Introduction to Evolution: Darwin

1. Introduction to Evolution: Darwin

2. Evolution Controversy: 1800’s • Beliefs at the time: • Earth is just a few thousand years old • Earth is populated by forms of life have been here, unchanged, since the beginning • Many scientists engaged in study • Lyell stated that geologic processes have shaped the planet and are ongoing “the present is key to the past” • Lamarck proposed “acquired traits”, did believe in evolution, did not believe in extinction • Cuvier studied fossils, firmly established extinction occurs, did not believe in evolution

3. Charles Darwin • His theory of evolution as expressed in The Origin of Species (1859): • Earth is more than a few thousand years old • Earth is populated by forms of life that change over time. • Some life forms become extinct • In more than 150 years, there is no evidence that disproves his theory

4. Mechanism of Evolution Natural Selection

5. Evolution Evolution: A change in the gene pool of a population Gene pool: The total group of genes in a population.

6. Mechanism of Evolution • Principles of Natural Selection • 1. Within any population, there is genetic diversity.

7. Mechanism of Evolution • Principles of Natural Selection • 2. All populations live in an environment in which they compete for resources. • 3. In their environment, some individuals have a better ability to survive and reproduce than other individuals. • 4. Those individuals that survive and reproduce pass on their more successful traits to the next generation. • The less successful individuals do not pass on their traits because they don’t survive. • The environment selects the most fit organisms (“survival of the fittest”) This is called natural selection.

8. Natural Selection • If the environment changes, the individuals that can survive and reproduce may change. • Example: English peppered moth

9. Current Evolutionary Events There are contemporary examples of evolution as well Antibiotic-resistant strains of bacteria Herbicide-resistant varieties of plants Pesticide-resistant varieties of insects

10. Artificial Selection Artificial selection: The process by which species are modified by humans. Plants and animals are chosen with the desired goal of producing offspring with specific traits. Traits are “successful” if they are chosen by humans to be passed on to the next generation Examples include all domesticated animals (horses, dogs, cats, etc.) Another example: wild mustard

11. Lateral buds Terminal bud Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Kale Stem Flower and stems Broccoli Wild mustard Kohlrabi Artificial selection

12. Speciation • Over long periods of time, natural selection can give rise to new species. • Adaptive radiation occurs when many new species arise from a single common ancestor • Example: Galápagos finches

13. (a) Cactus eater. The long,sharp beak of the cactusground finch (Geospizascandens) helps it tearand eat cactus flowersand pulp. (c) Seed eater. The large groundfinch (Geospiza magnirostris)has a large beak adapted forcracking seeds that fall fromplants to the ground. (b) Insect eater. The green warbler finch (Certhidea olivacea) uses itsnarrow, pointed beak to grasp insects. Beak variation in Galápagos finches

14. Evidence for Evolution

15. I. Fossils • Found in sedimentary rock, remains or traces of organisms from the past. These organisms may or may not still exist. • Paleontology is the study of fossils. • Dragonfly fossil from Brazil, more than 100 million years old

16. Petrified tree in Arizona, 190 my Leaf fossil, 40 my Dinosaur bones Ammonites, 375 my Insects in amber 23,000 year-old mammoth tusk in Siberian ice 150 my dinosaur track in Colorado Fossils

17. Fossils • Darwin’s theory explains the succession of forms in the fossil record. • Transitional fossils have been found that link ancient organisms to modern species • This is an extinct whale with a hind leg limb

18. Remarkable CreaturesBy Tracy Chevalier Mary Anning 1799-1847

19. Lyme Regis • The south coast of England, on the Dorset-Devon border. For centuries it was a fishing village and port. • The cliffs by Lyme Regis expose a layer of Jurassic limestone rich with fossils, which has attracted fossil enthusiasts for over 200 years.

20. Mary Anning • In 1812, at age 12, she discovered the first complete specimen of an ichthyosaur, a marine reptile about 200 million years old (illustration below). • Also discovered first complete plesiosaur and first British pterodactyl

21. Human Cat Bat Whale II. Homologous Structures • Related species share characteristics resulting from a common ancestry. • Same structure, different functions are anatomical signs of evolution (forelimbs of bats, humans & whales)

22. Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide Species 100% Human Rhesus monkey 95% Mouse 87% Chicken 69% Frog 54% 14% Lamprey III. Molecular Homologies • Organisms share the same molecules • The same genetic code written in DNA, RNA and proteins. • Molecular evidence for shared ancestry.

23. IV. Eukaryote Structure All eukaryotes have similar internal structure & organization Endosymbioic Theory proposes that eukaryotes originated when large prokaryotes ingested and assimilated smaller prokaryotes. Evidence All eukaryotes have mitochondria for energy transformation The mitochondrial DNA originates solely from the mother Autotrophs have chloroplasts for photosynthesis Both mitochondria and chloroplasts grow and divide on their own Both resemble modern bacteria. Porphyridium: DNA in the plastids of this red seaweed is closer in sequence to that of a bacterium than it is to the DNA in the nucleus of that seaweed

24. Endosymbiotic Theory

25. Pharyngeal pouches Post-anal tail Human embryo V. Similarities Between Embryos Human Embryo Chick Embryo Comparing early stages of different animal embryos shows many similarities that are not visible in adult organisms. “Ontogeny recapitulates phylogeny”

26. VI. Vestigial Structures The blind mole rat (Spalax typhlus) has tiny eyes completely covered by a layer of skin. Python with vestigial appendage (hind limb bud). Have no apparent function in extant (living) organism They resemble structures held by their extinct ancestors Demonstrated in fossil record (pelvis & leg bones of snakes).

27. VII. Biogeography The geographic distribution of a species. Species that live closer to one another tend to be more closely related than those that do not. Example: Australia has a diverse population of native marsupial mammals but almost no placental mammals.