Emergence of Evolutionary Thought Evolution: Change in populations of organisms over time Early Explanation of life’s diversity Species individually created at one time and one place Questions arising from such thoughts Why were organisms different in different regions of earth? Why are current organisms different from ancient organisms? If each species is different, why are there the same fundamental structures (bone plans) that do different things in animals? New Ideas Scientists thought that species changed over time Both animals, though very different, exhibit similar wing structures Extinction, fossil record, and Carbon-14 dating suggest that organisms arose (and became extinct) at different time periods Dinosaurs- Arise ~ 200 myaExtinct 65 mya Chimps- Arose on earth ~6 million years ago Woolly Mammoth- Extinct 4500 years ago Different regions of planet have animals with unique traits that help them survive New Ideas Scientists thought that species changed over time Lamarck’s Disproven Theory of Evolution Jean Baptiste Lamarck Believed that an animal’s physical needs determine its development and genes Exp. Giraffe Early Giraffes stretched their necks to feed Long neck was then passed off to offspring WRONG!!! Charles Darwin 1809-1882 Putting the Picture Together Darwin Travels to the Galapagos Islands Witnessed tremendous diversity of animal life Fascinated by differences among beaks on finches Becomes convinced that species change over time Young bull Old bull Thomas Malthus & Charles Darwin Malthus Populations tend to grow faster than the food supply needed to feed it Charles Lyell & Charles Darwin Lyell Changes occur over time in geology; land formations move and topography changes Darwn’s Descent with Modification Evolutionary pathway resembled a branched tree NOT a ladder from lower forms to higher forms No species that exists today was an ancestor to another living species Darwin’s Observations •Individuals in a population vary, some of these variations are inheritable •Populations produce more offspring than the environment’s food, space, and other assets. •Therefore, species compete for resources Lions and cheetahs compete for food Dolphins compete for baitfish The Mechanism of Natural Selection Natural Selection greater reproductive success displayed by individuals with favorable traits Nature selects that are passed on to the next generation Variation differences within a population Adaptations traits that are selected for because they help an organism survive and reproduce Evolution occurs when genes in a population change shift to enhance survival and reproduction Exp. Giraffe How Do Variations Arise? •Natural selection IS NOT the cause of variation •Mutation-> Random changes in DNA sequences in the parents genome •Gene Shuffling mixing of parental chromosomes can create new genetic combinations •Variation arises randomly. Variations are then selected on by nature. •Variations which are selected for are called adaptations Adaptations and Speciation Types of Adaptations Structural Adaptations Involve structure or anatomy Bird’s beak, Anteaters sticky tongue Physiological Adaptations Functions in organisms Poison Venom in a snake, ink of an octopus Behavioral Adaptations Behavior aids in survival and reproduction Wildabeasts/ Caribou/ Bird Migration Wolves Hunt in Packs Fish swim in schools Types of Adaptations Structural Physiological Wolf Pack Herd of African Gazelles Species & Speciation Species group of organisms that can interbreed and produce fertile offspring Horses + Donkey = Mule…Not the same species Human male + human female = human baby…same species! Speciation Organisms which are separated by distance + gene pool will no longer interbreed. Each group becomes new species Horse Donkey Mule Types of Natural Selection Directional Selection shifts a population toward one extreme form of a trait Example: 4 million years ago; heavy cheetahs Over time, light, fast animals reproduced more successfully Natural selection favored the genes that pushed the cheetah’s weight in one direction…lighter Types of Natural Selection Stabilizing Selection shifts a population toward intermediate (medium) traits Example: Most human babies weight ~ 7pounds Disruptive Selection Extreme phenotypes are more common Example: African butterflies appear as either bright orange or bright blue These colors mimic other butterflies that are foul-tasting; less likely to be eaten Intermediate butterflies look like neither, and are more likely to be eaten Patterns of Evolution Species become dissimilar or more alike over time Gradual Change Genetic changes occur slowly over many generations Divergent Evolution Single population is split into 2 or more populations. Exp. Ground squirrels in the Grand Canyon were split into 2 populations after canyon widened Patterns of Evolution Adaptive Radiation Organisms occupy different niches in an environment and diverge from one another Exp. Darwin’s Finches Convergent Evolution 2 dissimilar species evolve in ways to make them LOOK more similar Exp. Sugar Gliders winged marsupials in Australia Flying Squirrels Winged squirrels in Northern Hemisphere Sugar Glider Flying Squirrel Pace of Evolution Gradualism Over time, new species arise as environment change If true, we should see intermediate species in fossil record…not always true Punctuated Equilibrium Species exist for long periods of time without changes, then large changes occur over short periods of time Populations & Evolution • Larger populations tend to have more genetic variation • Smaller populations tend to have less genetic variation • Genetic Drift/Founder Effect Loss of genetic variation due small population sizes. Extinction more likely • 10,000 years ago, almost all cheetahs go extinct due to climate changes. Resulting cheetahs have little genetic diversity Evidence for Evolution Fossil trail of animal that is preserved in rock Found in Sedimentary Rock Fossils show overall structural scheme of how living things evolved Body scheme Feeding behavior Mobility Society? New fossils in upper layers, older fossils in lower layers Examples Burgess Shale Location : British Columbia, Canada Development: Foot of continental shelf Organisms: Early Marine worms (Hallucigenia) Badlands, SD Development: Shallow ocean Organisms: Early Squid, octopus Badlands Importance Land masses move Were once covered under oceanic water Species adapt and go extinct Comparative Anatomy Homologous structures Similar structures in related organisms Suggests that organism arose from a common ancestor Exp. Cheetah forelimb = human hand Wing = Whale flipper Vestigial Organs Organs with no apparent use, but resemble functional structures in ancestors Whale Pelvis Whale femur Wisdom Teeth Appendix Comparative Embryology Organisms with common descent have similar organs Vertebrates breathe though lungs As embryos, vertebrates have gills (turns into Eustachian tube) Biochemistry Common ancestors have similar fundamental body chemistry Most organisms have: Same 4 bases in DNA Same 20 AA Biogeography Study of species distribution on Galapagos Islands look similar to South American species Each island would have to had it own special creation event for each species; more likely migrated from South America Direct Evidence Bacteria & Antibiotics Fruit Flies (Drosophila) Artificial Selection Artificial selection (or selective breeding) describes intentional breeding for certain traits, or combination of traits Dogs are a prime example. Bulldogs selectively bred for increasingly large heads. Most bulldogs delivered via Caesarian Section. Trait not favored in nature, but selected for by humans