Transcript Theory of Natural Selection

Theory of Natural Selection
Charles Darwin (1809-1882)
Theory of Natural Selection
• Charles Darwin was born into a
rich family - his father was a
physician. At his father’s urgings,
Darwin studied medicine, but
gave it up. He then pursued
theology to become a minister in
the Church of England and gave
that up as well for his real love
which was nature - studying
animals.
HMS Beagle
• When he was 22 years old,
Darwin applied to be the
naturalist aboard a ship, HMS
Beagle, that was setting out
from England to go chart the
coastline around South
America. The expedition was to
last 2 years, but ended up
lasting 5. During that time,
Darwin collected many
specimens and made detailed
observations about the species
he encountered.
The 5-Year Journey
Darwin’s Journey
Galapagos Islands
The most significant
of Darwin’s
observations were
those he made on the
Galapagos Islands off
the coast of Ecuador.
He found species
here that were similar
to ones on the
mainland, but they
were slightly different
in certain
characteristics.
Darwin’s Finches
Galapagos Island Fauna
Blue-footed Booby
Marine Iguana
Theory of Natural Selection
Consists of 5 main ideas:
1. Variation that is inheritable.
2. Overproduction
3. Struggle for existence
4. Survival of the fittest
5. Origin of new species by inheritance
of successful variations
Natural Selection, cont’d
1) Variation
– Individuals within a species are not
identical; they have variations.
– These variations may affect the individual’s
ability to get food, escape predators, find a
mate, etc.
– These variations can be passed on to
offspring
Natural Selection, cont’d
2) Overproduction
– Most species produce far more offspring
than are needed to maintain the
population.
Natural Selection, cont’d
3) Struggle for existence
– Living space and food is limited and so
individuals within a species must compete
with each other in order to live long enough
to reproduce.
Natural Selection, cont’d
4) Survival of the fittest
– The individuals with traits that give them an
advantage are better able to compete,
survive, and reproduce, thus passing their
“successful” genes onto their offspring.
– Nature “selects” the creatures that are best
adapted to their environment.
Natural Selection, cont’d
5) Origin of new species
– Over many generations, favorable
adaptations gradually accumulate in the
species and unfavorable ones disappear.
– Eventually the changes become so great
that the end result is a new species.