© 2013 Pearson Education, Inc. Lectures by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition – Eric J. Simon, Jean L. Dickey, and Jane B. Reece Chapter 13 How Populations Evolve

Biology and Society: Mosquitoes, Microbes, and Malaria In the 1960s, the World Health Organization (WHO) launched a campaign to eradicate the mosquitoes that transmit malaria. It used DDT, to which some mosquitoes have evolved resistance. © 2013 Pearson Education, Inc.

Figure 13.0

The evolution of pesticide-resistant insects is just one of the ways that evolution affects our lives. An understanding of evolution informs every field of biology, for example, –medicine, –agriculture, –biotechnology, and –conservation biology. Biology and Society: Mosquitoes, Microbes, and Malaria © 2013 Pearson Education, Inc.

CHARLES DARWIN AND THE ORIGIN OF SPECIES Biology came of age on November 24, Charles Darwin published On the Origin of Species by Means of Natural Selection, an assemblage of facts about the natural world. © 2013 Pearson Education, Inc.

Darwin made three observations from these facts. 1.Life shows rich diversity. 2.There are similarities in life that allow the classification of organisms into groups nested within broader groups. 3.Organisms display many striking ways in which they are suited for their environments. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Figure 13.1 (a) The diversity of life (b) Patterns of similarities (c) An insect suited to its environment

In The Origin of Species, Darwin –proposed a hypothesis, a scientific explanation for his observations, –used hundreds of pages in his book to describe the evidence supporting his hypothesis, –made testable predictions, and –reported the results of numerous experiments he had performed. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Darwin hypothesized that –present-day species are the descendents of ancient ancestors that they still resemble in some ways and –change occurs as a result of “descent with modification,” with natural selection as the mechanism. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Figure 13.2

Natural selection is a process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics. As a result of natural selection, a population, a group of individuals of the same species living in the same place at the same time, changes over generations. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Natural selection leads to evolutionary adaptation, a population’s increase in the frequency of traits suited to the environment. Natural selection thus leads to evolution, seen either as –a change in the genetic composition of a population over time or –on a grander scale, the entire biological history, from the earliest microbes to the enormous diversity of organisms that live on Earth today. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Natural selection leads to –a population (a group of individuals of the same species living in the same place at the same time) changing over generations and –evolutionary adaptation. In one modern definition of evolution, the genetic composition of a population changes over time. CHARLES DARWIN AND THE ORIGIN OF SPECIES © 2013 Pearson Education, Inc.

Darwin’s Cultural and Scientific Context The Origin of Species was fundamentally different from the prevailing scientific and cultural views of Darwin’s time. Let’s place Darwin’s ideas in their historical context. © 2013 Pearson Education, Inc.

The Idea of Fixed Species The Greek philosopher Aristotle held the belief that species are fixed and do not evolve. The Judeo-Christian culture fortified this idea with –a literal interpretation of the biblical book of Genesis and –the suggestion that Earth may only be 6,000 years old. Naturalists were grappling with the interpretation of fossils, imprints or remains of organisms that lived in the past. © 2013 Pearson Education, Inc.

Figure 13.3 (a) “Snakestone”(b) Ichthyosaur skull and paddle-like forelimb

Lamarck and Evolutionary Adaptations Naturalists compared fossil forms with living species and noted patterns of similarities and differences. In the early 1800s, French naturalist Jean Baptiste Lamarck suggested that life evolves, and explained this evolution as the refinement of traits that equip organisms to perform successfully in their environment. © 2013 Pearson Education, Inc.

Lamarck suggested a mechanism that we now know is wrong. Lamarck proposed that by using or not using its body parts, an individual may develop certain traits that it passes on to its offspring, thus, acquired traits are inherited. Lamarck helped set the stage for Darwin by proposing that species evolve as a result of interactions between organisms and their environment. Lamarck and Evolutionary Adaptations © 2013 Pearson Education, Inc.

