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Changes in the genetic makeup of populations

Microevolution. Changes in the genetic makeup of populations. Natural Selection. Populations tend to overproduce offspring. Natural Selection. 2. Genetic variation exists within populations. Natural Selection.

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Changes in the genetic makeup of populations

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  1. Microevolution Changes in the genetic makeup of populations

  2. Natural Selection • Populations tend to overproduce offspring.

  3. Natural Selection 2. Genetic variation exists within populations.

  4. Natural Selection 3. Scarce resources favor the best adapted organisms in the struggle for survival.

  5. Natural Selection 4. The best adapted organisms survive and reproduce in greater numbers.

  6. Adaptation • An inherited trait that increases an org’s chance of survival and reproduction in its particular environment. Represents fitness or success

  7. Natural Selection • The environment determines success of traits • Overproduction • Genetic variation • Struggle for survival • Differential reproduction

  8. Natural Selection

  9. Hardy-Weinberg Conditions Hypothetical conditions that must exist in a population for no evolution to occur.

  10. Population Characteristics Hindrances of Evolution (Hardy-Weinberg Conditions) Large Population Random Mating Isolation Genetic Consistency Mechanisms of Evolution (Natural Conditions) Genetic Drift Natural Selection Gene Flow Mutations POPULATION SIZE MATE SELECTION INTERACTION W/ OTHER POPS GENETIC CHANGE

  11. Genetic Drift • Evolution by random chance • Blues eliminated by chance (17%) • Blues eliminated by chance (1.4%) • The smaller the population, the greater chance of genetic drift.

  12. Genetic Drift • Bottleneck Effect • Catastrophe cuts pop size leaving less variety of alleles

  13. Genetic Drift • Founder Effect • Small group emigrates to new habitat 

  14. Gene Flow • Introduction of new alleles through immigration • New traits  altered genetic makeup 

  15. Modes of Selection • Stabilizing • Environment is stable • Initially adaptive form becoming more numerous from many generations of natural selection MOST ADAPTIVE FORM RANGE OF PHENOTYPES

  16. Modes of Selection • Directional • Environment is changing (or has changed) • Formerly adaptive form is no longer adaptive • Pop evolves toward newly adaptive form MOST ADAPTIVE FORM RANGE OF PHENOTYPES

  17. Modes of Selection • Disruptive (Diversifying) • Intermediate form is undesirable and decreases in # RANGE OF PHENOTYPES MOST ADAPTIVE FORMS MOST ADAPTIVE FORMS

  18. Evolution of the Ctukis • Ctukis are creatures from a planet you’ve never heard of. • You will construct a ctuki out of a single 8½x11 sheet of paper. • Do not add any materials. • Put your names on the ctuki’s underside. • Your ctuki must be able to asexually reproduce in class (it should take no more than one minute).

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