Evolution and Natural Selection How species change over time

Evolution The theory that organisms today developed from more simple life forms and have changed (evolved) over time

Natural Selection Organisms that are best adapted to their environment have a better chance of surviving and reproducing

Early Beliefs Earth was only a few thousand years old. We now know it is billions of years old. Neither the planet nor the species that inhabited it had changed since the beginning of time. We now know the planet has changed and, through fossils, discovered organisms have changed, as well.

Evolution Pre-Darwin Beliefs Jean Pierre Lamark believed that organisms can change their traits during their lifetime by use or disuse. He thought that these traits are passed on to offspring. Over time this would cause change in a species. Larmark was wrong

Charles Darwin Scientist credited with the Theory of Evolution & Natural Selection Voyage of the HMS Beagle – a 5 year voyage to South America and the South Pacific, collecting specimens, making observations and keeping a scientific journal of his findings

Voyage of the Beagle What did Darwin find? The finches on each island in the Galapagos had different types of beaks. Discuss the graphic with the students.

2. The tortoises on each island in the Galapagos had different types of shells.

Darwin’s Hypothesis? Darwin hypothesized that organisms had a common ancestor, but had adapted to their particular environments and changed over time. He further proposed that only members if a species best suited for their environment will survive and reproduce. He called this Natural Selection Darwin published his research in 1859

Key Ideas that led to Darwin’s Theory Overproduction-plants and animals will more offspring than can possibly survive Variation-within a species there will be natural differences that are passed on through mutations Adaptation-inheritance of traits that give an organism an advantage in a particular environment Selection –adaptations allow organisms to survive long enough to reproduce Speciation-new species arises with enough accumulated differences usually because a species is isolated

Natural Selection For natural selection to occur, there must be at least two varieties of a species. For example: the peppered moth

Peppered Moths At the beginning of the Industrial Revolution in England, coal burning produced soot that covered the countryside in many areas

What do you think happened?

Evolution/Natural Selection White moths became easier to see, while the black moths became harder to see. The black moths were more likely to survive and pass on the gene for dark color to their offspring. Over time, the black moths have become more common.

Evidence for Evolution Common Ancestry: If species evolved from a common ancestor, then they should share common anatomical (physical) traits Hawaiian Honeycreeper: family of birds in Hawaii that have similar skeletons and muscles, indicating they are closely related. Over time, their common ancestor evolved into several species, each with a specialized bill for eating certain foods. Just like Darwin’s finches on the Galapagos!

2. Homologous Structures If animals evolved from a common ancestor, then they should share common structures – and they do! These are called homologous structures They look similar but are adapted for different uses.

3. Embryo Development Similarities early in development in many organisms.

4. Vestigial Organs- structures or organs that may have been useful to ancestors but, over time no longer have a useful function Kiwi (flightless bird) Whales (hind leg bones) Humans (tailbone, appendix)

5. Fossils-similar fossils were found in several different geographic locations and layers

Any Questions?