The Voyage of the Beagle Darwin was born on February 12, 1809, the same day that Abraham Lincoln was born. In December 1831, Darwin left Great Britain on the HMS Beagle on a five-year voyage around the world. © 2013 Pearson Education, Inc.

Figure 13.4 Darwin in 1840 North America Great Britain Europe Asia Africa South America Cape of Good Hope Cape Horn Tierra del Fuego Australia Tasmania New Zealand HMS Beagle ATLANTIC OCEAN PACIFIC OCEAN Equator PACIFIC OCEAN Fernandina Isabela Pinta Marchena Santiago Pinzón Daphne Islands Genovesa Florenza Española Santa Cruz Santa Fe San Cristobal 40 km 40 miles 0 0 Galápagos Islands

Figure 13.4a Darwin in 1840

Figure 13.4b HMS Beagle

Figure 13.4c Equator PACIFIC OCEAN Fernandina Isabela Pinta Marchena Santiago Pinzón Daphne Islands Genovesa Florenza Española Santa Cruz Santa Fe San Cristobal 40 km 40 miles 0 0 Galápagos Islands

On his journey on the Beagle, Darwin –collected thousands of specimens and –observed various adaptations in organisms. The Voyage of the Beagle © 2013 Pearson Education, Inc.

Darwin was intrigued by –the geographic distribution of organisms on the Galápagos Islands and –similarities between organisms in the Galápagos and those in South America. The Voyage of the Beagle © 2013 Pearson Education, Inc.

Figure 13.5a

Figure 13.5b

Darwin was strongly influenced by the writings of geologist Charles Lyell. Lyell suggested that Earth –is very old and –was sculpted by gradual geological processes that continue today. The Voyage of the Beagle © 2013 Pearson Education, Inc.

Darwin reasoned that the extended time scale would allow for gradual changes to occur –in species and –in geologic features. The Voyage of the Beagle © 2013 Pearson Education, Inc.

Descent with Modification Darwin made two main points in The Origin of Species. 1.Organisms inhabiting Earth today descended from ancestral species. 2.Natural selection is the mechanism for descent with modification. © 2013 Pearson Education, Inc.

EVIDENCE OF EVOLUTION Evolution leaves observable signs. We will examine five of the many lines of evidence in support of evolution: 1.the fossil record, 2.biogeography, 3.comparative anatomy, 4.comparative embryology, and 5.molecular biology. © 2013 Pearson Education, Inc.

The Fossil Record Fossils are –imprints or remains of organisms that lived in the past –often found in sedimentary rocks. © 2013 Pearson Education, Inc.

The Fossil Record The fossil record –is the ordered sequence of fossils as they appear in rock layers, –reveals the appearance of organisms in a historical sequence, and –fits with the molecular and cellular evidence that prokaryotes are the ancestors of all life. © 2013 Pearson Education, Inc.

Figure 13.6

NZMhttps:// NZM Fossils and Evolution (5.01)

Paleontologists (scientists who study fossils) have discovered many transitional forms that link past and present. Transitional fossils include evidence that –birds descended from one branch of dinosaurs and –whales descended from four-legged land mammals. The Fossil Record © 2013 Pearson Education, Inc.

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Biogeography Biogeography, the study of the geographic distribution of species, first suggested to Darwin that today’s organisms evolved from ancestral forms. Darwin noted that Galápagos animals resembled species of the South American mainland more than they resembled animals on similar but distant islands. © 2013 Pearson Education, Inc.

Many examples from biogeography would be difficult to understand, except from an evolutionary perspective. One example is the distribution of marsupial mammals in Australia. Biogeography © 2013 Pearson Education, Inc.

Figure 13.8 Common ringtail possum Red kangaroo Common wombat Australia Koala

Historical Biogeography (6.21)

Comparative Anatomy Comparative anatomy –is the comparison of body structure between different species and –attests that evolution is a remodeling process in which ancestral structures become modified as they take on new functions. © 2013 Pearson Education, Inc.

