Biological Evolution Common Questions

Question 1

Reasons why 1 similar characteristic is not sufficient to place several organisms in a single genus

Answer 1

1. biochemical / morphological trait was not derived from the same recent common ancestor
   (e.g. QV: different branches in phylogenetic tree)
2. biochemical / morphological trait could have evolved independently in each of the different genera the organisms belonged to
3. one characteristic is not enough to classify them into the same genus

Question 2

Reasons why a certain characteristic may be limited to just a few specific families/species of organisms

Answer 2

characteristic originated from a random mutation to a gene which resulted in an allele for the trait
-> allele resulting in phenotype with certain characteristic is heritable / inheritable in those few families/species
=> present in only these specific families/species

Question 3

Reasons for a high number of species at a particular place

Answer 3

1. high habitat diversity, with abundant niches/microhabitats
2. location aids species with their survival
   (e.g. coral reefs provide shelter/camouflage against predators)

Question 4

Challenges of using morphology to classify species

Answer 4

1. subjectivity
2. difficulty in determining differences
3. non-quantitative

Question 5

Conclusions that can be drawn from comparison of similar DNA sequences

Answer 5

1. the smaller the number of differences, the more closely related they are / the more recently diverged they are
2. (commonly missed out) all the species share a recent common ancestor

Question 6

Reasons why comparing nucleotide sequences alone is insufficient to draw conclusions about evolutionary relationships

Answer 6

1. nucleotide sequence is only a small fraction of the whole genome
2. sequences come from one individual from each species
3. variation within each species

Question 7

Link between genetic variation and natural selection

Answer 7

1. processes in meiosis (crossing over + independent assortment) increases genetic variation in gametes formed
2. thus increasing genetic variation in genotype and phenotype of offspring formed by random fertilisation of the gametes
3. most of the genetic variation in a population arises from variation in individuals