DIVERSITY

Targets A. Provide evidence that species and environmental conditions have changed over time. B. Explain the impact of environmental changes on species. C. Describe environmental conditions that may cause gradual and rapid 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. Geologic Time Scale A. Life’s History In Rock 1. Living things have changed through gradual processes over long periods of time. 2. About 99% of species that have lived in the past are now extinct.

B. Family Trees  Shows the relationship between groups of species.  Different species share common ancestors  Trees, not ladders

II. Cause of Diversity A. Two 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)

Galapagos Finches

Galapagos Tortoises

III. Importance of Variation A. Impact of Environmental Change 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.

Pepper Moths simulation simulation

B. Causes of Variation natural selectionnatural selection 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.

C. 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

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.

 Index Fossils : A fossil that lived in a particular geologic age (time period) used to date the rock layer in which it is found. 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.

4. Gaps : Why a lack of 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  How do fossils indicate ancient environments? A. Fossil Record

1. Type of Fossils temperatetropical

2. Location of Fossils MarineTerrestrial

3. Growth Rings (dendrochronology) TreesCoral

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.