Global Community

When all the food chains in a habitat are joined up together they form a food web. Here is an example of a food web

Although it looks complex, it is just several food chains joined together. Here are some of the food chains in this food web:

grass → insect → vole → hawk

grass → insect → frog → fox

grass → insect → vole → fox

Grass→Grasshopper→Frog→Hawk       Producer   Consumer   Consumer   Consumer     Primary consumer   Secondary consumer   Tertiary consumer     Herbivore   Carnivore   Carnivore

food chain shows the different organisms that live in a habitat, and what eats what.

DNA  is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C).

Without genetic variation, some of the basic mechanisms of evolutionary change cannot operate.

There are three primary sources of genetic variation,

Mutations are changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations.

Gene flow  is any movement of genes from one population to another and is an important source of genetic variation.