Reproductive isolation, Biology

REPRODUCTIVE ISOLATION -

According to the biological species concept, members of one species are reproductively isolated from members of all other species.

Accordingly, reproductive isolation, that prevents the exchange of genes between populations, is the first step leading to the formation of new species.

ISOLATING MECHANISM -

Pre-zygotic isolating mechanisms -

  1. Ecological isolation: Different habitat requirements separate groups, even though the inhabitants may exits in the same general location, e.g., Head and body lice are morphologically very similar, yet they live in different habitats on a single human body.
  2. Head lice live and lay eggs in the hair on the head of a human, whereas body lice live and lay their eggs in clothing. Both suck blood for nutrition.
  3. Geographical isolation: Geographic barriers such as emerging mountains; islands, rivers, lakes, oceans, moving glaciers, and other geographic barriers keep groups isolated e.g., different tortoises are found on different Galapagos Islands; surrounding oceans keep tortoise populations isolated.
  4. Temporal Isolation: Two species living in different habitat cannot meet, e.g. fresh water fish cannot breed with sea fish.
  5. Behavioural Isolation: Different animals have their own kind of courtship behaviour which is recognised by the fair sex of the same species only.
  6. Seasonal isolation: Differences in breeding seasons prevent gene flow, even when populations are found in the same area e.g. Such isolation is very common in plants and frequently occurs in insects and certain other invertebrates.
  7. Mechanical isolation: Differences in matting behavior prevent reproduction e.g.,many animals have evolved complicated, courtship activities before breeding.
  8. Gamete isolation: Sperm and egg are incompatible. Gamete isolation is a common isolating mechanism in many plant and animal species.

Post-zygotic isolating mechanism -

  1. Hybrid inviability: Zygotes or embryo fail to reach reproductive maturity e.g., hybrid embryos formed between two species of fruit flies fail to develop.
  2. Hybrid sterility: Fertilization is successful between two species, but hybrid progeny are sterile e.g., a mule is a sterile hybrid produced from a mating between a female horse and a male donkey. Hinny is sterile hybrid between female ass and male horse (stallion).
  3. Hybrid breakdown: Sometimes hybrids are fertile and give rise to offspring which do not continue to survive in F2 generation.
Posted Date: 10/9/2012 1:49:10 AM | Location : United States







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

Write discussion on Reproductive isolation
Your posts are moderated
Related Questions
Q. How is heart contraction triggered? Heart contraction is independent from neuronal stimulus although it can be modulated by the autonomous nervous system in the heart there

Pikas (component 1), also known as "rock rabbits" or "coneys", are small relatives of rabbits belonging to the genus Ochotona. The 30 species in this genus are confined to high alt

What is the optimum percentage of forest area recommended by the national forest policy (1988) for the plains and the hills respectively? List any four problems caused because of d

Bronchial asthma: Bronchial asthma is characterised by bouts of  dyspnoea as a result of  temporary narrowing of bronchi due to bronchial spasm, mucosal edema and thick secret

briefly explain the following feeding mechanisms in holozoic animals a) filter feeding b) fluid feeding c)deposit feeding

what are structural adaptation of flatworm to it''s enviroment /

Define Assessment of Calcium Status and Calcium Requirements? There is no biochemical indicator, which can clearly reflect calcium status. It has also been seen that in case of

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Define Determinants of Food Security - Food Access? Food access is linked to its affordability. Food access is ensured when households and all individuals within them have adeq

Define the working of pH Meter? The pH of a solution, we know, measures the degree of acidity or alkalinity relative to the ionization of water sample. A pH meter is a sophisti