Unit 3 Test - Evidence for Evolution

Lines of Evidence for Evolution: Fossil Record, Structural and Molecular Homology

Relative Dating

determining the age of fossils by their specific presence in older or younger layers of rock in Earth’s history. 

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comparing fossils by location in rock layers

Radiometric Dating 

scientists are able to estimate a fossil’s age based on the known *radioactive* decay rates of various isotopes that accumulated in the organism when it was alive.

Transitional Fossils

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Also known as “intermediate" fossils, have a mixture of features found in two different, but related, groups of organisms

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Examples: Archaeopteryx, Tiktaalik, whales

Structural Homology

organisms that share a common ancestor

Homologous Structure

features found in different organisms that share structural similarities but may have very different functions

Analogous Structures 

Structures evolve independently in groups of unrelated organisms as adaptations to similar environmental pressures

Divergent Evolution

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Represents the evolutionary pattern in which species sharing a common ancestry become more distinct due to differential selection pressure which gradually leads to speciation over an evolutionary time period.

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ex: pentadactyl limb

Convergent Evolution

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When species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures.

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ex: insect and bird wings

Vestigial Structure

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Evidence for evolution; an anatomical feature that no longer seems to have a purpose in the current form of an organism

Molecular Evidence  

By comparing DNA of different organisms it's possible to document genetic change over time.

DNA

Universal code; every living organism contains this and it is made up of four types of nucleotide “bases” arranged in a particular order to form genetic code

Genetic Sequences

Determines the order of the four chemical building blocks - called "bases" - that make up the DNA molecule.

DNA Sequences

Scientists can determine the genetic codes of different species.

Natural Selection

The Mechanism of Evolution; is the process whereby organisms better adapted to their environment tend to survive and produce more offspring.

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About the reproduction - rather than survival - of the fittest.

Evolution

The change in heritable characteristics of biological populations over successive generations.

Changing environmental conditions

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A change or disturbance of the environment is most often caused by human influences and natural ecological processes.

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Changes include various factors, such as natural disasters, human interference, or animal interaction.

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Ex: tuskless elephants, peppered moths

Overproduction 

Individuals of all species produce more offspring than can survive.

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Each generation has more offspring than can be supported by the environment.

Competition 

Individuals in a population compete for limited resource and are not successful.

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A result of overpopulation; takes the place for limited resources, logistic growth

Genetic Variation 

Individuals in a population show variation -- they have a variety of traits and some traits are better suited to the environment.

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Importance: strengthens the ability of species and populations to resist diseases, pests, changes in climate, and other stresses

Inheritance 

Traits are heritable -- passed on from parent to offspring.

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Occurs only if that character is passed from one generation to the next during reproduction; a crucial factor in natural selection

Adaptation

A modification of an organism or its parts that makes it more fit for existence

Fitness

A measure of the ability of an organism to survive and produce more offspring than other members of the population in a given environment.

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The ability of organisms— or, more rarely, populations or species— to survive and reproduce in the environment in which they find themselves.