Transcript 1.1-BIO-EVO-naturalselection

NATURAL SELECTION!!
• Watch DISCOVERY VIDEO on natural selection
• How have marine environments played an
important role in study the development of
populations?
Darwin’s Finches
Review Key Terms!
What is a variation?
Variations – differences among organisms of the same species
* For example, a species of rabbit has different colors of
like white, grey, mixed
* Occurs largely as a results of SEXUAL reproduction
* Can also occur because of mutations
fur
Review Key Terms!
What is an adapation?
Adaptations - an inherited characteristic that increases an
organism's chance of survival
*for example, cats have night vision to better hunt prey
Reviewing and USING Key Terms!
There are two tropical birds in the jungle, named
Megan and Sammy. Megan and Sammy are
brother and sister, but Megan’s wings are
about 4 inches longer than Sammy’s wings.
1. What is the variation between the birds?
2. Which bird has the adaptation?
3. What is the adaptation?
Add to “Natural Selection Notes!”
What is fitness?
Fitness- the ability to survive
AND reproduce
*fitness is the result of
adaptations
*fitness depends on the
environment
*those that are more fit will
reproduce, those that are less
fit will die
What is natural selection?
Natural selection is the process of evolution.
Individuals that are better suited to their environment are
able to survive and reproduce more successfully (they have
adaptations to be more fit)
*this is also known as survival of the fittest
*after many generations of time, only certain individuals of
a population produce new individuals
Which variation of cheetah is best adapted to live in
the environment shown here?
“Nerds Natural Selection Lab!”
• Groups of 2
– 1 warden (timer), 1 hunters
– Warden: spread Nerds onto environment
– Environment Cloth
– 15 seconds per hunt!
(3 trials)
____picked
up
Trial 1
Trial 2
Trial 3
_____picked ____picked
up
up
“Nerds Natural Selection Lab!”
RESULTS:
• EVERYONE: graph results
– POINTS will be awarded as follows:
• Name on graph
• Data on graph
• Labeled X axis
• Labeled Y axis
• Title for graph
“Nerds Natural Selection Lab!”
CONCLUSION SHORT ESSAY:
1. What were the
variations of nerds?
2. What variation of nerd
was best adapted to
survive in your
environment?
3. What is this process
called?
Review Key Terms!
What is NATURAL SELECTION?:
1. the process of evolution
2. Those individuals who are favored in the
environment are SELECTED FOR, and therefore
reproduce and pass traits to their offspring!
SHORT ESSAY – Evolution and Natural Selection
A species of birds lives on an island. The thickness of the birds' beaks varies
within the population. The birds feed mainly on seeds from plants. Birds with
thinner beaks can eat only small seeds. Only birds with thicker beaks can crush
and eat large seeds. There are many small seeds during years with more rain.
During dry years, there are very few small seeds and many large seeds. The
large seeds are harder to crush than small seeds.
The graph below shows the average beak thickness in the
bird population from 1979 to 1985: 1980 and 1982 were
dry years; 1984 was a wet year; 1979, 1981, 1983, and
1985 received normal rainfall.
•Explain why the average beak thickness changed
between wet and dry years.
•Explain how beak thickness would have changed
during the next ten years, 1986 to 1996, if these years
were wet years.
•Name and explain the process that led to this change.
Extra Slides Below
Optional BSCS Independent Research
Mutations as a Source of Variation
• Read this selection beginning on
Page 139 of the BSCS BOOK!
• Summarize the reading in your own
words.
• Explain the following:
Mutations  variations  adaptations
• How are mutations a part of natural
selection?
Polar Bear and Brown Bears
1. What variations must have existed to begin this process?
What possibly caused these variations?
2. What did the original bear population look like in the Artic?
Which bears were more fit for the environment? How did
the population change over 100,000 years?
3. Describe several ‘differences’ that have enabled polar
bears to survive in their environment. What are these
‘differences’ called?
4. What scientific process does this scenario illustrate?
Polar Bear and Brown Bears
1. What variations must have existed to begin this process?
What possibly caused these variations?
Variations in fur color; caused by differences in genes through
either sexual reproduction or mutations
2. What did the original bear population look like in the Artic?
Which bears were more fit for the environment? How did
the population change over 100,000 years?
Original population was probably brown, but lighter bears were
more fit. The bears with the lightest (whitest) coats survived the
best.
Polar Bear and Brown Bears
3. Describe several ‘differences’ that have enabled polar
bears to survive in their environment. What are these
‘differences’ called?
These ‘differences’ are called ADAPTATIONS!
• Better sense of smell, vision and hearing
• Sharper teeth
• Longer neck
• Warm thick fur and large paws
4. What scientific process does this scenario illustrate?
NATURAL SELECTION ! ! !
Evolution by Natural Selection
1. Variations exist in a population.
2. Some organisms are better suited for the environment (more
fit).
3. Nature “selects” the best individuals to survive! (Usually
based on specific adaptations.)
4. The surviving individuals reproduce more offspring like
themselves.
5. Over many generations, the population changes and new
species evolve.