Question

PLEASE ANSWER THE FOLLOWING IN FULL DETAIL:

1. Is there likely to be a relationship between the level of interspecific variability within a population and extinction risk? If so, please describe the relationship.

2. List two (2) factors that might limit the progress of evolution within a population.

Answer 1

2.Factors limiting the progress of evolution in a population--

Genetic Drift- Genetic drift is a change in allele frequencies in a population from generation to generation due to occurrence of some events.Changes in allele frequencies are not caused by selection. Rather allele frequencies are changed randomly within a population. Genetic drift is caused due to sampling error.Here a sampling error can be explained as the selection of wrong alleles for next generation from the gene pool of current generation.It is more prevalent among a population of small size. Genetic drift does not take into account, whether the allele selected for next generation is harmful or beneficial. A beneficial allele can be lost,or a harmful allele can acquire fixation or permanent selection.

a)Bottleneck Effect- Bottleneck effect is a type of genetic drift, in which there is remarkable reduction in a size of population may be due to natural disasters like earthquake,flood etc. When such things happen,that causes a population to be reduced in size,leaving a small number of people.In such cases,the alleles occur in the existing population is completely different from the ones,that occurred in that particular population before the disastrous event. Some of the beneficial alleles are completely lost.Thus bottleneck effect causes beneficial alleles to be lost,which in turn limits the ability of the population to be evolved.

b)Founder Effect- Founder effect is another type of genetic drift whic is observed when a small portion of a population separates from the group and establishes them as a new different population.The number of alleles present in the new population is different from the previous population. The type of alleles present in new population may not contain all beneficial alleles.Also the founding population is smaller in number.Hence it leads to limiting evolution in that particular founding population

Mutation - The word mutation is derived from the Latin word mutate which means to change.Mutation causes permanent changes in hereditary material. Changes in hereditary material cause alternation in gene sequences. Usually genetic changes caused by mutations are recessive by nature.It's Phenotypic effects are only seen in the next generation when the recessive gene gets a chance to recombine with another recessive gene.A sudden appearance of hereditary character in a population is possibly caused by mutant gene.However mutation of cancerous gene or antibiotic resistant genes or other hazardous genes that might causes occurrence of any disease in the next generation might result in the reduction in population size,which in turn limits evolution

1.Relationship between intraspecific variation and Extinction of a population-

Intraspecific variation is the differences within a population.A variation can be observed as a change in phenotype(physical appearance) or Genotype. Intraspecific variations occur due to genetic factors or environmental factors.All individuals present in a species carries same gene.But there is a difference in the form of gene (alleles) present in each individual.The different alleles cause variations in the phenotype.Some genetic factors are inherited from one generation and passed onto the next generation.

Environmental factors are also responsible for intraspecific variations.For example,plants show differences in growth due to variations in the presence of minerals,water in soil.

Intraspecific variation leads to occurrence of new characteristics in a population that equips it to adapt to the environmental changes.Extinction is caused by various environmental, Anthropogenic and genetic factors. Variation is important from that point of view to prevent extinction of any species caused by the above mentioned factors .Intraspecific variability is related with the risk of extinction of a population ,if it does not occur within a species.This variation increases the chances of survival in unfavorable condition of existence.