biology

1. Animals with mouths that develop from or near the blastopore
5. the inner germ layer that develops into the lining of the digestive and respiratory systems
6. Echinoderms and chordates are
8. Process by which two species evolve in response to changes in each other
11. Diagram that shows the evolutionary relationships among a group of organisms
13. Ability of an organism to survive and reproduce in its environment
15. hollow ball of cells
16. the diminishing of a conditioned response; occurs in classical conditioning when an unconditioned stimulus (US) does not follow a conditioned stimulus (CS); occurs in operant conditioning when a response is no longer reinforced.
17. Change in allele frequencies in a population over generations.
18. Change over time
19. fertilized egg
20. A hypothesis that has been tested with a significant amount of data

2. study of embryos and their development
3. A scientist who studies fossils
4. the middle layer of an embryo in early development, between the endoderm and ectoderm.
7. skin and nervous system
9. Formation of new species
10. these cells migrate becoming reorganized into a hollow ball that folds inwards at one location to form a layered structure
12. A trait that helps an organism survive and reproduce
14. large-scale evolutionary changes that take place over long periods of time