Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET 2021
The factor that leads to Founder effect in a population is:
1. Mutation
2. Genetic drift
3. Natural selection
4. Genetic recombination
Answer:2. Genetic drift
👉Five factors are known to affect Hardy-Weinberg equilibrium. These
are gene migration or gene flow, genetic drift, mutation, genetic
recombination and natural selection.
👉When migration of a section of
population to another place and population occurs, gene frequencies
change in the original as well as in the new population.
👉There would be a gene flow if this gene migration, happens multiple times
👉If the same change occurs by chance, it is called genetic drift. Sometimes
the change in allele frequency is so different in the new sample of population
that they become a different species. The original drifted population
becomes founders and the effect is called founder effect.
👉Microbial experiments show that pre-existing advantageous
mutations when selected will result in observation of new phenotypes.
Over few generations, this would result in Speciation.
👉Natural selection is
a process in which heritable variations enabling better survival are enabled
to reproduce and leave greater number of progeny.
👉Natural selection can lead to stabilisation (in
which more individuals acquire mean character value), directional change
(more individuals acquire value other than the mean character value) or
disruption (more individuals acquire peripheral character value at both
ends of the distribution curve)
👉The first mammals were like shrews. Their fossils are small sized.
👉When reptiles came down mammals took over this earth.
👉There were in South America mammals resembling horse, hippopotamus,
bear, rabbit, etc. Due to continental drift, when South America joined
North America, these animals were overridden by North American fauna.
👉Due to the same continental drift pouched mammals of Australia survived
because of lack of competition from any other mammal.
👉It is generally believed that variations in a population result in
variable fitness. Other phenomena like habitat fragmentation and
genetic drift may accentuate these variations leading to appearance
of new species and hence evolution.
