chapter nine: determining the relatedness over time

Question 1

understand that we use various forms of evidence to determine relationships between species

Answer 1

• nucleotide sequences
• homologous structures
• vestigial structures
• analogous structures

Question 2

give examples of homologous structures and explain how the arise

Answer 2

homologous structures show:

• a species relatedness over time
• the idea that they were deprived from the same ancestor but evolved differently due to different selection pressures
• shows that they are related
• e.g. forelimbs of vertebrates

Question 3

state how vestigial structures provide evidence of evolution using an example

Answer 3

vestigial structures show:

• shows that there has been evolution
• they are the non-functional remanants that are passed on from ancestors that were once functional in their lives
• e.g. Tailbone

Question 4

Define molecular homology

Answer 4

molecular homogology involves comparing the similarities in DNA and protein sequences to infer relatedness

Question 5

Describe the link between similarities in DNA or amino acid sequences between species and time since the species shared a common ancestor

Answer 5

• species that are more closely related to related are expected to have fewer differences in the aminos acid sequence of their corresponding proteins that species that are more distantly related to

Question 6

State why the differences in molecules can indicate time since a common ancestor was shared

Answer 6

the more differences in molecules, the more time has passes since a common ancestor was shared.

• this is because over time, more mutations would occur, meaning more molecules would be different and the more distinct the differences would be from the current species and their pass ancestors.

Question 7

explain why conserved proteins are more useful to determine the relatedness of species

Answer 7

conserved proteins have the same function, even in different organisms and species.

• it determines the relatedness because you would be able to tell the difference between mutations if they are similar, rather than a protein that has gone through so many mutations that it is not recognisable

Question 8

explain whether the use of structural morphology or molecular homology will allow a more accurate understanding of relatedness

Answer 8

molecular homology will more accurately prove relatedness because:

• DNA can more accurately prove whether a species is closely related or not dur to the nucleotide sequences
• structural morphology can tell whether a species is related but it isn’t as accurate since different species can evolve under the same selection pressures
• molecular homology can tell the exact different between the DNA molecules between two species

Question 9

features of a phylogenetic tree

Answer 9

• tips represents species or group
• nodes show the common ancestors
• line length indicates time
• branch indicates speciation event
• root indicates the common ancestor of all the descendant groups in the tree

Question 10

what information is displayed in phylogenetic trees

Answer 10

evolutionary relationships between species