The three-domain system is primarily based on ____________.

Fertilization in the earthworm is accomplished by the use of the ________________.

Anatomical features that are fully developed and functional in one group of organisms but reduced and functionless in a similar group are termed ____________.

A closed circulatory system is found in _____________.

Many fireflies have flash patterns unique to their species and use them to identify other members of their species. This is an example of _____________.

The major insect body parts are ___________.

The age of the earth is estimated to be about ____________.

For natural selection to act on a population, there must be ______________.

When a natural disaster kills off a large proportion of the population, resulting in a severe reduction in the gene pool, it is called __________.

Which of the following types of genes produces an effect only in the homozygous state?