Any species cannot live everywhere because this would effect the natural balance. Also one species cannot adapt to all the different environments of our planet. For example a marine creature can only live underwater and cannot live on ground.

2. Explain how the activities of some species can lead to:

b) a decrease in the population size of another species.

Some species act as population controllers of other species. There must be a 'balance' between the two and this is important to a healthy landscape. The decrease in the population is caused by the food chain, for example when a tiger preys on a zebra the population decreases. The increase of the population of a species is caused by the predator when it stops feeding on a species lower than the predator in the food chain. So when the predator stops or reduces the amount of feeding on a species, the population of the species would start to increase.

3. It is seldom possible to count all the individuals in a given space. Explain one method by which biologists can study population densities without obtaining such data.

Scientist barely ever count the amount of individuals in a certain area because it wo

10. Describe how their non-living environment affects organisms and how organisms can affect their non-living environment.

Community: is a group of individuals in an area

A pond or aquarium may contain some microhabitats and different microenvironments. For example, one might be the microhabitat on a plant, and this would contain all sorts of bacteria and other small life forms.

13. Write brief essay on a major environmental problem facing our world today.

The Greenhouse effect is mainly caused by the use of fossil fuels and other chemicals that are released into the air. The amount of carbon dioxide in the atmosphere has nearly doubled during the past one hundred years. The main problem which has caused this is the excessive use of fossil fuels and the number of trees that are cut down has made the problem worse. As trees remove carbon dioxide from the air as a part of their natural processes but humans are cutting down too many forests and too much usage of fossil fuels. As humans have been cutting down trees, the capacity of trees to remove carbon dioxide from the air has heavily decreased.

Some common words found in the essay are:
, HAWK HERBIVORE, Global Warming, Effect' Greenhouse, Polar Ice, United Nation's, fossil fuels, food chain, global warming, Meteorological Office, carbon dioxide, food web, earth's temperature, sea level rise, caused fossil fuels, increase earth's temperature, remove carbon, survival society, greenhouse effect, dioxide air, usage fossil fuels, food chain predator,
Approximate Word count = 1379
Approximate Pages = 6 (250 words per page double spaced)