Control and Coordination Introduction INTRODUCTION o Movement is the characteristic property of living organisms. o All living organisms move in response to the change in the environment. o Changes in the environment to which the organisms respond and react are called stimuli. o The movement of the body parts of organisms in response to the stimuli carefully controlled and co-ordinated. o The control and co-ordination is controlled by two agencies- I) the nervous system II) hormonal system. Fig. Nervous system, Hormonal system NERVOUS SYSTEM IN ANIMALS o The nervous system is concerned with receiving of stimuli from the external and internal environment of the body. o The action of nervous system are performed by highly specialized cells called neurons which can receive the messages and conduct them to the brain where the they are interpreted and then returned to the concerned parts of the body.

o The nervous tissue is made up of an organized network of nerve cells which are specialized for conducting electrical impulse form one part of the body to another. o Impulse is the signal transmitted along a nerve fibre. o Neurons or nerve cells are the structural ad functional units of nervous system. Structure of neuron 1. I) Cell body- it is rich in cytoplasm and has a spherical nucleus. 2. II) Dendrites- short and branched tips of nerve cell stretching out from the cell body and detect the information of the environment. III) Axon- long cylindrical structure arising from the cell body. The information from the environment travels through the axon and reaches the next nerve to reach the brain. 1. IV) Nerve ending- branched ending of axon which helps in neurotransmission Fig. Neuron Neurotransmission o Neurotransmission is the travelling of impulse to the brain through the nerve cells. o Impulse is the signal transmitted along a nerve fibre. o Any change in the environment is detected by the specialized tips of nerve cells called dendrites in the form of message. o Dendrites are present in the sense organs. o The message acquired sets off a chemical reaction which creates an electrical impulse. o Electrical impulse travels from the dendrite to the cell body and then along the axon to the nerve endings. o At the nerve endings, the electrical impulse sets off the release of chemicals. o Synapse is the gap between two nerve cells, across which impulses pass to reach the next nerve cell.

o The chemicals released at the nerve endings, cross the synapse and start a similar electrical impulse in a dendrite of the next neuron and the process goes on. o A similar synapse allows delivery of impulses from neurons to other types of cells such as muscle cells or glands. Fig.chemicals released at the nerve endings REFLEX ACTION Reflex action is the extremely quick, automatic, sudden action in response to something in the environment. Example- i) Immediately pulling back of fingers after touching a hot plate. ii) Closing of eyes when flashed with high intensity light. iii) Salivation when hungry. o Reflex arc is the pathway of nerve involved in reflex action. o Reflex arc involveso Receptors- receive the message from external environment. o Sensory neuron- carries the message from the receptor to the central nervous system. o Central nervous system- processes the message and sends impulses to the concerned part of the body in the form of response. o Motor neuron- carries the message from the central nervous system to the effector. o Effector- responses against the stimulus.

Fig. Reflex arc involved in reflex action CENTRAL NERVOUS SYSTEM o The brain and spinal cord together constitutes the central nervous system. o Central nervous system receives the message from all the parts of the body and integrates it. o The spinal cord is a long, tubular bundle of neurons which carry information between the brain and the rest of the body. o Human brain is covered by a bony box inside which the brain is contained in a fluid-filled balloon which provides shock absorption. o Spinal cord is enclosed in the vertebral column. Fig. brain and spinal cord form the central nervous system Human brain o Human brain consists of three major parts- fore-brain, mid-brain and hindbrain. o Fore brain is the main thinking part of the brain. o Separate areas of the forebrain are specialized for hearing, smell, sight etc. o Involuntary actions of the body which are not under our control are controlled by the mid brain and hind brain. o Hind brain is divided into two parts cerebellum and medulla. o Cerebellum of the hind brain controls balance, posture and smooth movement of muscles.

