evolution and natural selection

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Across
  1. 4. the fact or process of a species, family, or other group of animals or plants becoming extinct.
  2. 7. the change in frequency of an existing gene variant in the population due to random chance.
  3. 10. occurs when a group within a species separates from other members of its species and develops its own unique characteristics.
  4. 12. fertilization inside the body or in the external environment.
  5. 14. one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
  6. 16. the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities.
  7. 17. one of the primary methods by which biological communities are organized
  8. 19. the study of development of an embryo from the stage of ovum fertilization through to the fetal stage
Down
  1. 1. physical or behavioral feature of an animal that helps them better survive in their environment
  2. 2. the loss of genetic variation that occurs after outside forces destroy most of a population.
  3. 3. an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
  4. 5. the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin and is now believed to be the main process that brings about evolution.
  5. 6. the biological mechanism by which organisms adjust to new environments or to changes
  6. 7. the transfer of genetic material from one population to another.
  7. 8. reduction in genetic variation that results when a small subset of a large
  8. 9. a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some that can cause disease.
  9. 11. the process by which individuals compete for access to mates and fertilization opportunities.
  10. 13. the production of new organisms by the combination of genetic information of two individuals of different sexes
  11. 15. specific characteristic of an individual
  12. 18. provides a record of how creatures evolved and how this process can be represented by a 'tree of life', showing that all species are related to each other