Lecture 9

Question 1

Define adaptation.

Answer 1

A trait that increases the fitness of an organism in its environment. Genetically determined and therefore heritable. Happens on an evolutionary timescale.

Question 2

What are some examples of adaptation?

Answer 2

Darwin’s Finches are an example of a structural adaptation.

Hibernation is an example of a behavioural adaptation.

Question 3

Define acclimation.

Answer 3

Physiological, compensatory response to environmental change. Can be immediate or build up over time. Short term response to the environment that isn’t heritable.

Question 4

What is the difference between acclimation and acclimatisation?

Answer 4

They are the same other than that acclimation is experimental and not natural (E.g. sweating in a hot room) and acclimatisation is natural (E.g. shedding winter coat to adjust to seasonal changes in temperature).

Question 5

Define plasticity.

Answer 5

Ability of an organism to change their state in response to any stimuli.

Question 6

Where does plasticity happen?

Answer 6

Any level of complexity: molecular, cellular, systemic, behavioural.

Question 7

How does plasticity differ?

Answer 7

Ability differs between individuals and species E.g. Rockhopper penguins are highly plastic in strategies in foraging behaviour which allows them to survive in Sub-arctic to sub-tropical coastal waters.

Question 8

What are the differences between low altitude and high altitude?

Answer 8

Low altitude has high barometric pressure and high O2 concentration (100 at 100m).
High altitude has low barometric pressure and low O2 concentration (60 at 400m).

Question 9

What are the 2 populations in the altitude case study?

Answer 9

Andeans: lived at 4000m above sea level for 13,000 yrs.
Tibetans: lived at 4000m above sea level for 25,000 yrs.

Question 10

How is oxygen transported?

Answer 10

O2 in lungs binds to haem groups (4 binding sites on each haemoglobin) which is then released into the tissue that needs it.

Question 11

What is oxygen saturation?

Answer 11

% of haemoglobin binding sites that carry oxygen.

Question 12

How does O2 partial pressure differ in the lungs and muscles?

Answer 12

High O2 partial pressure in the lungs means haemoglobin has high affinity and O2 binds to it readily.
Low O2 partial pressure in the muscles means haemoglobin has low affinity and O2 is released into the tissue.

Question 13

What effect does high altitude have on O2 partial pressure?

Answer 13

High altitude decreases O2 partial pressure so highest possible O2 saturation is lower.

Question 14

What does this lead to?

Answer 14

Hypoxia: a deficiency of O2 reaching tissue and so the O2 transport system must respond to maintain sufficient tissue O2 concentration.

Question 15

How is haemoglobin concentration used to measure physiological stress?

Answer 15

High altitude causes high altitude erythrocytosis, an increase in red blood cell mass.

Question 16

What are the differences in haemoglobin concentrations between the 2 populations?

Answer 16

Andeans have higher haemoglobin concentration concentration than their closest lowland ancestors which shows they are experiencing and responding to hypoxia.
Tibetans have the same haemoglobin concentration than their closest lowland ancestors.

Question 17

How is O2 saturation used to measure physiological stress?

Answer 17

Oxygen saturation is the % of haemoglobin binding sites that carry O2.

Question 18

How does O2 saturation differ in the 2 populations?

Answer 18

Andeans & Tibetans both have lower O2 concentrations than their lowland ancestors.
Andeans had higher O2 saturation which suggests that they were less stressed by hypoxia at the same altitude.

Question 19

How did the Tibetan’s response to altitude differ from the Andeans’?

Answer 19

Tibetans have a higher respiration rate and higher nitic oxide which increases vasodilation, whereas Andeans have a higher haemoglobin count.

Question 20

What effect do haemoglobin and O2 saturation combined have?

Answer 20

They determine arterial O2 concentration.

Question 21

What is the effect of the Andean’s higher haemoglobin concentration?

Answer 21

Leads to more viscous blood which put strains the heart. Therefore it is better at dealing with hypoxia but the strain on the heart is greater.

Question 22

Where are the altitude responses seen in the 2 different populations?

Answer 22

Andeans: above 1600m
Tibetans: above 4000m- require a stronger stimulus and have a smaller response.

Question 23

Which group is better adapted to the high altitude?

Answer 23

Tibetans as they require a stronger stimulus to initiate compensation strategies and their response is smaller.

Question 24

Is high haemoglobin concentration heritable?

Answer 24

There is high heritability in both populations and potential for natural selection to act on both populations.

Question 25

Is O2 saturation heritable?

Answer 25

Only significantly heritable in Tibetans. There is a dominant autosomal gene for O2 saturation that confers a 5-6% higher O2 saturation.

Question 26

What effect does the O2 saturation gene have on individuals?

Answer 26

Heterozygous dominant individuals experience less hypoxic stress than those who are homozygous recessive.

Question 27

What does this suggest?

Answer 27

There are population genetic differences. Higher O2 saturation allele may be favoured by natural selection.

Question 28

What other data was collected from Tibetans?

Answer 28

O2 saturation, geneology, female fertility.

Question 29

What effect did gene have in Tibetans?

Answer 29

No effect on number of pregnancies on live birth but homozygous recessive mothers had children that were less likely to survive than heterozygous mothers.
Shows hypoxia acts as an agent of natural selection.