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Evolution Overview Charles Darwin. Proposed the Theory of Evolution Evolution -gradual change in a species through adaptations over time Theory of Evolution= Natural Selection. Natural Selection. Natural selection is based on the following ideas: natural variation

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evolution overview charles darwin
Evolution OverviewCharles Darwin
  • Proposed the Theory of Evolution
  • Evolution-gradual change in a species through adaptations over time
  • Theory of Evolution= Natural Selection
natural selection
Natural Selection
  • Natural selection is based on the following ideas:
    • natural variation
    • production of more offspring than can survive
    • competition for resources, and to escape predators
    • differential survival based on traits
  • Organisms with traits well suited to an environment are more likely to survive and produce more offspring than organisms without these favorable traits.
evidence for evolution
Evidence for Evolution
  • Evolution occurs over millions of years and cannot be seen in one lifetime
  • Scientists rely on evidence to support the Theory of Evolution
1 adaptations
1.) Adaptations
  • Adaptation- structure or behavior that helps an organism better survive in its environment.

Mimicry- a structural adaptation that enables one species to resemble another species.

  • Camouflage- a structural adaptation that allows a species to blend in with its surroundings

Physiological Adaptation- changes in an organism’s metabolism that occurs quickly. Many bacteria have become resistant to penicillin over the last 50 years

2 fossil record
2.) Fossil Record
  • Fossil-trace of a dead organism. Examples bones, dinosaur track, insects trapped in tree sap, impressions of leaves, animals buried in tar or ice
  • Give clues are to what ancient organisms looked like
  • Compare fossils to organisms we know today
  • Today’s species had to evolved from ancient species
3 comparative anatomy
3.) Comparative Anatomy
  • Homolgous Structures- body structures on different organisms that are similar in structure or function and evolved from the same ancestor

Analogous Structures- Body structures on different organisms that are similar in function but did not evolve from the same ancestor.


Vestigial Structures- Body structure in an organism that no longer serves its original purpose but was useful to the ancestor


Embryo- earliest stage of growth and development of both plant and animals

  • Human embryos and embryos of all other vertebrates are very similar which suggests that all vertebrates are related

Nearly all organisms have DNA, ATP, and many of the same enzymes

  • The DNA of closely related organisms looks very similar
natural selection1
Natural Selection
  • Occurs in populations over time not individuals
  • Population- all the members of a species that live in an area
  • Gene Pool- all of the alleles of the population’s genes

Genetic Equilibrium- the frequency of alleles remains the same over generations

  • Populations in genetic equilibrium are not changing so they are not evolving
  • Anything that changes the genes in the populations gene pool will cause evolution to occur
what causes changes in the gene pool
What Causes Changes in the Gene Pool?
  • 1. Mutations that occur by chance or by radiation and chemicals
  • 2. Genetic drift: frequency of alleles are changed by random events in an isolated population

3. Gene flow: the transport of genes by traveling individuals

  • 4. Non-random mating: Individuals selecting mates with specific heritable traits (sexual selection)
  • 5. Natural selection
3 conditions of natural selection
3 Conditions of Natural Selection
  • Struggle for existence: more offspring are produced than can survive so organisms compete for survival
  • Natural variation among individuals
  • Survival of the fittest
3 types of natural selection
3 Types of Natural Selection
  • Stabilizing selection: favors average individuals in a population
  • Directional selection: favors one of the extreme variations of a trait
  • Disruptive/diversifying selection: favors individuals with either extreme of a trait
  • Evolution of a new species that occurs when members of similar populations no longer breed with each other to produce fertile offspring

There are several reasons why similar populations no longer breed

    • Geographic isolation: when a physical barrier (lava from volcanic eruptions, sea level changes, etc.) divides a population

Reproductive isolation: occurs when organisms no longer breed with each other to produce fertile offspring because of

  • Differences in genes
  • Mating times change
  • Different numbers of chromosomes
how fast does speciation occur
How fast does speciation occur?
  • Gradualism: idea that species originate through a gradual change of adaptations (longer than 10,000 years)
  • Punctuated equilibrium: idea that species originate in rapid bursts (10,000 years or less) with long periods of genetic equilibrium in between
two types of evolution
Two types of evolution
  • Divergent evolution (adaptive radiation): species that once were similar become increasingly different
  • Convergent evolution: distantly related organisms evolve similar traits