Evolution and Natural Selection How species change over time

Evolution and Natural Selection Genetic variations are passed on through reproduction Natural selection leads to evolution Our understanding of evolution has changed over time

Evolution The theory that organisms have changed (evolved) over time.

Natural Selection The theory that states that those organisms best adapted to their environment have a better chance of surviving and reproducing.

Charles Darwin 1809 - 1882

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.

Voyage of the Beagle What did Darwin find? The tortoises on each island in the Galapagos had different types of shells.

What was Darwin’s hypothesis? Darwin hypothesized that organisms had adapted to their particular environments and changed over time. Darwin published his research in 1859

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

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?

Peppered moth activity You will simulate how changes in genetic traits change over several generations have occurred through natural selection Materials: Prey circle papers, colored pen or marker, journals and stopwatch Predator-checks off prey circles Time keeper-15 seconds Everyone records

What does your data show about how prey are selected by predators? What moth coloration is the best adaptation for a light colored background? Dark colored background? How do you know( justify your evidence from the trials)? Based on the surviving “prey circles” what would you expect the next generation of moths to look like after trial 1? After trial 2? After trial 3?

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 Common Ancestry: If species evolved from a common ancestor, then they should share common anatomical 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!

Evidence for Evolution: Vestigial Organs Some organisms have structures or organs that no longer have a useful function. These structures or organs may have been useful to the ancestors of a species, but over time have evolved into what we term vestigial organs.

Examples of Vestigial Organs Kiwi (flightless bird) Whales (hind leg bones) Humans (tailbone, appendix)

Evidence for Evolution Fossils Fossils provide a look into the past Scientists can trace how a species has evolved by studying fossils