Comparative Anatomy Homology is –the similarity in structures due to common ancestry and –illustrated by the remodeling of the pattern of bones forming the forelimbs of mammals for different functions. © 2013 Pearson Education, Inc.

Figure 13.9 HumanCatWhale Bat

vf6XqEohttps:// vf6XqEo Homologous Evolution (6.56)

Vestigial structures –are remnants of features that served important functions in an organism’s ancestors and –now have only marginal, if any, importance. Comparative Anatomy © 2013 Pearson Education, Inc.

Comparative Embryology Early stages of development in different animal species reveal additional homologous relationships. –For example, pharyngeal pouches appear on the side of the embryo’s throat, which –develop into gill structures in fish and –form parts of the ear and throat in humans. –Comparative embryology of vertebrates supports evolutionary theory. © 2013 Pearson Education, Inc.

Figure Post-anal tail Chicken embryo Pharyngeal pouches Human embryo

Figure 13.10a Post-anal tail Chicken embryo Pharyngeal pouches

Figure 13.10b Post-anal tail Human embryo Pharyngeal pouches

Molecular Biology The hereditary background of an organism is documented in –its DNA and –the proteins encoded by the DNA. Evolutionary relationships among species can be determined by comparing –genes and –proteins of different organisms. © 2013 Pearson Education, Inc.

Figure Percent of selected DNA sequences that match a chimpanzee’s DNA Chimpanzee 100% 96% 92% Human Gibbon Orangutan Gorilla Primate Old World monkey

NATURAL SELECTION Darwin noted the close relationship between adaptation to the environment and the origin of new species. The evolution of finches on the Galápagos Islands is an excellent example. © 2013 Pearson Education, Inc.

Figure (a) The large ground finch (b) The warbler finch (c) The woodpecker finch

Figure 13.12a (a) The large ground finch

Figure 13.12b (b) The warbler finch

Figure 13.12c (c) The woodpecker finch

Darwin’s Theory of Natural Selection Darwin based his theory of natural selection on two key observations. 1.All species tend to produce excessive numbers of offspring. 2.Organisms vary, and much of this variation is heritable. © 2013 Pearson Education, Inc.

Observation 1: Overproduction and competition –All species have the potential to produce many more offspring than the environment can support. –This leads to inevitable competition among individuals. Darwin’s Theory of Natural Selection © 2013 Pearson Education, Inc.

Figure 13.13

Observation 2: Individual variation –Variation exists among individuals in a population. –Much of this variation is heritable. Darwin’s Theory of Natural Selection © 2013 Pearson Education, Inc.

Figure 13.14

Inference: Unequal reproductive success (natural selection) –Those individuals with traits best suited to the local environment generally leave a larger share of surviving, fertile offspring. Darwin’s Theory of Natural Selection © 2013 Pearson Education, Inc.

Natural Selection in Action Examples of natural selection include –pesticide-resistant insects, –antibiotic-resistant bacteria, and –drug-resistant strains of HIV. © 2013 Pearson Education, Inc.

Figure Chromosome with gene conferring resistance to pesticide Insecticide application

Figure Chromosome with gene conferring resistance to pesticide Insecticide application

Figure Chromosome with gene conferring resistance to pesticide Reproduction Survivors Insecticide application

OPQhttps:// OPQ Examples of Natural Selection (8.52)

Observation: Flat-tailed horned lizards defend against attack by –thrusting their heads backward and –stabbing a shrike with the spiked horns on the rear of their skull. Question: Are longer horn length and spread a survival advantage? Hypothesis: Longer horn length and spread are a survival advantage. The Process of Science: Does Predation Drive the Evolution of Lizard Horn Length? © 2013 Pearson Education, Inc.

Prediction: Live horned lizards have longer and more widely spread horns than dead ones. Experiment: Measure the horn lengths and the tip- to-tip spread distance of side horns from the skulls of –29 killed and –155 living lizards. The Process of Science: Does Predation Drive the Evolution of Lizard Horn Length? © 2013 Pearson Education, Inc.

