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1 Chapter 27 Evolution of Life Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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1 1 Chapter 27 Evolution of Life Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 2 Religion and Evolution The Clergy Project ( ) lists over 13,000 Christian and Jewish clergy members who support the idea of evolution “We believe that the theory of evolution is a fundamental scientific truth, one that has stood up to rigorous scrutiny and upon which much of human knowledge and achievement rests…We ask that science remain science and that religion remain religion, two very different, but complementary, forms of truth.”

3 3 Religion and Evolution Official statements of acceptance of evolution: 1.American Jewish Congress 2.General Convention of the Episcopal Church 3.Unitarian – Universalist Association 4.United Presbyterian Church in the USA 5.United Methodist Church 6.Central Conference of the American Rabbis 7.United Church of Christ 8.Roman Catholic Church

4 4 Religion and Evolution “(T)here is no contradiction between an evolutionary theory of human origins and the doctrine of God as Creator.” - General Assembly of the Presbyterian Church “(S)tudents’ ignorance about evolution will seriously undermine their understanding of the world and the natural laws governing it, and their introduction to other explanations described as ‘scientific’ will give them false ideas about scientific methods and criteria.” - Central Conference of American Rabbis

5 5 Religion and Evolution “In his encyclical Humani Generis (1950), my predecessor Pius XII has already affirmed that there is no conflict between evolution and the doctrine of the faith regarding man and his vocation…” - Pope John Paul II “Nowadays there is nothing to debate. Evolution is a fact and, from a Christian perspective, one of the greatest of God’s works.” - Lord Harries, Bishop of Oxford

6 Theory of Evolution Evolution can be defined as “change over time” Biological evol. is a scientific theory - an idea (or several related ideas) which is supported by a large body of evidence, has yet to be shown false, and can be used to make predictions

7 7 Charles Darwin and Alfred Wallace proposed the theory of natural selection which is HOW evolution occurs The theory states: A population can change over time when individuals differ in one or more heritable traits responsible for differences in the ability to survive and reproduce Can lead to increased fitness (an individual’s adaptation to an environment, measured by its relative genetic contribution to future generations)

8 8 Evol. does not change individuals, it changes a population (all the individ.’s of a species living in the same place at the same time) Traits (= alleles) in a pop. vary among individ.’s Some traits allow the individ. to survive and reproduce better than others and are passed on to offspring

9 9 Over time, two things happen: 1.the alleles that produce the more successful phenotypes will increase in the pop. 2.the less successful alleles will become less common

10 Evidence of Evolution Evol. is supported by numerous types of evidence including: 1.Geologic evidence 2.Comparative morphology 3.Comparative embryology 4.Comparative biochemistry

11 11 Geologic Evidence Many rock layers contain fossils (remains of once living organisms that have been turned to stone) Most fossils seem to be related to known species Often, a series of changes can be traced from old fossils to younger fossils

12 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Ambulocetus50 MYA b. Basilosaurus40 MYA c. Rightwhale modern a (fossil foot): © J.G.M. Thewissen, Northeastern Ohio Universities College of Medicine.

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14 14 Comparative Morphology Is the study of similarities and differences in bodies and structures of organisms Evol. and comp. morph. can explain why: 1.Some distantly related organisms have similar morph. 2.Some closely related organisms have different morph. 3.Some structures seem to have no function

15 15 Convergent Evolution Unrelated species that have similar morph. are the result of convergent evol. Two species start off with different morph. If each species is faced with a similar ecological problem, they may come up with the same “solution” independently As their morph. changes, the result is unrelated species that appear similar

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17 17 Divergent Evolution Divergent evol. starts with related species that look very similar but are faced with different ecol. problems Over time, their body parts became modified differently to fit their own set of conditions The result is related organisms that have different morphologies

18 18 humerus ulna phalanges whalehuman bird bat cathorse radius metacarpals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 27.7

19 19 Vestigial Structures Vestigial structures are those that have no obvious function at the present time They are “leftovers” from an ancestor that did use that part

20 20 Comparative Embryology Each organism proceeds through a series of changes in form (= development) Changes in how devel. occurs produce different final morphologies (even if the initial devel. is very similar)

21 21 Comparative Biochemistry Comparisons of DNA, RNA, and proteins can reveal evolutionary relationships The similarity of the molecules implies a common starting point but the differences record change

22 Microevolution Microevolution is a change in the alleles frequencies of a pop. over time Genetic equilibrium is when allele freq.’s for a gene are not changing (= no evol.)

