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Transcript of BIOLOGY
Structural Organisation of the Cell
The Cell is the basic structural unit of every living thing and most plants and animals are composed of millions of them .
Study which deals with the cell is called cytology
Cell was first discovered by Robert Hooke in 1665 in sections of cork , he only coined the term '' cell '' .
Types of Cell
In a typical cell , the protoplasm consists of nucleus and cytoplasm .
Depending on the type of nucleus present , the cells are of two types :
Prokaryotic cells ( found in blue-green algae , bacteria and Pleuropneumonia like organisms ( PPLO )
Eukaryotic cell .
On the basis of number of cells the organisms are classified as unicellular and Multi-cellular organisms .
Huxley called protoplasm '' physical basis of life ' ;
Ostrich egg is the largest cell in size
Human nerve cell is the longest animal cell .
Largest acellular plant Acetabularia is 10cm and animal is Amoeba , which is 1 min .
In human beings , cells of kidney are the smallest .
Smallest cell is 0.1 - 0.3 in size , it is PPLO ( Mycoplasma gallisepticum .
Cells are enclosed by a thin film like membrane called plasma membrane , cytoplasmic membrane or plasmalemma .
Lies immediately outside the cytoplasm .
Structure was defined by Singer and Nicholson '' fluid Mosaic Model '' .
Selectively permeable in nature .
: Taking of substance inside the cell by the plasma membrane , it is of two types .
Phagocytosis : Cell eating .
Pincoytosis : Cell drinking
Reverse of endocytosis , i.e., material is removed from the cells including reverse pinocytosis
It is a part of protoplasm lying between plasma membrane and nucleus , jelly - like fluid .
Participates in the intracellular distribution of nutrients , metabolites and enzymes .
Cell of most fungi , prokaryotes bacteria and blue-green algae ) and plants ( except gametes ) are surrounded by the cell wall , it is absent in animals .
In true bacteria and cyanobacteria , cell wall is of peptidoglycan , in some fungi it is of chitin and in most of the algae and higher green plants it is of cellulose .
Discovered by Robert Brown .
Every eukaryotic cell consists of atleast one ,almost sperical , dense , highly specialised structure called nucleus , although ,sieve tube element of mature pkloem and RBCs of mammals don't have necleus .
Contains nucleoplasm ( nuclear sap ) which contains chromatin ( chromatin is composed of DNA mainly
Chromatin organises itself into thread like structures called chromosomes , the function of chromosomes is to carry genetic information from one cell generation to another .
Nucleolus is also present which helps in the production of ribosomes .
Nucleus controls the metabolic activities of the cell by controlling the synthesis of enzymes .
Waldeyer coined the term chromosome .
Sutton and Boveri proved that chromosome is the physical basis of hereditary .
Each chromosome is made up of DNA and this DNa by replication gives rise to messanger RNA which carry the genetic information in the form of code , this m-RNA comes out of the nuclear wall into the cytoplasm where it helps to form a particular kind of protein needed by the cell or body .
Number is constant for a particular species , Diploid number ( 2n ) of chromosomes are there in somatic cells ( all body cells except sperms and ova ) and haploid number ( n ) of chromosomes are there in gametes ( sperms and ova ) .
In humans , the diploid number is 46 , of these 23 are form egg cell and 23 from sperm cell .
Powerhouse of the cell or energy converting organells , as oxidation of ' fuel ' occurs stepwise in these , resulting in the release of chemical energy , this energy is strored as ATP .
From mitochondria , ATP molecules are shifted to cytoplasm , which is the cheif site of their utilization .
They are semi-autonomous organells , they contains DMNA , m-RNA , ribosomes and can synthesize some of their own proteins .
Each mitochodria is enclosed by a double membrane envelope , outer and inner ,
Fluid ( called matrix ) is there between these 2 layers , inner membrane has many folds called cristae
Endoplasmic reticulum .
Provides an increased surface area for various metabolic activities within the cell .
Provides mechanical support to the cytoplasm .
Both smooth endoplasmic reticulum and rough endoplasmic reticulum form passages for transport of secretory proteins , lipids and sterols .
Rough endoplasmic reticulum collect and stores the proteins synthesised by its surface bound ribosomes .
Main function is secretion , secretion of bile by liver , of synovial fluid synovial membrane, in the production of enamel of teeth by amenoblast and the formation of fatty yolk in egg are some of the examples .
Also forms lysosomes , it stroes hydrolic enzymes for the digestion of cellular .
Secretions are in the form of granules in cytoplasm ( called Zymogen Granules ) .
