Evidence Of Relatedness

Question 1

Homologous structures

Answer 1

Features present in two or more species that may look and function very differently in each species but are derived from a common ancestor

Question 2

What are homologous structures a physical evidence of?

Answer 2

Divergent evolution - process by which a common ancestor evolves into two or more descendant species

Question 3

Analogous structures

Answer 3

Features present in two or more species that serve the same function but do not originate from a common ancestor such as wings of a bat and an insect

Question 4

What are analagous structures an evidence of?

Answer 4

Convergent evolution - the process in which distantly related species evolve similar traits over time due to similar selection pressures

Question 5

Vestigial structures

Answer 5

A feature that no longer has a purpose in the current form of a species, but did in its ancestor

Question 6

Molecular homology

Answer 6

Study of similarities in the nucleotide sequences of DNA or amino acid sequences in proteins between organisms to establish relatedness

Question 7

Two types of molecular homology

Answer 7

Amino acid sequencing, DNA sequencing

Question 8

Molecular clock theory

Answer 8

The greater the difference, the longer the divergence has occurred. We can assume a mutation rate to help us calculate the time passed.

Question 9

Mutation rate

Answer 9

A term we use to describe the average number of mutations that occur in a gene or genome over time

Question 10

Limitation of mutation rate

Answer 10

Mutation rate is not constant - it can vary over time, within the genome (some regions are hotspots for mutations), between species (some have lower mutation rates), within species (male gametes have higher mutation rates than female gametes)

Question 11

Amino acid sequence similarity

Answer 11

We cannot compare amino acids from any part of the body, only analyse proteins from conserved genes

Question 12

Conserved genes

Answer 12

Genes that have remained largely unchanged throughout evolution, and are found across the genomes of many species (mtDNA and haemoglobin)

Question 13

DNA sequence similarity

Answer 13

Comparing base sequences

Question 14

Limitation to amino acid sequencing

Answer 14

Closely related species are likely to share very similar sequences as a result of the degenerate nature of the genetic code, so it is only used to determine relatedness in more distantly related species