o Medulla of the hind brain controls heart rate, breathing rate and reflexes such as sneezing, swallowing, vomiting etc. Fig.Human brain HORMONAL SYSTEM IN ANIMALS Electrical impulses are excellent means for transmission of information but there are few limitations of using electrical impulsesImpulses reach only those cells that are connected with nervous tissue. Cells cannot continuously create and transmit impulse, the cells need some time to reset the mechanism before these can create and generate a new impulse. Due the limitations, instead of generating electrical impulse, the stimulated cells release a chemical compound called hormones. Hormones will diffuse to all the cells of the body and the cells have receptors to detect the hormones and to receive the information and transmit it. Hormones are the chemical messengers which are secreted by the endocrine gland into the blood. Different animal hormones areThyroxin hormoneo Secreted by thyroid gland with the use of iodine. o Helps in the regulation of carbohydrates, proteins and fat metabolism in the body. o Deficiency of the hormone causes goitre. o Enlargedneck is the characteristic symptom of goitre.

Fig. goitre Growth hormoneo Secreted by pituitary gland. o Regulates growth and development of the body. o Deficiency of the hormone leads to dwarfism. Sex hormones o Reproductive glands secrete testosterone in males and estrogen in females. o Development of sexual characters. Insulin o Secreted by pancreas. o Regulates blood sugar level. o Deficiency of the hormone causes diabetes mellitus, increase in blood sugar level. Fig. endocrine system Feedback mechanism o Hormones should be secreted in precise quantity. o Excess amount as well as deficiency of hormones causes disorder. o A mechanism is used by the body to regulate the secretion of hormone which is called as feedback mechanism.

For eg. If sugar level increases in blood, cells of the pancreas can detect this and produce more amount of insulin to control blood sugar and as the blood sugar level falls, secretion of insulin reduces. COORDINATION IN PLANTS o Plants do not have nervous system or muscles to respond to the stimulus. o Plants show two different types of movement in respond to the stimulus i) one dependent on growth ii) another independent of growth. Movement dependent on growth Plants respond to stimuli by growing in a particular direction and because of the directional growth it appears as if the plant is moving. Tropic movement or tropism is the plant movement that is determined by the direction of an environmental stimulus. Tropic movements can be towards the stimulus or away from it. The tropic movements are of various types depending on the nature of stimuluso Phototropism – Here, the stimulus is light. Shoots respond by bending towards light while roots respond by bending away from it. Fig. phototropism o Geotropism- Here, the stimulus is gravity. Roots of plants grow downward towards gravity whereas shoots grow upward against gravity.

Fig. Roots grow towards gravity o Hydrotropism- In hydrotropism, stimulus is water. Roots always grow towards water. Fig. hydrotropism o Chemotropism- the movement in response to chemical stimulus is called as chemotropism. Growth of pollen tubes towards ovules, where ovules produce chemicals for the growth and passage of pollen tubes. Fig. chemotropism Movement independent of growth o As no growth is involved, so plants move by changing the shape of the cells. For eg. i) In sensitive plants, the plants move its leaves in response to touch ii) The movement takes place at a point different from the point of touch. iii) Some cells change shape by changing the amount of water in them and as a result the cells either shrink or swell and therefore change shapes. Fig. sensitive plant

HORMONAL SYSTEM ON PLANTS o Different kinds of hormones are responsible for growth, development and response to the stimulus. o Auxin- i) A plant hormone, synthesized at the shoot tips and helps the cells to grow longer ii)When plants detect light auxins are synthesized and when light comes from one side of the shoot auxins diffuse towards the shaded side of the shoot. iii) Concentration of auxin in the shaded side stimulates the cells to grow longer on the shaded side of the shoot and thus plants appear to bend towards light. o Gibberellins- Plant hormone gibberellins help in the growth of stem. Fig. growth of stem o Cytokinins– This hormone promotes cell division and concentration is high in fruits and seeds. o Abscisic acid- Unlikeauxin, gibberellins, cytokinis which promote growth, abscisic acid stops growth and causes wilting of leaves. Fig. wilting of leaf

