V.C.E. Biology Unit 2

Environmental factors and adaptations

Environmental Factors

Tolerance Range – the range of a specific environmental factor, such as pH that an organism can survive in.

Limiting Factors – a requirement of an organism that is in short supply, eg. Nest sites.

Distribution – these two concepts limit the places where an organism can be found.

Adaptation – unless it changes itself in some way to survive within broader ranges or with less of a limiting factor.

Structural Adaptations

Structural adaptations are special body parts of an organism that help it to survive in its natural habitat, for example, its skin color, shape and body covering.

For example, xerophytes – arid land plants, have thicker waxy cuticles, hairs that cover the leaves, fewer stomata that are sunken in pits, reduced leaf size and orient their leaves away from the sun. All this is done to avoid water loss.

Physiological Adaptations

Physiological adaptations are systems present in an organism that allow it to perform certain biochemistry reactions.

For example: making venom, secreting slime, or being able to keep a constant body temperature.

Behavioural Adaptations

Behavioural adaptations are special ways a particular organism behaves to survive in its natural habitat

For example, many burrowing animals huddle together under ground during winter to share body heat and keep warm.

Living in Water

pH – the pH range of Australian inland waters is about 6 – 9. Organisms must be able to tolerate this range.

Temperature – this fluctuates from summer to winter, but in Australia our organisms rarely need to deal with frozen water.

Light – Blue light is able to penetrate up to 20m in clear water, but the other wavelengths diminish much earlier, limiting the spread of plants in aquatic environments.

Marine Environments

Coastal marine environments show large daily variations with the movement of the tides determining the availability of food, shelter, water, sunlight etc.

Other marine environments are also ever changing with the availability of food and water temperature changing seasonally and even daily, but the ranges tend to be less severe.

Terrestrial Environments

There are many harsh environments on land. Organisms need to be able to tolerate wide variations in water availability, temperature, light availability, soil conditions, wind conditions and the seasonal availability of food.

They have a broad range of adaptations to achieve this.

Surviving Disturbances

Australian organisms need to be able to cope with broad scale disturbances to their environment.

Flood Drought Fire – there are some special adaptations in

plants with epicormic buds, lignotubers, particularly tough seeds, but this is much harder for animals.