Results: The average horn length and spread of live lizards is about 10% greater than that of killed lizards. The Process of Science: Does Predation Drive the Evolution of Lizard Horn Length? © 2013 Pearson Education, Inc.

Figure Side horns (tip to tip) Killed Live Killed Live Rear horns Length (mm) (c) Results of measurement of lizard horns (b) The remains of a lizard impaled by a shrike (a) A flat-tailed horned lizard

Figure 13.16a (a) A flat-tailed horned lizard

Figure 13.16b (b) The remains of a lizard impaled by a shrike

Figure 13.16c Side horns (tip to tip) Killed Live Killed Live Rear horns Length (mm) (c) Results of measurement of lizard horns

s8https:// s8 Evidence for Evolution (13.03)

Evolutionary Trees Darwin saw the history of life as analogous to a tree. –The first forms of life on Earth form the common trunk. –At each fork is the last common ancestor to all the branches extending from that fork. –The tips of millions of twigs represent the species living today. © 2013 Pearson Education, Inc.

Figure Tetrapod limbs Amnion Feathers Lungfishes Mammals Amphibians Lizards and snakes Crocodiles Hawks and other birds Ostriches Amniotes Tetrapods Birds Common ancestor of lineages to the right Homologous trait shared by all groups to the right

THE MODERN SYNTHESIS: DARWINISM MEETS GENETICS The modern synthesis is the fusion of –genetics with –evolutionary biology. © 2013 Pearson Education, Inc.

Populations as the Units of Evolution A population is –a group of individuals of the same species, living in the same place at the same time and –the smallest biological unit that can evolve. © 2013 Pearson Education, Inc.

Figure (a) Two dense populations of trees separated by a lake (b) A nighttime satellite view of North America

The total collection of alleles in a population at any one time is the gene pool. When the relative frequency of alleles changes over a number of generations, evolution is occurring on its smallest scale. Populations as the Units of Evolution © 2013 Pearson Education, Inc.

Genetic Variation in Populations Individual variation abounds in all species. –Not all variation in a population is heritable. –Only the genetic component of variation is relevant to natural selection. © 2013 Pearson Education, Inc.

Figure 13.19

Variable traits in a population may be –polygenic, resulting from the combined effects of several genes, or –determined by a single gene. Polygenic traits tend to produce phenotypes that vary more or less continuously. Single-gene traits tend to produce only a few distinct phenotypes. Genetic Variation in Populations © 2013 Pearson Education, Inc.

Sources of Genetic Variation Genetic variation results from processes that both involve randomness: 1.mutations, changes in the nucleotide sequence of DNA, and 2.sexual recombination, the shuffling of alleles during meiosis. © 2013 Pearson Education, Inc.

Sources of Genetic Variation For any given gene locus, mutation alone has little effect on a large population in a single generation. Organisms with very short generation spans, such as bacteria, can evolve rapidly with mutation as the only source of genetic variation. © 2013 Pearson Education, Inc.

Analyzing Gene Pools A gene pool –consists of all the alleles in a population at any one time and –is a reservoir from which the next generation draws its alleles. Alleles in a gene pool occur in certain frequencies. © 2013 Pearson Education, Inc.

Alleles can be symbolized by –p for the relative frequency of the dominant allele in the population, –q for the frequency of the recessive allele in the population, and –p + q = 1. Note that if we know the frequency of either allele in the gene pool, we can subtract it from 1 to calculate the frequency of the other allele. Analyzing Gene Pools © 2013 Pearson Education, Inc.

Genotype frequencies can be calculated from allele frequencies (if the gene pool is stable = not evolving). The Hardy-Weinberg formula –p 2 + 2pq + q 2 = 1 –can be used to calculate the frequencies of genotypes in a gene pool from the frequencies of alleles. Analyzing Gene Pools © 2013 Pearson Education, Inc.

