“from so simple a beginning, endless forms most beautiful and most wonderful have been, and are being, evolved.” – On the Origin of Species
I. Darwin’s Travels 1. In 1831, Charles Darwin traveled on the HMS Beagle (a ship) around the world from England. He went to the Galapagos Islands off of Ecuador. 2. He made observations of plants and animals and collected specimens. This led him to propose a revolutionary hypothesis on evolution.
Evolution is change over time. It is the process by which modern organisms descended from ancient ones.
II. Darwin’s Observations He asked questions! - Why aren’t there any rabbits in Australia even though climate is right? - Why are there no kangaroos in England? - Why is there such variety in living things, i.e. biological diversity. - How are species so well suited to their habitats? - Why had so many species disappeared? - How are they related to living ones?
• Fossils would be the answer to many of his questions. Fossils are the remains of ancient organisms. Some ancient fossils resemble modern living organisms. Some fossils didn’t look like ANYTHING he’d seen before. WHAT HAPPENED?
Why were there so many different types of tortoises, finches etc. Why not just one type since they all lived on the Galapagos Islands? • –Islands are far apart w/ different climates, different species.
The tortoises varied in predictable ways from one island to another. Shell shape and neck length could identify the island the tortoise came from.
• The finches on the different island had different beaks for different foods. • The changes in beak shape were driven by competition for food. •Common ancestor???
III. Darwin’s Conclusions/Hypothesis
•These separate species of animals must have come from one common ancestor!
IV. Ideas that Shaped Darwin’s Thinking
• A. At this time people thought: 1. World and life were created 1000 years ago! 2. Nothing had changed since then!
V. New Ideas
A. Hutton and Lyell: Geologists 1. Through fossils and geologic formations showed Earth was millions of years old and that it was constantly changing over time.
This all influenced Darwin… • a. If Earth could change over time, couldn’t living things????? • b. IF Earth were old (like they are saying) it would give time for organisms to change!!
VI. Lamarck
A. His Ideas: • Jean-Baptiste Lamarck said (before Darwin) that by using something a lot or not using something, an organism acquired or lost traits during their life. These traits could be passed on to the babies. “Use it or lose it” theory.
• Ex. Lamarck thought that if a giraffe stretched its neck, it could pass this longer neck onto its baby. (Acquired = gained)
• Ex. Or, say a swimmer builds up large strong shoulders, he/she would pass large shoulders on to their child.
• B. Lamarck didn’t quite get it right. He didn’t know that an organism’s behavior doesn’t influence what traits are passed on to offspring. He did not know about genes.
• Still, he was one of the first to develop a theory of evolution and recognize that organisms are adapted to their environments. He paved the way for Darwin! VII. Darwin Speaks Out
A. On the Origin of Species • He didn’t publish the book for 25 years! (A little afraid of what would happen!) ….i.e. “dangerous” idea. • His theory was Natural Selection AKA “Survival of the Fittest” • In sum: the organisms best suited to their environment will survive.
1.Artificial Selection: •Farmers, Breeders pick the “best” to breed/survive!
This Chihuahua mix and Great Dane show the wide range of dog breed sizes created using Pigs are artificially selected by man to artificial selection. produce the largest amount of meat. Evolution by Natural Selection
Survival of the Fittest:
• In biology, an adaptation is ANY inherited characteristic that increases an organism’s chance for survival. The possibilities are limitless! Just look at an organism and see how it works well in its habitat. Ex of adaptations: camouflage, mimicry, behavioral adaptations
Camouflage - blending in with one’s surroundings to increase chances of survival http://www.youtube.com/watch?v=7ch1277quZo
Mimicry- looking like another organism to increase chances of survival
• Day flying • Paper wasp moth Mimicry »Red on yellow - kills a fellow« or »Red touching black - is a friend of Jack« Mimicry
• Monarch Viceroy: harmless! poisonous Hunting in a Pack! • Wolf Park in Battleground, IN • In biology, fitness is the ability of an organism to survive and reproduce.
• Organisms within a species are in a struggle for existence, a competition for resources like food, space, mates.
Individuals with adaptations that make them well- suited to their environment have increased fitness.
• They are “…harder, better, faster, stronger” – according to Kanye.
• They could also be good at hiding like your peppered moths!
• Darwin called this process survival of the fittest or natural selection.
• Natural selection is Darwin’s theory about the mechanism for evolution, his explanation of how it occurred. (Lamarck’s mechanism was inheritance of acquired traits).
Darwin called his theory natural selection to distinguish it from artificial selection.
In artificial selection, humans “select” or choose the variations that will survive and reproduce. Ex. crops, livestock Darwin concluded that something like this worked in nature.
• In natural selection, the environment “selects” the organisms that will survive and reproduce. These are the organisms with the adaptations that give them an advantage in fitness.
B. Summary of Darwin’s Theory of Natural Selection
• 3 Ingredients: VARIATION, SELECTION, TIME! • http://learn.genetics.utah.edu/content/selecti on/recipe/ 1)VARIATION: There is variation within a population. (variation = some individual differences) Some variations are better than others (they are adaptations that increase fitness).
2) SELECTION: The most “fit” organisms survive and reproduce. They are “selected” by how well adapted they are to their environment.
3) TIME: The future generations inherit the favorable variations. Over time, the inherited characteristics of a population change. = evolution!!! (descent with modification)
NOTE: The variations are caused by MUTATIONS!