Evolution

Vocabulary Evolution: the process in which inherited characteristics within a population change over generations such that new species arise. Population: a group of organisms of the same species that live in a specific geographical area. Species: a group of organisms that are closely related and can mate to produce fertile offspring.

Evolutionary Theories Jean Babtist de Lamarck: proposed the first known theory of evolution. Lamarck believe that characteristics acquired during an organism’s lifetime could be passed down to its offspring. (Example: the lengthening of a giraffe’s neck). This theory has since been disproved by modern genetics.

Evolutionary Theories Punctuated equilibrium: theory that species can remain unchanged for millions of years and then have a sudden, drastic change in response to sudden environmental changes. This can also lead to speciation. The idea of quick bursts of evolutionary change is supported by a lack of transitional fossils in the fossil record. Gradualism: theory that changes in species occur slowly and steadily over thousands of years.

Natural Selection Natural Selection: a theory developed by naturalist Charles Darwin that explains how gradualism occurs

Steps of Natural Selection Natural Selection is specifically defined as the process by which organisms better suited to their environment survive and reproduce more successfully than less well adapted organisms of the same species do. Natural Selection results from the following: 1. Overproduction- more offspring are born than can survive. 2. Inherited Variation: Traits are passed down to successive generations, but offspring are not identical 3. Struggle to Survive- organisms must compete for resources. Some are better equipped for survival.   4. Successful Reproduction- Organisms that are better adapted will survive to reproduce and pass on their traits.

Keys to Natural Selection Mutations: occur randomly, but some may be advantageous Variation: differences between organisms within a species Adaptations: variations that are helpful to survival (beneficial changes) Successive Generations: generations that follow Speciation: the creation of a new species

Steps to Speciation Separation: or geographic isolations (part of the populations is separated from the rest and therefore no longer mating and sharing genetic information) Adaptation: natural selection occurs and selects the most beneficial traits Division: over time the two separated groups have changed so much that they are no longer able to successfully reproduce together and a new species has been created.

Evidence for Evolution Fossils are the remains or imprints of once-living organisms found in layers of rock, They are formed when layers of sand, dust or soils are deposited in an orderly fashion on top of older layers. When these sediments are compacted, they bury the things lying beneath and create sedimentary rock. Fossil Record: a historical timeline of life indicated by physical similarities of fossils and their estimated age. In undisturbed areas, older fossils are assumed to be buried beneath newer fossils.

Evidence for Evolution 3. Relative Dating: matching rock layers with fossils to determine the approximate age of the fossil based on where it is found in a geologic column.   4. Radiometric Dating: determining the approximate age of rock by analyzing certain radioactive substances in rocks and their known rates of decay.

Evidence for Evolution 5. Vestigial Structures: body structure that has ______ _______________ in a present day organism, but was probably useful to an ancestor. Examples: Pelvic bone in whale Appendix in humans

Evidence for Evolution 6. Homologous Structures: body parts from organisms of different species that are similar in structure and suggest the organisms share a common ancestor. Example

Evidence for Evolution DNA- all organisms have DNA and scientists believe that the more similar the DNA between organisms, the more closely related they ate. The fact that all organisms have DNA indicates a common ancestor.