Evolution and Biodiversity Apes Chapter 5 Darwins Ideas

Evolution and Biodiversity Apes Chapter 5

Darwin’s Ideas – An “evolution”, not a “revolution” z. Pre-darwininan ideas y. Species are fixed, permanent, no change y. Earth young – less than 10, 000 years old z. New ideas y. Georges Buffon – earth much older – fossils y. Lamark x. Species changed, process of adaptation x. Inheritance of acquired characteristics

Voyage of the Beagle z 1831 z Charles Darwin – 22 -year old college student z The Galapagos Islands – Why Important? z Lyell and geology – y. Earth’s geological features changing over very long periods of time – Earth is OLD y. Results in a changing environments – living things faced with constant change

Darwin Analyzes Data – And Formulates his Theory z. Thomas Malthus – Populations can grow much faster than food supplies, other resources – exponential growth y. Darwin’s interpretation – Struggle for Survival z. Published The Origin of Species - 1859

Darwin’s Main Points z. What were Darwin’s two main points? y. Descent with Modification y. Natural Selection

Why is this type of rock important?

Dating Fossils z. Sedimentary rock – relative ages z. Radiometric dating y. Half-life of radioactive elements x. U-238 – 4. 5 billion x. C-14 – 5600 years z. How does carbon get into living organisms? y. Accurate to 50, 000 years

Homologous Structures What are some similarities? How is the use of these structures different? Do you think homologous are evidence of common ancestors? Explain.

Evidence - vestigial structures

Evidence Similarities in embryological development

Evidence in molecules of life z Proteins such as hemoglobin (page 304) z DNA analysis - humans and chimps - 2% difference in species

Microevolution (14. 4) z What is a gene pool ? y What is “stored” in a population’s gene pool? Ø Microevolution – genetic changes in an organisms gene pool. z Evolution acts on populations – not on individuals

Changes in Gene Pools z Microevolution: the frequency of alleles in a gene pool changes; evolution on the smallest scale

“Ingredients” for microevolution (101) z. Variation within population z. Trait must be inherited (genetic basis) z. Trait must lead to differential reproduction

Why Variation? z Mutation – most often random y. Can chances be increased y. May not offer any advantage or disadvantage z Especially important in changing gene pool in asexual, rapidly reproducing individuals y. Examples? ? z In Sexually reproducing organisms – variation also caused by: y“shuffling” of different chromosomes – independent assortment y. Crossing over during meiosis

Natural Selection y. Variation is always present in a population due to genetic variation (variation in gene pool of the population) y. What decides what individuals survive and reproduce? x. If organisms reproduce, genetic makeup is passed to their young! y. Thus, organisms that are better adapted have better chance of survival to reproductive age – and pass on genetic traits

Natural Selection – Not by Chance z. Think of peppered moth, pesticide resistance, AIDS z. This selection leads to adaptations x. Is a favorable adaptation always remain a favorable adaptation? EXPLAIN

Snail coloration best adapted to conditions Average Natural selection Number of individuals Directional Natural Selection New average Coloration of snails Average shifts Coloration of snails Proportion of light-colored snails in population increases Figure 5 -6 (1) Page 102 Previous average

Intermediate-colored snails are selected against Light coloration is favored Dark coloration is favored Natural selection Number of individuals Diversifying Natural Selection Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases Figure 5 -6 (3) Page 102 Snails with light and dark colors dominate

Peppered Moth – directional microevolution

Evolution of antibiotic resistance z. Drug kills most bacteria z. Survivors reproduce quickly – develop resistant population

What Else can cause changes in Gene Pool? Chance changes in allele frequency - no selection for advantageous traits v Genetic Drift 1. Bottleneck Effect 2. Founder Effect v Gene Flow v Mutation

Founder Effect z. Small population migrates to a location z. Limited gene pool z. Population may differ from original population

Gene Flow z. Migration of organisms from “outside” populations

Artificial Selection z. Humans act as environment - choose those genetic traits that will survive y. What are some factors that “replace” humans in natural selection? z

Coevolution z. Interaction between species results in microevolution in both species populations z. Predator-prey z. Symbiosis – may be much more important than proposed by Darwin

Convergent evolution z. Are similar structures always evidence of evolutionary relationships? • NO!! z. Consider - animals that eat insects z. Called analogous structures z. Examples

Convergent Evolution (from PBS website)

Convergent Evolution Are these homologous structures? Why or why not?

Ecological Niches and Adaptation (103) z. Niche – species “way of life” or functional role in ecosystem x. Range of tolerance for physical/chemical conditions x. Resources it uses x. Interactions x. Role in food webs/energy cycling z. Habitat z. Functional niche vs realized niche

Number of individuals Generalist vs. Specialist Niche separation Generalist species with a narrow niche Niche breadth Generalist species with a broad niche Region of niche overlap Resource use Figure 5 -7 Page 104 What are examples of generalist vs. specialist species?

Why not a superorganism? z. Traits must be already present “somewhere” in population for organism to adapt to changing environmental conditions z. Limited by reproductive potential z. Only so much DNA

Macroevolution z Changes that move beyond changes in allele frequency z Including origin of new species - speciation, y. Explains development of new genera and beyond z Explains major new features of living organisms y. Progressive and incremental – example – complex eyes y. In many cases links between simple and complex are “missing”

Are these different species?

How about these animals?

Defining a Species z. Population of organisms that can and do: y. Interbreed y. Produce fertile offspring

Origin of Species The Ultimate of Divergent Evolution

Animation Disruptive selection animation.

Northern population Early fox population Spreads northward and southward and separates Arctic Fox Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Different environmental conditions lead to different selective pressures and evolution into two different species. Southern population Gray Fox Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat.

Reproductive Isolation – Why can’t different species interbreed? z Timing - skunks yfrogs in same pond z Behavior ybirds - songs ycourtship rituals z Other reproductive barriers yzygote does not develop - chromosomal differences z Live in different geographical areas or in different habitats

What comes first? ? z Geographical isolation always precedes reproductive isolation z What is geographical isolation? z How can this lead, usually over long time periods, to reproductive isolation? z Continual microevolution causes populations to become so different, no longer interbreed x. Natural selection (in the different environments) x. Genetic drift and random mutations

Tempo of Speciation z Darwin’s theory – relatively slow progression to new species as result of geographical isolation z Punctuated equilibrium– y. Long periods, little change, THEN. . xrapid changes to new species y. May be caused by rapid changes in environment z Most species last 5 million years before extinction

Plate Tectonics z. Why matching Mesozoic fossils in West Africa and Brazil z. How does crust movements affect life’s evolution? z. Pangea – When began to split?

PA NG AE A 120° 80° LAURASIA 40° 80° 120° GONDWANALAND 135 million years ago 225 million years ago NORTH AMERICA EURASIA AFRICA 120° 80° SOUTH AMERICA INDIA MADAGASCAR 120° 0° AUSTRALIA ANTARCTICA 65 million years ago Figure 5 -9 Page 106 Present 40° 120°

Mass Extinctions z. End of Cretaceous – y. What changes in life forms? y. What was the cause? y. What organisms underwent widespread adaptive radiation? z. End of Permian – 90% of life went extinct

Rate of Extinction z Biodiversity = speciation minus extinction z Background vs mass extinctions z As species become extinct, genes “remain” from ancestral species z Estimate – human caused extinction increase of 100 X to 1000 X background z READ: The Future of Evolution – answer #1, then #2 (assume you agree) x. What could be the effect on humans of a mass extinction?