Unit 9- Evolution
VOCABULARY LIST
1. Theory- A well-supported explanation of some aspect of the natural world
that can incorporate facts, laws, and tested hypotheses.
2. The process by which modern organisms have descended from ancient
organisms is evolution (change over time).
3. artificial selection- selection by humans for breeding of useful traits from
the natural variation among different organisms
4. struggle for existence- competition among members of a species for food,
living space, and the other necessities of life
5. fitness- the ability of an organism to survive and reproduce in its
environment
6. natural selection- process by which individuals that are better suited to
their environment survive and reproduce most successfully; also known as
survival of the fittest
7. descent with modification- principle that each living species has
descended, with changes, from other species over time
8. common descent- principle that all living things have a common ancestor
9. homologous structure- structures that have different mature forms in
different organisms but develop from the same embryonic tissues
10. analogous structure- same function; different structure (ex: bird wings and
butterfly wings)
11. vestigial organ- organ that serves no useful function in an organism
12. gene pool- all of the genes, including all the different alleles, that are
present in the population
13. relative frequency- the number of times that the allele occurs in a gene
pool compared with the number of times other alleles for the same gene
occur
14. phylogeny- the study of evolutionary relationships among organisms
15. cladogram- also known as “phylogenetic trees,” a diagram that shows the
evolutionary relationship among a group of organisms (Chapter 18,
section 2, pages 451-453)
16. speciation- the formation of a new species
17. reproductive isolation- when members of 2 populations cannot interbreed
and produce fertile offspring
18. behavioral isolation- 2 populations of offspring are capable of
interbreeding but don’t because of differences in courtship rituals or other
reproductive strategies (ex: the western and eastern meadowlarks share
the same habitat but have different songs to attract mates)
19. geographic isolation-2 populations are separated by geographic barriers
such as rivers, bodies of water, or mountains
20. temporal isolation- form of reproductive isolations in which 2 populations
reproduce at different time
21. anatomical homology: a similarity in physical structure among different
groups that reflects their descent from a common ancestral group
22. biogeography: the science that observes and explains the distributions of
populations, species, and ecological communities on Earth
23. developmental homology: a similarity in structure of the embryo or fetus in
different groups that reflects their descent from a common ancestral group
24. fossils: the preserved bodies, imprints, or traces of organisms which lived
in prehistoric times
25. molecular homology: a similarity in chemical compounds among different
groups that reflects their descent from a common ancestral group
26. population: a group of organisms of the same species living in the same
environment
27. species: a group of organisms with similar characteristics that can breed
and produce fertile offspring
28. adaptation: an inherited characteristic that increases an individual’s
chance for survival and reproduction
29. endosymbiont: an organism that lives and reproduces inside another
organism
30. endosymbiont hypothesis: a hypothesis developed by Lynn Margulis to
explain the complexity of eukaryotic cells
31. directional selection: selection that favors individuals with an extreme
value of some feature, so that a population will shift in one direction
32. disruptive selection: selection that tends to divide a population into two
categories
33. stabilizing selection: selection that tends to maintain some feature of a
population at an average value
34. founder effect: formation of a population which has a low level of genetic
variation due to its descent from just a few individuals
35. gene flow: gain or loss of alleles from a population due to the movement
of individuals or gametes
36. genetic drift: random loss of genes from a population