BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections Evolution Lesson I Modules 13.1 – 13.3

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Evolution Evolution is genetic change in a population over time. Charles Darwin was the first scientist to propose the theory of evolution, in 1859.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin was born in In 1831, he was on a boat that was mapping coastlines, the HMS Beagle. He studied plants and animals on the Galapagos Islands The Voyage of the Beagle EVIDENCE OF EVOLUTION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin observed: –similarities between living and fossil organisms –the diversity of life on the Galápagos Islands, such as finches (birds) and giant tortoises Figure 13.1A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin concluded that: –The Earth was old and constantly changing (4.6 billion years old) –Living things also change (evolve) over generations. –Living things are related to animals and plants that used to exist but are now extinct.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Evidence for Evolution Fossils Biogeography Comparative Anatomy Comparative Embryology Molecular Biology

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fossils are the preserved remains of dead organisms. They show how life has changed over time. Examples: –Hominid skull: an early relative 13.2 Fossils Figure 13.2A, B –Petrified trees: trees turned to stone

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Ammonite casts: 375 million year old aquatic organisms –Fossilized organic matter in a leaf: molecular and cellular structures are preserved. Figure 13.2C, D

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Scorpion in amber: 30 million years old, intact DNA –“Ice Man”: 5,000 years old, cells and DNA preserved. Figure 13.2E, F

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The fossil record shows that organisms have appeared in a historical sequence Many fossils link early extinct species with species living today Figure 13.2G, H

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biogeography Biogeography is the geographic distribution of species (where animals live). Plants and animals in different parts of the world are related because they share common ancestors.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Comparative Anatomy Anatomical similarities among many species show signs of common descent. Humans, cats, whales, and bats have the same skeletal elements because we all evolved from a common ancestor. Human CatWhaleBat

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Comparative Embryology Closely related organisms often have similar stages in their embryonic development. Fish, frogs, snakes, birds, apes, and people all have pharyngeal slits as embryos which develop into either gills or lungs. We are all related!

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Molecular Biology Scientists can compare DNA sequences and amino acid sequences between species to see how closely related we are. Humans and chimps share 98.5% of their DNA.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin observed that –organisms produce more offspring than the environment can support –organisms vary in many characteristics –these variations can be inherited Natural Selection

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Natural Selection Darwin concluded that individuals best suited for a particular environment are more likely to survive and reproduce than those less well adapted Aka: survival of the fittest (giraffe example)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin saw natural selection as the basic mechanism of evolution –As a result, the proportion of individuals with favorable characteristics increases –Populations gradually change in response to the environment –Phenotypes that are better reproduce more, eventually, better genotypes become more common.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Darwin also saw that when humans choose organisms with specific characteristics as breeding stock, they are performing the role of the environment –This is called artificial selection –Example of artificial selection in plants: five vegetables derived from wild mustard Figure 13.4A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Example of artificial selection in animals: dog breeding Figure 13.4B German shepherdYorkshire terrier English springer spaniel Mini-dachshundGolden retriever Hundreds to thousands of years of breeding (artificial selection) Ancestral dog

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings These five canine species evolved from a common ancestor through natural selection Figure 13.4C African wild dog CoyoteFoxWolfJackal Thousands to millions of years of natural selection Ancestral canine

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A species is a group of populations whose individuals can interbreed and produce fertile offspring –People (and animals) are more likely to choose mates locally Populations are the units of evolution Figure 13.6

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A gene pool is the total collection of genes in a population at any one time Microevolution is a change in the relative frequencies of alleles in a gene pool New mutations are constantly being generated in a gene pool, by accident or as a response to environmental changes Microevolution

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings What causes evolution? Genetic drift Bottleneck Effect Founder Effect Gene Flow Mutation

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Genetic drift is a change in a gene pool due to chance –Genetic drift can cause the bottleneck effect: an event that drastically reduces population size (fire, flood, earthquake) Genetic Drift Figure 13.11A Original population Bottlenecking event Surviving population

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Genetic drift… If a population is very diverse and something bad happens, at least a few individuals will survive. These individuals will then reproduce and the species will evolve, or change.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –The founder effect is when some individuals leave a population and start living somewhere new. –Only a few people or animals leave, and the new population will be closely related to due lack of genetic diversity. Figure 13.11B, C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gene flow can change a gene pool due to the movement of genes into or out of a population (new organisms move in or leave) Mutation changes alleles, these are random changes in DNA that can create new proteins or new characteristics.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Showing that evolution has to happen by showing that characteristics in nature are always changing... Hardy-Weinberg equilibrium states that the shuffling of genes during sexual reproduction does not alter the proportions of different alleles in a gene pool Populations are always evolving and not usually in equilibrium Hardy-Weinberg Equilibrium Figure 13.8A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The population is very large The population is isolated Mutations do not alter the gene pool Mating is random All individuals are equal in reproductive success ***This does not happen in nature! Five conditions are required for Hardy- Weinberg equilibrium

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Equation (yes you have to do math) p 2 + 2pq + q 2 = 1 p + q = 1 p = frequency of the dominant allele in the population (A) q = frequency of the recessive allele in the population (a) p 2 = percentage of homozygous dominant individuals (AA) q 2 = percentage of homozygous recessive individuals (aa) 2pq = percentage of heterozygous individuals (Aa)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Practice Problem: p 2 + 2pq + q 2 = 1 p + q = 1 You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following: The percent of the “aa” genotype. The frequency of the "a" allele. The frequency of the "A" allele The percent of the “AA” genotype The percent of the “Aa” genotype