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Principles of Evolution :

Principles of Evolution :. 1. Natural Selection. Require a “struggle for existence” Occurs at individual level “nature” selects individuals to die or survive Traits better adapted for their environment become more common.

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Principles of Evolution :

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  1. Principles of Evolution:

  2. 1. Natural Selection • Require a “struggle for existence” • Occurs at individual level • “nature” selects individuals to die or survive • Traits better adapted for their environment become more common

  3. 2. Adaptation: any heritable characteristic which improves an organism’s chance of survival • Does not arise in an individual • Requires variation • Individuals selected for/against based on their adaptations

  4. 3. Fitness: the ability of an organism to survive and reproduce • Measured by relative contribution to gene pool • Survival of the Fittest: individuals best adapted to the environment survive and reproduce

  5. 1. Variation: pheno/genotypic differences between members of the same species

  6. 2. Struggle for Existence: the competition for needed resources/reproduction

  7. 3. Fitness: the ability to survive and reproduce – based on genetic contribution to gene pool

  8. 4. Adaptation: inherited characteristics that improve an organism’s chances of survival

  9. 5. Survival of the Fittest: the organisms best adapted to their environmental conditions survive and reproduce

  10. 6. Natural Selection: organisms displaying the best adaptations/traits become more common over generations

  11. Populations: units of evolution • Individuals do not evolve in a lifetime -Nature selects some for survival some for death based on traits * Rate of evolution = change in certain allele prevalence • Gene pool: collection of genes in a population at a given time

  12. Mutation: change in nucleotide sequence of DNA • Typically harmless • If it affects protein = harmful • Rarely beneficial • Leads to variations • Usually not heritable, unless it happens in gametes

  13. Evidence For Evolution:

  14. 1. Fossil Evidence -Supports the theory – especially in aquatic organisms -many holes still in the fossil record

  15. 2. Homologous Structures: similar structures with different functions/same embryological origin

  16. 3. Vestigial Organs: organs/structures which have lost function over geological time

  17. 4. Embryological Similarities: all vertebrates have similar embryological development

  18. 5. Radiometric Dating: the use of radioactive elements to calculate the age of geological substances • Half life: the length of time required for half of the radioactive atoms in a sample to decay into non-radioactive atoms • Ex: Carbon-14 decays to form carbon 12 (5730 years) – comparing the amount of C14 to C12 allows us to age samples

  19. 6. DNA similarities: genomic data indicate that all life forms are closely related to one another Ex. Humans and Bananas share 50% of the same DNA -Humans and Chimps= 98.5%

  20. Types of Evolution:

  21. Adaptive Radiation: process of a single species or small group evolving into a diverse group of organisms

  22. Convergent Evolution: unrelated organisms come to resemble one another

  23. Coevolution: process by which two species evolve in response to changes in each other

  24. Gradualism: life is in a constant, small state of flux and small changes evolve slowly into large differences

  25. Punctuated Equilibrium: life is stable, for long periods of time but is interrupted with periods of dramatic change

  26. Speciation:creation of new species Species: a group of individuals which bear similar characteristics, can breed with one another, and produce viable offspring Two Types of Speciation:

  27. 1. Allopatric Speciation: a population is separated and their genes drift apart • Only occurs if environmental differences are significant • Genetic Drift: change in allele frequency in a population

  28. 2. Sympatric Speciation: new species arise in the same area - Arises due to changes in sexual selection and habitat preference

  29. Genetic Drift: in populations, one allele becomes more common in descendents

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