredium & Archegonium sex organs develop on the ventral surface of prothallus. Q11) What are the various classes of Pteridophyta?
Ans: On the basis of organization of the plant body including the nature of the leaf, vascular system and location of sporangia, Pteridophyta is divided into four classes . These are;
a) Psilopsida b) Lycopsida c) Sphenopsida d) Pteropsida
Q12) What are Gymnosperms. Mention their general characters.
Ans: Earlier Gymnosperms were not recognized as a separate group and the members now included in this group are treated as Angeosperms. But Robert Brown (1827) for the first time recognized them as a separate group.
Gymnosperms are most primitive & simpler spermatophytes with naked ovules borne unprotected on the surface of Megasporophylls. They are some times also called as phanerogames without ovary. Thus in them the naked seeds are produced.
i) Most of the gymnosperms are evergreen trees or shrubs with xerophytic adaptation .
ii) Plant body is sporophytic and is differentiated into roots , stem and leaves.
iii) Plants posses a well developed tap root system.
iv) Stem is usually erect , profusely branched (unbranched in cycas) and woody (but in zamia it is tuberous).
v) Presence of leafy scars on the stem is a characteristic feature of gymnosperms.
vi) Leaves are generally dimorphic and are of Foliage and Scaly type. In some taxa e.g; Ephedra only Scaly leaves are present.
vii) The leaves have thick cuticle and sunken stomata.
viii) The xylem consists of only tracheids and xylem parenchyma . Vessels are absent except in the members of Gnetales. ix) Phloem consists of sieve tubes and phloem parenchyma. Companion cells are absent.
x) Mesophyll of leaf may be undifferentiated (e.g; pinus, cedrus) or differentiated into pallasade and spongy parenchyma(e.g; Cycas). xi) They are heterosporous and Mega and Microsporangia occur on Mega and Microsporophylls respectively, which usually aggregate to form compact cones or strobili.
xii) Ovules are orthrotropous and unitegmic but are bitegmic in Gnetales.
xiii) All gymnosperous are wind pollinated . xiv) Arehegonia lack neck canal cells.
Q12) What are Angiosperms .Mention their general characters?
Ans: Angiosperms are vascular seed plants, in which the ovule (egg) is fertilized & develops into a seed in an enclosed hollow ovary. The ovary itself is usually enclosed in a flower.
There are more than 300000 species of flowering plants (Angiosperms) . These also represent the largest and most diverse group with in kingdom plantae.
General characters of Angiosperms:-
i) Angiosperms have well developed vascular tissue that make them well adapted to terrestrial habitats.
ii) Angiosperms have ovules that are enclosed in an ovary. There are two subtypes of Angiosperms : monocotyledous & dicotyledoous, these have one and two colyledous in their embryos respectively. iii) Angiosperms are able to grow in a variety of habitats. They can grow as trees, shrubs , bushes as well as herbs. iv) They have a very complex root system.
v) They bear flowers , which act as a reproductive organ.
Q1) Which division among plants has the simplest organisms?
Ans: Division Thalophyta.
Q2) How are pteridophytes different from phanerogames?
Ans: Pteriophytes differ from Phanerogames in different ways. The two remarkable differences between them are as:
1) In Phanerogames, seed formation takes place, while as no seed formation occurs in pteridophytes.
2) Pteriodophytes posses a primitive vascular system, while as in comparision, phanerogames posses a well developed vascular system.
Q3) How do gymnosperms and Angiosperms differ from each other .
Ans: The Angiosperms and Gymnosperms differ in many ways, like;
i) Angiosperms are normally seed bearing plants, where the seeds are contained in an ovary , which is inside a fruit.While as the Gymnosperms are those seed plants which have exposed seeds(not closed in an ovule). ii) The leaves of Angiosperms are flat, while as the leaves of Gymnosperms are cone bearing or needle like. iii) Gymnosperms are only pollinated by the agency of wind , while as the Angiosperms are pollinated by means of different agencies like wind, water, insects, birds, etc. iv) The xylem and phloem of Gymnosperms lack vessels and companion cells, while as no such absence of vessels and companion cells is found in the xylem and phloem of Angiosperms.
Lesson No: 4
Why Do We Fall Ill
Health:- A state of complete physical, mental and social well being is called health.
Physical dimension:- The physical health implies perfect functioning of all the body parts i.e., various organs and organ system.
Mental dimensions:- Mental health implies harmony between the individual and its environment. A mentally sound individual is free from tension and anxiety and therefore performs his functions in a better way.
