Abiotic and biotic factors and how they affect organisms and their distribution

We have been learning about Niche and competition What is a niche? A niche is the role that an organism plays within a community. What kind of resources will organisms be using in their ecosystem? Light, temperature and nutrient availability. What types of interactions occur between organisms in a community? Competition and predation.

In this section we are learning more about specific factors affecting organisms and ultimately biodiversity. Biotic and abiotic factors affect organisms and the biodiversity in environments and ecosystems Grazing, diseases, food availability and predation are biotic factors Light intensity, moisture, pH, and temperature are abiotic factors Human activities can have an impact on biodiversity Natural hazards can have an impact on biodiversity At the end of the section you should have an improved understanding of these factors and how they affect organisms, their distribution and biodiversity

Biotic factors These are factors that are living including diseases, predation, food availability, and grazing. How would these affect organisms and their distribution? (Remember you already discussed this in a previous lesson). How might these factors affect biodiversity?

Grazing What is grazing? Animals that eat plants to gain their energy are called grazers. Commonly sheep, deer and rabbits are thought of as grazers. How can these animals affect biodiversity by grazing? It depends on the type of grazer. Sheep are selective grazers. They select the more dominant competitive grasses to eat. How might this help the other plants growing in the area? The other weaker species get the opportunity to grow more so biodiversity is kept high. However too many sheep would over graze the area and reduce biodiversity.

Rabbits are relatively unselective grazers. What does this mean? By eating almost all types of plants on grassland they maintain a high diversity. The more vigorous plants are kept in check. Obviously a massive population of rabbits overgrazing an area would decrease the biodiversity.

Temperature would affect the growth rate of organisms. Abiotic factors These are factors that are non living including light intensity, moisture, pH, temperature, O2 and CO2. How might these factors affect organisms and their distribution? How might these affect biodiversity? Temperature would affect the growth rate of organisms. Why would temperature affect growth rate? All organisms rely on enzymes to control chemical reactions. As the temperature increases reactions happen faster, up to a certain point so growth could increase. At lower temperatures there will be slower growth.

pH is another factor that can affect organisms especially living in aquatic environments. Why would pH affect organisms in aquatic environments? Organisms work at their best in a small pH range. If the pH changes then the biodiversity may be affected as an organisms chances of survival may be affected. Examples of this include fish and corals growing in aquatic environments.

The affect of human activities on the distribution of organisms and biodiversity How are humans affecting the survival of plants and animals on the planet? If animal and plant numbers decrease, biodiversity decreases. If humans alter ecosystems the distribution of organisms will change. Watch Episode 2 from State of the Planet DVD. Make a note of the 5 ways humans are affecting biodiversity (with examples) as the DVD is playing.

Review Here are 2 short clips to recap some of the work on distribution of organisms vimeo.com/14105623 http://www.youtube.com/watch?v=HA3xNMJnFuo