Heredity and Evolution Introduction Introduction Heredity is the passing of traits from parents/ancestors to offspring. Heredity occurs through inheritance of genes. Biological inheritance is what is related to heredity. Study of heredity is termed as Genetics. Inheritance from a previous generation provides a common basic body design and few changes in it for the next generation. A trait that is genetically passed down from one generation to another is termed as ‘Inherited trait’. Some of the common examples of inherited traits are hair colour (Black, brown, red etc.), eye colour(Black, brown, blue), height (tall, short), Ear lobes (free, attached) You might be wondering how exactly the traits get inherited. To answer this, we will have to look at Mendelian Inheritance in Genetics. The terms Heredity and Inheritance often sound similar; but they are not the same. Heredity refers to the passing off traits through genes from generation to the next. Whereas, the term Inheritance refers to the passing of property, rights etc.. on death of one generation to the next. Mendelian Inheritance Gregor Mendel started studying inheritance in peas. He performed series of experiments with pea plants for 7 long years (1856- 1863). He kept proper count

of individuals exhibiting a particular trait in each generation. Mendel, with his experiments found out the principles based on which it could be guesses how characters get inherited or passed to the offspring. Many rules of heredity were established often termed as “LAWS OF MENDELIAN INHERITANCE”. Mendel is known as the ‘Father of Genetics’ due to his significant contribution to establish the basic principles in Genetics. Mendel’s Pea plant Mendel chose pea plant for his experiments because of the following reasons: o Pea plant has several contrasting characters like height, flower color, seed color & shape o Self pollinated plant in nature o Cross pollination is easy to be done artificially o Short life span o Easy to cultivate Mendel cross-pollinated tall pea plants with dwarf pea plants. (Pollen grains from flowers of tall plants dusted over the stigma of short plants) Mendel found that the 1st filial generation (F1 generation) consisted of all Tall plants In the second half of the experiment, he self-pollinated the Tall plants (F1 generation ones). He found that in F2 generation, 75% plants were tall and 25% were short

Mendel’s Conclusion: The ‘dwarf’ trait was also carried, but remained hidden in F1 generation. This trait got expressed only in F2 generation. Dominant and Recessive traits o Dominant trait o Trait that gets expressed in the offspring o Takes over the other inherited trait o For example, ‘Tall’ is a dominant trait of pea plants o Recessive trait o Trait that remains hidden, dominated by the dominant trait o For example, ‘Dwarf’ is a recessive trait of pea plant

Some other examples of dominant and recessive traits are as follows: o ‘Free’ ear lobes is a dominant trait, whereas ‘attached’ ear lobes is a recessive trait o ‘ Brown/ Black’ eye colour is a dominant trait, whereas ‘ Blue’ eye colour is a recessive trait A recessive trait appears only if the offspring inherits a copy of the gene from both parents

1 sex chromosome). These together make the 46 chromosomes of the zygote (child).

Autosomes & Sex chromosomes o Autosomes o Chromosomes other than the sex chromosomes o Exist in pairs, each of which has same form o Control somatic traits o In humans, 22 pairs of autosomes exist o Sex chromosomes o Chromosome which determine sex o In humans, 1 pair of sex chromosome exists Haploid & Diploid cells o Diploid o Cell with two complete sets of chromosomes

o Haploid o Cell with a single complete set of chromosomes Normally, all cells in the human body are diploid i.e. chromosomes exist in pairs. Except the male /female sex cells are haploid (have half number of chromosomes, i.e 23 chromosomes). Homologous & Heterologous chromosomes Homologous chromosome: o A set of one maternal chromosome and one paternal chromosome that pair up with each other inside a cell o Same size & shape o Bears corresponding genes governing the same traits o Homologous regions code for the same gene Heterologous chromosome: o Differ in shape, size or function o Do not belong to the same pair Allele

o One member of a pair of gene that occupy a given position on a homologous chromosome o For example: TT, Tt, tT, tt Each‘t’ or ‘T’ is an allele (Capital letter denotes Dominant allele, whereas Small letter denotes Recessive allele) Homozygous & Heterozygous organisms o Homozygous organism o Organism with identical alleles on homologous chromosomes o Examples: TT, tt o If self bred, give rise to offsprings with same traits o Heterozygous organism o Organism with different alleles for a character on homologous chromosomes o Also termed as ‘Hybrid’ o Examples: Tt, tT

