What are the differences between ‘facts’ and ‘theories’? What do you believe the phrase ‘survival of the fittest’ means? Do you believe evolution occurs slowly, rapidly or both?

In science, theories are statements or models that have been tested and confirmed many times. In science, the term "Theory" does not express doubt. They explain a wide variety of data and observations They can be used to make predictions They are not absolute, can be changed as new evidence is found

Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale? Why is the sequence of DNA very similar in some groups of organisms but not in others? Why do the embryos of animals look very similar at an early stage?

Charles Darwin: Published the 1st convincing case for evolution in a book “On the Origin of Species by Means of Natural Selection” in 1859 based on his voyage on the HMS Beagle. Theory of Evolution: Change in characteristics of populations/species over time resulting from mutations and natural selection

During his travels on the Beagle, Darwin was able to observe adaptations of plants and animals from many diverse environments. Rainforests of Brazil Grasslands of Argentina Mountains of Peru One of the most important visits he made was to the Galápagos Islands west of South America

NORTH AMERICA SOUTH AMERICA AFRICA EUROPE AUSTRALIA PACIFIC OCEAN ATLANTIC OCEAN England Cape of Good Hope Cape Horn Tierra del Fuego Galápagos Islands Darwin in 1840, after his return HMS Beagle in port Equator Tasmania New Zealand Andes

Darwin found animals on these islands that weren’t found anywhere else in the entire world. He theorized that the animals had migrated from South America and then began developing specific adaptations to their new environment.

The ideas of Origin of Species can be summarized with these two main points: Evolution explains life’s unity and diversity. Natural selection is a cause of evolution.

Natural Selection - "The survival of the fittest" the first proposed explanation of variation of life on Earth. It is now considered the mechanism of evolution. It states that survival is based on fitness of the organism. Fit is now defined as best able to pass on genetic material to offspring. (Charles Darwin, 19th century)

Darwin noted many adaptations, or characteristics that enhanced the organisms chances of survival. He began to form a theory that as organisms gradually accumulated new adaptations, they would form a new species. One of the best examples of this theory is the different species of finches on the islands. The birds were all very similar except for their beaks.

The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.

Darwin did not call his theory “evolution”. He used the phrase descent with modification. This means that all organisms are related. All species came from a common ancestor. In the Darwinian view, the history of life is like a tree with branches representing each new species. Each new species is simply a “modified” version of its ancestor.

Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Years ago 0 10, Millions of years ago Moeritherium Barytherium Deinotherium Mammut Platybelodon Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa)

Charles Darwin’s theory can be broken down into five different observations. Observation #1: For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully.

Observation #2: Populations tend to be stable in size, except for seasonal fluctuations Observation #3: Resources are limited Observation #4: Members of a population vary in their characteristics; no two individuals are exactly alike

Observation #5: Much of this variation is heritable

Inference #1: More individuals are produced than the environment can support; Frogs lay thousands of eggs at a time, but only about 1% survive to adulthood.

Inference #2: Survival depends in part on inherited traits. Individuals with traits that give them an advantage are more likely to reproduce and have offspring.

Inference #3: Individuals that reproduce the most will pass favorable characteristics to their offspring. Over generations, these characteristics will accumulate.

Natural selection affects populations/species rather than individuals. Natural selection is differential success in reproduction from interaction between individuals that vary in heritable traits and their environment Natural selection produces an increase over time in adaptation of organisms to their environment If an environment changes over time, natural selection may result in adaptation to these new conditions

Types of Natural Selection: 1. Directional - One phenotype is favored in the environment. (ex. "dark" peppered moths have higher survival rates in soot covered forests)

2. Stabilizing - Organisms with extreme phenotypes are eliminated. (ex. birth weight in humans, low survival rate for extremes)

3. Disruptive - Organisms with common traits are eliminated, extremes are favored. (ex. small female and large male elephant seals)

4.Artificial - A breeder chooses which traits to favor. (ex. seedless grapes)