Biology Chapter 17/18

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Across
  1. 4. structure that is inherited from ancestors but has lost much or all of its original function
  2. 6. trait controlled by one gene that has two alleles
  3. 7. all the genes, including all the different alleles for each gene, that are present in a population at any one time
  4. 8. random change in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common in a population
  5. 12. structures that are similar in different species of common ancestry
  6. 13. a group of homeotic genes clustered together that determine the head to tail identity of body parts in animals. All of these contain the homeobox DNA sequence
  7. 15. when individuals select mates based on heritable traits
  8. 16. formation of a new species
  9. 18. form of reproductive isolations in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding
  10. 19. preserved remains or traces of ancient organisms
  11. 23. how well an organism can survive and reproduce in its environment
  12. 26. form of natural selection when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
  13. 27. body parts that share a common function, but not structure
  14. 28. change over time: the process by which modern organisms have descended from ancient organisms
  15. 29. natural selection in which individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve
Down
  1. 1. principle that states that allele frequencies in a population remain constant unless one or more factors cause those frequencies to change
  2. 2. selective breeding of plants and animals to promote the occurrence of desirable traits in offspring
  3. 3. the study of past and present distribution of organisms
  4. 5. the movement of genes into or out of a population
  5. 9. trait controlled by two or more genes
  6. 10. form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains, or bodies of water, leading to the formation of two separate subspecies
  7. 11. form of natural selection in which individuals near the center of a distribution curve have higher fitness than individuals at either end of the curve
  8. 14. change in allele frequencies as a result of the migration of a small subgroup of a population
  9. 17. process by which organisms that are most suited to their environment survive and reproduce most successfully; also called survival of the fittest
  10. 20. form of reproductive isolation in which two or more species reproduces at different times
  11. 21. situation in which allele frequencies in a population remain the same
  12. 22. a change in allele frequency following a dramatic reduction in the size of a population
  13. 24. the number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene
  14. 25. heritable characteristic that increases an organism’s ability to survive and reproduce in an environment