What is gradualism and punctuated evolution? Agenda Theories of Evolution Notes Theories coloring worksheet Darwin’s postulates worksheet

History of the theory The idea of evolution was common among scientists in the early 1800s Georges Cuvier – fossils in lower strata are more dissimilar than present-day organisms James Hutton – Gradualism: major changes in Earth’s geologic history due to slow and continuous processes Charles Lyell – Uniformitarianism: those continuous processes are STILL working today

Jean Baptiste de Lamarck Use and Disuse – the more you use something, the greater it becomes; the less you use something, the more it deteriorates Organisms acquire traits and then pass these traits on to their offspring Acquired trait – a trait that arises during the lifetime of an organism

Lamarck

Lamarck’s Influence Incorrect Not all traits acquired get passed on Important Introduced change over time Realized organisms are changing

Charles Darwin Naturalist Traveled on the HMS Beagle (1831-1836) South America, Galapagos Islands, Australia Wrote The Origin of Species

Galapagos Islands small group of volcanic islands no land mammals or amphibians Back in England he looked at his findings Tortoises and Finches

Tortoises Similar BUT tortoises on different islands had different shell morphologies Could tell which island a tortoise came from just by looking at its shell

Finches Finches – collected 13 similar but separate species of finches Each had a distinct bill (beak) Observed finches doing very "unfinch-like things" e.g. one behaved like a hummingbird, another like a flycatcher, another like a woodpecker Conclusion: an ancestral group of finches colonized the islands and then, colonizers gradually changed into the specialized finches that he saw Implied shared common ancestor

People influenced Darwin Charles Lyell Malthus left unchecked, populations can growth exponentially since they don’t, they must be limited by war, disease, or limited resources This led to Darwin’s idea that there’s a struggle for existence

Darwin’s Theories Descent with Modification Man changed domestic species (dogs) Over time and generations traits with reproductive advantage become more common All species descended from one or a few original types of life

Darwin’s Theory Natural selection – organisms best suited for their environment reproduce more successfully than other organisms Over several generations organisms with favorable traits increase

Darwin’s Theory

Variation within a population Traits are inherited/passed on

More offspring are produced than can survive Surviving offspring will be favored by the environment - "natural selection“

Those organisms that survive have favorable variations (known as adaptations) Over time, these favored variations will accumulate -- this is "descent with modification" or evolution

2 types of Adaptations Camouflage and mimicry

Modification by Natural Selection An organism’s genetic contribution to the next generation is fitness Greater fitness = better adapted to env’t = reproduces more successfully Favorable traits give organisms an adaptive advantage Environment “selects” traits Favorable traits depend on demands of env’t

Summary of Darwin Natural Selection – organisms best suited/best adapted to the environment survive and reproduce Adaptations the population is the unit of evolution individuals do not evolve during their lifetimes

Theory of Evolution Evolution – change in the inherited traits of a population of organisms over time NOT new species arising from pre-existing species Part but not all of evolution

Cheetahs are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could run only 20 mph?

A long time ago, some cheetahs were faster than the others The cheetahs that could run faster were able to catch their prey and were better able to survive The slow cheetahs died off, or weren’t able to reproduce as successfully The cheetahs that survived were the ones that could run faster

How did the heavy coat in polar bears evolve if their ancestors had thinner coats? 1. A long time ago, some polar bears had thicker fur than others 2. The thicker coat was favorable 3. The polar bears with thin coats died off. 4. The ones with thicker coats survived and reproduced.

Peppered Moths