Category: Biology Second Paper

The reproduction that takes place without the union of sperm and egg is called asexual. Asexual reproduction in hydra is – budding and fission.
1. Budding: Budding is an asexual reproductive process in Hydra. This process does not require male or female hydra to reproduce. So it is a simple method. During summer, the environment has more food. Hydra grows physically by consuming food. Then budding occurs in hydra. The higher the number of buds, the faster the number of hydra will grow.
(i) During summer, hydra grows by taking food from the environment and increases in size. Siddique Publications
(ii) Interstitial cells in the middle or lower part of the body divide rapidly to form a small swollen area.
(iii) The swollen part enlarges into a hollow and cylindrical bud.
(iv) Epidermis, mesoglia and gastrodermis gradually develop in bud.
(v) Cilantron gradually expands from mother hydra to bud.
(vi) The bud grows by receiving nutrients from the mother hydra.
(vii) The bud consists of stomata, hypostome and karshika.
(viii) A circular groove is formed at the junction of mother hydra and bud.
(ix) The furrow gradually deepens to separate the offspring hydra from the mother hydra.
(x) Padatal is formed after the disintegration of Aptya Hydra. It then attaches itself to submerged objects and lives independently.
A hydra can produce several buds simultaneously. New buds can be formed from each bud. At this time the matrihydra seems to be a gregarious animal. It takes about three weeks to hatch and live independently from the mother hydra.
2. Fission
When a hydra’s body splits into two or more segments, a new hydra grows from each segment. This is called regeneration. Hydra is divided in two ways. Longitudinal division and transverse division. Dr. Siddiq Publications
(i) Longitudinal division: When the hydra body is divided longitudinally into two or more segments, a new hydra is formed from each segment.
(ii) Transverse division: When the body of hydra is divided transversely into two or more segments, new hydra originates from each segment.

Development: The zygote divides repeatedly and turns into a full-fledged organism is called development. The division of the zygote in Hydra is holoblastic or complete. The stages of its development are as follows.
1. Morula stage: The zygote divides repeatedly by cleavage to become multicellular, sterile and round cells. This is called Marula Dasha. Two types of cells are formed in marula dasha. Micromere and macromere. Dr. Siddiq Publications
2. Blastula stage: In the blastulation process, the cells of the morula stage are arranged in a certain layer and form a hollow spherical structure. This is called blastula dasha. The cavity in the center of the blastula is called the blastocell. The blastular wall is called blastoderm and the cells are called blastomere.
3. Gastrula Stage: In the process of gastulation, the cells of the blastomere form a two-layered nerate and spherical structure. This is called gastrula dasha. The gastrula of hydra is called stereogastula because it is attached to the mother body. The outer layer of the gastrula is called ectoderm and the inner layer is called endoderm. Between the ectoderm and endoderm are jelly-like acellular mesoglia. The gastrular cavity is called the primitive cilenteron.
4. Cyst: Gastula is surrounded by spiny sheath made of chitin. It is called a cyst.
5. Hydrilla: Embryo elongates inside the cyst at favorable temperatures during spring. In the embryo, the mouth opening, hypostome, trachea and foot wheel are formed. This condition of the fetus is called hydrula. Dr. Siddiq Publications

The process by which organisms reproduce is called reproduction. Hydra reproduces in two ways. Asexual reproduction and sexual reproduction. Dr. Siddiq Publications

Asexual reproduction: The reproduction that takes place without the union of sperm and egg is called asexual. Asexual reproduction in hydra is – budding and fission.
1. Budding: Budding is an asexual reproductive process in Hydra. This process does not require male or female hydra to reproduce. So it is a simple method. During summer, the environment has more food. Hydra grows physically by consuming food. Then budding occurs in hydra. The higher the number of buds, the faster the number of hydra will grow.
(i) During summer, hydra grows by taking food from the environment and increases in size. Siddique Publications
(ii) Interstitial cells in the middle or lower part of the body divide rapidly to form a small swollen area.
(iii) The swollen part enlarges into a hollow and cylindrical bud.
(iv) Epidermis, mesoglia and gastrodermis gradually develop in bud.
(v) Cilantron gradually expands from mother hydra to bud.
(vi) The bud grows by receiving nutrients from the mother hydra.
(vii) The bud consists of stomata, hypostome and karshika.
(viii) A circular groove is formed at the junction of mother hydra and bud.
(ix) The furrow gradually deepens to separate the offspring hydra from the mother hydra.
(x) Padatal is formed after the disintegration of Aptya Hydra. It then attaches itself to submerged objects and lives independently.
A hydra can produce several buds simultaneously. New buds can be formed from each bud. At this time the matrihydra seems to be a gregarious animal. It takes about three weeks to hatch and live independently from the mother hydra.
2. Fission
When a hydra’s body splits into two or more segments, a new hydra grows from each segment. This is called regeneration. Hydra is divided in two ways. Longitudinal division and transverse division. Dr. Siddiq Publications
(i) Longitudinal division: When the hydra body is divided longitudinally into two or more segments, a new hydra is formed from each segment.
(ii) Transverse division: When the body of hydra is divided transversely into two or more segments, new hydra originates from each segment.

