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Evolution Review Power Point The purpose of this presentation is to provide a basic overview of the concepts of evolution. The topics for review were taken.

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Presentation on theme: "Evolution Review Power Point The purpose of this presentation is to provide a basic overview of the concepts of evolution. The topics for review were taken."— Presentation transcript:

1 Evolution Review Power Point The purpose of this presentation is to provide a basic overview of the concepts of evolution. The topics for review were taken directly from the Biology Keystone Assessment Anchors and Eligible content. Content for this lesson was derived from online sources and the Pearson, Prentice Hall Biology: Exploring Life book (pages listed correspond to this book) You are NOT required to review this presentation we just felt it would be helpful for those who were not taught this information or who need a review.

2 Evolution Mechanisms and Evidence Chapters 14.2, 14.4, 15.1, 15.2, 15.3 Pages 299-304, 314-315, 310-316, & 324-340

3 Objectives Explain how natural selection can impact allele frequencies of a population Describe the factors that can contribute to the development of new species (e.g., isolating mechanisms, genetic drift, founder effect, migration). Explain how genetic mutations may result in genotypic and phenotypic variations within a population. Interpret evidence supporting the theory of evolution (i.e., fossil, anatomical, physiological, embryological, biochemical, and universal genetic code). Distinguish between the scientific terms: hypothesis, inference, law, theory, principle, fact, and observation.

4 Populations and Gene Pools A biological population is a local group of individuals belonging to the same species Smallest level at which evolution can occur

5 Individuals and Evolution Natural selection acts on individuals AND affects reproductive success Natural selection ONLY becomes clear when an entire population is tracked over time

6 Evolutions of Populations Gene pool - all of the alleles in all the individuals that make up a population Reservoir from which the next generation draws its genes…..where genetic variation (raw material of evolution) is stored.

7 Changes in Gene Pools Mutations & sexual recombination lead to genetic variation….& are RANDOM Natural selection (evolution) is NOT random Environment favors genetic combinations that increase survival and reproductive success

8 Changes in Gene Pools Some alleles may become more common in the gene pool Change in frequency of alleles – Usually expressed as decimal or percentage

9 Changes in Gene Pools Be the bird eat the bug – Activity shows how allele frequencies change overtime online/evolution/what-is- evolution/natural-selection-game/the- evolution-experience.html

10 Changes in Gene Pools Microevolution – evolution on the smallest scale – a generation-to- generation change in the frequencies of alleles within a population. Evolution based on genetic changes

11 Changes in Gene Pools Populations that do not undergo change to their gene pools are not presently evolving….. Hardy-Weinberg equilibrium Frequency of alleles in that gene pool are constant over time. Natural populations don’t stay in this for long

12 Genetic Drift Genetic drift – change in the gene pool of a population due to chance. All populations subject to some Smaller populations are impacted more by genetic drift….in smaller populations allele frequencies can vary from one generation to the next

13 Genetic Drift Bottleneck Effect Genetic variation in a population decreases significantly due to a drastic reduction of population size (and gene pool).

14 Genetic Drift Bottleneck Effect May be due to disasters (earthquakes, floods, droughts, and fires) Could reduce the ability of population to adapt to environmental change

15 Genetic Drift Founder Effect Change relates to genetic makeup of the founders of the colony A few individuals colonize a new habitat (isolated island, lake, etc.) Smaller colony, less genetic makeup diversity than that of the larger population Chance reduces genetic variation Finches of Galapagos Islands

16 Gene flow Gene flow –exchange of genes between populations Occurs when fertile individuals (or gametes) migrate between populations Reduces genetic differences between populations. Can mix neighboring pops into a single pop w/common gene pool

17 Mutation p.314 Natural selection, genetic drift, or both can influence whether the frequency of a new mutation increases in a population If mutation is beneficial allele increases If mutation is harmful allele decreases

18 Mutation Key role in evolution as the original source of genetic variation that is the raw material for natural selection. Esp important as a source of variation in asexually reproducing organisms (bacteria) In sexually reproducing organisms variation is mostly due to scrambling of existing alleles

19 Genetic drift, gene flow, and mutation can cause microevolution (changes in allele frequencies) Do NOT necessarily lead to adaptation

20 Natural Selection and Fitness p.314-315 Natural selection = blend of chance and sorting Chance… from mutation and sexual recombination of alleles -> genetic variation…RANDOM Sorting … accomplished by differences in reproductive success… NOT random

21 Natural Selection and Fitness Fitness – contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals. Individuals whom are more fit/healthy or well adapted to their environment are more likely to survive to pass on genes to offspring.

