Evolution Notes

Indirect Evidence  Data gathered by looking at the effects of an event rather than witnessing the actual event.

Evolution  is a change in the inherited traits of a population from one generation to the next. This process causes organisms to change over time.inheritedtraits populationgeneration

Conditions required for fossils to form  Sediments like sand or silt  Quick burial of organism  Bones or shells

Do all dead organisms make fossils?  No!!  Most organisms are eaten, decomposed, broken apart, etc instead of becoming fossils.

Types of fossils  Amber = hardened tree sap  Bones and petrification  Molds, casts, and imprints

Ice

Bones and petrification

Molds, casts

Imprints and trace fossils

Relative dating  Relative dating

Radioactive Dating  The radiocarbon dating method was developed in the 1940's by Willard F. Libby and a team of scientists at the University of Chicago. It subsequently evolved into the most powerful method of dating late Pleistocene and Holocene artifacts and geologic events up to about 50,000 years in age.

Index Fossils  Common, widespread, fossils that only existed for a “short” time.  Useful for estimating a time period for rock strata that contains these fossils.

Transitional forms/ missing links  An organism that shows the transition from one species to another.

Comparative cytology

Comparative biochemistry  DNA  Amino Acid sequences  Enzymes

Comparative anatomy  Homologous structures

Comparative anatomy  Analogous Structures

Comparative anatomy  Vestigial structures

Comparative embryology

Origins of Life  Spontaneous generation –Some used to think that flies came from rotting meat and mice came from hay

Origins of life  space seed hypothesis –Bacteria from a meteor from another planet  In 1969 a meteorite (left-over bits from the origin of the solar system) landed near Allende, Mexico. The Allende Meteorite (and others of its sort) have been analyzed and found to contain amino acids  special creation theory –A creator (god) made the first cells  Heterotroph Hypothesis –The first living things ate chemicals from the “primordial soup”

Early earth conditions  The atmosphere was methane, ammonia, water, and hydrogen gas. X-rays and UV rays from the sun were not blocked by the atmosphere.

Present Earth Conditions UV Rays are blocked by the ozone layer X-rays are absorbed by Nitrogen and Oxygen in the atmosphere Atmosphere is made of Nitrogen, Oxygen, a little carbon dioxide, and some water vapor. Our oxygen comes from autotrophs!

Stanley Miller Experiment

Amino Acids were formed

Hydrothermal vent where chemotrophs live

Lamark: Law of use and disuse

Lamark  Inheritance of acquired traits

August Weismann:  Disproved acquired inheritance.

Darwin  English naturalist  Took a 5 year trip around the world  Was one of the people who developed the idea of evolution.

 Overproduction –Most species produce far more offspring than are needed to maintain current population levels  Competition –Food, space and other resources are limited. Not all organisms will get their needs met.  Variation –There are differences between members of a species.  Adaptations –Some variations increase an organisms chance of survival.  Natural Selection –The environment “selects” organisms with advantageous traits, they survive, reproduce, and pass on the good traits to their offspring.

What is a species?  Organisms that are able to reproduce and make viable offspring are of the same species.  Speciation = formation of a new species.

Modern Theory of Evolution  How do natural variations occur? –Mutations  A change in the DNA –Sexual reproduction (crossing over)

Natural Selection  This is the mechanism of evolution.  Traits that help you survive will be passed on to your offspring. The frequency of that useful trait will increase in the population = change

Examples of natural selection  Mosquitos that are resistant to DDT

Examples of natural selection  Penicillin resistant bacteria

Examples  Peppered moths

Camouflage

Warning Coloration

Mimicry

Types of natural selection  Directional

Types of natural selection  Stabilizing

Types of natural selection  Disruptive

Speciation  Range  Where an organism lives

Speciation  Geographic isolation: species adapt to new environments

Bottleneck effect

Speciation  Reproductive isolation –Genetic, behavioral, timing differences

Speciation  Polyploidy –More than the normal # of chromos omes

Speciation  Adaptive radiation –One species evolves into many different species.

Convergent evolution  Natural selection that causes unrelated species to resemble each other.

Co-evolution: two or more species that evolve in response to each other

Gradualism

 Gradualism: slow and gradual changes regularly over time.  Punctuated Equilibrium: quick and sudden changes followed by a long period of stability.

Population  A group of species in an area.  Evolution is a change in the frequency of a gene in a population of organisms over time.

Gene Pool  A gene pool is the sum of all the individual genes in a given population

Extinction

Microevolution vs. Macroevolution