Understanding Mendel’s Experiment Experiment a) o Cross pollinated homozygous tall plants and homozygous dwarf plants Experiment b) o Self pollinated plants of F1 generation

Mendel’s 2nd experiment with pea plants o Mendel cross-pollinated pea plants with : o Homozygous round & yellow seeds o Homozygous wrinkled & green seeds In F1 generation, dominant trait (Round & Yellow) got displayed; while the recessive trait (Wrinkled/ Green) remained hidden. This is the Principle of Dominance. Does that mean the hidden trait is lost or got modified into something else? Let’s look at the F2 generation.. o Later, Self pollinated F1 generation

In F2 generation, the hidden trait (green/ wrinkled) reappears. This trait [wrinkled(r); green (y)] was present in F1 generation but remained hidden, however retained its identity. Different forms of traits retain their identity. This formed the basis of Principle of Segregation. In this experiment, Mendel took 2 contrasting characters- colour of seed and shape of seed of the pea plant. It was observed that colour & shape of the seeds were independent of each other. Though we started with Round-Yellow & GreenWrinkled combinations, we obtained even Round-Green and Yellow-Wrinkled combinations in F2 generation. Mendel’s Observations o F1 generation displayed only one of the parental trait o Hidden trait in F1 generation reappeared unchanged in F2 generation o 4 types of plants were obtained in F2 generation in dihybrid cross o Principle of Dominance o In heterozygous organisms, only one out of the two alleles expresses itself (Dominant trait) while the other remains hidden (recessive trait) o Example: In Tt (heterozygous tall plant), T is dominant and t is recessive

o o Principle of Segregation o Each allele retains its distinct identity, even though they remain together in an individual; they segregate only during gamete formation o Example: In a hybrid tall plant Tt, ‘T’ & ‘t’ segregate only during gamete formation o o Principle of Independent Assortment o During gamete formation, segregation of alleles of one pair is independent of the segregation of alleles of the other pair o Example: Self pollination of hybrid plants with Round & Yellow seeds o In this experiment, Mendel took 2 contrasting characters- colour of seed and shape of seed of the pea plant. It was observed that colour & shape of the seeds were independent of each other. Though we started with RoundYellow & Green-Wrinkled combinations, we obtained even Round-Green and Yellow-Wrinkled combinations in F2 generation. This shows that the alleles R,r and Y,y segregate independently.

o o Expression of traits o Genes control the traits of living organisms. o o Let’s take the example of Mendel’s 1st Experiment with Tall & dwarf plants. Height of the plant depends on the growth hormone, Auxin. If this hormone is more, height is more. The hormone is secreted by respective glands, which in turn is controlled by the proteins. Gene has the information for synthesis of proteins. If a gene has alteration, enzyme can be less or more efficient which in turn can make the height less or more.

o Sex determination o Females have a perfect pair of sex chromosome, XX o Males have mismatched pair of sex chromosomes, XY If the male sex chromosome is X, then the child is Female (XX) If the male sex chromosome is Y, then the child is Male (XY) Evolution There exists a huge variety of living organisms on Earth. Each reproduces to bring more organisms of its kind on Earth. It is believed that all organisms evolved from a common ancestor.

We will see how reproduction can give rise to variations, which in turn can give rise to new organisms or species. This is Evolution. Variation during Asexual reproduction In asexual reproduction, DNA gets copied. During copying, some errors occur (by chance) which give rise to variation in the offspring

1 sex chromosome). These together make the 46 chromosomes of the zygote (child). Therefore, the child tends to get mix traits of both parents- some paternal, some maternal and some new traits. Small new traits in an organism over a period of several years give rise to a different organism altogether. What is Evolution? o Change in the inherited characteristics of biological populations over successive generations o Gradual continuous process in which something changes into a different and usually more complex or better form

Evolution: Darwin’s finches Some birds reached the Galapogos islands in the Pacific several years ago by storm. These were seed-eating birds. Due to good climate and no predators, they reproduced fast, and increased in number very fast. Due to the increase in their population, there was scarcity of food. Every bird wanted to survive. Due to variation, it was observed that some birds had long beak than others. In sometime, the long-beaked bird started eating worm and hard seeds. So these birds got a survival advantage. The short-beaked birds continued to eat seeds. Thus, the birds got divided into 2 groups.

