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Change Over Time
7.3 Biological evolution accounts for the diversity of species developed through gradual processes over many generations. As a basis for understanding this concept:a. Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.b. Students know the reasoning used by Charles Darwin in reaching his conclusion that natural selection is the mechanism of evolution.c. Students know how independent lines of evidence from geology, fossils, and comparative anatomy provide the bases for the theory of evolution.d. Students know how to construct a simple branching diagram to classify living groups of organisms by shared derived characteristics and how to expand the diagram to include fossil organisms.e. Students know that extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient for its survival.

Darwin
He discovered many fossils of extinct animals that were similar to modern species

Found many variations in plants and animals that led to the formations of his theories

Species- a group of organisms that resemble one another and are able to reproduce among themselves

Traits- genetic characteristics among similar organisms in a species that is passed from one generation to another

Offspring- child of a parent

Darwins Voyage
Charles Darwin sailed on the Beagle, from England to the Galpagos Islands.
Discovered many fossils of extinct animals that were similar to modern speciesFound many variations in plants and animals that led to the formations of his theories

Overproduction and Variation
Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species.
Variations- a difference in a characteristic or trait from one organism in a species to another in the same species

Competition and Selection
Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce.
Survival of the fittest- theory of natural evolutionary processes that enables organisms that are best suited for their environment to survive

Evolution- overall change of a populations gene pool over time through processes such as mutation and natural selection

Section 2: Evidence of Evolution

Key concept: Similar body structures, patterns of early development, molecular structure, and fossils all provide evidence that organisms have changed over time.Homologous structures- similar structures that related species have inherited from a common ancestorComparative anatomy- comparison of the structures of different organisms
Forms of Evidence
The structure of the bones in a dolphins flipper, a birds wing, and a dogs leg is similar. Homologous bones are shown in the same color.

Forms of Evidence
Early Development- how different species develop before birthScientists make inferences about relationships based on early developmentSimilarities in DNA and proteins- if two species have similar DNA and proteins, probably evolved from same ancestor

How Do Fossils Form?
Most fossils form when organisms that die become buried in sediments.

How Do Fossils Form?
Mold- hollow area in sediment in the shape of an organism or part of an organismCast- solid copy of the shape of an organismCast is the opposite of a moldPetrified fossils- fossils in which minerals replace all or part of an organismTrace fossils- fossils that provide evidence of the activities of ancient organisms, like footprintsPreserved remains- processes that preserves the remains of organisms with little or no change (tar, amber, and freezing

Learning From Fossils
The fossils record provides evidence about the history of life and past environments on Earth. In addition, scientists use fossils to study the rate at which evolution has occurred.

Learning From Fossils
Paleontologists- scientists who study fossilsFossils build a picture of Earths past environmentsFossils show how an environment has changedGradualism- proposes that evolution occurs slowly but steadilyPunctuated equilibria- accounts for gaps in the fossil record, periods of rapid change separated by long periods of little or no change

Section 3: Evolution of Species
What factors have contributed to the diversity of species?How do new species form?How do scientists infer evolutionary relationships among species?What causes the extinction of species?

A Variety of Species
Key concept: Over time, different environments and genetic variation have produced, through natural selection, the variety of organisms that exist today.Over millions of years, natural selection has produced different species with adaptations enabling them to live in specific habitatshabitats- specific environment that provides the things organisms need to live, grow, and reproduce

A Variety of Species
Genetic diversity- organisms within the same species are not identicalSome genetic diversity is because of mutations in DNASome genetic diversity is caused by rearrangement of genes during meiosisSpecies that have a lot of variety adapt to changes in the environmentMost organism are genetically similar, they have a difficulty surviving environmental change

Kaibab and Aberts Squirrels
These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species.

A Branching Tree
This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related.

Extinction of Species
Extinction is caused by a change in species' environment. The members of a species may not have adaptations that allow them to survive and reproduce in the changed environment.

Section 5: Branching Trees
How does a branching tree diagram show evolutionary relationships?

A Branching Tree
Branching trees such as this show relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved.

Shared Derived Characteristics
A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristics.
Reptiles
Amphibians
Egg with shell
Fishes
Four limbs
Backbone
Invertebrates
Ancestor of animals