Evolution: modern organisms have changed over time and all organisms share a common ancestor Evidence for Evolution Homologous Structures Fossil Record Embryology Vestigial organs DNA Comparison

Homologous Structures

Fossil Record

Vestigial Organs

Embryology

DNA comparison

Natural Selection--DARWIN Natural selection is the process by which those heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. It is a key mechanism of evolution.

-Natural selection acts on the phenotype, or the observable characteristics of an organism, but the genetic (heritable) basis of any phenotype which gives a reproductive advantage will become more common in a population. -Over time, this process can result in adaptations that specialize organisms for particular environment.

4 parts to Natural Selection Overproduction: Variation in a population: Competition: Selection : survival of the fittest

-Genetic variation is essential for natural selection. -The natural genetic variation within a population of organisms means that some individuals will survive and reproduce more successfully than others in their current environment.

Charles Darwin proposed his theory of evolution based on observations of nature. Which observation that contributed to his theory is illustrated by this population of beetles? A.Species produce more offspring than can survive. B.Populations remain stable over time. C. Individuals within a population may vary widely. D. Environmental resources are limited.

-A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions. -Speciation is a lineage- splitting event that produces two or more separate species.

Kinds of Speciation Allopatric speciation is just a fancy name for speciation by geographic isolation Parapatric speciation refers to the formation of two or more descendant species from a single ancestral species which are not isolated be geographic boundaries.

Causes of Speciation 1.Geographic Isolation 2.Temporal Isolation 3.Behavioral Isolation

This diagram illustrates what kind of speciation? ASympatricBAllopatric CGeographicDCatastrophic River

Fossil Record Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The fossil record contains many examples that could be interpreted to mean that species evolved from more ancient organisms. Absolute dating: dating of fossils that involves radioactive dating of elements—gives a specific time period Relative dating: dating of fossils using the placement in the layers of the earth—chronological order of fossils but not exact years

Geologic Time Scale Live begins Mass extinction of marine animals: 90% Mass extinction dinosaurs

Sample Question Which of the following is usually most helpful in determining the age of the fossils found in rock strata? Athe size of the fossils Bthe color of the fossils Cthe water content of the rock layer where the fossils were located Dthe depth of the rock layer where the fossils were found

Sample Question Which of the following best explains how the fossil record provides evidence that evolution has occurred? AIt indicates the exact cause of structural and behavioral adaptations of organisms. BIt shows that the form and structure of groups of organisms have changed over time. CIt shows how the embryos of many different vertebrate species are very similar. DIt indicates that forms of life existed on Earth at least 3.5 billion years ago.