Each group reproduced amongst themselves. As a result, different types of finches arose. Currently, there are around 13-15 species of finches on the Galapogos islands. These finches are called Galapogos finches. They were first collected by Charles Darwin on the Galápagos Islands during the second voyage of the Beagle, hence called Darwin’s finches. Evolution: Beetles Red beetles lived in green bushes. They underwent sexual reproduction, increased in number. Due to variation, 1 green beetle was formed. Crows eat Beetles (they ate the Red ones, the Green one was not visible on the green bushes). The Green beetle got the survival advantage. It participated in reproduction, as a result gradually the population of Green beetles increased. Eventually, there arrived a time when there were no Red beetles and all Green Beetles

Green beetles continued to increase in number by reproduction. Variation occurred. 1 Blue beetle was formed. With reproduction, blue beetles and green beetles were both increasing in number. However, Green ones were much more in number. Accidently, an elephant stepped onto the bushes on that side where most of the green beetles lived. Suddenly, the green beetles reduced in number. Blue beetles survived accidently and continued to reproduce. Eventually, there arrived a time when there were no Green beetles and all Blue Beetles. The story of the beetles shows that the frequency of an inherited trait (certain genes) changes over generations. Mechanisms of evolution o Mutation o Change in DNA sequence o Generates variation o Evolution of a single green/blue beetle which later gave rise to more

o Natural selection o Change in frequency of some genes in a population which give survival advantage o Evolution of finches with larger beaks o Evolution of the green beetles o Genetic drift o Change in frequency of some lucky genes in a population even though these do not give any survival advantage o Evolution of the Blue beetles

o Migration o Movement by organisms from one place to another o Evolution of pink beetles Acquired and Inherited traits o Acquired traits o Traits acquired by organisms during their lifetime o Not passed from one generation to another o Inherited traits o Traits controlled by genes o Passed on from one generation to the next Some examples: Muscles of weight-lifters, scars, length of hair are examples of Acquired traits

Natural hair colour, shape of the ear lobe, eye colour and feet shape are examples of Inherited traits Speciation o Origin of new species from an existing species is termed as Speciation o Evolution leads to speciation How does Speciation occur?

There are two localities, 1 and 2. o Locality 1 has more crows (which feed on Red beetles). Therefore, more green beetles survive and reproduce, therefore increase in number. Locality 2 has crow, hence more red beetles survive and reproduce in locality 2 o Green beetles are not much encouraged in locality 2, but encouraged in locality 1 by Natural selection o Localities 1 and 2 remain isolated from each other. Not much breeding happens between these two localities o As a result of mutation, migration, genetic drift and natural selection, micro evolution keep occurring in each locality 1 and 2. o After a long time, it is seen that beetles in localities 1 and 2 cannot reproduce. o Hence, new species are formed resulting in Speciation. Evidences of Evolution 1. Following evolutionary relationships, we find all organisms have come from a common ancestor. The more common characteristics, the more closely they are related. Brothers/ sisters have a lot more similarities than first cousins. Similarly, second cousins share even lesser similarities.

2. Evidence from Fossils 3. Evidence from Morphology and Anatomy Evidence from Fossils Fossils are preserved remains of living organisms from remote past. Fossil mainly preserves only a portion of the dead organism (eg: skeleton, bone, teeth etc..) Fossils may vary from microscopic (single bacterial cell) to dinosaurs. Layers of fossils are formed one after another over years. Deeper the layer where the fossil is found, older it is. Composition of the fossils helps in age estimation. Age estimation detects ratios of isotopes of different elements. Each isotope has a specific half-life. For example, C-12, C-14 are isotopes of Carbon. Knowing the isotopes, we will know their half-lives. With that, we can calculate for how long it has been there, which in turn estimates the age of fossil. o Fossils at upper layers are more complex than that at lower layers

