Hormones are see concept 45.1 (page 998) signals that must interact with dna in order to be effective always proteins produced only in response to environmental stress chemical signals between cells, transported in blood or hemolymph are all under the control of the pituitary gland

sexual reproduction produces offspring with novel combinations of genes. species that reproduce sexually must maintain two different types of individuals, males and females, which can limit the ability to colonize new habitats as both sexes must be present.

an adaptation is a change or process by which an organism takes to be better suited for its environment. for example; migration is a behavioral adaptation, this is needed because birds are not built to last extremely cold climates. there are different adaptations because there are different species needing to adjust to different things, bears don't migrate; they hibernate.