Relatedness of organisms

Question 1

Genetic profiling

Answer 1

• Creates a unique banding pattern by gel electrophoresis
• The pattern relates to the base sequences of an organism’s DNA
• The more closely related species are, the more similar their banding patterns

Question 2

Biochemical methods

Answer 2

Avoids classification mistakes due to convergent evolution

Genetic comparisons using DNA and Proteins:
-Similar species will share more DNA/amino acid sequences

DNA Hybridisation:

• Hybrids from distantly related species split at lower temperatures
• Hybrids from closely related species split at higher temperatures

Amino acid sequencing of specific proteins:

• A common protein that all species being compared have is chosen e.g. haemoglobin in all vertebrates
• The number of similarities/differences in amino acid sequences can be calculated

Question 3

Homologous structures

Answer 3

• Structures that have a similar arrangement of component parts that have evolved for different functions
• They arise due to divergent evolution
• These organisms are closely related

Question 4

Analogous structures

Answer 4

• Similar function but different structures
• Arise due to convergent evolution
• These organisms don’t share an evolutionary origin
• These organisms are not closely related

Question 5

Convergent evolution

Answer 5

• Different ancestor
• Converge to produce analogous structures
• Species appearance becomes more similar over time
• Species are unrelated

E.g. Wings in insects, birds and bats

Question 6

Divergent evolution

Answer 6

• Common ancestor
• Diverge to produce homologous structures
• Species appearance becomes more different over time
• Species are closely related

E.g. Pentadactyl limb structure in reptiles, birds and mammals

Question 7

The species concept

Answer 7

• Phenotypically similar organisms
• They can interbreed to produce fertile offspring
• They live together in the same environment