o Fossils records show there is a link between birds & reptiles o Fossils records show how evolution occurred in some mammals with time Evidence from Morphology and Anatomy o Comparative embryology of animals All animals go through these similar stages of early development of fetus: Zygote (single-celled) -> Group of cells -> Embryo (2-layered) -> Embryo (3- layered)

o Homologous and Analogous organs o Organs with common origin & structure but different functions are termed as Homologous organs o This tells us that there exists an evolutionary relationship between different species, may be they originated from the same species with fore-limbs, gradually got changes as per their needs for survival. So, we can say that they share a common ancestor. o Example: Forelimbs of amphibians, reptiles, birds, mammals o Organs which perform similar function but have different origin & structures are termed as Analogous organs o Example: Wings of bat, birds, insects Evolution by stages o Evolution by eyes Eyes are the organs of sight. Eyes are complex in vertebrates like humans. They did not evolve all of a sudden, but evolved gradually. In earlier forms of organisms like euglena, a small eye spot was seen hidden.

Flatworms have eye spots to detect light. These eyespots gave survival advantage to flatworms. Gradually, with time, eyes developed. All vertebrates (mammals) have similar basic structure of eye. o Evolution of feathers Feathers evolved in dinosaurs for insulation against cold weather. Later, birds adopted feathers for flight. o Artificial selection Process of selecting desired traits to breed other plants/animals to get desirable traits is termed as Artificial selection

Artificial selection Natural selection Process conducted by man Natural phenomenon Traits selected are beneficial to man Traits selected are beneficial to species Less time needed to yield results Long time is needed for the results ntroduction Reproduction is the process by which living organisms produce new organisms similar to themselves. Reproduction plays an important role in the following ways: o Retain a particular species of living organisms o Transmission of characters from one generation to the next o Variations lead to the origin of new species

Pic: Variations in Dogs There are 2 modes of reproduction: o Asexual reproduction o Sexual reproduction Asexual Reproduction o Mode of reproduction in which new individuals are formed from a single parent o No sex involved o New individuals are identical to the parent o Faster mode of reproduction o Seen in Amoeba, Hydra, Flatworms, many plants like rose, potato, onion etc.. Various types of asexual reproduction are: o Fission

o Budding o Regeneration o Fragmentation o Spore formation o Vegetative propagation Fission An organism splits to form two/more new individuals Types: o Binary fission o Multiple fission Binary fission o Two new individuals are formed o Nucleus divides only once o Unicellular organisms like amoeba, paramecium, euglena, bacteria Multiple fission o Many new individuals are formed o Nucleus divides repeatedly o Takes place during unfavorable conditions (cyst formation takes place) o Amoeba, plasmodium, many algae Budding o New individual is formed as an outgrowth of parent o Daughter separates away & parent continues to exist

o Hydra, Yeast Pic. Budding in Yeast Pic. Budding in Hydra Fragmentation o Parent breaks into multiple pieces on maturity, each of which gives rise to a new individual o Seen in simple multicellular organisms (Spirogyra) Regeneration o Parent if cut/broken into multiple pieces , each gives rise to a new individual

o This is an accidental process o Hydra, flatworm, tapeworm Pic. Regeneration in Planaria Spore formation o Formation of new individual by germination of spores Spores are unicellular bodies in the parent that are capable of growing into a new individual Pic. Spore formation in fungi, Rhizopus o Conidia o Non-motile spores of fungus (Penicilium) o Termed as Mitospores o Zoospores o Motile spores o Uses Flagellum for locomotion o Used as a mode of asexual reproduction by some algae, bacteria & fungi

Pic: Zoospore formation in Chlamydomonas under favorable conditions Vegetative Propagation It is the mode of asexual reproduction in plants. Plant parts are detached from the parent & form a new plant. Structures which help in vegetative propagation are called Vegetative propagules. Example: Rhizome, tuber etc. Natural vegetative propagation o Root o Stem o Leaves Pic. Vegetative propagation by stems in plants like strawberry Artificial vegetative propagation o Cutting o Layering o Grafting

