(U2) The Adaptation Of Organisms

Question 1

What is an ecological niche?

Answer 1

A particular part of a habitat with a very particular function

Question 2

Why do organisms adapt? (3)

Answer 2

In order to:

• survive
• reproduce
• pass on alleles

Question 3

What are the 3 types of adaptation?

Explain what each are and give an example

Answer 3

• behavioural: an aspect of behaviour that enables an organism to survive and reproduce e.g. a mating ritual
• physiological: where there is appropriate functioning of the organism or its cellular processes, so it is able to survive e.g. ability to anaerobically respire
• morphological: a structure that enhances the survival of an organism e.g. spines on a cactus

Question 4

State some examples of adaptations of xerophytes (6)

Answer 4

• behavioural: close stomata when little water is available and only open them at night when there is reduced transpiration
• physiological: some have cells that store water e.g. in succulent leaves or stems for use in a shortage
• morphological:
  1. Less air spaces - increased local humidity, decreased diffusion gradient - less transpirational water loss
  2. Rolled leaves with epidermal hairs - trap moist air and lower diffusion gradient - less transpirational water loss
  3. Sunken stomata - decreases exposure to air currents and traps a layer of moist air, lowering diffusion gradient - less transpirational water loss
  4. Thicker waxy cuticle - hydrophobic - less transpirational water loss

Question 5

What are the 3 broad factors which affect distribution of organisms in their ecosystem?

Answer 5

• climatic
• edaphic (soil)
• biotic

Question 6

State 5 climatic factors which affect distribution of organisms in an ecosystem

Explain how / give examples

Answer 6

1. temperature range:

• can cause enzyme denaturation in times of fluctuation
• aquatic organisms don’t have this issue as much due to the heat capacity of water buffering fluctuations

2. availability of water:

• some plants conserve to counteract desiccation, others don’t and live in humid conditions,
• also some fish live purely in freshwater and have mechanisms to reduce osmotic gain, fish in saltwater don’t have this issue

3. Light intensity:

• some plants can grow with low light intensity, others only grow with high light intensity
• algae and hydrophytes grow on the surface of the water

4. Light quality:

• e.g. blue light passes through water where other wavelengths are absorbed
• red algae contains a red pigment to absorb this blue light and photosynthesis at greater depths

5. Day length:

• longer day length - more growth due to photosynthesis

Question 7

State 4 edaphic factors which affect distribution of organisms in an ecosystem

Explain how / give examples

Answer 7

1. pH values:

• plants like heathers can live and dominate in very low pH, cowslip etc can live in high pH
• most plants live near neutral pH

2. Availability of nutrients:

• blue-green algae grows rapidly and dominates with heightened levels of phosphates
• plants generally grow where their demands for ions are met

3. Water content:

• waterlogged soil creates anaerobic conditions
• rushes etc have air spaces in roots that allow diffusion of oxygen to supply the roots

4. Aeration of soils:

• necessary for aerobic microorganisms that decompose humus