23 23 In order for a pop. to be in gen. equil., 5 conditions must be met: 1.No mutations –Changes in the DNA might create a new allele 2.No genetic drift –Changes due to random chance (effect can be reduced by large pop. size) 27.4 The Process of Evolution

24 24 3.No gene flow –Immigration/emigration moves individuals and their alleles in/out of a population 4.Random mating –Every individual must have the same chance of passing on their alleles 5.No natural selection

25 25 In real life, these conditions are rarely met This means microevol. occurs and the pop. moves slowly away from gen. equil. These small-scale changes in allele freq.’s are brought about by: 1.Natural selection 2.Genetic drift 3.Gene flow

26 26 Natural Selection Nat. sel. can occur in three patterns: 1.stabilizing sel. (favors the intermediates and works against the extremes) 2.directional sel. (favors one of the extremes over the intermed. and other extreme) 3.disruptive sel. (favors both extremes over the intermed.)

27 27 Stabilizing selectionDirectional selectionDisruptive selection Range of a particular characteristic (in this instance, lightness or darkness of coloration) In stabilizing selection, individuals that possess extreme values of a characteristic—here, both the lightest and the darkest colors—are selected against and die or fail to reproduce. Over succeeding generations, an increasing proportion of the population becomes average in coloration. In directional selection, one of the extremes of a characteristic is better suited to the environment, meaning that individuals at the other extreme are selected against. Over succeeding generations, the coloration of the population moves in a direction—in this case toward darker coloration. In disruptive selection, individuals with average coloration are selected against and die. Over succeeding generations, part of the population becomes lighter, while part becomes darker meaning the range of color variation in the population has increased. Time (many generations)

28 28 Percent of Births in Population Percent Infant Mortality Birth Weight (in kilograms) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

29 29 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Equus After TimeInitial DistributionAfter More Time Body Size Hyracotherium Merychippus b. Number of Individuals Number of Individuals Number of Individuals Directional Selection Figure 27.17

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32 32 Genetic Drift Genetic drift is change in a population’s allele frequencies over time, due to chance Can occur in two ways: 1.Bottleneck: Drastic reduction in pop. size – the survivors may not be representative of the original pop. 2.Founder effect: Small group of individuals start a new pop. – the founders may not be representative of the original pop.

33 33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10% of population natural disaster kills five green frogs 20% of population Genetic Drift Figure 27.14

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35 35 Gene Flow Gene flow is the movement of alleles into or out of a population by immigration or emigration It may remove rare alleles from a pop. It may introduce a new allele into a pop. It can also help keep populations of the same species similar by acting as a genetic “blender”, mixing the alleles of the pop.’s together

36 Speciation Is the formation of new species as the result of genetic divergence Gen. diverg. is the slow build-up of differences in the genes between populations Speciation can be allopatric or sympatric

37 37 Allopatric Speciation Requires two or more populations that become physically isolated from each other A geographic barrier stops gene flow between the pop.’s Over time, pop.’s undergo gen. diverg. With enough time and diverg., the pop.’s become so genetically different from each that they cannot interbreed, even if the barrier is removed

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39 39 Sympatric Speciation Occurs without members of a pop. being physically separated from each other Members form sub-groups that only breed with others in their sub-group Slowly, changes build up in the sub-groups that prevent them from breeding with other sub- groups and eventually, the sub-groups become separate species Is less common than allo. spec.

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41 41 Chapter 30 Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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