Evolution is when organisms change over time. So, modern organisms descended from ancient ones
Evolution is a Theory – Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science is a well tested hypothesis, not just a guess BUT an explanation to an observation
Theories Theories have been tested many times by many scientists, A theory BEST explains a certain observation People have tried to refute Charles Darwin’s theory of evolution, but so far have been unsuccessful, therefore it remains
Who influenced Darwin’s ideas? Geologists: Hutton and Lyell Fundamentalists said that the earth was around 6000 years old Hutton and Lyell argued that the earth is many millions of years old b/c –layers of rock take time to form –processes such as volcanoes and earthquakes shaped the earth and still occur today
Lamark Theory of acquired characteristics Lamark said organisms acquired traits by using their bodies in new ways These new characteristics were passed to offspring Lamark was totally wrong!
Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone
Darwin finally published his ideas in 1859 Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.
Artificial Selection nature provides variation, humans select variations that are useful. Example - a farmer breeds only his best livestock
Natural Selection The traits that help an organism survive in a particular environment are “selected” in natural selection
Descent with Modification Each living species has descended with changes from other species over time
Summary of Darwin’s Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors
Evidence of Evolution 1.Fossil Record 2.Geographic Distribution of Living Species 3.Homologous Body structures 4.Similarities in Embryology
Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time
Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Drawbacks – provides no info about age in years
Absolute dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain Drawbacks - part of the fossil is destroyed during the test
Evidence of Evolution Homologous Body Structures –Structures that have different mature forms but develop from the same embryonic tissues e.g. Wing of bat, human arm, leg of turtle Turtle Alligator Bird
Natural Selection Acts on PHENOTYPE not genotype Only the Phenotype of an organism determines if the organism survives
Natural Selection The allele for long tongue (L) is dominant over the short tongue allele (l). Lizards that have long tongues have a better shot of surviving because the are better at catching dinner (flies). Of the lizards listed below, which have a better shot of surviving? LL, Ll, ll
Natural Selection The allele for long tongue (L) is dominant over the short tongue allele (l). Lizards that have long tongues have a better shot of surviving because the are better at catching dinner (flies). Of the lizards listed below, which have a better shot of surviving? LL, Ll, ll BOTH LL and Ll have long tongues, so natural selection acts on the phenotype NOT the genotypes
Natural Selection Each finch is best adapted to feed itself in the environment that they lived in. Does it matter if they are homozygous or heterozygous for the trait?
Recessive Lethal Alleles An allele that is lethal will cause a death in an individual if homozygous for the allele Example: Tay-Sachs Disease, is an autosomal recessive genetic disorderautosomal recessivegenetic disorder Tay-Sachs disease is caused by a genetic mutation on the HEXA gene on chromosome 15 mutationHEXA chromosome 15
Recessive lethal diseases Recessive lethal diseases are not very common, even though an organism with a lethal homozygous disorder will die before reproducing the lethal allele remains in the gene pool… Why?
“Carriers” A “carrier” of a disease is a heterozygous individual. The individual expresses the non-lethal normal allele BUT still carries a copy of the lethal allele. Two heterozygous individuals have a ¼ chance of getting a homozygous recessive individual, try the cross.
Mutations Can be beneficial because the create genetic variety Can be harmful because they can lead to an abnormal protein production ARE random
As the environment changes, so must the traits that are best fit for it How does change occur? –Mutations –Crossing Over during Prophase I of meiosis –Sexual Reproduction The greater the genetic variety of a population the better the chances of that population surviving change
When the Earth changes too quickly When the environment changes quickly, organisms might not survive and may go extinct because they may no longer be fit for the “new” environment Having a diversity of organisms gives the species a better chance of some of its organisms surviving Some examples…