DIVERSITY

Targets A. Explain what causes species to change over time. B. Provide evidence that species and environmental conditions have changed over time. C. Describe sudden and gradual environmental changes that would cause extinctions.

Targets D. Explain the importance of variation in traits (diversity) of a specie. E. Describe the causes of variations in species. F. Explain how the age of fossils can be determined.

Targets G. Compare relative and absolute dating methods. H. Define transitional form and index fossil. I. Explain what can be determined about extinct species from the fossil record.

I. Evolution Living things have changed through gradual processes over long periods of time. Results in diversity About 99% of species that have lived in the past are now extinct.

A. Family Trees (Phylogenies) 1. Traces patterns of shared ancestors between families. 2. Root = Ancestors, Branches = Descendants Forks = Speciation Event 3. Each family has shared and unique ancestors.

B. The Pace of Evolution 1. Gradual : slow, steady change overtime. Transitional forms found. 2. Punctuated : short periods of rapid change. Transitional forms may not be found.

Gradual Punctuated

Transitional Forms

Link between ancestor and descendent

3. Gaps : Why a lack of transitional forms?

a. Fossils may not have been preserved by the environment. b a. Fossils may not have been preserved by the environment. b. Fossils may have been destroyed by tectonic activity.

II. Cause of Evolution A. Competing Theories 1. Acquired Characteristics Jean-Babtiste Lamarck, 1809 : The idea that individuals can acquire new traits in response to environmental changes, then pass those traits to their offspring. (after)

2. Natural Selection Charles Darwin, 1850’s : Populations that have inherited the most favorable traits will survive environmental changes and pass those traits to their offspring. (before)

Lamark Darwin

B. Principles of Natural Selection Variations are found among individuals of a species. (differences) Individuals with helpful variations survive and then reproduce more than others. (survival of the fittest) Over time, individuals with helpful variations or adaptations make up a larger part of a population. Allows speciation to occur. (development of new species)

III. Variation A. Importance 1. Changes in the environment can affect how beneficial a trait will be for survival and reproductive success of a species.

2. Variation increases the chance that some individuals will have traits necessary to survive under changed conditions. 3. If species do not adapt to changes or move to another location, they may become extinct.

Galapagos Finches

Galapagos Finches amoeba sisters

Galapagos Tortoises

Natural Selection

Pepper Moths

4. Environmental Changes a. Sudden: Catastrophic event such as a meteor or volcanic eruption. b. Gradual: Changes in climate, predators or food sources.

B. Causes of Variation 1. Mutations Random changes in the DNA code that may cause offspring to develop traits different from the parents.

2. Migration Variation is increased when members of a group introduce their genes into another group. (gene flow)

3. Isolation Populations separated by geography will change in different ways. Changes that occur in one population will not be passed to the other. Over time, the separated populations may not interbreed, creating a new specie.

4. Sexual Reproduction Mixing of genes results in different genetic combinations, which allows offspring to be different in form.

IV. Evidence for Evolution A. Fossil Record Disappearance of a specie: Extinction Appearance of a specie : Evolution

1. Relative Dating (determines order)

a. Principle of Superposition: Rock layers are deposited in time sequence, oldest rocks on the bottom, youngest on top.

b. Principle of Faunal Succession Fossils succeed each other vertically, in a specific, reliable order. Fossils found in a rock layer are the same age as the rock.

c. Index Fossils : A fossil that lived in a particular geologic age used to date the rock layer, or other fossils, in which it is found. They must be abundant and widespread.

2. Absolute Dating (numerical age) Radiometric : compares the amount of naturally occurring radioactive isotope with its decay products. Ex: Uranium / Lead (710 m to 4.5 b yrs) Potassium / Argon (1.3 billion yrs) Carbon 14 / Nitrogen (5,730 yrs)

3. Info from Fossil Record Age, size and shape can be determined Diet, movement, soft parts, color, sounds, behaviors may be inferred. Predicts transitional forms.

B. DNA : The more similar the DNA, the more closely related two organisms are.

C. Comparative Anatomy : comparing skeletons of extinct and living organisms. 1. Homologous: similar structures that may not have a common function in related species. 2. Analogous: similar structures that serve the same function in unrelated species.

analogous

homologous

analogous

homologous

analogous

vestigial structures: loss of ancestral function, but remain in the descendant.

D. Comparative Embryology

V. Paleo Environments A. Fossil Record 1. Fossil Type How do fossils indicate ancient environments? A. Fossil Record 1. Fossil Type

Temperate or Tropical

Terrestrial or Marine

2. Growth Rings (dendrochronology) Trees Coral

B. Geologic Record 1. Sediment Type Different types of rock form in different environments. EX: Limestone / Dolomite: warm ocean water. Shale : mud Sandstone : continental / freshwater Coal measures : swampy forests

2. Ice Cores Ice contains gas bubbles, radioactive substances, dust, ash and pollen from previous climates.