Chapter 22 Descent with Modification: A Darwinian View of Life Mrs. MacWilliams AP Biology

Darwin Introduces a Revolutionary Theory the many species of organisms presently inhabiting Earth are descendants of ancestral species that were different from the modern species mechanism for this evolutionary process was natural selection… the result of natural selection is evolutionary adaptation

The Darwinian view challenged traditional views

What did these people contribute/believe NOT EVOLUTION! Aristotle scala naturae Carolus Linnaeus binomial naming of species Georges Cuvier catastrophism Old Testament species designed by God The two geologists: James Hutton changes in Earth’s surface can result from slow continuous actions still operating today Charles Lyell uniformitarianism (change over time is constant)

What did these people contribute/believe Thomas Malthus potential for human population to increase faster than food supplies and other resources (influenced Darwin) Alfred Wallace Published his paper on natural selection at the same time Darwin did Jean-Baptiste de Lamarck species evolve through use and disuse of body parts and the inheritance of acquired characteristics Unsupported by evidence

Lamarck’s Giraffes According to Lamarck’s theory of inheritance of acquired characteristics ancestral short-necked giraffes stretched their necks to reach leaves high on trees. Their offspring were born with longer necks Incorrect!!!!

What did these people contribute/believe Charles Darwin Descent with modification explains life’s unity and diversity Natural selection is a cause of adaptive evolution Wrote On the Origin of Species by Means of Natural Selection aka The Origin of Species

Darwin’ Research Observed adaptations of plants and animals in diverse environments Species resembled other species of the same climate Fossils and geologic observations pointed to the fact that Earth has been changing Galapagos Islands inhabited by species from South America then diversified…ADAPTATIONS!!! Natural selection is the mechanism of evolution….biological diversity is the product of evolution

The Origin of Species Evolution explains life’s unity and diversity Natural selection is a cause of adaptive evolution

Descent With Modification “evolution”

Artificial Selection…Selective Breeding

Darwin’s 4 Observations and 2 Inferences Observation #1: Members of a population often vary greatly in their traits Observation #2: Traits are INHERITED from parents to offspring Observation #3: All species are capable of producing more offspring than their environment can support Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

OBSERVATION #1 Figure 22.10 Variation in a population

Observations 2, 3, and 4 Spore cloud Figure 22.11 Overproduction of offspring

Darwin’s 4 Observations and 2 Inferences Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.

Summary of Natural Selection Differential Reproductive success Increase the adaptation to a environment New species may arise Can amplify or diminish heritable traits POPULATIONS evolve…individuals don’t!!!!

Why don’t individuals evolve?? The word 'evolution' in biology is reserved for *species*, not individual organisms. Genetically, every individual organism does not change, but a *population* changes over time. Darwin explained of how species change (evolve). Even though each individual dies with the same genes it is born with, some individuals will survive better than others, and reproduce more. Those individuals with traits that give them a slight edge in this competition for survival and reproduction, will ON AVERAGE produce more offspring. And *THAT* is why the population changes (evolves) over time.

(a) A flower mantid in Malaysia (b) A stick mantid in Africa Fig. 22-12 (a) A flower mantid in Malaysia (b) A stick mantid in Africa Figure 22.12 Camouflage as an example of evolutionary adaptation

4 Lines of Evidence for Evolutionary Change Direct Observations Example: Predation and Coloration in Guppies Example: Evolution of Drug Resistant HIV

Example: Natural Selection in Action Can predation pressure select for size & age at maturity in guppies? Change in predator resulted in different variations in the population being favored

Example: Natural Selection in Action HIV resistant to 3TC Drug Natural selection “edits”…it doesn’t create Natural selection favors characteristics that increase “fitness”

2. The Fossil Record

3. Homology similarity resulting from common ancestry **Prefix “HOMO” means SAME

Homology/Embryology anatomical homologies not visible in adult organisms

Homology/Embryology Pharyngeal pouches Post-anal tail Fig. 22-18 Homology/Embryology Pharyngeal pouches Post-anal tail Figure 22.18 Anatomical similarities in vertebrate embryos Chick embryo (LM) Human embryo

Homology Vestigial structures Remnants of features that served important functions in the organism’s ancestors Examples in humans: coccyx, wisdom teeth, appendix (?), “goosebumps”, external ear muscles, etc. (see Human Vestigial PPT if time)

Homology/Molecular

Homology/Convergent Evolution Evolution of similar, or analogous, features in distantly related groups Analogous traits arise when groups independently adapt to similar environments in similar ways Convergent evolution does not provide information about ancestry

Homology/Convergent Evolution

4. Biogeography Geographic distribution of species Influenced by continental drift from the large continent of Pangea over 200 million years ago Example: Horses originated on North America when South America was not yet connected. Earliest horse fossils will be found only on North America. ENDEMIC- species of plants and animals found only in one place and nowhere else on earth.

You should now be able to: Explain that, prior to Darwin, it was believed that species do not change and the Earth was very young (a few thousand years old). Describe the contributions to evolutionary theory made by Linnaeus, Cuvier, Lyell, Lamarck, Malthus, and Wallace Describe Lamarck’s theories, and explain why they have been rejected *Lemarck’s giraffes Explain what Darwin meant by “descent with modification” Describe how Darwin was the first person to propose evidence for Natural Selection Explain Darwin’s 4 Observations and 2 Inferences

You should now be able to: Explain why an individual organism cannot evolve Describe at least four lines of evidence for evolution by natural selection **Strongest evidence: all organisms share essentially the same genetic code (DNA with A, T, G, and C) 7. Describe the two examples of direct observation of evolution (“Predation and Coloration in Guppies” and “Drug Resistant HIV”) 8. Define Homologous/Analogous and Vestigial structures 9. Describe convergent evolution with examples (flying squirrel/sugar glider) 9. Explain artificial selection using the wild mustard plant as an example