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  • Evolution – the process of biological change in a species by which descendants come to differ from their ancestors
  • Species – a group of organisms so similar to one another that they can reproduce fertile offspring
  • Population – all the individuals of a species that live in an area
  • Carolus Linnaeus :
  • 1700’s
  • Proposed a system of organization of all living things based on physical similarities
  • Proposed that organisms might have arisen from crossing between two similar species
  • Ex. – a mustang can mate with a miniature horse and produce a pony that an reproduce because the parents are from the same species; a horse and donkey can mate but the mule produced will not be fertile
  • Jean-Baptiste Lamarck :
  • 1809
  • Believe in decent from common ancestry
  • Proposed that organisms have a tendency towards perfection and needed to change to better fit their environment
  • Through selective use and disuse of organs, organisms acquired or lost certain traits during their lifetime
  • By passing on these acquired traits to their offspring, a species can change over time
  • Acquired trait – a characteristic which develops in your life time (such as throwing a baseball far)
  • Charles Darwin :
  • Took 5 year voyage to Galapagos Island
  • Noticed tortoises’ difference in shape of shell and how the variations of finches were suited to their environment and diet
  • Theory of Natural Selection :
  • In a population there are variations
  • Populations tend to overpopulate
  • Organisms with the best variation will be better suited to the environment and survive
  • Survival of the fittest :
  • Fitness- measure of ability to survive and produce the most offspring
  • Those members of the population with the best natural variations (adaptations) will survive and pass those traits onto their offspring
  • Adaption– feature that allows an organism to better survive in its environment
  • Fitness is measured in the number of grandchildren someone has
  • Ex. – a person who lives to be 60 with 20 grandchildren is more fit than a person who lives to be 100 but has no children

Natural Selection / Artificial Selection
The environment acts as the selecting agent / Process where humans change a species by breeding it for certain traits
  • Proof of Evolution
  • Fossils – trace of an organism that existed in the pasts such as dinosaur footprints or an imprint in a rock or bones
  • The earth is 4.6 billion years old
  • Embryology
  • Anatomy
  • Thomas Malthus :
  • Stated that whenever a population gets too large, there are limited resources available to them
  • Sooner or later, there will not be enough space, food or water
  • War, famine and disease are the only forces to keep the population size from outdistancing food supply
  • Darwin’s theory of natural selection was influenced by this idea
  • Homologous vs. Analogous Structures

Homologous Structures / Analogous Structures
Same structures but different functions
/ Have same function but different structure and occupy the same niche

  • Vestigial Structure – structures which no longer have a function to an organism
  • Ex. Appendix, hair, coccyx, wisdom teeth
  • Population – all the individuals of the same species in a given area
  • ex: You are a population of Biology students in room A46.
  • Gene Pool – the combined alleles (different form of the gene individuals in a population)
  • Allele frequency – measure of how common an allele is in the population
  • Mutation – a random change in the DNA of a gene
  • Gene mutations are inheritable if in gamete
  • SPONANEOUS
  • Recombination – due to meiosis, new combinations of chromosomes and therefore genes may occur
  • Factors that can change allele frequency:
  1. Gene Flow
  2. The movement of alleles from one population to another
  1. Genetic Drift
  2. In a small population, a particular allele may occur more or less frequently even though it was purely due to chance; leads to a loss of variation in a population
  3. Ex: Amish population and polydactylism
  1. Bottleneck effect
  2. Effect of a destructive event that leaves a few survivors in a population (form of Genetic drift)

  1. Sexual Selection
  2. Certain traits increase the likelihood of finding a mate and therefore passing on genes (fitter)
  3. Ex: Why the pale peacock is so colorful.
  • Reproductive Isolation - occurs when members of different populations can no longer mate and produce successfully with each other.
  • Geographic Isolation – a physical barrier such as a river or mountains, separates two populations resulting in eventual reproductive isolation.
  • Behavioral Isolation – isolation caused by differences in courtship or mating behaviors
  • Scents, dances, songs, signals

  • Coevolution – two totally unrelated species evolve in response to changes in each over time
  • Ex: Bees see yellow and blue, thus most bee pollinated flowers are blue and yellow
  • Gradualism – evolution is a constant process and occurs at a steady rate
  • Punctuated equilibrium – periods of equilibrium followed by rapid periods of change
  • Changes occur with environmental pressures
  • Species arise quickly and then have long periods of little change

  • Convergent evolution – occurs when unrelated organisms occupy the same niche and tend to have similar characteristics (analogous structures)
  • Ex: shark and dolphin
  • Divergent evolution – closely related species evolved in different directions, becoming increasingly different
  • Ex: dogs share a common ancestry with the wolf.