Pic. Artificial vegetative propagation: Grafting Natural Vegetative propagation By roots o Buds develop in thick, fleshy roots which later, when put into soil develop into new plants o Guava, sweet potato, dahlia By stems Runners o Stems that grow horizontally above ground o Examples: Grass, strawberry

Underground stems o Potato’s tubers which are fleshy are underground storage structures. Buds give rise to aerial shoots under favorable conditions. o Ginger’s rhizomes are modified stems found underground. Buds appear at their nodes which can give rise to new plants. o Onion’s bulbs are short underground vertical shoots with thickened leaves. Roots emerge from underside of the stem. By leaves o Buds are formed along leaf margins which later give rise to a new plant o Examples: Bryophyllum Artificial Vegetative Propagation Cutting A plant part is cut from the parent & put into the soil which later give rise to a new plant. o Stem cutting: Rose, sugarcane

o Root cutting: Dahlia Pic: Stem cutting in Rose plant Layering o New plants are formed from stems of parent plant without detaching them initially from the parent. A variety of plants can be grown by this method like strawberry, guava, lemon, china rose etc.. o Mound layering A branch is pulled towards ground and then a part of it is covered with moist soil. New roots later develop from this part, after which it gets detached from the parent plant. o Air layering An aerial branch is scraped and covered with moist mud which is then covered with plastic. New roots develop after sometime, after which the new part gets detached from the parent.

Grafting Stems cut from two different plants are attached to grow as a single plant. This improves the quality of certain plants. Sexual Reproduction o Mode of reproduction in which new individuals are formed from two parents o Sex is involved (Fusion between male & female gametes give rise to the new organism) o New individuals are not identical to the parents o Variations occur o Relatively slower mode of reproduction

Advantages of Sexual reproduction o To incorporate variations in species which in turn ensures survival of a species o Each individual in a species has its own uniqueness & identity o Enables organisms to survive under unfavorable conditions Gametes o Gametes are the Sex cells o In some organisms, Male & Female gametes are identical to each other (Isogamy) Example: Spirogyra o While in some others, Male & Female gametes are different from each other (Anisogamy) Example: Human beings o Male gamete: motile o Female gamete: food storage o Fusion of male & female gametes gives rise to a new organism

Sexual Reproduction in Plants Flower is the Reproductive organ of a plant A flower is said to be : Unisexual: o if either male/ female reproductive part is present in it o g: papaya, watermelon Bisexual: o if both male & female reproductive parts are present in it o g: china rose, mustard

Sexual vs. Asexual reproduction in plants Asexual Reproduction o Easier & faster mode of reproduction o Seedless plants can also be grown by vegetative propagation o Desired traits can be preserved through generations o New plants formed are genetically identical to parents o More prone to diseases o No genetic variations Sexual Reproduction o Relatively slower mode of reproduction o Genetic variations are seen o Less prone to diseases Sexual vs. Asexual reproduction in plants Asexual Reproduction o Easier & faster mode of reproduction o Seedless plants can also be grown by vegetative propagation o Desired traits can be preserved through generations o New plants formed are genetically identical to parents o More prone to diseases o No genetic variations Sexual Reproduction o Relatively slower mode of reproduction

o Genetic variations are seen o Less prone to diseases Structure of a Flower o Stalk: Holds the flower o Thalamus: Swollen upper portion of stalk o Petals: Colored parts of a flower which attracts insects o Sepals: Ensures protection o Stamen: Male reproductive organ which produce male gametes (pollen grains) o Carpel: Female reproductive organ which produce female gametes (ovum/egg) Male reproductive structure in a Flower : Stamen Stamens are the male reproductive structures in a plant. The structure of a stamen consists of 3 important parts: o Filament o Stalk that bears anthers o Anther o Bilobed structure at the tip of filament o Each lobe has 2 pollen sacs o A total of 4 pollen sacs are present in a anther o Each sac produces spores, which later develop into pollen grains, the male gametes o Connective