Also called sucidal bags ,
Contain powerful enzymes ( acid hydrolases ) , rupture of lysosomes membrane releases these enzymes .
Found on endoplasmic Reticulum , made of RNA and proteins in equal amounts .
Sites of protein synthesis ( Ribosomes are inactive for protein synthesis, but after combining with in RNA form polyribosomes which play important role in protein synthesis .
Found in plant cells only .
Membrane surrounding the vacuole is tonoplast .
: Regulation of water , in osmoregulation , in storage and in digestion .
Found in plant cells only , Are of different types .
: Green , contains the pigment chlorophyll , contains the matrix ( fluid ) , stroma which has many flat membranous structures called thylakoids .
Colorless , occur in large no in cells of fruits , seeds , etc . they store nutrients ( eg., amyloplasts of potato store starch
Colored , containing fat soluble yellow , orange and red pigments ( chiefly carotinoids ) Found in flowers and fruits .
Found in animal cells and cells of lower plants ( eg , Algae ) only .
The first indication that the cells is about to divide is generally given by the centrosome .
The Major Groups ( Kingdoms ) of Organisms
Scientists can identify many kinds of organisms because they have been described by a system of classification , the science of classification or organisms is called Taxonomy , the taxonomy of organisms should reflect their evolutionary relationships .
The grouping of diverse organisms into only two kingdoms as suggested by Linnaeus has appeared unsatifactory to many biologists .
The Five Kingdoms are :
Have a primitive cell structure lacking a nuclear membrane - PROKARYOTE
Most of this kingdom are unicellular ( some exist in multicellular clusters ) .
: Bacteria ( heterotrophic ) , Blue-green algae ( autotrophic ) .
Has a membrane around the nucleus of the cell-EUKARYOTIC .
: Protozoa -animal like nutrition ( hetrotrophic )
paramecia , ameba
Algae - plant like nutrition ( autotrophic )
Has a membrane around the nucleus of the cell-EUKARYOTIC
Absorbs food from its environment ( heterotrophic ) , does NOT ingest it !
Organized into branched , multinucleated filaments
bread molds ( multicellular ) , mushrooms ( multicellular ) , yeast ( unicellular ) .
Has a membrane around the nucleus of the cell-EUKARYOTIC
Photosynthetic organisms ( autotrophic) .
Largest of 5 kingdoms , has a membrane around the nucleus of the cell-EUKARYOTIC
Multicellular , Ingests their food ( heterotrophic )
Four main types
Coelenterates ( soul-en-ter-ates )
Has only two layers of cells , has a hollow body cavity
Hydra , jellyfish
Has segmented body walls ( rings )
; earthworm , sandworm
: Has an exoskeleton ( exo = outside ) , has jointed appendages .
grasshopper , lobster , spiders , insects .
Have a dorsal ( back ) never cord , have an endoskelenton ( endo = inside )
sharks , frogs , humans , cats
Chordates have many Classes ( the next sub - group )
ex ; fish
ex ; frogs
ex ; Lizards
ex ; birds
( ex ; humans cats , dogs , whales )
All the organisms that make their own food are called plants ,
kingdom plantae is grouped into four major Phyla , namely .
Thallophyta ( bacteria , fungi , lichens and algae
Bryophyta ( liverworts , hornworts and mosses )
Spermatophyta ( have two groups , Gymnosperms and Angiosperms )
Phylum Thallophyta includes fungi lichens and algae , we will take up algae in detail since they are the most plant-like among the four .
Algae can make their own food , algae can be green , red , or brown .
Ulva is an example of a green algae , it is some times called as Sea lettuce .
All round the rock pools and even in the water there are plants , these plants are called as Seaweeaeds .
Sea weeds are plants that belong in the group alga , Corallina is an example of a Red Seaweed .
Algae live in seawater , there are other types of algae that live in the freshwater ponds river or just very wetplaces , Algae do not have roots , stems or leaves .
( Bryon = moss , phyto= plant) , they are small plants that grow densely together is moist and shady places .
They form green carpets on damp soil , rocks or bark of trees and on abandoned walls , during the rainy season .
There are two groups of bryphytes namely liver worts and mosses ,
Pteridohytes ( ferns )
( pteris = fern , phyton = plant ) these are primitive vascular plants , they are mainly found in humid tropical regions , they are collectively called ferns .
Gymnoperms ( Seed Plant without Flower
In Greek , Gymnosperm means '' a plant with naked seeds '' ( gymno = naked = seed ) these include the confers ( such as pine ) and cycads , this is because the seeds of a gymnosperm are not inside a fruit .
