Reproduction In Unicellular Organisms And Invertebrates

Reproduction In Amoeba Amoeba undergoes asexual reproduction through binary fission and multiple fission (sporulation) in adverse conditions.   In binary fission, when Amoeba reaches full size, it ceases movement and divides into two equal parts, starting from the nucleus. Subsequently, the cytoplasm undergoes division, resulting in the formation of two daughter amoebae.   During multiple […]

Reproduction In Amoeba

Amoeba undergoes asexual reproduction through binary fission and multiple fission (sporulation) in adverse conditions.

 

In binary fission, when Amoeba reaches full size, it ceases movement and divides into two equal parts, starting from the nucleus. Subsequently, the cytoplasm undergoes division, resulting in the formation of two daughter amoebae.

 

During multiple fission, Amoeba becomes rounded and secretes a cyst around itself. Inside the cyst, the nucleus undergoes multiple divisions. When conditions become favorable, the cyst bursts, and each nucleus, surrounded by a portion of the parent cytoplasm, gives rise to very small amoebae.

 

Reproduction In Paramecium

Paramecium reproduces asexually through binary fission and sexually through conjugation.

 

Under favorable conditions, binary fission occurs as the micronucleus undergoes mitosis, dividing into two halves. Each half moves to opposite sides of the cell, the meganucleus elongates, and the cytoplasm constricts, resulting in the production of two young paramecia.

 

Sexual reproduction in Paramecium involves conjugation between two individuals of different descent lines. Conjugation stages include the fusion of mature paramecia through their oral grooves, micronucleus division through meiosis, exchange of smaller micronuclei, fusion of migratory and stationary micronuclei to form a zygote, and subsequent division to produce new paramecia.

 

Reproduction In Spirogyra

Spirogyra reproduces asexually via fragmentation and sexually through conjugation.

In fragmentation, when a filament reaches a certain length, parts break away, growing into new filaments.

Conjugation in Spirogyra involves two filaments lying side by side, forming a conjugation tube. One filament’s cells act as male gametes, and the other as female gametes. The male gamete passes through the conjugation tube, fusing with the female gamete to form a zygote. The zygote secretes a resistant wall, forming a zygospore, which, after a period of rest and favorable conditions, grows into a new filament.

 

Reproduction In Earthworm

Earthworms, being hermaphrodites, have both male and female sex organs, and reproduction occurs through sexual means.

 

During copulation, two earthworms come together with their ventral surfaces touching. Copulation takes place at night, outside burrows, with reproductive organs located anteriorly. After copulation, eggs are laid and fertilized in a cocoon secreted by the clitellum. Embryo development occurs inside the cocoon, and a worm hatches from a batch of eggs in each cocoon.

 

Reproduction In Cockroach

Cockroaches undergo sexual reproduction with internal fertilization. Mating occurs between male and female cockroaches, with the male introducing sperm into the female’s genital opening. Sperm is stored in a pouch until eggs are released from the ovaries. Fertilized eggs are then laid in a protective egg case (ootheca), which the female carries before depositing it in a secure location. After a period of 30–100 days, the eggs hatch into wingless, small, whitish nymphs. Metamorphosis is incomplete, requiring 11–20 months for development from eggs to adults.

 

Reproduction In Housefly

Houseflies undergo sexual reproduction and complete metamorphosis.

After mating, female houseflies lay 2–7 batches of eggs in a moist, dirty environment, with 100–150 eggs in each batch. The eggs hatch into white larvae within 8–24 hours, developing into maggots with segmented bodies and spiny pads for movement. The larvae molt several times and last about 5–14 days before moving to a dry place to enter the pupal stage. The pupa, or puparium, eventually gives rise to a young adult housefly through a sac-like organ (ptilinum), which breaks open the puparium. The adult housefly, or imago, emerges and flies away when its wings are dry.

 

Reproduction In Snail

Reproduction in land snails is hermaphroditic and involves internal fertilization. The female snail has a fertilization pouch for sperm to travel into, and spermatophores are transferred to the epiphallus. The sperm is then transported to the bursa duct, where fertilization occurs. Snail development involves a 180o twist called torsion, bringing the anus and mantle cavity forward above the head.

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