Biology – Module 1 – A Local Ecosystem
The distribution, diversity and numbers of plants and animals found in ecosystems are determined by biotic and abiotic factors.
Compare the abiotic characteristics of aquatic and terrestrial environments.
An aquatic environment is one that consists in water.
The abiotic characteristics of an aquatic environment include:
Buoyancy – This refers to the upward pressure (or thrust) that is applied on the organism by its medium. Buoyancy is determined by the density of the medium and determines the floating ability of an organism. Water provides sufficient buoyancy for many organisms, e.g., the jellyfish. If a jellyfish is taken out of ...view middle of the document...
Availability of water – In aquatic environments water availability can be a problem as osmosis occurs. Organisms are suited to a particular type of water – either fresh water or salt water. If the organism is placed in the wrong type of water they will die, thus water-availability is an issue. In this scenario, the salinity of the water is another factor.
Light penetration – Light is only able to penetrate about 100m in oceans and seas. Thus as the depth increases the light penetration decreases. Light is essential for all aquatic plants, thus the plants needed to have specific adaptations that allow them to retrieve enough sunlight to survive? The light penetration is also dependent upon water clarity.
Exposures to natural forces – Different aquatic environments are exposed to different natural forces such as tides, currents, waves etc. Marine organisms must be adapted to survive in such conditions.
A terrestrial environment is one that consists on land.
The characteristics of a terrestrial environment include:
Temperature – There are much larger temperature variations on land rather than in water. Land organisms must therefore have adaptations to cope with such large temperature changes.
Landscape position – Slope and aspect may affect temperature, water and light availability as well as impact on soil quality. Run-off and erosion may also be prominent in particular landscapes.
Rainfall and water availability – Water is not freely abundant in land. It must be sourced from the soil or consumed. Organisms must have adaptations that allow them to survive using the amount of water available to them
Salinity – Different soils have different salinity levels and only particular organisms thrive in certain salinity levels. Plants must have adaptations that enable them to cope with the different levels of salinity.
PH (acidity/alkalinity) – Soil pH can vary. Dissolved salts play an important role in determining the pH of the soil and some plants need to have a particular pH to survive. Plants need to have adaptations that allow them to cope with the pH of the soil in their environment.
Buoyancy – Air provides minimal buoyancy and therefore land organisms need to have a skeletal and muscle structures that enable them to support them.
Exposure to natural forces – Wind, rain, floods, droughts, monsoons, cyclones, storms etc. are all part of the terrestrial environment and organisms need to be able to adapt to most if not all of these forces.
Identify the factors determining the distribution and abundance of a species in each environment.
Distribution – refers to the region where an organism is found.
Abundance – refers to the number of individuals in the area and is usually described as a density.
Aquatic - There are several abiotic factors that affect abundance and distribution of organisms in aquatic environments including:
Pressure Variations – ranging from low pressures in surface...