Figure 13.20

Figure Allele frequencies Genotype frequencies Sperm Eggs p  0.8 (R) q  0.2 (r) p  0.8 R q  0.2 r RR p  0.8 R q  0.2 r p 2  0.64 rR pq  0.16 q 2  0.04 rr pq  0.16 Rr (RR) p 2  0.64 q 2  0.04 (rr) 2pq  0.32 (Rr)

0kwhttps:// 0kw Hardy Weinberg Equilibrium (11.46)

Population Genetics and Health Science The Hardy-Weinberg formula can be used to calculate the percentage of a human population that carries the allele for a particular inherited disease. © 2013 Pearson Education, Inc.

Population Genetics and Health Science PKU –is a recessive allele that prevents the breakdown of the amino acid phenylalanine and –occurs in about one out of every 10,000 babies born in the United States. People with PKU must strictly regulate their dietary intake of the amino acid phenylalanine. © 2013 Pearson Education, Inc.

Figure INGREDIENTS: SORBITOL, MAGNESIUM STEARATE, ARTIFICIAL FLAVOR, ASPARTAME † (SWEETENER), ARTIFICIAL COLOR (YELLOW 5 LAKE, BLUE 1 LAKE), ZINC GLUCONATE. † PHENYLKETONURICS: CONTAINS PHENYLALANINE

Microevolution as Change in a Gene Pool How can we tell if a population is evolving? A non-evolving population is in genetic equilibrium, also known as Hardy-Weinberg equilibrium, meaning the population’s gene pool is constant over time. From a genetic perspective, evolution can be defined as a generation-to-generation change in a population’s frequencies of alleles, sometimes called microevolution. © 2013 Pearson Education, Inc.

MECHANISMS OF EVOLUTION The main causes of evolutionary change are –genetic drift, –gene flow, and –natural selection. Natural selection is the most important, because it is the only process that promotes adaptation. © 2013 Pearson Education, Inc.

Genetic Drift Genetic drift is a change in the gene pool of a small population due to chance. © 2013 Pearson Education, Inc.

Figure RR rr Rr RR Rr RR Rr Generation 1 p  0.7 q  0.3

Figure Only 5 of 10 plants leave offspring RR rr Rr RR Rr RR Rr rr RR Rr rr RR Rr rr Generation 1 p  0.7 q  0.3 Generation 2 p  0.5 q  0.5

Figure Only 5 of 10 plants leave offspring RR rr Rr RR Rr RR Rr Only 2 of 10 plants leave offspring RR rr RR Rr rr RR Rr rr RR Generation 1 p  0.7 q  0.3 Generation 2 p  0.5 q  0.5 Generation 3 p  1.0 q  0.0

The Bottleneck Effect The bottleneck effect –is an example of genetic drift and –results from a drastic reduction in population size. Passing through a “bottleneck,” a severe reduction in population size, –decreases the overall genetic variability in a population because at least some alleles are lost from the gene pool, and –results in a loss of individual variation and hence adaptability. © 2013 Pearson Education, Inc.

Figure Original population

Figure Original population Bottleneck event

Figure Original population Bottleneck event Surviving population

Cheetahs appear to have experienced at least two genetic bottlenecks: 1.during the last ice age, about 10,000 years ago, and 2.during the 1800s, when farmers hunted the animals to near extinction. With so little variability, cheetahs today have a reduced capacity to adapt to environmental challenges. The Bottleneck Effect © 2013 Pearson Education, Inc.

Figure 13.25

The Founder Effect The founder effect is likely when a few individuals colonize an isolated habitat. This represents genetic drift in a new colony. The founder effect explains the relatively high frequency of certain inherited disorders in some small human populations. © 2013 Pearson Education, Inc.

Figure South America Tristan da Cunha Africa

Figure 13.26a

Figure 13.26b South America Tristan da Cunha Africa

tshttps:// ts Bottleneck, Founder Effect, Genetic Drift (4.54)

Gene Flow Gene flow –is another source of evolutionary change, –is separate from genetic drift, –is genetic exchange with another population, –may result in the gain or loss of alleles, and –tends to reduce genetic differences between populations. © 2013 Pearson Education, Inc.

