Download Darwin`s Theory

Warm-Up: Evolution
• Each table will be given a clip-art image
with a number.
– Copy the number of the scratch paper side of
the paper.
– Person 1 will draw this clip art image on the
other side of the paper. Teacher will collect
original picture.
– Drawing from person 1 will rotate to person 2
at the next table and they will repeat above.
– This will continue with 2 other tables so that
persons 3 and 4 produce a drawing.
Darwin’s Theory
(set paper up as shown below using a ruler)
Test
Questions
Teacher Notes
Notes will go in this
section
Picture (1 per
slide)
Darwin’s Theory
Galapagos Islands
Who is he?
• December 1831, HMS Beagle
(British ship) went on a 5-year
trip around the world
• 22 year old Charles Darwin –
naturalist
- observed plants and animals
- led him to develop the theory
of evolution by natural
selection
I. Darwin’s Observations
• Included:
1) the diversity of organisms,
2) remains of ancient organisms,
3) and characteristics of organisms
on Galapagos Islands
• A) Diversity
– Saw tremendous diversity
– Scientists have now identified 1.7
million species
– Def. species: organisms that can
mate & produce fertile offspring
Darwin’s Observations (cont.)
• B) Fossils
• Def. fossil: the preserved remains or traces of an
organism that lived in the past
Giant Sloth
• Darwin saw bones of past sloths
that were larger than
when he
lived.
II. Galapagos Organisms
• Darwin found similarities between Galapagos
organisms & South American organisms
• A) Comparisons to S. American Organisms
– Many similarities as main land
– Important differences:
Islands
Mainland
Fed on
seaweed
Fed on leaves
Large claws
Small claws
– Small number of plants and animals
had to reach island
• End of part I
Galapagos Organisms (cont.)
• B) Comparisons Among Islands
– Saddle shape vs. dome shaped
shells for tortoises
– The beaks of finches also differed
(figure 3 p. 227)
• C) Adaptation
• Def. adaptation: a trait that helps an
organism survive and reproduce in
its environment
• Examples
1. Beak structure determines type of food.
2. Poisonous or bad tasting milkweed
3. Bright colored flowers attract insects
III. Evolution
• A) Darwin’s Reasoning
1. Plants & animals on island
face environmental factors
different from mainland
2. Species gradually change
3. Species become better
adapted to new environment
• Def. evolution: gradual change in a species
over time
• Def. Theory: concept that explains wide range
of observations
Evolution (cont.)
• B) Selective Breeding
When humans select a
specific trait they want to
pass to offspring
(ex1) Sheep with fine wool
(ex2) Pigeons with more
than average number of
feathers
IV. Natural Selection
• Def: individuals that are
better adapted to
environment and more
likely to survive and
reproduce
• Factors that affect process:
(fig. 5)
1. Overproduction
2. Variations
3. Competition
Natural Selection (cont.)
• A) Overproduction
only strong survive since there
isn’t enough food, water and
living space
• B) Variations
slight differences in traits
(ex) Insects food choices
• C) Competition
food and other resources are
limited
Natural Selection (cont.)
• D) Selection
- some variations
make individuals
better adapted to their
environment
- environment “selects”
organism with helpful
trait
- can cause change
Natural Selection (cont.)
• E) Environmental Factors
- can affect organism’s
ability to survive
(ex1) Copper in soil with
monkey flower
(ex2) Smoke on trees with
moths
Natural Selection (cont.)
• F) Genes and Natural Selection
- variations in organisms can
result due to mutations in genes