The concept of Evolution was first suggested by Charles Darwin.

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The concept of Evolution was first suggested by
Charles Darwin.
He called it descent with modification.
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Since then massive amounts of evidence has been
collected by thousands of scientists. The concept
has been tested and confirmed in many different
ways making the idea into a
Theory
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Evolution occurs over time because of the
process of
Natural selection
Darwin thought that the process of evolution is
controlled by nature. Natural selection suggests
that traits that help an organism survive in a
changing environment are passed on to the next
generation. Favorable Traits Over many
generations, species change.
According to Charles Darwin, Natural Selection
can influence evolution by
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1. Overproduction of Offspring
Species can produce more offspring than can
possibly survive. In a stable environment,
populations remain the same from year to the next
because not all of the offspring that are born or
hatched survive.
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So. Overproduction, leads to a struggle.
Organisms compete for food, water and shelter.
Those well suited to their surroundings, survive
and reproduce. The rest die.
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2. The struggle to survive
Organisms within the same niche, compete for
limited (finite) resources food, water,
shelter. Battle environmental conditions
temperature, disease, predators.
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3. Variations
Organisms within a species are never exactly
alike. Members of a population differ so that
only some survive if the environment changes.
survival of the fittest. They can differ in
structure, size and color.
Variations among individuals can lead to changes
in an entire species.
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In sexually reproducing organisms, only changes
in the genes of sex cells can become the basis
for evolutionary change.
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selective breeding
Man breeds organisms with specific traits that we
have selected. This is opposite to Natural
Selection.
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• The differences among offspring are due to
  genetic variation. The unique combination of
  traits each organism inherits from its
  parents.Variability is the raw material for
  natural selection to work upon.
• Genetic Variability comes from
• Mutations A change in the base sequence of a DNA
  molecule. When it happens in sperm or eggs, the
  mutation is passed on to the offspring.
• Radiation (X-rays) Chemicals ( Drugs)

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2. Independent Assortment. During Meiosis the
genes (on the chromosomes) get shuffled
randomly into the egg and sperm. This creates
different kindsof sperm and eggs.
a.
fertilization
The genes recombine during
Note that two of the four offspring in the
punnett square at the right have a completely
different genetic makeup than that of either
parent.
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3. Crossing-over of portions of chromatids
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Remember.. Only changes in sex cells can be
passed on to offspring. Example If a father
builds huge muscles from working out, will not
pass large muscles on to his offspring. A mom
gets a nice tan, the baby will not be tan.
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Certain variations (appearances or behavior) are
beneficial or an advantage, those best adapted to
their environment by having certain traits,
survive, and reproduce passing those traits on to
their offspring. A trait that helps an organism
survive in its environment is said to have
adaptive value. So. The number of organisms with
this useful trait increase.
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Offspring of survivors make up a larger portion
of the population
Beneficial traits become more common in a
population. (gene pool) Harmful traits become
less common in a population. As this happens
over time it is said the species is evolving.