22 Speciation 15.1 p. 324-330 Speciation – formation of new species

23 Development of New Species 4 factors that lead to Speciation 1. Behavioral/Reproductive Isolation 2. Geographic Isolation 3. Migration 4. Genetic Drift Founder effect

24 Behavioral Reproductive Isolation p. 325-326 Timing – different breeding seasons Behavior - Two populations are capable of interbreeding, but they have different behaviors that prevent them from breeding.

25 Behavioral Reproductive Isolation p. 325-326 Habitat – species adapted to different habitats in the same general area. Ex. one fish adapted to living along lake edge others to open water. Others – reproductive structures incompatible, reproductive facilitators (insects) may only frequent one species, zygote may fail to develop.

26 Geographic Isolation p. 327-328 Form of reproductive isolation in which two populations are separated physically. Steps: 1. Start with an interbreeding population of one species. 2. The population becomes divided by a physical barrier. This can happen when some of the population migrates or is dispersed, or when the geography changes catastrophically (e.g., earthquakes, volcanoes, floods) or gradually (erosion, continental drift). 3. The two populations can over time change relative to each other, because each population has slightly different gene pools (random), different environments with different food sources, shelter, predators, and each gene pool undergoes its own mutation and natural selection. 4. Even if the barrier is removed and the two populations meet again, they are now so different that they can no longer breed. They are reproductively isolated and are two distinct species.

27 Geographic Isolation p. 327-328 Examples: A pond dries up to make two ponds. A river is re-routed through a field. A new road goes up. A few seeds stuck on a bird’s feather fall on a new island. A flood washes a few lizards or insects to an island.

28 Geographic Isolation

29 Development of New Species 4 factors that lead to Speciation 3.Migration: Movement of animals from one place to another. Changes the gene pool of a population when animals with different genes enter or leave. 4.Genetic Drift: Random change in allele frequencies that occurs in small populations. Founder effect: Extreme example of genetic drift. Change in allele frequencies as a result of the migration of a small group in a population. If a population begins with a few individuals—and one or more carry a particular allele—that allele may come to be represented in many of the descendants.

30 Rate of Speciation Punctuated Speciation – evolutionary model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change. *NOTE: relatively rapid change here is referring to GEOLOGIC time. So these changes still take a very long time to occur if we were to measure this compared to a human life span.


32 Fossil 14.2 p 299-300 15.3 Fossils typically form in sedimentary rock Oldest layers tend to be at the bottom of a series of bands of rock and therefore oldest organisms are typically found in the deepest (bottom) layers.

33 Fossil 14.2 p 299-300 15.3 Fossil evidence shows that ancient whales evolved from ancestors with hind limbs. Whales today have the remains of what appear to be hipbones but do not have hind limbs.

34 Fossil 14.2 p 299-300 15.3 Fossils provide scientists with information about ancient animal’s structures, behaviors, feeding patterns, etc. Within the fossil record scientists have found evidence of organisms changing over time.

35 Anatomical and Physiological 14.2 p. 301 Homologous structures – similar structure found in more than one species that share a common ancestor The front limbs of primates, cats, whales, and bats all have similar arrangements of bones even though they each use these front limbs in different ways.

36 Anatomical and Physiological 14.2 p. 301 Vestigial structures – remnant of a structure that may have had an important function in a species’ ancestors, but has no clear function in the modern species. Ex. Whales today have small vestigial hipbones but lack hind legs

37 Embryological 14.2 p. 302 15.2 p. 333 Embryos of closely related organisms often have similar stages in development

38 Biochemical and Universal Genetic Code 14.2 p. 303 Siblings have similar DNA and protein sequences Sequences of unrelated individuals of the same species show more differences Likewise, species with similar DNA and protein sequences probably had a common ancestor The greater the number of differences the less likely they are to share a close common ancestor

39 Distinguish between the scientific terms Hypothesis – suggested, testable answer to a well-defined scientific question Inference – logical conclusion based on observations

40 Distinguish between the scientific terms Law – governs a single action or situation, generalizes observations made about that action or situation Theory – explanation of an entire group of phenomena (much more broad, complex, and dynamic); explains many related observations and is well supported by scientific evidence

41 Distinguish between the scientific terms Law – a descriptive statement or equation that reliably predicts events under certain conditions Theory – well-tested explanation that makes sense of a great variety of scientific observations Principle – “a rule or law concerning a natural phenomenon or the function of a complex system; ‘the principle of the conservation of mass”’ -

42 Distinguish between the scientific terms Fact – a reality or truth Observation – use of the senses to gather and record information about structures or processes in nature

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