Natural selection
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NATURAL SELECTION. EVOLUTION. Process of natural selection over time; genetic change (variety and diversity) combined with constantly changing environments. the mechanism of evolution organisms that are better suited to survive in a given environment are more likely to survive & reproduce

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NATURAL SELECTION

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Natural selection

NATURAL SELECTION


Evolution

EVOLUTION

Process of natural selection over time; genetic change (variety and diversity) combined with constantly changing environments

the mechanism of evolution

  • organisms that are better suited to survive in a given environment are more likely to survive & reproduce

  • determines the differential survival of groups of organisms

  • creates biodiversity & variationbiodiversity= sum of diff kinds of ALL organisms in an ecosystem

NATURAL SELECTION


Natural selection1

NATURAL SELECTION

Elements required:

  • Population is growing

  • Variation among individuals in population

  • That individual variation is heritable

  • Stress or competition for resources (“struggle for survival”)


Adaptation

ADAPTATION

A feature produced or preserved by natural selection

  • Traits= GENETIC characteristic that helps an organism survive

  • Adaptive traits are helpful:they are “selected FOR” Ex/ Camouflage

  • Disadvantageous traits are NOT helpful; they are “selected AGAINST”Ex/ coloration that stands out


Adaptation1

ADAPTATION

Can be structural or behavioral

  • Behavioral adaptations

    things the organism does to survive;

    Ex/ migration

  • Structural adaptations

    • features of the organism;

    • Ex/camouflage


More on adaptation

MORE ON ADAPTATION

More diversity = increased chance that at least some individuals will adapt to survive future environmental change

  • diverse bacteria

  • ecological opportunity for antibiotic-resistant bacteria

  • new population of antibiotic-resistant bacteria


Natural selection revistied

NATURAL SELECTION REVISTIED

How are organisms “favored?”

The organisms that are well-suited have advantageous traits (adaptations)

  • They are better at surviving and reproducing – so the traits (genetic change) is passed on

  • “selected FOR” example: camouflage

The organisms that are not well-suited are not as well adapted, and may die before they can pass their traits on to the next generation

As an environment changes, the selection for the adaptive traits is realigned with the change

Over time, populations evolve to have traits that are adapted to their environments.


Natural selection

NATURAL SELECTION CLASSIC EXAMPLE:Industrial Revolution & the Peppered Moth

  • 2 varieties of moth: dark and light

  • Pre-Industrial Revolution  dark moth was rare

  • During the Industrial Revolution  light moth became rare

  • WHY? Some moths had an adaptive advantage that  fitnessThose adaptations were passed on and that trait was selected FOR.


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