SPECIES-

2. SPECIES- • A group of individuals that look similar and whose members are capable of producing fertile offspring.

3. The definition of species derived from two different “concepts”… 1) Morphological Species Concept: • Based on internal and external similarities and differences. • MORPHOLOGY

4. 2) Biological Species Concept; • Classification based on an organisms ability to reproduce and produce fertile offspring.

5. HYBRID: The offspring of two morphologically dissimilar organisms

6. *POPULATION- • All members of the same species that live in a particular area at the same time.

7. Within a population, individuals vary in many observable traits • These can be presented on a BELL CURVE.

8. What causes variations within species… • Environmental factors: • Amount and quality of food 2) Heredity: (3 impacts) • mutations • genetic recombination • crossing over

9. Allele Frequency and Genetic Equilibrium A population is a collection of genes GENE POOL- • A collection of genes for all the traits of a population.

10. ALLELE FREQUENCY- • The % of a specific allele of a certain gene in the gene pool GENETIC EQUILIBRIUM- • A population in which allele frequency does not change.

11. The Hardy-Weinberg Principle Weinberg: German physician Hardy: British mathematician * Observed that allele frequencies in populations remain relatively the same unless acted on by outside influences

12. Assumptions for Equilibrium: • No mutations occur • Individuals neither enter nor leave through migration • The population is large (ideally infinitely large) • Individuals mate randomly • Natural selection doesn’t occur p2 + 2pq + q2 = 1.0 DEMO PROBLEMS:

13. Disruption of Genetic Equilibrium • Mutations- • Physical change of genes or chromosomes • Produce totally new alleles for a trait • Can change the frequency of alleles

14. B. Migration- immigration: • movement into a population emigration: • movement out of a population *Gene flow- The movement of genes into or out of a population through migration.

15. C. Genetic Drift- • Allele frequency in a population changes as result of a random event

17. Genetic Drift- • Significant only in small and medium sized populations • An allele may disappear completely in a small population • More stable in larger populations

18. D. Non-Random Mating • Random mating is a requirement for genetic equilibrium • Many species DO NOT follow random mating. • Mating is influenced by a variety of factors…

19. Reasons for Non-Random Mating: • Geographic proximity • Selection based on similar physical characteristics • ASSORTIVE MATING PROBLEMS FROM NON-RANDOM MATING: • Mating may amplify certain recessive disorders.

20. E. Natural Selection- “Survival of the fittest” • Some members of a population are more likely to contribute genes

21. Types of Natural Selection

22. 1. Stabilizing Selection- • Natural selection in which individuals with the average form of a trait have the advantage.

23. 2. Directional Selection • Natural selection in which individuals with one of the extreme forms of a trait has an advantage.

24. 3. Disruptive Selection • Type of natural selection in which individuals with either of extreme forms of a trait have advantage.

25. 4. Sexual Selection- • Mate selection based on the presence of a specific trait.

26. Speciation- • The formation of a new species

27. Isolated Populations… 1. Geographic Isolation- • A physical separation of members of a population. EX: Deep canyon or body of water separating the populations

28. 2. Reproductive Isolation- • Inability of former interbreeding organism to produce offspring Prezygotic Isolation: • Obstacle occurs before fertilization Examples: • Incompatible behavior • Different mating calls • Different mating seasons

29. Postzygotic Isolation: • Obstacle occurs after fertilization Examples: • Offspring may not develop completely • Offspring may die early • Offspring may not be fertile

30. Patterns of Evolution Coevolution: • The change of 2 or more species in close association with each other • EX: Predator/prey • The interaction between bats and flowering plants (fur on bats face and flowers that are light colored)

31. Convergent Evolution • Organisms that are not closely related become more similar. • Environment selects similar phenotypes • EX: Sharks and Porposes

32. Divergent Evolution • 2 or more related species become more and more dissimilar. • Response to differing habitats Adaptive Radiation: • Related species came from a common ancestor (Darwin’s finches)

33. RATES OF SPECIATION 2 major theories regarding the rate of speciation: Gradualism: • The idea that divergence of species occurs smoothly and gradually over time

34. PUNCTUATED EQUALIBRIUM- The idea that things live in Genetic Equilibriumthen changed in short spurts of time. • Unicellular organisms may evolve in months or even day • Other evidence suggests within thousands of years

35. EXTINCTION: • The point at which no organisms of a particular species are available to reproduce • change • Disruption of habitat

36. Natural process, ongoing • Once gone, gone forever Causes: • environmental