Reproduction in Animals

Q1: What is metamorphosis? Give examples.

Answer: 

Metamorphosis, which occurs during an invertebrate or amphibian’s life cycle, is the process by which an animal transforms from a larva to an adult. For instance, a frog and a butterfly.

Q2: What are the two types of animals categorized based on giving birth? Give an example.

Answer: 

Two types of animals categorized based on giving birth are:

  1. Viviparous animals E.g. Dogs
  2. Oviparous animals E.g. Birds

Q3:  What is binary fission?

Answer: 

Binary fission is an asexual reproduction process in which first the nucleus divides and forms two nuclei; later cytoplasm gets divided where each part gets a nucleus thus producing a single parent.

Q4: Write a short note on the process of sexual reproduction.

Answer: 

Sexual reproduction is the method by which new individuals are formed by the fusion of male and female gametes.  Sperm is the male gamete, whereas egg or ovum is the female gamete. Male and female gametes fuse to form the zygote by fertilisation. The zygote undergoes cell division several times to develop into an embryo. Thereby new individuals are formed.



NCERT Notes for Class 8 Science Chapter 6: Reproduction in Animals

NCERT Notes for Class 8 Science Chapter – 6: Reproduction in Animals: Reproduction is essential for species to survive; it ensures their continued existence for many generations by passing on traits from one generation to the next.  Without it, individuals of similar genetic makeup would not continue beyond a single generation. Through these notes, the students will be able to revise essential topics like different modes of reproduction, sexual reproduction, Male reproductive organ, female reproductive organ, fertilization, test tube babies, external fertilization, development of an embryo, internal; fertilization, asexual reproduction, budding, binary fission and an introduction to the cloning process and the story of Dolly the sheep.

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Reproduction

Reproduction is a vital process that is essential for the survival of all living organisms. In animals, reproduction involves the production of offspring that share genetic traits with their parents. The process of animal reproduction can be complex and varied, with different species exhibiting unique reproductive strategies....

Sexual Reproduction

Animals have separate reproductive systems for males and females, just like plants. The male and female gametes combine to form the zygote, which then develops into a new individual in both plants and animals. Sexual reproduction is the process of reproduction that starts with the fusion of male and female gametes....

Fertilization

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Development of Embryo

During fertilization, a zygote is created and it then starts the process of development into an embryo.  The zygote divides multiple times, creating a cluster of cells. Subsequently, these cells group together to form various body tissues and organs. An embryo is the initial stage of a growing organism in the uterus.  After being implanted into the uterine wall, it begins to develop further into its complete form with all its body parts such as hands, legs, head, eyes, and ears. The fetal stage is when the baby is still in the womb and its body parts are identifiable.  After the fetus has finished developing, it’s time for the mother to give birth to the newborn....

Viviparous and Oviparous Animals

Viviparous animals are those that reproduce by giving birth to offspring. The infants are born by their mothers. A few examples of viviparous creatures are dogs, cats, cows, etc. Oviparous animals are defined as those that lay eggs. This is because the mother will lay them in an external environment instead of keeping them inside her own body....

Asexual Reproduction

Only one parent is involved in asexual reproduction. It occurs in microbes like amoebas and small creatures like hydras. Regenerative cells are used by Hydra to give rise to new individuals during its budding phase. This happens due to repeated cell division at one single point which causes the formation of buds as an outgrowth....

Story of Dolly

A team of researchers led by Ian Wilmut at the Roslin Institute in Scotland, achieved a scientific milestone when they cloned a sheep named Dolly. C Cloning is the process of producing an exact replica or copy of cells, other living components, or organisms. On July 5th, 1996, a historic event occurred as Dolly became the world’s first cloned animal.  A cell was taken from a female Finn Dorsett sheep’s mammary gland and an egg was extracted from a Scottish Blackface ewe for this cloning process. The nucleus of the egg was removed and replaced with the nucleus of a mammary gland cell from a Finn Dorsett sheep using a Scottish Blackface ewe as the host.  The ewe then successfully implanted and carried this egg to completion. After a successful development, Dolly was born and it was revealed that her genetic material had been sourced from Finn Dorsett sheep. Despite being delivered by a Scottish Blackface ewe, she was an exact clone of the donor sheep. Contrary to what one may think, Dolly did not exhibit the traits of a Scottish blackface ewe since the nucleus from its egg was removed.  Dolly was actually born healthy and she went on to have several offspring through traditional mating. Sadly, Dolly died from a lung-related ailment on 14th February 2003.  Subsequent clone attempts have proven to be unsuccessful, with most passing away either pre- or post-birth. This has sparked contemplation about the ethics of cloning in general....

FAQs on Reproduction in Animals

Q1: What is metamorphosis? Give examples....