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

Darwin’s Voyage Charles 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 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 population’s gene pool over time through processes such as mutation and natural selection

Section 2: Evidence of Evolution

Forms of Evidence 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 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 Squirrels Two 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

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 Tree This 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 Tree Branching 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 Reptiles Amphibians Fishes Egg with shell Invertebrates Four limbs Backbone 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).