here is a great site with 1800 biology questions
Pedigrees - 1
Biology teacher Andrew Douch describes evolutionary time by scaling it to fit into a single calendar year
A rap song with pictures that highlights the processes of photosynthesis
Introduction: Punnett squares allow geneticists to determine the possible genotypes of offspring when the genotypes of parents are known. The genes of one parent are arranged across the top of the square, and the genes of the other parent are arranged down the side, much like a multiplication table. The possible genotypes of offspring are also determined in a manner similar to a multiplication table - by taking the gene represented on the top and the gene represented along the side and placing both in their corresponding boxes.
By looking at characteristics of a plant or animal and using a dichotomous key, you can identify most living things to the species. In this situation the term "dichotomous" means to divide into two groups that are not alike and most dichotomous keys work by using the individuals characteristics to place the organism into smaller and smaller groups until it can be identified to the species. Dichotomous keys usually include only certain groups of organisms, like trees or butterflies. The usefulness of a key is only as good as the author's purpose. Some keys are intended to cover only the most common species, while others are very comprehensive and require extensive knowledge of biology or botany.