Which of the following is true of environmental changes?
a. they cannot be caused by human activity.
b. they may affect several populations in an ecosystem.
c. they affect food chains, but not food webs.
d. they have no effect on living organisms in an ecosystem?

Which supports the idea that birds and butterflies both have wings but they do not have a common ancestor with wings? the wings are analogous structures that evolved differently and do not have a similar internal structure. the wings are homologous structures that evolved differently and do not have a similar internal structure. wings of birds are vestigial structures, but the wing structures of bats are not vestigial. wings of bats are vestigial structures, but the wing structures of birds are not vestigial.

Dwarf galaxies are select one: a. relatively rare. b. not very bright c. mostly spiral shaped. d. none of these.

Why was the sample heated in step 5? describe the chemical principles involved in the reasoning behind this step?