Instead , gymnosperm has its seeds inside cones , when cones open , the seeds fall out ,
Gynosprems include Cycads , Firtrees , Pine tress , Cypress , Spruce , Ginkgo and Redwoods
Angiosperms ( Flowering Plants )
( angio = enclosed ; sperm = seed ) they are the most important and advanced group of plants , the angiosperms all are flowering plants , the seeds of these plants develop in an organ called the ovary in the flower .
There are between 200,000 and 300 , 000 different species of angiosperms ( flowering plants ) knows .
Structure of plant
: The epidermis consists of a single layer of living cells which are closely packed , the walls are thickened and covered with a thin waterproof layer called the cuticle .
The epidermis protects the underlying tissues
This region comprises the collenchyma , parenchyam and endodermis , it is situated to the inside of the epidermis
: These cells lie under the epidermis and constitute three to four layers of cells with cell walls thickened at the corners .
Functions of the Collenchyma
This tissue serves to strengthen the young stem , The chloroplasts are responsible for the synthesis of organic food during photosynthesis
Beneath the collenchyma cells are a few layers of thin-walled cells , parenchyma , with intercellular spaces , the parenchyma cells make up the bulk of the cortex .
Functions of the Parenchyma
: The synthesized organic food ( mainly starch ) is stored here .
Eridodermis or Strach Sheath
The endodermis or starch sheath forms the innermost layer of the cortex
Functions of the Endodermis
The cells of this tissue store strach , it allows solution to pass from the vascular bundles to the cortex
iii . vascular Cylinder or stele :
This region comprises the pericycle , vascular bundles and pith ( medulla ) .
: The pericycle is made up sclerenchyma , cells which are lignified , dead fiber cells , these cells have thick , woody walls and tapering ends .
Functions of the Pericycle :
It strengthens the stem .
The vascular bundles are situated in a ring on the inside of the pericycle of the plant
Functions of the Vascular Bundles
The xylem provides a passage for water and dissolved ions from the root system to the leaves , the xylem also strengthens and supports the stem
Pith ( Medulla
The pith occupies the large central part of the stem , it consists of thin walled parenchyma cells with intercellular air space , between each vascular bundle is a band of parenchyma , the medullary rays , continuous with the cortex and the pith
Function of the Pith or Medulla
The cells of the pith store water and starch , they allow for the exchange of gages through the intercellular air space
This region is composed of small thick walled sclerenchyma on the inside of the epidermis , these layers of cells are followed by large thin walled parenchyma cells
sclerenchyma tissue strengths the stem , Parenchyma tissue stores synthesised organic food such as strach
: The part of leaf attaced to the stem or branch is known as leaf base , Different plants have different types of leaf base .
Pulvinous - Delonix
Auriculate - Calotropis
Amplexicaul - Emilia
: Leaves of some plants he lateral appendages on each of leaf base , known as stipules , the leaves without stipules are known as exstipulate , stipules are usually green , but some times appear withered also , main function of these structures is to protect the leaf in the bud .
Free lateral - malvaceae
Adnate - Rosa
Interoeliolar - Ixora
Petiole is the part of leaf connecting the lamina with the branch or stem , its upper part remains embedded in lamina in the form of mid
rib , and lower part remains attached with the branch in the form of leaf base .
Tendrillar - Clematis
Swollen - Eichornia
Ochreate - polygonum
Interpetioles - Gardenia
: The leaf blades of some plants show indentations or clefts , if these indentations reach all the way to the midrib so that , the leaf blade is divided into a number of smaller pinnae ( leaflets ) , the leaf is called a
, if the leaf blade is not divided into leaflets , the leaf is termed a simple leaf , most monocots have simple leaves , while dicots can have simple or compound leaves .
Flower is a group of reproductive organs of the flowering plant , which develops fruit and seeds and thus helps in forming new offspring of the plan , from morphological point of view flower is a highly condensed and modified shoot , its function is reproduction
The calyx on the outside .
The corolla lying inside the calyx
The stamens enclosed by the corolla
The pistil in the center of the flower .
The calyx is the outermost whorl of a flower , it consists of sepals , that are green
The calyx encloses and protects the inner whorls in the bud stage .
