Unit 4 review chapters 22-23

1. Unit 4 review chapters 22-23 • The Darwinian view of life was in contrast to the traditional beliefs of that time • Natural selection-concept that says a population can change over generations in individuals w/heritable traits produce more viable offspring than others.

2. Evolutionary adaptation-result of natural selection; accumulation of inherited char’s that enhance an organisms’ ability to survive & reproduce in specific environments

3. Taxonomy-branch of biology for naming and classifying organisms • Carolus Linnaeus-binomial nomenclature • Fossils-sedimentary rock, remains of parts of organisms from the past • paleontology-study of fossils

4. Gradualism-geologic theory that states that profound changes in Earth’s features over the course of geologic time are the result of slow, continuous processes • Uniformitarianism-geologic processes that have shaped the earth have not changed in earth’s history

5. Lamarck-early theory of evolution; acquired characteristics could be passed on **characteristics acquired in an indiv’s lifetime cannot generally be passed on through genes Descent w/modification-Darwin’s idea that all living organisms are related by descent from a remote common ancestor

6. Both Darwin's & Lamarck's ideas regarding evolution included the interaction of organisms w/ their environment is impt in the evolutionary process.

7. Darwin’s theory of natural selection states: 1.) natural selection is the differential success in reproduction that results from the interaction b/w individuals that vary in heritable traits & their environment 2.) natural selection can produce an ↑ over time in the adaptation of organisms to their environ.

8. 3.) if an environ changes over time, or if indiv’s of a particular spp move to a new environ, natural selection may result in adaptation to these new conditions, sometimes giving rise to new spp in the process • Natural selection can only work on heritable traits

9. Natural selection is based on: • variation exists w/in populations • the fittest individuals tend to leave the most offspring • there is differential reproductive success w/in populations • Pop’s tend to produce more indiv’s than the environment can support

10. One example of humans undergoing evolution is the event of the reduction of body hair

11. Artificial selection-is when species are modified by humans (plants/animals are chosen to breed in order to maintain desired traits) • Population-group of interbreeding indiv’s who live in a specific area (smallest unit that can evolve)

12. The more similar 2 spp are the more recently they shared a common ancestor • Over time many organisms lose many structures (some deep-sea fish lose their eyes, as well as cave bats, etc…) How does natural selection account for this? • Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits

13. Darwin’s theory explains a wide range of observations; in living populations, homology, vestigial organs, molecular homologies, biogeography, & fossils • Natural selection explains changes in living pop’s: ongoing evolution of bacteria and viruses

14. Homology-related species share characteristics resulting from common ancestry (homologous structures) • Vestigial organs-no longer much use • Molecular homologies-shared charact. At the molecular level DNA • Fossils-succession in the fossil record

15. What are some examples of homologous structures? • Variation in homologous structures can be explained by the variations in the development of the structures as the embryo’s grow • Wings of a bat & arm of a human represent homology • Wings of a bird & wings of an insect do not represent homology

16. Biogeography-distribution of spp. (endemism) • ex: spp in temperate S. America looked more like plants in tropical S. America than they did the plants in temperate Europe

17. Alfred Wallace came to the same conclusions as Darwin while in Malaysia & so they came out with the “descent with modification” idea together

18. Chapter 23 • Population genetics gives a foundation for studying evolution (pop change over time) • Microevolution-smallest scale (change in pop’s from generation to generation) • Modern synthesis-a comprehensive theory of evolution that integrates ideas from many fields, such as genetics, statistics, biogeography, & paleontology

19. Gene pool-total aggregate of genes in a population at any one time (all alleles at all loci) • Fixed allele-when all members of a population are homozygous for the same allele

20. **If the blending hypothesis was true then Members of a breeding pop should become more uniform in phenotype

21. The hardy-Weinberg theorem that a population is not evolving at long as the gene frequency of a population is unchanging (Hardy-Weinberg equilibrium) • p2 + 2pg +q2 = 1 • p2 = homozygous dominant • Q2=homozygous recessive • 2pq=heterozygous

22. HW cond’s • A pop will be in HW equilibrium if there is: • a large pop, • no migration, • no mutation, • no natural selection, • & random mating occurs

23. In a Hardy-Weinberg population w/ 2 alleles, A and a, that are in equilibrium, the frequency of allele a is 0.7. What is the % of the population that is homozygous for this allele? • p + q = 1 • q=0.7 • q2 = 0.49

24. p .5 q .5 P .5 P2 .25 pq .25 pq .25 Q .5 q2 .25

25. Mutation & recombination provides the variation necessary for evolution • New genes & alleles originate by mutations (changes in nt sequence of DNA); somatic cell mutations disappear when someone dies, only mutations in cells that make gametes are passed on • **harmful recessive alleles in a sexual spp are usually found in indiv’s heterozygous for that allele

26. Point mutations • Chromosomal mutations • Most genetic differences in a pop. are due to recombination; new combinations arise each generation

27. Natural selection, genetic drift, & gene flow are 3 main factors that can alter a pop’s allele freq’s • Indiv’s better suited to the environment tend to produce more offspring

28. Genetic drift is an unpredictable fluctuation in allele freq’s from 1 generation to the next (ex: bottleneck effect, founder effect)

29. Bottleneck effect: when a small isolated pop of organisms undergo some kind of event in which only a few indiv’s from the original pop survive;thus changing the allele freq’s of the new pop • Founder effect—a few indiv’s become isolated from a larger pop establishing a new pop w/a diff gene pool

30. Polymorphic-2 or more forms of a trait in a pop (different flower colors) • Geographic variation-diff’s in gene pools, among pop’s or parts of pop’s • Cline-graded change in a trait along a geographic axis (ex: a ↓ in size of plants as you ↑ in altitude)

31. Heterozygous advantage are individuals that are heterozygous at a certain locus which gives them an advantage for survival (sickle cell disease) • Fitness-contribution an organism makes to the gene pool of the next generation relative to the contributions of other members • Ms. Douglas has a fitness of ZERO

32. There are 3 modes of selection: • Directional-one end or the other (fossils show that capybara’s have gotton smaller over time) • Disruptive-favors low/high not median (a bug has 2 very diff color patterns) • Stabalizing-favors median (a bird that produces 4-6 eggs per clutch)

33. Sexual selection– natural selection for mating success (bright colored male birds get more chicks than duller colored birds) • This can result in sexual dimorphism (big diff’s b/w sexes)

34. Often, mature males are much larger than mature females. This size difference can be attributed to: • male hormones having more effect on body size than female hormones do • intrasexual selection • females preferentially selecting larger males as mates

35. Natural selection cannot produce perfection b/c: • Evolution limited by historical restraints • Adaptations are often compromises • Chance & natural selection interact • Selection can only edit existing variations

36. Biologists are interested in preserving the diversity of living organisms on the planet. • Explain 3 of the following processes or phenomena, using an appropriate example for each. • -mutation • -adaptive radiation • -polyploidy • -population bottlenecks • -growth of human population

37. For a particular genetic locus in a population, the frequency of the recessive allele (a) is 0.4 and the frequency of the dominant allele is (A) 0.6 • What is the freq of each genotype AA, Aa, aa in this pop? What is the freq of the dominant phenotype? • How can the H-W principle of genetic equilibrium be used to determine whether this pop is evolving? • Identify a particular environmental change & describe how it might alter allelic freq’s in this pop. Explain which condition of the H-W principle would not be met.