Reproduction, Biology

Reproduction

Living things do not arise spontaneously. They arise only from pre-existing living things This is one of the fundamental tenets of biology. The ability of an organism to reproduce its kind is characteristic of living things. Reproduction involves transmission of information by the remarkable hereditary material deoxyribonucleic acid (DNA) contained in the nucleus. The heredity material is subject to change or mutation. When provided with necessary conditions the DNA molecule is capable of replicating itself. The DNA codes for the information regarding structure and function of the organisms.

For example, DNA ensures that cats always produce kittens, never pups. In simple organisms such as protists, reproduction may be asexual. For example, a protist like amoeba reproduces by simple division. When the amoeba grows to a certain size it makes a duplicate copy of its DNA, each copy separating into a nucleus. The amoeba divides into two, each daughter amoeba thus possessing a nucleus with a copy of DNA. However, higher plants and animals reproduce sexually. This involves the union of a male gamete and female gamete. The male gamete is the sperm whereas the female gamete is the egg.

The sperm fertilizes the egg to form a zygote which then develops into a new individual. Each gamete has ope complete copy of genes (DNA) derived from its parents. So gametes are haploid. Union of two gametes and fusion of their nuclei result in the doubling of the DNA content in the zygole, which is hence diploid. All cells derived from the zygote are diploid. Thus, each offspring is not a mere duplicate of a single parent but is the product of the interaction of various genes (DNA) contributed by both mother and father. This results in genetic variation which is important from the point of view of evolution and adaptation. Thus, though an individual dies, it perpetuates itself by the process Of reproduction, and the race continues.

2499_Reproduction.png

Figure: Approaches to reproduction - (a) in asexual reproduction, one individual gives rise to offsprings which are identical to the parent. (b) In sexual reproduction, each parent contributes a sex cell; these join to give rise to the offspring which thus has the genes and traits of both parents.

Posted Date: 1/12/2013 2:22:55 AM | Location : United States







Related Discussions:- Reproduction, Assignment Help, Ask Question on Reproduction, Get Answer, Expert's Help, Reproduction Discussions

Write discussion on Reproduction
Your posts are moderated
Related Questions
What is Congenital Heart Operations And Interventions Aftercare of the children who have undergone cardiac procedures and surgeries is as important, and in some occasions, more

Which of the below describes the type of fruit characterized as a dry, simple, one-seeded indehiscent (pron: in-deh-HISS-ent) fruit with seed attached to one ovary wall at only one

Q. Discovery of insulin? The discovery of insulin has dramatically changed the lives of people having type 1 diabetes. With this wonder drug diabetics can lead a normal, enjoya

Explain Theory or Principle of Determination of Coliforms? Coliforms are gram negative, non-spore forming, facultative anaerobic bacteria which produce acid and gas on lactose

Genes and Alleles The inheritance of any character can be studied only when thcre are two contrasting conditions, such as yellow versus green seed colour (as observed by Mendel

Acellular and Cellular Organisms you should be able to characterise living and non- living matter. However, the boundary-line between the two is not very precise. As you have

Define How to Prevent the Cancer? A continuing and urgent need is there to take all steps to prevent cancer. Cancer rates are set to increase another 50 percent by the year 202

If experiments do not support the hypothesis, the hypothesis is always rejected or wrong. True or False?

X-Linked Dominant Genes Dominant X-linked genes are always expressed in both the sexes just as in autosomal traits. One dose of X-linked dominant allele produces its effects in

Mixed Tricuspid Stenosis and Regurgitation:  Rheumatic involvement of the tricuspid valve is often seen in association with involvement of mitral and rarely aortic valve. Isolated