The corolla is found on the inside of the calyx and is the most conspicuous part in the flower because it is usually white/ brightly coloured
The brightly-coloured corolla attracts agent of pollination such as insects and birds .
iii . Stamens
The stamens form the third whorl on the inside of the corolla , each stamen is made up of a slender flexible filament which support the anther at it end , the anther is the male reproductive organ in a flower
It is the third and male whorl of the flower and is made up of one or more stamens or microsporophylls , each stamen has 3 parts
: Lower thread like part of stamen is called filament , it may be sbsent in some stamens .
This is the upper swollen part of stamen usually having two lobes , each lobe contain 2 microsporangia , the two lobed anther is called as dithecouanther
The filament of the stamen is extended in between the two anther lobes and is called connective
The anther produces pollen grains which contain the male reproductive cells
The filament bears and supports the their in the most suitable position for pollen transfer to take place .
The pistil is the fourth and the innermost whorl of the flower , it consists of a basal , swollen portion , the ovary , from which a long and slender style ( arises ) , the stigma is found at the tip of the style , the pistil is the female reproductive organ .
: It is made of one or more carpels ( megasporophyllus ) , each gynocium is differentiated into three parts .
The lowest swollen part containing ovules the ovary
: The ovules are attached on the inner surface of the ovary walls on one or more cushion called placenta , the manner in which placenta are arranged on the ovary wall is known as placentation .
The ovary is a hollow cavity which contains the ovules , each ovule contains an egg cell
The elongated style bears the stigma in the most suitable position for receiving pollen during pollination , the sticky stigma at the tip of the style can receive or trap the pollen grains .
: Animals inhale oxygen and exhale carbon dioxide Green plants are the only plants that produce oxygen and make food , which is called photosynthesis , photosynthesis means ''
putting together with light
'' . this takes place in chloroplasts , which have chlorophyll in them .
Chlorophyll absorbs the sunlight , from green plants combine carbon dioxide and water to make sugar and oxygen , green plants use sugar to make strach , fats and proteins .
Germination happens when a baby plant is growing the plant is between the cotyledons , this is a seed , is underground and is collecting nutrients , when a seed starts to grow , we say it germinates , the cotyledons store food for the baby plant inside the seed
Reproduction in Plants
Different methods of reproduction can be broadly grouped into two types
The genetic material from two plants recombines in production the off spring is called sexual reproduction
Flowering plants ( Datura ) .
: Pollination is defined as the process of transfer of pollen grains , from an anther to the stigma of the same flower or different flower , bees can be help flowers make seeds .
This is mainly two types
Self pollination or autogamy
If the pollen grains are transferred from an anther to the stigma of the same flower the process is called as self pollination or autogamy
Cross - pollination or allogamy
: If these are transferred to the stigma of different flower on the same plant or different plant of different species it is called cross-pollination or allogamy ,
this is again three types
Pollen grains of a flower transferred to stigma of a different flower on the same plant
Pollen grains of a flower transferred o stigma of a different flower on a different plant of
same species .
: Pollen grains of a flower transferred to stigma of a different flower of a different plant of different species .
: It is the process of fusion of male and female gamates , for the fusion of male and female gamates , pollen grains have to reach the surface of the stigma , when the pollen from one flower is to fertilize the female gamate of the same flower of the
same plant ( self pollination )
either other plant of the flower by insects ( cross pollination )
Pollen grains received by the stigma germinate and give rise to pollen tubes , only one pollen tube finally reaches the embryo -sac , this tubewill have two male nuclei , which migrate to the tip of the pollen tube at the time of fertilisation , usually the pollen tube enters the ovule through micropyle , the tube discharges the two male gametes into its embryo -sac .
One male nucleus approaches the egg and fuses with it to form a diploid
( ' 2n ' ) ZYGOTE
this is first fertilisation , the other male nucleus reaches the secoundary nucleus
( which is already in ' 2n ' condition )
and fuses with it to form
which will be triploid ( 3n ) , this is second fertilisation in the embryo -sac , which is unique in flowering plants
The endosperm may develop to form endopermic seeds (
ex ; maize , wheat , rice , castor etc
) or it may be digested and absorbed to form non-endospermic seeds (
ex ; bean , pea , bengal gram etc )
: It involve a single organism , asexual reproduction occurs in many different ways in different organisms like veasts , fungialgae , mosses , ferns and flowering plants , asexual reproduction takes place by means of specialised reproduction units produced in the parent .
Spores in fungi ( mcor ) .
This method of reproduction is similar to asexual reproduction where there is no involvement of male and female gamates and involves on parent , the offspring will be similar to the parent plant
This method of propagation in plants is called
Examples for vegetative propagation
In chrysanthenum ( chamanthi ) a special branch develops from the underground part of the stem of
the parent plant
Grass plant , this is having nodes & internodes to form a roots & axillary buds , when they are cut ,
these buds are develop into independent new plant .
