Evolution andNatural SelectionHow species change over time
Evolution and Natural Selection GSE’s Genetic variations are passed on through reproduction Evidence for evolution illustrates how organisms are related Natural selection leads to evolution Our understanding of evolution has changed over time
EvolutionThe theory thatorganisms todaydeveloped from moresimple life forms andhave changed (evolved)over time
Natural SelectionThe theory that statesthat those organismsbest adapted to theirenvironment have abetter chance ofsurviving andreproducing
Evolution Pre-Darwin 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
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 1809 - 1882 Scientistcredited 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,
Voyage of the Beagle What did Darwin find? Thefinches on each island in the Galapagos had different types of beaks.
Voyage of the Beagle What did Darwin find?The tortoises on each island in theGalapagos had different types ofshells.
What was Darwin’s hypothesis? Darwin hypothesized that organisms had a common ancestor, but 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
Peppered Moths Atthe beginning of the Industrial Revolution in England, coal burning produced soot that covered the countryside in many areas
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
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:Homologous Structures Ifanimals evolved from a common ancestor, then they should share common structures – and they do! These are called homologous structures
Evidence for Evolution Embryo Development What do you notice? List 2 observations
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
Wrap Up the Evidence Common Ancestry Homologous Structures Vestigial Organs Embryonic Development Fossils