Hydra Sexual reproduction
The process by which sperm and egg unite to form a zygote is called sex. Sexual reproduction in hydra takes place in two stages. Gametogenesis and fertilization.
1. Gametogenesis: The process by which gametes i.e. sperm and egg are produced is called gametogenesis. It is of two types. Spermatogenesis and oogenesis. Dr. Siddiq Publications
(i) Spermatogenesis: The process by which sperm are produced is called spermatogenesis. Spermatozoa are formed on the upper side of the hydra’s body. The interstitial cells of the testis divide repeatedly in the process of mitosis to form spermatogonia. Each spermatogonia enlarges in size by taking food and develops into spermatocytes. Each spermatocyte divides by meiosis to produce 4 spermatids. Each spermatid is transformed into a sperm in the process of spermiogenesis.
(ii) Oogenesis: The process by which eggs are produced is called oogenesis. Ovaries are formed on the underside of the hydra’s body. Ovarian interstitial cells divide repeatedly in the process of mitosis to form oogonia. Each oogonia grows in size by taking food and turns into an oocyte. Each oocyte divides by meiosis to produce 3 small polar bodies and one oocyte. The oocyte transforms into an egg. Ovum is covered with a slippery coat of gelatin.
2. Fertilization: The union of sperm and egg is called fertilization. The spermatozoa break through the nipple of the spermatic cord and come out and swim in the water in swarms. Within 24-48 hours, the sperm unites with the egg to form a zygote.

1. Touch: Pricking the hydra with a needle causes the body to contract. Leaves, aquatic plants, objects, etc. are stuck by hydra treads.
2. Hunger: A hungry hydra contracts and expands its muscles. Moves the body at a very fast speed to search for food. If they are not hungry, they slow down.
3. Temperature: Hydra always prefers cool water with a temperature of 20 degrees Celsius. When the surface temperature of the reservoir rises, the hydra slowly moves down. Dr. Siddiq Publications
4. Light: Hydra does not like either too much light or darkness. Always like moderate light. Dr. Siddiq Publications
5. Current: A continuous current causes the hydride body to bend towards the anode. Later, the whole body contracts. Dr. Siddiq Publications

Hydra is a suborder of animals. Their bodies have a weak nervous system. In the animal world, hydra or nidarians developed the first nervous system. Nervous system emerges from their afferent neurons and joins to form neural network. Neurons do not have axons or dendrites and never form synapses. Mesoglia has one nerve plexus on either side. Nerves are attached to the epidermis and gastrodermis. Nerves are densely located in the mouth and foot. Neurons are connected to each other and to sensory cells and muscle cells. Sensory cells receive light, touch and chemical stimuli from the environment. Then through the nerve network sent to the muscle cells. Dr. Siddiq Publications

Hydra has no specific excretory organs. Metabolism in cells produces nitrogenous waste products. The waste material generated is released into the water during the diffusion process.

Hydra has no specific respiratory organs. It causes the exchange of gaseous substances through the epidermis and gastrodermis.
1. Epidermis: Dissolved oxygen from the water around the body enters the epidermal cells by diffusion. The absorbed oxygen reaches the various cells of the body and completes the respiration process. Carbon dioxide produced as a result of respiration is released outside the body in the process of diffusion. Dr. Siddiq Publications
2. Gastrodermis: Gastrodermis consists of flagellated cells. Flagellar movement causes a constant flow of water into the stomata. Dissolved oxygen from water enters the gastrodermal cells by the process of diffusion. The absorbed oxygen reaches the various cells of the body and completes the respiration process. Carbon dioxide produced as a result of respiration is released outside the body in the process of diffusion.

If bubbles are not created in the body, the body becomes heavy. The body sinks faster due to its heaviness. It is called submerged movement. Dr. Siddiq Publications

Hydra relaxes the body and causes contraction and expansion of muscle cells. In this the body size becomes shorter and longer. As a result, a kind of movement is created and the place changes.

Hydra clings to branches of submerged plants by tentacles. Releases and shrinks the soles. Then put the floor in a new place. Thus changes the space through contraction.