Evolution and natural selection

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Across
  1. 8. something an animal does usually in response to some type of external stimulus in order to survive.
  2. 10. process that results in the adaptation of an organism to its environment by means of selectively reproducing changes in its genotype, or genetic constitution.
  3. 11. any cell or organism that possesses a clearly defined nucleus.
  4. 13. an organism combines the genetic information from each of its parents and is genetically unique.
  5. 16. the introduction of genetic material (by interbreeding) from one population of a species to another, thereby changing the composition of the gene pool of the receiving population.
  6. 17. an individual that possesses characteristics different from the others of the same kind.
  7. 19. defined as organisms that are microscopic, unicellular, independently reproducing, and mostly free-living.
  8. 20. describes how the individuals are distributed, or spread throughout their habitat.
Down
  1. 1. an extreme example of genetic drift that happens when the size of a population is severely reduced.
  2. 2. type of structural modification made to a part of the body.
  3. 3. organisms best adjusted to their environment are the most successful in surviving and reproducing.
  4. 4. when a group within a species separates from other members of its species and develops its own unique characteristics.
  5. 5. the reduction in genomic variability that occurs when a small group of individuals becomes separated from a larger population.
  6. 6. a type of cell that does not have a true nucleus or membrane-bound organelles.
  7. 7. a type of asexual reproduction where a parent cell divides, resulting in two identical cells, each having the potential to grow to the size of the original cell.
  8. 9. one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
  9. 12. involves one parent and produces offspring that are genetically identical to each other and to the parent.
  10. 14. the change in frequency of an existing gene variant in the population due to random chance.
  11. 15. the complete disappearance of a species from Earth.
  12. 18. the adjustment of organisms to their environment in order to improve their chances at survival in that environment.