1.4 - Interdependence & Adaptation

Organisms are well adapted to survive in their normal environment. Population size depends on a variety of factors including competition, predation, disease and human influences. Changes in the environment may affect the distribution and behaviour of organisms.

Candidates should use their skills, knowledge and understanding to:

• suggest how organisms are adapted to the conditions in which they live
• observe the adaptations, eg body shape, of a range of organisms from different habitats
• develop an understanding of the ways in which adaptations enable organisms to survive
• suggest the factors for which organisms are competing in a given habitat
• evaluate data concerned with the effect of environmental changes on the distribution and behaviour of living organisms.

B1.4.1 Adaptations

a) To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there.

b) Plants often compete with each other for light and space, and for water and nutrients from the soil.

c) Animals often compete with each other for food, mates and territory.

d) Organisms, including microorganisms, have features (adaptations) that enable them to survive in the conditions in which they normally live.

e) Some organisms live in environments that are very extreme. Extremophiles may be tolerant to high levels of salt, high temperatures or high pressures.

f) Animals and plants may be adapted for survival in the conditions where they normally live, eg deserts, the Arctic.

Animals may be adapted for survival in dry and arctic environments by means of:

• changes to surface area
• thickness of insulating coat
• amount of body fat
• camouflage.

Plants may be adapted to survive in dry environmentsby means of:

• changes to surface area, particularly of the leaves
• water-storage tissues
• extensive root systems.

g) Animals and plants may be adapted to cope with specific features of their environment, eg thorns, poisons and warning colours to deter predators.

B1.4.2 Environmental change

a) Changes in the environment affect the distribution of living organisms. 

b) Animals and plants are subjected to environmental changes. Such changes may be caused by living or non-living factors such as a change in a competitor, or in the average temperature or rainfall.

c) Living organisms can be used as indicators of pollution:

• lichens can be used as air pollution indicators, particularly of the concentration of sulfur dioxide in the atmosphere

• invertebrate animals can be used as water pollution indicators and are used as indicators of the concentration of dissolved oxygen in water.

d) Environmental changes can be measured using non-living indicators such as oxygen levels, temperature and rainfall.

Suggested ideas for practical work to develop skills and understanding include the following:

• investigations of environmental conditions and organisms in a habitat such as a pond
• ‘hunt the cocktail stick’ using red and green cocktail sticks on a green background
• investigate the distribution of European banded snails
• investigate the behaviour of woodlice using choice chambers
• investigate the effect on plant growth of varying their environmental conditions, eg degrees of shade, density of sowing, supply of nutrients
• investigating particulate levels, eg with the use of sensors to measure environmental conditions
• the use of maximum–minimum thermometers, rainfall gauges and oxygen meters
• investigating the effect of phosphate on oxygen levels in water using jars with algae, water and varying numbers of drops of phosphate, then monitor oxygen using a meter
• computer simulations to model the effect on organisms of changes to the environment.