environmental selection pressures and selective breeding- unit 4 AOS 2

Question 1

environmental selection pressures

Answer 1

Environmental selection pressures are a factor in the environment (e.g. limited resources, deforestation, changing temperature, predation) that impacts an organism’s ability to survive and reproduce

Question 2

natural selection

Answer 2

• Organisms more suited to a particular environment are considered to have higher genetic fitness, due to the presence of their advantageous phenotype, which arises due to the presence of certain alleles.
• Natural selection a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles
• Over time, because the fitter organisms with the advantageous phenotype have a selective advantage and are more likely to survive, they are more likely to pass on their alleles to the next generation, increasing the allele frequency of the alleles that code for the advantageous phenotype.

Question 3

mechanisms of natural selection

Answer 3

variation - Individuals in a population vary genetically, which leads to phenotypic differences.

selection pressure - There is a struggle for all individuals in the gene pool to survive. Environmental selection pressures act upon the population

selective advantage - Individuals with phenotypes that are fitter or more advantageous under the environmental selection pressure are conferred a selective advantage, allowing them to survive and reproduce more successfully.

heritability - The advantageous trait must be heritable, allowing it to be passed on from the parents to their offspring. Therefore, over time, the frequency of the advantageous allele will increase.

Question 4

the effect of selection pressures on genetic diversity

Answer 4

• As advantageous traits become more common in a population, the allele frequencies of the population changes, with the frequency of the advantageous allele increasing. Eventually, the evolution of the species can occur.
• Due to the generational increase in the frequency of the advantageous allele, the
  genetic diversity of the population will also decrease as the phenotypes of the
  population are driven towards a specific allele.

Question 5

artificial selection/ selective breeding

Answer 5

• Selective breeding is an example of artificial selection. In this procedure, only those organisms that display a
  desirable trait in their phenotype or are known carriers of the trait are chosen to reproduce.

Question 6

mechanisms of artificial selection

Answer 6

variation - There is variation within the population’s gene pool.

selection pressure - Humans select individuals with a desirable trait.

These individuals breed (reproduce) and pass their alleles on to the next generation.

The alleles that lead to the desired phenotype will be inherited by subsequent generations and they can
increase in frequency in the gene pool over time.

Question 7

effect of artificial selection on genetic diversity

Answer 7

• Selective breeding can lead to smaller gene pools and overexpression of deleterious alleles, which can reduce adaptability and fitness within a population.
• Artificial selection in domesticated species, particularly in so-called show varieties, can favour features that are disadvantageous for survival and reproduction and would be selected against in the wild.