Evolution by Means of Natural Selection

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Evolution by Means of Natural Selection
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• Over a great period of time evolution can result
  in the formation of a new species.
• This is called?
• Speciation

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• Evolution only occurs when there is a change in
  ___________________________ within a population
  over time.
• GENE FREQUENCY

1st generation of Beetle population
Many generations later of the same population
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Mutation

• A change in a DNA sequence, usually occurring
  because of errors in replication or repair. This
  is the ultimate source of genetic variation.

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Migration
The chance of an individual moving to another
population and sharing its genes there.
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Genetic Drift

• The drift over time of allele frequencies in a
  population due to random sampling effects forming
  successive generations.

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Natural Selection

• A process of evolution in which traits that
  result in better fitness of an individual
  survives to the next generation.

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• "One obstacle to understanding evolution is the
  common misconception that individual organisms
  evolve.
• It is the population, not its individuals, that
  evolves, as some heritable variation becomes more
  common at the expense of others."

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What influenced Darwin to develop the theory of
evolution?

• Fossil Record

Fossil Record
Geographic Distribution
Embryology
Homologous Structures
Vestigial Structures
Artificial Selection
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What Do Modern Scientists use as evidence of
evolution?

• Similar Biochemistry
• DNA
• ATP
• Hormones

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Natural Selection
The Modern Understanding of Darwins Principles
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Adaptations

• Hereditary characteristic that helps an organism
  survive and reproduce under a certain set of
  environmental conditions.
• Example color patterns can be advantageous to an
  animal, making it inconspicuous to its predators

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The Co-evolution of Predator and Prey

• Consumption of one species (the prey) by another
  (the predator)
• Natural selection shapes the body forms and
  behaviors of both predator and prey

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Natural Selection, Predators, and Prey

• Prey that can survive attacks from predators will
  reproduce and pass those traits down to their
  offspring.
• Predator that can beat the competition for food
  will survive and reproduce, passing on their
  traits to their offspring

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• The predators with the best hunting equipment
  will survive and reproduce, passing on their good
  hunting traits

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Acute Senses
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• The prey with the best way of avoiding predators
  will survive and reproduce, passing their traits
  to the next generation.
• Predator and prey both evolve more efficient ways
  to interact. They adapt to each other.

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Mimicry - the ability of some creatures to
imitate others, either by sound or appearance for
protective purposes
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• Camouflage - Protective coloring or another
  feature that conceals an animal and enables it to
  blend into its surroundings.

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Chameleon
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Stick Bug
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Warning Coloration

• Conspicuously recognizable markings of an animal
  that serve to warn potential predators of the
  nuisance or harm that would come from attacking
  or eating it. The bold patterns of skunks and the
  bright colors of poison arrow frogs are examples
  of warning coloration.

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The Role of the Environment

• When the environment changes, organisms are
  forced to adapt.
• Hereditary characteristics help organisms survive
  and reproduce under a certain set of
  environmental conditions.
• What are some examples of big environmental
  changes?

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What Limits a Population?
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• Carrying Capacity the number of individuals
  that an environment can support
• Affected by predator prey relationships and the
  environment

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Competition- When two or more organisms go after
the same limited resources

• In an environment resources that support a
  population are limited.

There is only so much food, space, water, and
other essentials available to support the
population
We call these resources that support a population
but have the chance of running out, LIMITED
RESOURCES
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When populations grow, competition increases, as
limited resources decrease.
Only those with better adaptations will survive,
and the weak will struggle. SURVIVAL OF THE
FITTEST! Natural Selection
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Bear and Salmon
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A lag phase (very few organisms to begin with
reproduction is slow B acceleration phase C
exponential phase F population crash due to
limited resources
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Predator Prey Relationships Balance Populations

• Predator Prey relations are important to balance
  an ecosystems populations.

If prey populations increase what will happen to
the predator population?
It will increase due to the larger amounts of
food available.
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You can see an obvious cycle, prey numbers go up
followed by predator numbers going up, then prey
drops, predators drop
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If the deer population became out of control in
Effingham, what could be done to control or
balance the population?