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Today you will need. Something to write with. Evolution and Natural Selection . Continued. Evolution is…. The gradual change in a species over time. Things to keep in mind…. Populations, not individuals, evolve. It’s all about the genes!. Occurs over a LONG period of time. . - PowerPoint PPT Presentation
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Today you will need
•Something to write with.
Evolution and Natural Selection
Continued
The gradual change in a species over
time.
Evolution is…
Things to keep in mind…
Populations, not individuals, evolve.
It’s all about the genes!
Occurs over a LONG period of time.
Evidences of Evolution
Fossil Record
Biochemical - DNAComparative Anatomy
Biogeography
Observable Events
How does evolution
occur?
Mechanisms of Evolution
Bottleneck EffectAn event that kills off
a large number of members of a species randomly by chance therefore reducing
the genetic diversity.
Bottleneck Effect
Genetic DriftThe alteration of
allelic frequencies by chance events.
Genetic Drift
MutationsRandom genetic
changes that occur in a populations
DNA.
Mutations Most mutations are bad
Some are advantageous
Gene FlowThe transfer of alleles from one population
to another population through immigration
or emigration of individuals.
Gene Flow
A mechanism for change in a population.
Natural Selection is…
Survival of the FittestOrganisms with favorable
genetic variation survive to pass on their genes
Types of Natural Selection
1.Stabilizing2.Directional3.Disruptive
Stabilizing Selection:When the average is favored over
either of the extremes in a population.
Stabilizing Selection:
Directional Selection:This happens when one of the “extremes” is favored in an environment over the other extreme or the old average.
Directional Selection:
Disruptive Selection:This situation happens when
either extreme is favored over the average.
Disruptive Selection:
How are new species made?
Speciation: the evolution of a new species
How are Species Made?Speciation is always caused by isolationTypes of isolation:
1. Geographic2. Reproductive
Types of Isolation1. Geographic
IsolationA single species can become two different species because they are isolated by mountains, rivers, canyons, etc.
Types of Isolation2. Reproductive Isolation
› Animals in different areas of the country may develop different actions and behaviors.
› These different behaviors can cause groups to separate from each other and become different species.
Types of Isolation2. Reproductive
IsolationOrganisms may develop different mating seasons which do not correspond to one another
Individuals die, species go extinct
As the environment changes, organisms must have variations that allow them to survive (adapt) to those changes or dieIf an entire population of a species cannot adapt, that species becomes extinct.
There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyed
At least one of these has been attributed to
meteor impact and its
consequences.
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