Connect!
• Who was Gregor Mendel?
• What contributions did Mendel make to
the science of biology?
• Give 5 facts about Charles Darwin.
B. THEORIES OF EVOLUTION
• Theories of evolution attempt to explain the
diversity among species.
• A major part of these theories are adaptations.
Adaptations are features (structure, function, or
behavior) which make a species better suited to
live and reproduce in its environment.
Darwin’s Theory
• is based on variation and natural selection
• developed after he observed variations in
species.
• According to Darwin, evolution occurs because
of natural selection; organisms better adapted
to the environment survive and reproduce while
others do not.
Chunk!
• What does the Theory of Evolution
attempt to explain?
• Define adaptation, and give an example.
• What did Darwin base his theory on?
• Explain evolution in terms of variations,
adaptations, and natural selection.
Ideas in Darwin’s Theory:
1. Overproduction – Within a population,
more offspirng are born than can possibly
survive.
2. Competition – Because of overproduction,
there is a competition of a “struggle for
existence” between organisms for space,
food, water, or other limited resources.
Competition limits population size.
3. Variation – Members of a population
show variations or differences in traits
that make certain individuals better
adapted to survive (usually a structure,
function, or behavior)
4. Natural Selection – Since some
variations are more beneficial than others,
there is natural selection against organisms
that cannot adapt and they die off. “Survival
of the fittest” applies to the individuals who have
variations that enable them to survive.
5. Transmission of Variations – Organisms
with helpful variations are more likely to
survive and reproduce, passing on these
variations to their offspring.
6. Speciation – Over long periods of time,
variations accumulate in a population.
Eventually, the variations are so numerous
that the population is different from the original,
and represents a new species.
Chunk!
• Name the 6 parts to Darwin’s Theory.
• Give an example of each.
Darwin’s
Finches
• How did
all these
species of
finch
come to
exist on
the tiny
Galapagos
Islands?
Adaptive Radiation in Galapagos Finches
• THINK…why do you think this is called “adaptive
radiation”?
Learn how to read this chart…
•
•
•
•
•
Name two species that do not have to compete for their food.
Which species does the warbler finch have to compete with?
Why doesn’t the small ground finch compete with the small tree finch?
What species does the large ground finch have to compete with? Why?
What do the woodpecker finch, warbler finch and cactus finch have in
common?
• Although variations were a major part
of Darwin’s Theory, he did NOT
understand the basis for variations.
Some variations help in
survival, and are passed on
to offspring!
Inherited factors can
make offspring different!
• Explain
the
science
behind
this
cartoon.
DYGI?
(Do Ya Get IT?!)
Image Sources
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Darwin - selfexpressions.net/.../CharlesDarwin.jpg
Bird adaptations - animals.howstuffworks.com/.../printable
Baby snakes - fohn.net/.../baby-corn-snakes.jpg
Two snakes, winning snake - static.flickr.com/67/188076925_0c695850e3.jpg
Color variations - aqualandpetsplus.com/Snake94.jpg
Albino - grandpacliff.com/.../albino-snake-pine-b.jpg
Snake species - www.scielo.br/.../jvatitd/v15n4/a06fig02.jpg
Photos of Darwin’s finches - www.galapagoscruises.be/darwins-finches.jpg
Adaptive radiation - media-2.web.britannica.com/eb-media/11/54911-.
Chart - www.pbs.org/.../01/6/images/l_016_02_l.gif
Darwin clip art (modified from) - evolution.berkeley.edu/.../darwin_cartoon.gif
Mendel redwood cartoon - members.pioneer.net/~mchumor/00images/1818_fo.
Mendel clipart - www.larrygonick.com/images/sch/mendel.gif