Evidence of Evolution Unit 4: Chapters 10 & 12

Important Vocabulary 1. Species: A group of organisms that can breed together to produce fertile offspring. 2. Population: A localized group of individuals belonging to the same species. 3. Evolution: A slow change in a population over time.

Charles Darwin explained how Natural Selection could cause a population to adapt and change over time. (note he states- a “population” will change -not an “individual”)

What is a theory vs. a hypothesis? HypothesisTheory An educated guess that has to be testable by scientific methods Has to be well- supported and has been tested over and over Is an explanation of a phenomenon that has occurred in the natural world.

Who influenced Charles Darwin?

The Work of Lyell Influenced Darwin’s Ideas 1.Charles Lyell – English geologist a.Earth’s geologic features formed as a result of gradual processes. b.Floods, earthquakes, and glaciers of the present do not cause great destruction (ex: Grand Canyon) of Earth’s surfaces c.Must take millions of years to change geography, thus the earth must be millions of years old. 2. Darwin read Lyell’s work while on his voyage & agreed with Lyell’s conclusions Charles Lyell

The Work of Malthus Influenced Darwin’s Ideas : Thomas Malthus -- Englishman a.Essay on the Principle of Population b.Said that humans tend to have more offspring than nature can support c.Food production increases at a slower rate than population 2.Darwin read Malthus’s essay after he returned from his voyage 3.Darwin concluded that all organisms produce more offspring than the environment can support Thomas Malthus

Charles Darwin: An Unlikely Evolutionist 1.Charles Darwin a.1809: English-born naturalist b.Went on a 5 year voyage on the HMS Beagle as an unpaid scholar ▪Collected plants & animals during journey c.Darwin did not set out to develop a theory of evolution d.Observations and specimens collected helped Darwin formulate his theory of evolution. Charles Darwin

Route of Darwin’s 5 Year Trip Darwin spent a lot of time and collected a lot of specimens from the Galapagos Islands. Galapagos Islands

Darwin’s Observations 1.In Argentina, Darwin saw earthquakes raising the earth several feet 2.Shells of marine animals found far inland & at great heights in Andes Mts 3.Fossils of huge sloths & armadillo-like animals (both extinct) – similar to modern forms 4.Animals on Galapagos were similar but not same as those on mainland S. America & Antarctica Galapagos penguin 14 inches tall 5 lbs Eat small fish & sardines Nests in burrows Chinstrap penguin 28 inches tall 9-14 pounds Eat small fish & krill Build nests out of small stones

Darwin’s Observations on the Galapagos Islands 1.Fewer types of organisms on the islands 2.Island species differ from mainland species & from island to island 3.Finches on Galapagos resemble mainland finch, but there were more types on the islands

Pinta Island Intermediate shell Pinta Isabela Island Dome-shaped shell Hood Island Saddle-backed shell Hood Floreana Santa Fe Santa Cruz James Marchena Fernandina Isabela Tower Giant Tortoises of the Galapagos Islands Each island had a variation of tortoise; long & short neck corresponded to type of vegetation.

Darwin explained Evolution by Natural Selection : Darwin published On the Origin of Species a.Proposed that natural selection was the mechanism for evolution. Individuals vary in one or more traits & there can be slight differences in their ability to survive & reproduce. b.Nature selects those individuals w/ favorable traits to leave more offspring that are better suited (FIT) for their environment. c.Descent with modification occurs over time Each living species has descended, with changes, from other species over time Published 25 years after Darwin wrote it!

Evidence that Supports Evolution: Fossil Record 1.Fossil: preserved remains (bones, teeth, shells) or evidence (imprint or footprint) of ancient organisms. a.Fossils found in sedimentary rock b.Younger sediments deposited on top of older sediments c.Older sediments contain older, simpler fossils d.Younger sediments contain younger, more complex fossils 2.Fossils found in sediments of organisms that are extinct. Trilobites are extinct!

Age of Fossils Paleontologists determine the age of fossils using two techniques: 1.Relative dating: age of a fossil is determined by comparing its placement with that of fossils in other layers of rock. Paleontologists estimate the age based on the age of other fossils found near it. 1.Radioactive (absolute) dating: Scientists use radioactive decay to assign absolute ages to rocks.

Beaver NORTH AMERICA Muskrat Capybara SOUTH AMERICA Coypu Evidence that Supports Evolution: Geographic Distribution of Living Species Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara 1.Similar animals on each continent live in similar ecological conditions a.They were exposed to similar pressures of natural selection. b.Because of similar selection pressures, different animals ended up evolving similar characteristics

Evidence that Supports Evolution: Homologous Structures 1.Homologous structures: similar structures but different functions a.Structures develop from same clump of embryonic cells b.Provides evidence that four-limbed vertebrates descended from a common ancestor. 2.Vestigial structures: structures or organs that are reduced in size; do not seem to serve a useful function 3.Homologous & vestigial structures imply that common genes are involved. Homologous structures: forelimbs of vertebrates Pelvis & femur bones are vestigial in whales

Evidence that Supports Evolution: Similarities in Embryology 1.The embryos of vertebrates are very similar during early development. 2.The same groups of embryonic cells develop in the same order and in similar patterns to produce tissues & organs. 3.Common cells & tissues growing in similar ways produce homologous structures. 4.Implies that common genes are involved. Embryos of vertebrates develop gill slits and tails.