It is ability of living organisms to produce young ones of their own kind. Following are the two main types of reproduction.

Reproduction which doesn't involve fusion of male and female gamete is called asexual reproduction. Following are some important modes of asexual reproduction.

1. Fragmentation
2. Budding
3. Fission
4. Regeneration
5. Grafting
6. Cutting
7. Layering
8. Spore formation

In this type of reproduction parent body is broken into many small fragments each fragment develop into a new individual.

The spirogyra and ulothrix reproduction take place by fragmentation.

Bud is unicellular or multicellular outgrowth which develops laterally on parent body. It is detached from the parent body and develop into a new individual.

Hydra and yeast.

It is the most common method of asexual reproduction. It takes place in unicellular organisms. Parent cell is divided into two or more cells.

Parent cell divides into two cells.

Parent cell divides into many cells.

Amoeba, paramecium and most of the unicellular organisms reproduce by fission.

Development of new organisms from the broken part of the body of an organism.

It is well developed in sponges and star fish.

Spores are reproductive cells contain deploid number of chromosomes. They are surrounded by protective covering which protect them from infavourable conditions. Spores are capable to produce new individual when favourable conditions are available.

Fungi and plasmodium reproduce by spores.

It is an artificial technique of asexual reproduction. In this method different variety of plant are grafted onto the stem of healthy young plant. The grafted branch is called scion and the stem on which branch is grafted is called stock.

Mango

Healthy cuttings of plant are placed in soil. The root system is developed on the lower side. After some time this cutting is developeed into a new plant.

Rose

This type of asexual reproduction is observed in shrubs. Shrubs grow as bush and some times branches of these shrubs get buried in soil. Thin buried part is called layer. New roots are developed from layer and axial part develops into shoot. Thus if connection between layer and parent plant is cut the layer can give rise to a new plant.

Reproduction which involves fusion of male and female gamete is called sexual reproduction.

Pedicel is the stalk of the flower. The disc where all whorls of the flower are arranged is thalamus or receptacle.

Following are the whorls of flower from outside to inside.

It is the outermost whorl of the flower. It consist of many green leaves called sepals.

It is the second whorl of the flower. It consist of bright coloured petals.

This is third whorl of the flower and a male reproductive part. It consist of many stamens. Each stamen has two parts called anther and filament.

It is the innermost whorl and female reproductive part. It consist of pistal or carpel. Each pistol or carpel is mode up of three parts

1. Stigma
2. Style
3. Ovary

Ovary contains ovule.

It is the transference of pollen grains from anther to the stigma of the flower.

Following are the types of pollination.

Transference of pollen grains from anther to the stigma of the same flower.

Transference of pollen grains from anther of one flower to the stigma of another flower.

Following are the agencies of pollination.

1. Wind
2. Water
3. Animals / insects

Plants having very light weight pollen grains transfer their pollen grains to another flower through wind. E.g., grass, maze.

In aquatic plants pollination takes place through water. Flowers of these plants are submerged in water.

Plants having beautiful flower with fragrance and nectar transfer their pollen grains to another flower by animals or insects. E.g., china rose.

It is the process of fusion of male and female gametes. After pollination following processes take place for preparation of fertilization and after fertilization.

1. A pollen grain of right kind on stigma germinate to form pollen tube.
2. The pollen tube grows down the style and ovary wall to micropyle of the ovule.
3. One male gamete fuse with the ovum and form diploid zygote.
4. Second male gamete fuse with fusion nucleus to triploid nucleus.
5. Zygote divide by mitosis to form embryo. Embryo consist of plumule, radicle and cotyledons.
6. The integumens covering the ovule form seed coat.
7. Ovary wall grow into a fruit.
8. Most of the other parts of flower drop off.

Development of ovary into fruit without fertilization is called parthenocary. E.g., banana, seedless grapes and guava.

In many flowering plants there is no reduction division and fertilization in ovule. Embryos are formed in different ways. Some times they are formed from unfertilized egg and some times from cells other than egg.

Fruit serve two main functions.

Particularly important when fruit is eaten by animals.

The process by which seeds and fruits are carried from one place to another is called dispersal of fruits and seeds.

Plants having small and light seeds and fruits disperse their seeds and fruits by wind. E.g., calotropis.

It is the most common method of dispersal. It is usually seen in aquatic plants or in those plants which are near to water. E.g., water lily.

Some fruits and seeds have hooks. Fruits and seeds cling to the bodies of the animals and animals transfer them from one place to another.

Some fruits are edible and are eaten by animals and seeds are thrown away.

Some fruits explode and disperse their seeds in surrounding area. E.g., lady finger, cucumber.

Seed is covered by seed coat. There is small opening in seed called micropyle through which seed absorbs water.

For convenience seed can be divided into following parts.

1. Seed coat
2. Endosperm
3. Embryo

The outer hard part is testa while inner coat is called tegman.

It contain stored food which is utilize by embryo during development.

Embryo consist of plumule, radicle and cotyledons.

It develop to form shoot.

It develop to form root.

These are leaf like structures.

It is oval in shape and brown in colour. It is dicotyledonous seed.