Social dimension:- Human beings are social i.e., they live in groups regularly interacting with each other forming highly organized societies. Social health implies that every person living in a society possess basic requirements of life i.e., clean place of living, good earning, good food, a happy family, Cooperative interactions with neighbours and friends and leading a happy life. Health is therefore a state of being well enough to function well, physically, mentally and socially.
Disease: It is a condition in which a part or organ of the body is not functioning normally.
Q: What is difference between healthy and disease free?
Ans:- A healthy and a disease free state can be differentiated as:
Healthy Disease Free
• A person with a state of complete physical, mental and social well being is said to be healthy.
Healthy person is much more than disease free.
Behaves very well in society. •
• A person which is not having any kind of disease is said to be disease free.
Disease free person is not always healthy.
Does not behave well in society.
Causes of Diseases: Diseases are caused by various agents. An agent may be defined as a
substance or force which causes a disease by its excess, deficiency or absence.
Types of agents: the agents which causes diseases are of five main types:-
1. Biological Agents:- Biological agents include viruses, Bacteria, Fungi, Protozoans, helminthes. The biological agents are called pathogens.
2. Nutrient Agents:- These comprise food components such as carbohydrates, proteins, fats, minerals etc.
3. Chemical agents:- These include enzymes, hormones, urea, uric acid. Pollutants, spores etc.
4. Physical agents:- These include heat, cold, sound, radiations, electricity etc.
5. Mechanical agents:- These comprise chronic friction or other mechanical forces which result in injury, dislocation of bones or fracture.
Acute and Chronic diseases:-
Acute Diseases:- These diseases last for only short period of time and are not severe. The acute diseases don‟t cause long term bad effect on patient”s health. Acute diseases take little time to heal, cold, cough, typhoid,etc. are examples of acute diseases.
Chronic Diseases:- These diseases last for long time and have drastic long term effects on patient”s health. These diseases take avery long time to heal. Some chronic diseases may last even as much as lifetime. Diabetes, tuberculosis, cancer, elephantiasis,etc. are examples of chronic diseases.
Q: What are infectious diseases? How do communicable diseases spread from one person to another?
Ans:- Infectious diseases:- Infectious diseases are those diseases which spread from infected persons to others. These diseases spread in various ways i.e., through air, water, physical contact, sexual contact and insects (vectors). The causative agents of these diseases are known as pathogens or infectiou agents. These may be viruses, bacteria, fungi, protozoans (single-celled animals) and different kinds of worms.
Means of spread of communicable or infectious diseases:- The various means of spread of communicable diseases are
1. Through air
2. Through water
3. Through sexual contact
4. Through vectors
5. Through physical contact
1. Through Air:- Microbes that cause common cold, tuberculosis, pneumonia, etc. can spread through the air. In this case when an infected person sneezes or coughs the little droplets of water (saliva) are thrown out which contains microbes. Someone standing close by can breath in these droplets and thus microbe gets a chance to start a new infection in that person.
2. Through Water:- Many infectious diseases spread through water e.g., cholera-causing microbes tenter new host when fecal matter of infected person gets mixed with drinking water.
3. Through Sexual Contact:- Few infectious diseases such as syphilis and AIDS are transmitted by sexual contact from one person to other. The microorganisms responsible for causing these diseases however do not spread by casual physical contact such as handshake or hug.
4. Through Vectors:- Many animals living with us carry the infecting agents from an infected person to other host. These animals thus act as intermediaries and are termed as vectors. The vectors are therefore the carriers of the disease-causing pathogens. The most common vectors are the insects e.g, the mosquito (vector) carries plasmodium which causes Malaria. The housefly (vector) carries the pathogens of cholera, typhoid, dysentery,and tuberculosis on the legs.
5. Through Physical Contact:- The pathogens also spread through physical contact or through articles of use from infected person to the healthy person.
6. Non Infectious diseases:- These diseases remain confined to the person who develops them and does not spread to others. Noninfectious disease may occur due to
a. Malfunctioning of some important organs e.g., heart disease
b. Malnutrition diet or deficiency of carbohydrates, proteins, vitamins, minerals e.g., Kwashiorkor, Marasmus, Beri Beri, Scurvy, Anaemia, Rickets,etc.
c. Hypo or hypersecretion of hormones and enzymes e.g., diabetes, cretinism, myxodema, gigantism.
d. Malfunctioning of immune system e.g., allergy e.
Q: What is organ specific and tissue-specific manifestation?
Ans:- As compared to any type of pathogenic microbe, our body is quite large. Thus there are many possible regions, tissues or organs where a pathogen