The History of Life on Earth

A 4.6 BILLON YEAR STORY…

Relative dating and The Law of Superpostion: oldest materials are buried below younger materials.

Radiometric dating- Uses the amount of time it takes for half of the radioactive carbon, C14, to leave a sample. Can also use other atoms such as uranium or polonium: Gives an exact age (AKA: Knowing the half-life.)

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Era- divisions of geologic time

Precambrian- life starts…bacteria…Paleozoic- first fish, land plants, amphibians,

reptiles...Mesozoic- first dinosaurs, mammals, flowering

plants, birds…Cenozoic- Mammals dominate, humans evolve

Evolution- the scientific theory that explains how early life on earth changed into the diversity of life in present time.

Definition: Change in allele Frequency of a Population Over Time

Hypothesis- a suggested solution to a problem

Theory- an explanation of a set of related observations verified multiple times.

Law- a statement of fact meant to explain.

Jean Baptiste Lemarck- Wrote in 1809, after studying the fossil records, that the Earth is ancient.

Evolution driven by tendency toward increasing complexity

Proposed 3 mechanisms of evolution1. Use and disuse2. Inheritance of acquired

characteristics3. The want to change

Charles Darwin- A naturalist that signed on the HMS Beagle in 1831 to collect flora and fauna

HMS Beagle- A ship that voyaged to chart South American coastline

Darwin found…

Flora & fauna distinctly different from that of Europe

Climate not a key factor

Fossils resembled living species

Galapagos Islands- Group of volcanic island near the equator, 900 km west of South America

Most animals unique to islands, but resemble those from the mainland

The Origin of Species- Published in 1859 and first introduced the idea of evolution by natural selection

1.Descent with modification- Organisms related through descent from an ancestral population

2.Natural selection and adaptation- Some characteristics assure better chance of survival and successful reproduction

Natural Selection- the unequal ability of individuals within a population to survive and reproduce

“Survival of the fittest”- a quick way of describing natural selection.

Environmental Conditions- The state of an organisms surrounding at a particular time.

Differential Survival- Some organisms are “lucky” and end up with traits and adaptation that exceed other organisms.

Occurs through interaction between genetic variability of individuals of population and their environment

Niche- all of the interactions of a species with the other members of its community. The “job” of a species.

Fossil record- can be used as evidence of a transitional life over time.

Comparative anatomy- the study of the body structures of different species of animals

Homologous Body Structures- Body parts in different organisms that are similar, but do not necessarily serve the same function

Analogous structures- features of different species that are similar in function but not necessarily in structure.

Vestigial structures- Body structures that have no apparent function

Embryonic stages- Comparing different animals fetal developments to infer relationships between species

Chemical basis- organisms sharing similarity at a molecular level.

DNA- nucleotide sequences

Protein sequences- amino acid sequences

Cladogram- used to show ancestral relations between organisms

Speciation- The evolutionary formation of new biological species, usually by the division of a single species into two or more genetically.

Reproductive Isolation- occurs when members of two populations cannot interbreed. At that point, they have different gene pools.

Behavioral Isolation – Two populations capable of interbreeding but have differences in courtship rituals or other types of behavior.

Geographic Isolation – Populations are separated by geographic barriers such as rivers, mountains, or bodies of water.

Directional Selection – Evolution causes an increase in the number of individuals with the trait at one end of the curve.

Stabilizing selection - Individuals in the center of the curve and more fit and thus the curve narrows

Disruptive Selection- Individuals at the ends of the curve are more fit than the ones in the middle causing two curves to form and possible new species to form.

Types of selection

Mutation- A change in an individuals genes.

Migration- individuals moving from a population to another population.

Natural selection- Genetic changes from generation to generation by unequal ability to survive to reproduce.

Genetic Drift- Genetic changes by chance.

4 Mechanisms of evolution

Variation- any difference between individual organisms in a population.

Adaption- process whereby a population becomes better suited to its habitat.

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•Artificial selection- certain characteristics being selected for many years leading to breeds

Mechanism (8): Macroevolution

www.ingala.gov.ec/galapagosislands/images/stories/ingala_images/galapagos_take_a_tour/small_pics/galapagos_map_2.jpg

Galapagos finches

• However, if two populations of a

species become isolated from

one another for tens of thousands

of years, genetic difference may

become marked.

• If the two populations can no-longer

interbreed, new species are born.

This is called Macroevolution.

• Darwin’s Galapagos finches are

an example of this process in action.