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Transcript
1859: Charles Darwin:
The Theory of Evolution:
It works through Natural Selection.
Darwin’s Theory of Evolution
• Evolution occurs as a
result of natural
selection and
variation
Overproduction
• In each generation,
more offspring are
produced than can
survive
• This leads to :
Competition
• Individuals struggle to
survive by competing
for food, water,
shelter, mates etc
Variation
• Characteristics that
are different
among organisms
of the same
species
• Ex- size, strength,
color, disease
resistance
Example of Natural Selection:
1. Variety of neck
lengths existed.
2. Shorter necks
were weeded out.
3. Long necks
reproduced and
passed on the
long-neck gene.
Adaptations
• An inherited trait
that increases an
organism’s chance
of survival
Adaptations
Adaptations
Favorable Adaptations
= Helpful variations that are passed
through the species.
Survival of the Fittest
• The organisms that are best
adapted to the environment
will live long enough to
reproduce
How did deer evolve to be fast runners?
1. Variety existed.
2. Overproduction of
deer.
3. Predators apply
pressure.
4. Slow deer are weeded
out.
Reproduction
• Surviving individuals pass their traits on to
their offspring
Evolution of a New Species
• An accumulation of
passed on
variations will allow
a new species to
form
Formation of new species.
(When several changes build up over a long period of time.)
• Evolved from a common ancestor but
can no longer mate with each other.
All life on Earth is the
result of speciation ( the
evolution of new species).
Evolution
• Individuals do not evolve.
• Populations do.
A change in the genetic make-up of
a POPULATION over time.
Natural Selection STEPS:
1. Variety already exists due to…
•
•
MUTATION (radiation or replication mistakes)
SEXUAL REPRODUCTION (meiosis)
2. A “selective pressure” exists
which weeds out the “Less Fit”.
3. Only the fittest survive and
reproduce.
4. The population as a whole is
different than before.
Closure questions
• Answer the following question