Enduring Understanding: Change in the genetic makeup of a population over time is evolution Pearson Education, Inc.

Transcription

1 Enduring Understanding: Change in the genetic makeup of a population over time is evolution.

2 Objective: You will be able to identify the key concepts of evolution theory Do Now: Read the enduring understanding 1A

3 1677 what a year!

4 Essential knowledge: Natural selection is a major mechanism for evolution.

5 Natural Selection According to Darwin s theory of natural selection, competition for limited resources results in differential survival. Individuals with more favorable phenotypes are more likely to: Survive and reproduce more offspring Thus passing traits to subsequent generations. Evolutionary fitness is measured by reproductive success.

6 Genetic variation and mutation play roles in natural selection. Why? A diverse gene pool is important for the survival of a species in a changing environment.

7 Objective: You will be able to use mathematical concepts to show the rate and direction of evolution. Do Now:

8 Environments can be more or less stable or fluctuating This affects evolutionary rate and direction Different genetic variations can be selected in each generation

9 Objective: You will be able to use the Hardy-Weinberg formulas to determine the direction and rate of evolution. Do Now:

10 An adaptation is a genetic variation that is favored by selection and is manifested as a trait that provides an advantage to an organism in a particular environment. A genetic variation that is favored will increase each generation where an unfavorable variation will decrease. Provide an example of an adaptation for the finches on the Galapagos Islands.

11 Genotypes vs. Alleles Characterisitc = Height in pea plants Alleles are: T=Tall t = short Genotype: Homozygous dominant (TT) Heterozygous (Tt) Homozygous recessive (tt)

12 Practice Problem 500 individual wild flower plants 320 (AA) Pink 160 (Aa) Pink 20 (aa) White Find the frequencies of each genotype Find the frequencies of each allele This can tell us the changes in frequencies from one generation to the next. Both direction and rate.

13 Hardy-Weinberg Equations p + q = 1 p 2 + 2pq + q 2 = 1

14 Objective: You will be able to justify the conditions needed to maintain a population at the Hardy-Weinberg equilibrium. Do Now:

15 The Hardy-Weinberg Equilibrium Describes a population that is NOT evolving! But, in order for a population to NOT evolve, it needs to meet certain conditions Very large population No immigration/emigration (Gene flow) Random mating No mutations No natural selection

16 Name the one condition we have been following that has prevented populations from being in HW equilibrium? In addition to natural selection, chance and random events can influence the evolutionary process, especially for small populations. This is called genetic drift Is a nonselective process occurring in small populations Genetic drift describes how allele frequencies fluctuate due to chance from one generation to the next The smaller a sample, the more likely it is that chance alone will cause deviation from a predicted result

17 Figure C W C W C W C W C R C W 5 plants leave offspring C R C W C W C W 2 plants leave offspring C R C W C R C W C R C W C W C W C R C W Generation 1 p (frequency of C R ) 0.7 q (frequency of C W ) 0.3 C R C W p 0.5 q 0.5 C R C W Generation 2 Generation 3 p 1.0 q 0.0

18 Bottleneck Effect Reduction of genetic variation within a given population can increase the differences between populations Huh? Founder Effect

19 Conditions for a population to be in Hardy- Weinberg equilibrium are: Very large population or else genetic drift effects occur No immigration/emigration (Gene flow) Random mating No mutations No natural selection Work with a partner and explain why a deviation from EACH of these would cause the frequencies of alleles to change.

20 Objective: You will be able to connect evolutionary changes in a population over time to a change in the environment. Do Now: Essential knowledge: Natural selection acts on phenotypic variations in a population.

21 Environments change and act as a selective mechanism on populations. Examples: Flowering time in relation to global climate change Peppered moth

22 Connect evolutionary changes in a population over time to a change in the environment.

23 Connect evolutionary changes in a population over time to a change in the environment.

24 Phenotypic variations are not directed by the environment but occur through random changes in the DNA and through new gene combinations

25 Some phenotypic variations significantly increase or decrease fitness of the organism and the population. Examples: Peppered Moth DDT resistance in insects

26 Humans impact variation in other species. Examples: Artificial selection Loss of genetic diversity with a crop species Overuse of antibiotics

27 Objective: You will be able to evaluate evidence to support biological evolution. Do Now:

28 Essential knowledge: Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Scientific evidence of biological evolution uses information from geographical, geological, physical, chemical and mathematical applications. Molecular, morphological and genetic information of (extant) existing and extinct organisms add to our understanding of evolution.

29 Anatomy and Physiology Morphological homologies represent features shared by common ancestry.

30 Anatomy and Physiology Vestigial structures are remnants of functional structures, which can be compared to fossils and provide evidence for evolution.

31 Figure Other even-toed ungulates Hippopotamuses Pakicetus Common ancestor of cetaceans Rodhocetus Dorudon Living cetaceans Key Millions of years ago Pelvis Femur Tibia Foot

32 Fossils can be dated by a variety of methods that provide evidence for evolution. These include the: Age of the rocks where a fossil is found Rate of decay of isotopes including carbon-14 Relationships within phylogenetic trees

33 Biochemical and genetic similarities, in particular DNA nucleotide and protein sequences, provide evidence for evolution and ancestry.