Change Over Time7.3 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

Darwin’s VoyageCharles Darwin sailed on the Beagle, from England to the Galápagos Islands.

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

Overproduction and VariationNatural 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 SelectionVariations 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 population’s 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 ancestor

Comparative anatomy- comparison of the structures of different organisms

Forms of Evidence

The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color.

Forms of Evidence Early Development- how

different species develop before birth

Scientists make inferences about relationships based on early development

Similarities 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 organism Cast- solid copy of the shape of an organism Cast is the opposite of a mold Petrified fossils- fossils in which minerals

replace all or part of an organism Trace fossils- fossils that provide evidence of

the activities of ancient organisms, like footprints

Preserved 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 fossils Fossils build a picture of Earth’s past

environments Fossils show how an environment has changed Gradualism- proposes that evolution occurs

slowly but steadily Punctuated 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 habitats

habitats- 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 identical Some genetic diversity is because of

mutations in DNA Some genetic diversity is caused by

rearrangement of genes during meiosis Species that have a lot of variety adapt

to changes in the environment Most organism are genetically similar,

they have a difficulty surviving environmental change

How Do New Species Form? Key concept: A new species can form

when a group of individuals remains isolated from the rest of its species long enough to evolve different traits.

Geographic Isolation is one of the main ways new species form

Sometimes a group is separated by a river, volcano, or mountain range

A wave can sweep members of a species out to sea and wash them up on an island

Kaibab and Abert’s SquirrelsTwo kinds of squirrels

isolated from one another by the Grand Canyon for a long time

This isolation may result in two different species

They belong to the same species but have different characteristics*an example of Geographic Isolation

Kaibab Abert’s

Inferring Species Relationships

Key concept: Scientists have combined the evidence from DNA, protein structure, fossils, early development, and body structure to determine the evolutionary relationship among species.

Compare genes to determine how closely related species are

More similar DNA is more closely related organisms are

In most cases evidence from DNA and protein structure confirm hypotheses on fossils, embryos and body structures

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

Extinction of Species Key concept: 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.

Extinct- no members of the species are still alive

Causes of extinction: disease, predators, humans, climate change

Not all climate changes cause extinction, some species have been able to adapt

Just like we saw in the Beak game, many organisms can survive but if the organism doesn’t get enough of what it needs it will not be able to reproduce and the species will become extinct.

Section 5: Branching Trees

How does a branching tree diagram show evolutionary relationships?

A Branching TreeBranching Trees Diagram- show probable evolutionary relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved.

Shared Derived Characteristics Key concept: A branching tree diagram shows

evolutionary relationships by grouping organisms according to shared derived characteristics.

Shared Derived Characteristics- homologous structures that are shared by all organisms in a group ReptilesAmphibians

Egg with shellFishes

Four limbs

Backbone

Invertebrates

Ancestor of animals

Constructing a Branching Tree

Organism with none of the characteristics are at the bottom

Next fork put group with one shared derived characteristics

Branch above that put organism with two shared derived characteristics

Continue until you end with the organism that has the most shared derived characteristics

Reading a Branching Tree Diagram

1. Did crocodiles evolve from amphibians? No they are on

different branches of the branching tree.

2. Are rodents more closely related to primates or crocodiles?

Primates they are on a branch together with other.

3. Name a common ancestor between crocodiles and dinosaurs.

Two post-orbital fenestrae

Essay Question You are a wild rabbit and your species

currently lives in the desert. Most of the rabbits are brown but there are a few that are white. An asteroid hits the Earth and the environment you live in suddenly becomes very cold. It begins to snow leaving snow covering the ground. Will your species be able to adapt and live in the new environment? Explain and give details (what happens to white rabbits and brown rabbits).