| A | B |
|---|
| perpetual change | the earth is neither constant or cycling but always changing |
| ventral | front side |
| homologous structure | structure that is similar in different groups of animals but may have different function |
| vestigial structure | a structure with a reduced function;usually smaller in size than in ancestor. |
| gradualism | evolution that occurs at a slow pace |
| natural selection | organisms that are most fit are more likely to survive and reproduce |
| gene flow | occurs due to immigration and emigration |
| genetic drift | a random event that alters the allelic frequencies in a population |
| eukaryotic | having a nucleus and membrane-bound organelles |
| endocytosis | engulfing large molecules |
| exocytosis | large molecules leave the cell |
| binary fission | splitting into 2 identical cells |
| conjugation | exchange of DNA / genetic material |
| asconoid | simplest body plan in sponges |
| synconoid | body walls are folded; one opening for water to exit |
| leuconoid | body wall has many folds and many openings for water to enter and exit |
| osculum | opening on sponge for water to exit |
| spongocoel | sponge body cavity |
| sessile | does not move |
| choanocytes | ciliated cells that move water |
| polyp | body plan in which tentacles face up |
| medusa | body plan in which tentacles face down |
| cephalization | sensory structures located at the anterior end |
| acoelomate | no body cavity |
| diploblastic | two tissue layers |
| triploblastic | three tissue layers |
| pharnyx | throat |
| cuticle | in roundworms, structure that protects worm from host's digestive enzymes |
| tegument | in flatworms, structure that protects worm from host's digestive enzymes |
| pseudocoelomate | body cavity without linings |
| coelomate | body cavity with linings |
| dioecious | a distinct male and female |
| monoecious | organism produces both sperm and eggs |
| dimorphism | having 2 different appearances (ex. males are smaller than females) |
| radula | structure used by gastropods to scrape / chew leaves |
| closed circulatory system | blood is confined to vessels |
| open circulatory system | blood is not confined to vessels |
| visceral mass | contains a mollusk's internal organs |
| mantle | secretes a mollusk's shell |
| Platyhelminthes | the flatworms |
| Nematoda | the roundworms |
| cnidocytes | stinging cells (jellyfish, coral) |
| nematocyst | harpoon-like structure used to stun or paralyze prey (jellyfish, coral) |
| direct life cycle | parasite does not have an intermediate host |
| indirect life cycle | parasite requires intermediate host(s) |
| one-way digestive tract | food move from anterior to posterior direction |
| two-way digestive tract | food enters through same opening that waste products exit |
| anterior | head end |
| posterior | tail end |
| dorsal | back side |
| common descent | organisms descended from a common ancestor |
| septum | separates the segments in annelids |
| clitellum | ring-like structure on outer surface of earthworm; involved in reproduction |
| annelids | segmented worms |
| cuticle | in annelids, a mucus coating that helps retain moisture |
| cuticle | in nematodes, an outer covering that protects the animal from the host's digestive enzymes |
| tegument | in flatworms, the outer covering that protects it from the host's digestive enzymes |
| gizzard | grinds food |
| crop | moistens food |
| nacreous layer | innermost layer of mollusk's shell; mother-of-pearl |
| seminal receptacle | in annelids, receives sperm from another worm |
| seminal vessicle | in earthworms, stores sperm produced by the testes |
| aortic arches | another term for the earthworm's hearts |
