Download Evolution By Natural Selection

Evolution By Natural
Selection
Charles Darwin
In 1831 Charles Darwin sailed to the Galapagos islands
While exploring he made many observations about the plants
and animals there
He collected samples and notes and then studied them for 20
years at home in England
Through his studies he developed the 4 conditions for Natural
Selections
NATURAL SELECTION: the process whereby organisms better
adapted to their environment tend to survive and produce more
offspring. The theory of its action was first fully expounded by
Charles Darwin and is now believed to be the main process that
brings about evolution.
Darwin’s Four conditions
for natural selection
1.Traits in a population of
organisms exhibit variation
~ parents reproduce offspring that are not exactly the
same
~ offspring are “similar” but have differences
~ individuals can vary in traits that range from size and
shape to how they act or function chemically
2.Not all individuals survive to
reproduce
~ for some species like salmon, they lay
thousands of eggs while only one or two will
reach adulthood
~ even if an animal makes it to adulthood they
may not reproduce, especially if they can’t find
a suitable mate
3.Survival is not Random
~ survivors must have an
advantage over those that don’t
survive
~ this advantage is the result of a
particular “variation” in a
trait
4. Surviving individuals “good traits”
must be heritable (ability to be passed to new
generations)
~ Evolution can happen only if “good traits” or advantages can be
passed from one generation to the next
~ some individuals contribute more offspring to the next
generation and their traits will slowly grow more and more
common in the population, when this happens the population is
evolving
Along with developing the principals of Natural Selection
Darwin also developed the description of how animals
became so diverse with the explanation of “Adaptive
Radiation” which can also be called divergent evolution or
speciation.
Adaptive
Radiation
adaptive radiation is a process in
which organisms diversify rapidly
into a multitude of new forms,
particularly when a change in the
environment makes new resources
available, creates new challenges,
or opens new environmental
niches.