History of Evolutionary Thought Before 1850, most people believed… –Earth formed by supernatural events and never changed. –Earth only a few thousand years old. –Each species was made to fit its environment. –Species never changed and did not go extinct.

History of the Idea of Evolution Jean Baptiste Lamarck Proposed that species DO evolve ***PROPOSED EVOLUTION OCCURRED BY INHERITANCE OF ACQUIRED CHARACTERISTICS

Lamarck Lamarck’s Hypothesis: 1. Desire causes change Ex.) ancestors of birds had a desire to fly, so they did. 2. Use and Disuse Ex.) If species used its arms to swim over and over, it would develop flippers. If not, flippers would disappear. 3. Traits acquired during life can be passed on Ex.) Tiger Woods’ children will be great golfers. Ex.) Tiger Woods’ children will be great golfers.WRONG!!!!

History of the Idea of Evolution Alfred Wallace English teacher who collected plants and insects. Observed variations in organisms Proposed that species DO evolve  similar to Darwin’s  similar to Darwin’s Sent idea to Darwin

Charles Darwin At 22, sailed on the “HMS Beagle” to the Galapagos Islands. Was going to school to be a minister-believed God created each species to match its habitat and they never changed. Thought Earth was about 6,000 years old and didn’t change.

Charles Darwin cont. During journey, he made observations and recorded them in a journal. Darwin began to doubt that species remained “constant.”

Charles Darwin In 1859, Darwin published “The Origin of Species.” His book stirred up controversy. Proposed **EVOLUTION OCCURRED BY NATURAL SELECTION

Major points of Darwin’s book: Organisms have more offspring than can survive. Certain individuals are more likely to survive than others (survival of the fittest.) Species DO change over time. Gradual changes may cause members of one species to eventually evolve into new species. African apes are close genetic relatives of modern humans. Darwin Video

Scientific Theories Hypothesis: a testable explanation for an observation “Theory” in layman’s terms = a guess and this is NOT the same as a scientific theory. Scientific theory: Accepted as factual NO EVIDENCE AGAINST IT!

Evolution EVOLUTION IS A SCIENTIFIC THEORY! Not a hypothesis, or an educated guess Unending amount of evidence to support it Evolution is called “the unifying principle of Biology” Isn't Evolution JUST a Theory? Isn't Evolution JUST a Theory?

Types of Evolution Evolution - genetic change of a population of organisms over time- descent with modification Micro evolution: Small genetic changes of a population Can occur in shorter amount of time

Types of Evolution MACROevolution: –Accumulated microevolution and mutations lead to new species--speciation –Usually long time for noticeable changes to occur.

How does macroevolution work? dibosirdsaur 10 million years of accumulated mutations diosirdsaur ibosirdsaur 10 million years of accumulated mutations diosirdsaur iboirdsaur 10 million years of accumulated mutations dinoirdsaur boirdsaur 10 million years of accumulated mutations dinordsaur boirdsur 10 million years of accumulated mutations dinodsaur boirdsu 10 million years of accumulated mutations dinodsaurs boirds 10 million years of accumulated mutations dinosaurs birds

Natural Selection Natural selection: process by which organisms best suited to their environment survive and reproduce. –Darwin’s proposed mechanism of evolution –Nature “selects” which members of a species will succeed in struggle for existence. –Survival depends on the particular environmental conditions a species finds itself in. –If the environment changes, so do the populations that live there. Adaptation: using inherited genetic characteristics to increase chance of survival in new environment.

Natural Selection Three conditions necessary for natural selection to occur: 1. Genetic variation: Individuals within a population must be genetically different. This is due to mutation. ****Random mutations are the raw material for evolution to occur!!!!!!! 2. Overproduction of offspring: More organisms are born than can survive. 3. Differential reproduction: Certain traits enable individuals to survive and have more offspring than others.—SURVIVAL OF THE FITTEST Result: Genes that help a species survive stay in the gene pool. “Unfavorable” genes gradually decrease. This causes changes in gene frequencies  EVOLUTION!!!!! Evolution: How Does Evolution Really Work? Evolution: How Does Evolution Really Work?

Natural Selection Example The industrial revolution –In England in the early 1800’s industry boomed –Factories, trains, smoke and smog –Peppered moths were dark or light colored, and the dark ones that were once rare became more common. –Hypothesis?

The Peppered Moth –Kettlewell tested this hypothesis Released equal numbers of moths in polluted AND clean forests. In industrialized areas, dark gray moth was better camouflaged. They survived, had more offspring –The population *as a whole* evolved to be better suited to the environment  more gray and camouflaged  ADAPTATION! –This is an example of microevolution

The Peppered Moth Peppered Moth Simulation Peppered Moth Simulation

Types of Natural Selection 1. Directional selection 2. Stabilizing selection 3. Disruptive selection

Types of Natural Selection Directional selection- individuals at one end of the curve are favored so they contribute more offspring so the curve shifts in one direction. Directional selection Directional selection

Types of Natural Selection Stabilizing selection- average individuals are favored so the middle of the curve increases. Stabilizing Selection Stabilizing Selection

Types of Natural Selection Disruptive selection- individuals at both extremes are favored so they contribute more offspring and two peaks result over time. Disruptive selection Disruptive selection

Darwin and the Finches Darwin traveled to the Galapagos and took interest in the finches. He noticed the finch species on the islands were different, but all resembled one from S. America. Darwin thought some migrated and new species evolved. This is what he proposed:

Darwin’s Finches Finches migrated from S. America to the islands –Populations on different islands adapted to different environments and food sources they found there. –Microevolution and mutations accumulated so populations on the different islands became more and more different. Divergence: the accumulation of differences between species or populations.

Darwin’s Finches Over time the populations on the islands became so different they no longer mated-different species –Several new finch species evolved from a common ancestor from S. America –Speciation: the formation of a new species through accumulated changes. –This is an example of macroevolution

Another Example of Speciation Geographical isolation: members of a population are separated geographically  leads to speciation. –Due to volcanoes, earthquakes, flooding, etc. –Can lead to divergence and then speciation.

EVOLUTION by natural selection MACROevolutionMicroevolution Mainly changes in gene frequencies in a population Shorter times Examples: Peppered moth and Bengal tiger Mainly accumulated microevolution and mutations to form whole new species Longer times Examples: Darwin’s finches and geographical isolation

Artificial Selection Artificial selection: human intervention in animal or plant reproduction to ensure that certain desirable traits are represented in successive generations. Instead of NATURE selecting which traits are favorable, HUMANS select the favorable traits. Ex. dogs or racehorses