EVOLUTION CHAPTER 15

Natural Selection & the Evidence for Evolution Ch. 15, Sec. 1

Think, Pair, Share… 1) What is evolution? 2) What evidence do scientists have that suggests evolution actually occurs?

Evolution Gradual change in a species over time due to adaptations, There are exceptions, not always gradual Science is Tentative Development of new organisms from preexisting types of organisms Living things come from other living things New species come from other species

Characteristic changes in a population involve changes to genes These changes then get passed along through the genes 3) Who do you get your genes from? Supported by a lot of evidence and data Fossil, Anatomical, & DNA

Charles Darwin (1809-1882) Started off studying medicine 1831 signed on for a 5 year journey of South America on the HMS Beagle Enjoyed nature & making observations Noticed similar looking organisms on different continents

Darwin’s Clues Collected fossils Observed the adaptations of plants & animals allowing them to survive in particular environments Adaptation = a trait (which is coded for by DNA in a gene) that allows an organism to be successful in its environment Like tools that help them get the job done

4) How are these organisms adapted to their environment?

Galapagos Islands One of Darwin’s stops on the Beagle Group of volcanic islands off the west coast of South America

Home to several species of finches Each species is adapted to the type of food eaten 5) Would the warbler finch be able to eat what the Large Ground finch can eat? Why or Why not?

Darwin’s Hypotheses Darwin hypothesized that all the species descended from ancestral finches The ancestral finches flew to the Galapagos Islands from mainland South America Population changed over time to adapt to the specific environment of their island

Darwin’s Observations 1. Overproduction Most species produce large numbers of offspring (ex: rabbits) 6)But why isn’t the earth overrun by rabbits? The environment will set a limit on how big the population gets by causing deaths or limiting births 2. Individuals within a population compete with one another

Observations cont. 3. Genetic Variation Within populations organisms have different traits because of variations in genes Variations can be inherited 7) Did you inherit any interesting variations? Populations have multiple alleles for any given trait (dark fur/light fur, tall ears/short ears, etc.)

In summary… Organisms that have superior traits/tools are better adapted Therefore they’re more likely to survive Therefore they’re more likely to reproduce and pass on the genes for the superior traits/tools 8) What “chooses” the superior traits?

Artificial Selection Darwin worked with breeding different variations on pigeons Artificial Selection = humans select good traits in organisms to breed Ex: prettier roses, bigger chickens, sweeter oranges YOU see it all the time Darwin hypothesized: Something like Artificial Selection must be acting on the organisms living in the wild

Natural Selection Natural Selection = mechanism for change in populations; organisms with favorable variations survive, reproduce, & pass on the variation to the next generation (offspring) Organisms with the best adaptations (helpful traits, good “tools”) are most likely to survive & reproduce Through inheritance the adaptations will become more frequent in the population

Who gets to evolve? 9) Can YOU evolve? Why or why not? It is the population that evolves, not the individual 10) If you like swimming, can you choose to evolve gills? An individual can be born with a mutation If the mutation is an advantage (good “tool”) for living in a particular environment then that individual will be more likely to survive & pass on that mutation to its offspring Evolution Videos Field\Natural_Selection_512k.wmv

Structural Adaptations Why are these structures adaptations?

Mimicry = structural adaptation allowing one species to resemble another species

Camouflage = adaptations allows species to blend in with surroundings

Rapidly Developing Physiological Adaptations Evolution is not always a slow process Evident in antibiotic resistance (bacteria evolve too)

Resistance of insects to pesticides

Increased toxicity of snake poison

Fossil Evidence Fossils show that over time species forms have gradually changed A transitional species will have characteristics of both the ancient and modern organism there has to be something in between Ex: Do children automatically become adults? Ex: Modern whales evolved from an ancient, land mammal

Anatomical Evidence Studying anatomy can uncover structural evidence of a common ancestor Homologous Structure = similar in build, different function; anatomical structures in different species inherited from a common ancestor

An early ancestor of all 4 species had a forelimb with similar structure (common ancestor)

Analogous Structures = have closely related functions, but are built differently; does not indicate a common ancestor

Vestigial Structures = serve no function but resemble structures with functional roles in other animals

Embryology Embryology = the study of how organisms develop Early stages of vertebrate embryos look very similar As development continues embryos of different species start looking less alike

DNA Evidence All living organisms have DNA in common DNA codes for proteins The more closely related two species are…. The more similar their DNA…. The more similar the proteins made in their bodies are

Mechanisms of Evolution Ch. 15, Sec. 2

Population Genetics Gene Pool = all the alleles for a particular trait in a population are “pooled” together ex: all the alleles for short fur and long fur, all the alleles for brown fur and black fur Allelic Frequency = percentage of a specific allele in the gene pool % of brown fur alleles & % of black fur alleles Genetic Equilibrium = maintaining the same frequency of alleles over time

Changes in Genetic Equilibrium Mutations can cause variations to be added to the gene pool of a population Genetic Drift = chance events changing a population’s genetic equilibrium

Natural Selection Acts on Variations Stabilizing selection = natural selection that favors average individuals in a population

Directional selection = natural selection favors one of the extreme variations of a trait

Disruptive selection = individuals with either extreme of a trait’s variation are selected for

Evolution of a Species Changes to a gene pool can lead to the evolution of a new species Speciation = members of similar populations can no longer interbreed

Geological Isolation = physical barriers divide a population  Over time, the  divided populations may become two species that can no longer interbreed, even if reunited Evolution Videos Field\Biogeography_512k.wmv

Reproductive Isolation = occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring; 2 types 1. Genetic Isolation = genes of two populations are so different they cannot produce fertile offspring 2. Behavioral isolation (ex: one population mates in the spring, another population mates in the fall)

Change in Chromosome Numbers = mistakes in cell division lead to polyploid individuals (abnormal sets of chromosomes) Polyploids can be sterile, unable to reproduce Polyploids can also reproduce and generate a new species through interbreeding

Speciation Rates Gradualism = species originate through gradual change of adaptations Punctuated Equilibrium = speciation occurs in quick, rapid bursts

Patterns of Evolution Divergent Evolution = species that were once similar evolve to look differently Adaptive Radiation = ancestral species evolving to fit into a lots of different habitats

Convergent Evolution = very distantly related organisms evolving similar traits Evolution Videos Field\Convergent_256k.wmv

Hummingbird moths are night-flying insects whose behavior and appearance are similar to those of hummingbirds. Explain how these two organisms demonstrate convergent evolution and analogous structures. (1 paragraph, 5-8 sentences)