2 - How Human Heads Evolve

Question 1

What are the 4 mechanisms of evolutionary change?

Answer 1

1) Natural selection
2) Neutral drift
3) Phenotypic plasticity in response to environmental change
4) Population turnover

Question 2

How does natural selection manifest?

Answer 2

Changes driven by fitness associated with the trait in question.

Question 3

What does natural selection require for it to occur?

What also helps?

Answer 3

Requires association between trait and fitness

Requires genetic variation

Large population size.

Question 4

How does neutral drift manifest?

Answer 4

Change driven by random variation in smal populations.

null hypothesis

Question 5

What does neutral drift require?

Answer 5

Requires genetic variations

(also small population size - i.e. traits may be carried through generations by chance, particularly in small populations)

Question 6

How does phenotypic plasticity in response to environmental change manifest?

Answer 6

Change driven by environment.

Question 7

What is required in phenotypic plasticity in response to environmental change?

Answer 7

REQUIRES NO genetic variation

technically reversible if environmental change reversed

Question 8

How does population turnover manifest?

Answer 8

Change in genetic make-up as a result of immigration / emigration.

Results in change in average trait.

Question 9

What does population turnover require?

Answer 9

Migration

Genetic differences amongst populations.

Question 10

What are 2 examples of phenotypic plasticity in response to environmental change?

Answer 10

Nutrition (and its effect on height and weight)

Healthcare developments

Question 11

Define ‘Shape’

Answer 11

All the geometric features of an object, except for its size, position and orientation.

Question 12

Define ‘Landmarks’

Answer 12

Points that can be located precisely and correspond amongst specimens.

Question 13

How do you extract shape variation?

Answer 13

Use Procrustes Superimposition

Question 14

What are the 3 steps that are requires to undergo Procrustes Superimposition?

Answer 14

1) Change scale (all same size)
2) Superimpose (line up centres of gravity)
3) Rotate (minimise dispersion of corresponding points)

Question 15

Which two mechanisms of evolutionary change include / require genetic variation, and which two dont?

Answer 15

Genetic variation:

• Natural selection
• Neutral drift

No-genetic variation:

• Phenotypic plasticity to environmental change
• Population turnover