Eyes of Potato
Potato tubes is a modified stem , we can see sunker sposs on a healthy potato tuber , this part of the tuber has small centres , which have the capacity to give risse to a whole plant
In a modern system of classification , all animals can be divided into two groups
Vertebrates are animals that have a skeleton inside their bodies , Biologists call this an internal skeleton , an internal skeleton includes a backbone which is made up of bones called vertebrae .
Vertebra is one bone in a backbone ; vertebrae is more than one bone from a backbone , five groups of vertebrate are Amphibians , Reptiles , Fishes , mammals , and birds .
: Amphibians are cold-blooded , amphibians spend part of their lives under water and part of their lives on land .
They lay jelly - covered eggs in the water amphibians breath with gills or lungs or through their skin , baby amphibians live in water and breathe with scales .
An amphibians's skin is moist ( they do not have scales , amphibians are vertebrates - they have back-bones , most amphibians live in or near water or in damp places .
Many young amphibians do not look like their parents , young toads , frogs and salamanders are called tadpoles , frogs , toads , newts and salamanders are examples for amphibians .
: The dinosaurs of prehistroic time were reptiles , Reptiles are alike in the following ways , they have dry , scaly skin .
Fish are cold blooded , fish eggs , most fish are covered with scales , they have fins not legs , fish live in water and breathe through gills .
: Mammals are the most intelligent creatures on earth , they learn to adapt to many different climates and living conditions , some mammals are tames , some are wild , some are very large and some are small .
They have fur or hair , the babies drink milk from their moth's bodies . they have a backbone , they have four limbs ( arms , legs , flippers . )
: Next to mammals , birds are the most useful to man , there are thousands of different kinds of birds , they vary in size from the tiny humming bird to the large ostrich .
A bird is an animal with feathers , a bird have two legs and two wings , birds have a beak or a bill .
Invertebrates are animals that do not have back bones , 97% of the animals kingdom
is made up of invertebrates Some can be found in ponds , ocean and other water environments , insects and some other invertebrates have exoskeletons , an exoskeleton is a hard outer covering that protects an animals body and gives it support .
there are six groups of invertebrates , they are
They look like plants but they are animals , sponges stay fixed in one place , their bodies are full of holes and their skeleton is made of spiky fibers , water flows through the holes of their body which enables than to catch food
Corals , Hydras , Gellyfish
Corals looks like plants but they belong to the animal kingdom , they have soft tubelike bodies with a single opening surrounded by armike parts called tentacles , they feed catching tiny animals in their tentacles .
: Worms are tube shaped invertebrates which allows them to be put into group , they can be found in both land and water environments
They have a head and a tail , and flattened bodies , a tapeworms is a flat worm that can live inside the body of animals and humans , it can cauise you to became sick
They have rounded bodies , they live in damp places and they can also live inside humans , and other animals , they too can make people and other animals sick
: The earthworm belongs to this group of worms , their bodies are divided in segments , or sections , they prefer burrowing through moist soil , this allows them to move easily ait keeps them from drying out .
Functions of Cell Oraganelle
Cell Oraganelle / Part
Protects the cell cytoplasm
Controle the transfer of substances into and out of the cell
The power house of the cell, release energy by the
oxidation of the food
The colour plastids impart colour to the structure
In presence of light they manufacture (carbohydrates)
Increses the reations surface area for the metablic activties
Concentration of products of synthetic activities of the cell.
Suicidal bag of the cell as it stores hydorlytic enazymes for the digestion
of cellular components.
Help in phagocytosis and pinocytosis.
. Golgi apparatus.
Provide surface for the synthetic reactions and concentrations and their
Participate in Purine metabolism
store enzymes related to the peroxide metabolism
.Participate in the formation of spindle during cell division
Help in locomotion
Provide skeletal support to cell
Controls the sythesis of ribosomes & proteins
Controls nuclear and cell metabolism
Stores heredity information
Starfish and Sea Urchins :
It belongs to group of invertebrates that have tiny tube feet and body parts arranged around a central area.
A mollusk has a hard shell, a rough tongue, and a muscular a foot ,A snail is a mollusk with a single hard shell , A clam has two shells joined together by a hinge .
Arthopods are a group of investebrates with jointed legs and hard exoskeleton that protect the arthropod , As it grows , it molts , or sheds its old exoskeleton , then it grows a new exoskeleton that allows its body to continue to grow , a lobster sia an arthropod .