It is knob like outgrowth at one end of seed. It has spongy tissues which absorb water.

It is small depression near caruncle.

The small opening on one side of hilum is called micropyle

It consist of following parts.

1. Seed coat
2. Endosperm
3. Embryo

Seed coat consist of two layers the outer one is testa while the inner one is tegmen.

Inside the seed coat there is a food reserve in the form of albumen.

Embryo consist of plumule, radicle and cotyledon.

It develop to form shoot.

It develop to form root.

There are two cotyledons which come out after germination of seed and for short period of time performs the function of photosynthesis.

It is the process of activation of dormant embryo. Germination of castor seed involves following steps.

First moisture is absorbed by caruncle and water enter into the seed through micropyle. When it reach to the tegmen it rupture this covering. Finally it reach to endosperm and embryo. Water bring dissolve oxygen to embryo. Embryo starts to germinate. The radicle produces root and plumule produces shoot.

Following are the conditions necessary for the process of germination.

1. Water
2. Suitable temperature
3. Oxygen

Water makes seed soft and bring dissolve oxygen to the embryo.

The germinating seeds receive oxygen for respiration.

The process of germination is controlled by number of enzymes which works at specific range of temperature. The best temperature for germination is between 28° C to 37° C.

The germination in which cotyledon comes above the surface due rapid growth of hypocotyle. E.g., castor seed germination.

The germination in which cotyledons remain under the soil and plumule (shoot) comes above the soil due to rapid growth of epicotyle.

Higher plants complete their life history by passing through two stages.

The phase of life in which plant has diploid number of chromosomes and it produces spores (Spores are unicellular structures which can give rise to new individual without fertilization). Spores have diploid number of chromosomes.

In this phase of life history plants has haploid the number of chromosomes and it produces haploid gametes. These gametes fuse to form new sporophyte. In this way plant passes from sporophyte and gametophyte generation. This phenomenon is called alternation of generation.

It is an artificial mode of reproduction which takes place through vegetative parts. Vegetative reproduction is faster and give rise to exact copies of selected high quality plant. Methods of vegetative reproduction.

1. Cutting
2. Layering
3. Grafting
4. Use of underground modified stem

In this method embryonic tissues of selected plants are cultured using their ability of asexual reproduction in test tube or dishes. Hormones are added to speed up growth. The new plants so produced are free from disease and are transferred to field for large commercial scale production of vegetable and crop varieties.

There are two modes of reproduction in animals

1. Asexual
2. Sexual

Mode of reproduction which doesn't involve fusion of male and female gametes.

Reproduction which involves fusion of male and female gametes.

Amoeba reproduce asexually by fission. Fission is the process of splitting of parent cell into two (binary fission) or more than two (multiple fission) cells. Normally it reproduces by binary fission but during unfavourable conditions it reproduces by multiple fission.

Sexual reproduction involves fusion of male and female gametes which are produced by gonads i.e. testes and ovaries.

The process of formation of gametes is called gametogenesis.

It is the process by which ova are formed. It involves following steps.

1. Primodial germ cells divide many time mitotically to form oogenia. Oogonia increases their size to form primary oocyte. The number of chromosomes are still diploid.
2. The primary oocyte undergo first meiotic division and result in formation of secondary oocyte and first polar body.
3. As the result of second meiotic divisionj ovum and second polar are formed from secondary oocyte. First polar body give rise to two polar bodies.

It is the process of formation of sperms. It involves following steps.

1. Primodial germ cell pass through series of mitotic division and gives rise to spermatozoa.
2. Spermatozoa grow to form primary spermatocytes.
3. Two secondary spermatocytes are formed as the result of first meiotic division.
4. Spermatids are formed from secondary spermatocytes as a result of second meiotic division.
5. Spermatozoa are develop from spermatids.

It consist of head, neck and tail. Head contain nucleus. It is motile.

During breeding season, the male and female frog go to pond for mating. The female frog lays eggs in water and male sheds spermatozoa on eggs.

It is the process of fusion of male and female gametes. Zygote is the product of fertilization.

The zygote undergoes repeated mitotic division. This process is called cleavage.

This is 32- 64 celled stage in which its appearance is like a irregular ball.

It’s a stage in which a cavity called blastocoll is developed.

After blastula next stage is gastrula. In this stage blastocoll disappears and new cavity called archentron is formed. Many layered embryo is converted into three layered embryo. The three layers are ectoderm, mesoderm and endoderm. These layers are called germinal layers.

Ectoderm forms nervous system and outer part of the skin.

Develops into muscles, skeleton, circulatory, excretory and reproductive system.

Endoderm forms the alimentary canal and associated organs like liver and pancreas. Endoderm also develops into lungs.

The development continues and the embryo now acquires elongated shape. The sheath covering the embryo breaks and larva hatched out. This is a free swimming creature and is known as tadpole. It has head, body and tail. External gills for respiration. It is herbivorous and feed on algae.

These are entire post hatching changes through which tadpole larva is passed to attain more or less an adult frog. These changes are as follows.

1. The tail disappears.
2. Development of fore and hind limbs.
3. Gills are replaced by lungs.
4. Change of mode of nutrition from herbivorous to carnivorou

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