Transcript Natural Selection - ESC-2

Natural
Selection
What’s for dinner
1. Take the pink sheet of paper and lay it on
your desk.
2. Dump some of the Ziploc bag of dots onto
the white paper.
3. Spread the dots out evenly so that they do
not overlap each other.
What’s for dinner
4. Take the tweezers and get ready to pick up as
many dots as you can.
5. Your table partner will time you for 15
seconds. Pick up as many dots as you can with
the tweezers and place them in the petri dish.
6. Once time has been called, count how many
dots you have picked up. Place your data in
the table.
Color of Dots
Number Picked Up
white
pink
7. Which color was easier to pick
up?_________________________________
8. Why do you think that color was easier?
___________________________________
9. If you were a dot and did not want to be
eaten by the tweezer monster, which color
would you want to be?________________.
Charles Darwin
(1809-1882)
• Studied biology
• In 1831 at age 22, he accepted a job on the
HMS Beagle as a scientist
• The HMS Beagle docked at the Galapagos
Islands off the coast of South America
Charles Darwin
(1809-1882)
• Based on fossil evidence, Darwin knew plants
and animals change over time
• Believed organisms had changed slowly over
time and would keep changing
• The environment and adaptability of the
organisms controlled the changed.
What he saw in the Galapagos…
What he saw in the Galapagos…
• Each island had similar animals with slightly
different traits
– Long or short necked tortoises depending on the
plant height
What he saw in the Galapagos…
– Finches had
many different
beak sizes and
shapes
depending on
diet
Natural Selection
• Darwin’s theory that organisms changed over
time based on traits that helped them survive
• Survival of the fittest
Natural Selection
• Organisms with traits that help them survive
grow and reproduce passing on those traits to
their offspring
• Organisms with traits that don’t help them
survive are usually eaten or die and don’t pass
on their traits
Natural Selection
• Factors that can affect the process of natural
selection
– Overproduction of offspring in a species
– Competition among organisms of same species
– Genetic variations within a population
Peppered Moths
• In England there is a species of peppered
moth
• They come in two color variations
– Light
– dark
• The trees they lived on had a light bark color
• During the industrial revolution, factories
were built that produced soot
• The soot stained the tree bark black
Peppered Moths
• Use the moth and bark pictures on your desk to
answer.
• Which moths were better adapted to the trees before
pollution? light
• Which moths were adapted to the trees after the
pollution? dark
Elephant Example
• Let’s say a group of elephants had mostly
short trunks
• But a few of the elephants in the group had
slightly longer trunks than others
• When food and water became scarce, the
elephants with longer trunks could reach
higher for food and deeper into holes for
water
Elephant Example
• Elephants with shorter trunks would die of
thirst and starvation
• Elephants with longer trunks would survive
and reproduce passing on their longer trunks
• Over time, the group would consist mostly of
long trunked elephants
Elephant Example
• Put the elephant cards in the right order
Which Beak is Best Lab
When Charles Darwin explored the Galapagos
Islands, he discovered 31 different species of
ground finches with many different beak sizes
and shapes. He theorized that that over time,
different groups of finches adapted to their food
source by changing their beak shapes. Each
beak shape could be matched to the type of
food the bird ate.
Which Beak is Best Lab
Materials
spoon
tray with sand tweezers
pieces of string eye dropper
styrofoam fish
beaker of water graduated cylinder of water
Procedure
Look at the shapes of the bird beaks in the
chart. Under each bird’s picture, give at least
two things you think it might eat based on the
shape of it’s beak.
Which Beak is Best Lab
Which Beak is Best Lab
On each table there is a spoon, tweezers and
an eyedropper. These items are your beaks.
There is also a beach filled with worms, a
pond filled with fish and a flower with liquid
nectar. Using your beaks, decide which beak is
best suited to catch and eat each type of food.
Which Beak is Best Lab