Download Chapter 5, Section 1 notes

Chapter 5
Changes Over Time
Section 1
Darwin’s Voyage
What is Evolution?
•Evolution is a
change in a species
over time.
Mutations
• Mutations are changes because of a
mistake in the DNA code
• Mutations may be either helpful or
harmful
• Helpful mutations increase the species’
chances for survival
• Other mutations may decrease or have
no effect on the species’ ability to
survive
Adaptations
• Adaptations are traits that
help an organism survive.
• Example: beak shape
Natural Selection
• The Survival and reproduction of
the individuals in a population that
exhibit traits that are better suited
for their environment
• AKA: “Survival of the Fittest”
• Concept originated with Charles
Darwin
Factors that influence the
process of Natural Selection
• Overproduction
• Competition
• Variations
Overproduction
• Producing more offspring
than can survive
• Ex. Dandelions overproduce
their seeds to assure that at
least some seeds will survive
Competition
• Offspring must compete
with each other to survive
• Usually indirectly, ex.
Turtles may fail to find
enough food to eat
Variations
• There are small variations or
differences among the members of the
same species.
• Mutations increase the amount of
variations
Make certain individuals better adapted
to their environment because of the
helpful traits they possess.
•Over a long period of time,
natural selection can lead to
evolution
• Helpful variations gradually
accumulate in a species, while
unfavorable ones disappear.
Isolation
• Occurs when some members of a
species are cut off from the rest of the
species.
• A new species forms when individuals
remain separated from the rest of the
species long enough to evolve new
traits.
• Geographic isolation has occurred in
the past because of continental drift.
Continental Drift