Natural Selection: A Closer Look Of all causes of microevolution, only natural selection promotes adaptation. Evolutionary adaptation results from –chance, in the random generation of genetic variability, and –sorting, in the unequal reproductive success among the varying individuals. © 2013 Pearson Education, Inc.

Evolutionary Fitness Relative fitness is – the contribution an individual makes to the gene pool of the next generation – relative to the contributions of other individuals. © 2013 Pearson Education, Inc.

Three General Outcomes of Natural Selection If we graph the coat color of a population of mice, we get a bell-shaped curve. If natural selection favors certain fur-color phenotypes, –the populations of mice will change over the generations and –three general outcomes are possible. © 2013 Pearson Education, Inc.

1. Directional selection shifts the overall makeup of a population by selecting in favor of one extreme phenotype. 2. Disruptive selection can lead to a balance between two or more contrasting phenotypic forms in a population. 3. Stabilizing selection favors intermediate phenotypes, occurs in relatively stable environments, and is the most common. Three General Outcomes of Natural Selection © 2013 Pearson Education, Inc.

Figure (a) Directional selection (b) Disruptive selection (c) Stabilizing selection Original population Evolved population Original population Phenotypes (fur color) Frequency of individuals

Figure 13.29a (a) Directional selection

Figure 13.29b (b) Disruptive selection

Figure 13.29c (c) Stabilizing selection

Sexual Selection Sexual selection is a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates. Sexual dimorphism is a distinction in appearance between males and females not directly associated with reproduction or survival. © 2013 Pearson Education, Inc.

Figure (a) Sexual dimorphism in a finch species (b) Competing for mates

Figure 13.30a (a) Sexual dimorphism in a finch species

Figure 13.30b (b) Competing for mates

Evolution Connection: An Evolutionary Response to Malaria We can see the results of past natural selection in present-day humans. Malaria first emerged as a serious threat to people in Africa just 10,000 years ago, –long after humans had established populations around the globe, –therefore only producing evolutionary responses in malarial regions. © 2013 Pearson Education, Inc.

Sickle hemoglobin –is a mutation that denies the malarial parasite essential access to human hemoglobin and –distorts the shape of red blood cells. Individuals with one copy of this sickle allele (heterozygotes) are relatively resistant to malaria. Individuals with two copies (homozygotes) are usually fatally ill. Evolution Connection: An Evolutionary Response to Malaria © 2013 Pearson Education, Inc.

In the African tropics, –malaria is most common and –the frequency of the sickle-cell allele is highest. Evolution Connection: An Evolutionary Response to Malaria © 2013 Pearson Education, Inc.

Figure Areas with high incidence of malaria Frequencies of the sickle-cell allele 0–2.5% 10.0–12.5% 2.5–5.0% 5.0–7.5% 7.5–10.0%  12.5% Colorized SEM Africa Asia

Figure 13.31a Areas with high incidence of malaria Frequencies of the sickle-cell allele 0–2.5% 10.0–12.5% 2.5–5.0% 5.0–7.5% 7.5–10.0%  12.5% Africa Asia

Figure 13.31b Colorized SEM

Figure 13.UN01 Frequency of one allele Frequency of alternate allele

Figure 13.UN02 Frequency of heterozygotes Frequency of homozygotes for alternate allele Frequency of homozygotes for one allele

Figure 13.UN03

Figure 13.UN04

Figure 13.UN06

Figure 13.UN07

Figure 13.UN08

Figure 13.UN09 Individual variation Overproduction of offspring Observations Conclusion Natural selection: unequal reproductive success

Figure 13.UN10 Frequency of homozygotes for one allele Frequency of heterozygotes Frequency of homozygotes for alternate allele Frequency of one allele Frequency of alternate allele

Figure 13.UN11 Original population Evolved population Pressure of natural selection Directional selectionDisruptive selection Stabilizing selection