What factors have caused the evolution and diversity of organisms? You plant a packet of zinnia seeds, and later, the zinnias begin to bloom. You notice that no two plants are exactly alike. For example, some flowers have different colors than others. What accounts for these differences? Write an explanation.

Identify Multiple Meanings Word Everyday Meaning Scientific Meaning   n. A guess; an idea of how or why something might happen n. A well-tested concept that explains a wide range of observations theory Example: Emily has a theory that basketball is harder to play than baseball. Example: The cell theory says that all organisms are made of cells.

Apply It! In the sentences below, identify which meaning of the word theory was used—the everyday meaning or the scientific meaning. The theory of evolution explains how organisms have changed over time. Theory (science use) Do you have a theory about why Sarah is a vegetarian? Theory (everyday use)

Section 1: Darwin’s Theory Changes Over Time Section 1: Darwin’s Theory What important observations did Darwin make on his voyage? How did Darwin account for the diversity of species and the differences between similar species? How does natural selection lead to evolution?

Darwin’s Voyage Changes Over Time Charles Darwin sailed on the Beagle, from England to the Galápagos Islands.

Darwin’s Discoveries Comparisons to South American Organisms: 1. many island species were similar to mainland species. 2. species were different because of what they had to eat. Comparisons among the islands: 1. Species varied from island to island. Adaptation: A trait that helps an organism survive & reproduce.

EVOLUTION Darwin’s Reasoning: Species gradually changed over many generations & became better adapted to the new environments. Evolution- the gradual change in a species over time Scientific Theory- a well-tested concept that explains a wide range of observations. Selected Breeding- (used by breeders) selecting to breed species for certain traits (ex. Speed in race horses)

Overproduction and Variation Changes Over Time 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. Overproduction: Producing a lot of offspring. Variation: Differences in traits within a species.

Competition and Selection Changes Over Time 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. Selection: “survival of the FITTEST”. Competition: Species compete against each other to survive.

Environmental Factors: can effect an organism’s ability to survive. (ex. Pollution, hunting) Genes and Natural Selection: genes contribute to natural selection.

Links on Charles Darwin Changes Over Time Links on Charles Darwin Click the SciLinks button for links on Charles Darwin.

End of Section: Darwin’s Theory (write summary) Changes Over Time End of Section: Darwin’s Theory (write summary)

Section 2: Evidence of Evolution What evidence supports the theory of evolution? How do fossils form? What do scientists learn from fossils?

Forms of Evidence Body Structure Comparative Anatomy- comparing body structures of different organisms. Homologous structures- similar structures that related species inherited from common ancestor.

Homologous Structures 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.

Other Similarities: Similarities in Early Development- comparing how different species develop before birth. Similarities in DNA & Proteins- Similar DNA = common ancestor

A variety of species Over time, different environments and genetic variation have produced, through natural selection, the variety of organisms that exist today. Different Environments: habitat: specific environment that provides the things organisms need to LIVE, GROW & REPRODUCE. Genetic Diversity: species are not completely identical. -variations & mutations

How do New Species Form? New species can form when a group of individuals remain isolated from the rest of it’s species long enough to evolve different traits. How? Geographic Isolation- when some members of a species become cut off from the rest.

Kaibab and Abert’s 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.

Inferring Species Relationships Similarities in DNA- species inherited many of the same genes from common ancestors. Combining Evidence- Similar DNA + Protein structure = common ancestor

A Branching Tree This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related. Related by shared-derived characteristics.

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. ccc

Extinction and the Environment Extinct: When no members of that species are still alive This is caused by the species environment New disease Predators Hunting Climate Change- the leading cause of extinction Adaptation and Survival- Some organisms have traits that will help them adapt to the new environment and survive.

A Branching Tree Branching tree diagrams 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 characteristic, a homologous structure shared by all in a group. Reptiles Amphibians Fishes Egg with shell Invertebrates Four limbs Backbone Ancestor of animals

Order of Characteristics Evolutionary Groups The lower on the branch, the earlier it developed Groups within groups Reptiles Amphibians Fishes Egg with shell Invertebrates Four limbs Backbone Ancestor of animals Largest subgroup

Constructing a Branch Tree Group with 2 shared traits Group with 1 shared trait Group with none of characteristics Shared trait Shared trait Shared trait Common ancestor