Download Unit 8: Natural Selection

Unit 8:
Natural
Selection
(1) Genetic Variation & Diversity
• There must be variety / diversity for
evolution.
• Genetic Variation / Diversity 
Individuals in a population have all inherited a
unique combination of traits, giving each unique
skills/strengths/weaknesses/appearances.
• Genetic Variation allows for some individuals
to succeed during “rough times” / changes 
AND THIS ALLOWS THE POPULATION TO
SURVIVE!
(2) What About Mutations?
• Organisms CANNOT mutate whole, fully
functioning body parts.
• Organisms can pass on small body
mutations, over thousands of years, leading
to the development of a new body part.
• Mutations can either hurt, or provide an
advantage to individuals during times of
change.
– Both = Evolution
(3) What is Natural Selection?
• As the environment changes, certain
characteristics amongst living things will
help them to survive (Survival of the Fittest).
• If you don’t have these characteristics, you will
most likely die.
• Example: The Flu
– 1000’s of people die each year from the flu.
– Those with a strong enough immune system live.
– Those who have weak immunity, die.
(4) Struggle for Existence
• Living things are always competing to stay
alive AND pass on their genes:
– Limited food
– Limited water
– Limited shelter
– Changes in climate, disease transmission, etc.
• Those who can survive and reproduce
during tough times are best suited/adapted to
their environment.
(5) What does it mean to Adapt?
• Evolutionary Adaptation:
Having the traits necessary to remain living and
sexually attractive during times of change.
• It does NOT mean:
To change/grow body parts so that you can
(6) The End Result of Natural Selection
• There will be a change in the allele
frequencies in the population.
• Example:
– Start with a population of large lizards.
– Decrease in climate oxygen and available food +
water.
– Larger lizards do not survive during the change.
– End with a population of smaller lizards.
Now Let’s Watch This Video…
Natural Selection video
Hummingbirds
YouTube Video