BIOLOGY Presentati

on

How Do Organisms Reproduce?

Reproduction may be defined as the production of new generation of individuals of the same species that are physically independent of their parent

Types Of Reproduction

All the reproductive methods of living organisms are broadly categorized into two types :

1) Asexual Reproduction

2) Sexual Reproduction

Asexual ReproductionAsexual reproduction may be defined as the production of offspring by a single by a single parent without meiosis, formation of gametes fertilization and transfer of genetic materials between individuals.

Asexual Reproduction occurs in following ways:

Fission , Budding , Spore formation, Regeneration ,vegetative propagation

SEXUAL REPRODUCTIONSexual Reproduction may be defined as the production of offsprings by the fusion of two gametes to form a diploid zygote which develops into mature organisms.

The act of fusion of gametes is fertilization, which may be defined as fusion of two gametes to form a single cell (zygote).

SEXUAL REPRODUCTION IN PLANTS

In the flowering parts , all steps of sexual reproduction occur within specialized reproductive organs, called the Flowers .

Flower may be defined as a specialized condensed reproductive shoot of flowering plants on which are inserted the essential reproductive parts

MORE ABOUT THIS REPRODUCTION

The sex organs (or reproductive organs) of a plant are in its flowers.

The function of a flower is to make male and female gametes and to ensure that fertilization will take place to make new seeds for the reproduction of plant.

To a biologist, flowers are morphological and embryological marvels and the sites of sexual reproduction.

PARTS OF FLOWER

The main parts of a flower are:

Receptacle: The base of a flower to which all the parts of a flower are attached.

Sepals: The green leaf-like parts in their outermost circle of a flowers are called sepals.

Petals: The colorful parts of a flower are called petals.

SOME MORE PARTS.....

Stamen: Stamen is the male reproductive organ of the plant. It produces pollen grains. It is made of two parts: A filament and an anther

Carpel: Carpel is the female reproductive organ of the plant. It is made up of three parts: Stigma, Style, Ovary.

STEPS INVOLVED IN SEXUAL REPRODUCTION IN PLANTS

1) The male organ of a flower is called stamen.

2) The female organ of a flower is called carpel. Female gametes are present in ovules.

3) The male gametes present in pollen grain fertilize the female gametes.

4) The fertilized egg cell grow within ovules and become seeds.

5) Ovary becomes fruit.

MALE REPRODUCTIVE ORGAN: STAMEN

The two parts of a typical stamen are: the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther.

The number and length of stamens are variable in flowers of different species.

FEMALE REPRODUCTIVE ORGAN: CARPEL

The gynoecia may consist of a single pistil or may have more than one pistil.

Each pistil has three parts: the stigma, style and ovary. The stigma serves as a landing platform for pollen grains. The style is the elongated slender part beneath the stigma. The basal bulged part of the pistil is the ovary.

Transfer of pollen grains to the stigma of a pistil is termed pollination. Flowering plants have evolved an amazing array of adaptations to achieve pollination.

They make use of external agents to achieve pollination.

The agents of pollination are: Water, wind, animals, air.

Pollination

TYPES OF POLLINATION

Pollination may occur in two ways:

1)Self pollination2)Cross pollination

When the pollen grains from the anther of a flower are transferred to the stigma of the same flower( or another flower on the same plant), it is called Self Pollination

Self Pollination

When the pollen grains from the anther of a flower on one plant are transferred to stigma of a flower on another similar plant, it is called Cross Pollination.

Cross Pollination

Fertilization Fertilization occurs when the male

gamete present in pollen grain joins with the female gamete present in Ovule.

When a pollen grain falls on the stigma of the carpel, it bursts open and grows a

pollen tube downwards through the style

towards the female gamete in the Ovary. A male gamete moves down the pollen

tube. In ovary, the male gamete of pollen combines with the nucleus of female

gamete.

FORMATION OF FRUITS AND SEEDS

Following fertilization, the ovary develops into a fruit with seeds inside, while the rest of the flower dies.

Fruits help protect the seeds until they mature and help scatter seeds into new habitats.

One or two cotyledons forms, which form leaves that will be used by the germinating seedling.

Food is derived from the endosperm Thus, the seed is an undeveloped plant embryo with stored food and protective coats.

GERMINATION

When a seed gets water, air and warmth etc. , it begins to grow.

When a seed begins to grow, it is said to germinate.

Thus, beginning of the growth of seeds is called germination of seeds.

Germination begins when the seed absorbs water, swells and bursts through the seed coat.

Whether conservative or liberal, fundamentalist or agnostic, the more students learn of biology, the more they accept evolution

With this wonderful thought , we conclude our presentation. THANK YOU……!

COLLAGE ON FLOWERS; REPRODUCTIVE ORGANS

CREDITS:1)Gagan Garg (12)(Group leader) -editor, Management of slides&

animation.2) Sagar Bahl (31) -contribution in slides, file

management, compilation of slides

3)Siddharth Singh(38) -contribution in slides. 4) Jatin Shahji (28)5) Mohit Shukla(22)