the death of every member of a species

the formation of new species as a result of evolution

a group of organisms that are closely related and can mate to produce fertile offspring

the occurrence of hereditary or nonhereditary differences between different individuals of a population

The combination of inherited alleles is called a

physical characteristics, such as fur color

the proportion of gene copies in a population that are a given allele, expressed as a percentage

During early stages of cell division, DNA is organized into structures called

the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well-adapted individuals do; a theory to explain the mechanism of evolution

DNA is a chain of building blocks called

the process in which inherited characteristics within a population change over generations such that new species sometimes arise

one set of instructions for an inherited trait

a molecule that is made up of amino acids and that is needed to build and repair body structures and to regulate processes in the body

Proteins are made up of smaller molecules called

proteins that help speed up chemical reactions in the body

a change in the nucleotide-base sequence of a gene or DNA molecule

substances that cause genetic mutations

eggs and sperm

an inherited trait that improves an individual's ability to survive and reproduce in a particular environment