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Transcript
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
The Beaks of Finches
A Laboratory Activity for the Living Environment
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
1. All 14 species of Darwin’s finches differ from each other in body size and/or beak size and shape
2. Different sizes and shapes differ in their efficiency at performing particular task
3. Not only do beaks vary in shape, but so do the muscles used to operate them
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
Paper clip
Clothespin
Tweezer
Tong
Test tube holder
Pliers
1. Examine the different tools (“beaks” and seeds provided. Predict with “beak” will be
the most successful at picking up small seeds. Give the reason for you choice.
The tweezers,
because they are easy to handle, and the end is sharp and small
2. Predict which “beak” will be the least successful at picking up small seeds.
Give the reasons for your choice.
The test tube holder, because it has flat and thin end.
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
Paper clip
Clothespin
Tweezer
Tong
Test tube holder
Pliers
3. From this point on, you and your partner will model a finch feeding. The tool you
were assigned will be your “beak”. Describe what characteristics it has that make
it good for picking up small seeds. In the remaining space or on a separate sheet,
draw an outline of your assigned “beak”.
The paper clip is good for picking up small seeds because it can be used as a
bag to keep seeds inside.
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
Do Now: Write down 3 things you learned about
• adaptation
• variation,
• struggle for survival,
• survival of the fit,
• differential reproduction,
• accumulation of traits
in “The Beaks of Finches” lab
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
1. What characteristics of your “beak” interfered with feeding success on the original
island?
The size, shape, type of edge, ability to handle it.
2. Name three traits other than beak characteristics that could contribute to the ability
of a finch to compete successfully
Wing strength, distance from the feeding place to the nest, eye sight, sharp
claws, etc…
3. Describe at least three beak variations that could randomly appear and further
improve your species’ chances of survival when feeding on small seeds.
Medium size, sharp ends, solid and easy to handle
4. Why did some “beak” types survive on the new island (which large seeds) when
they could not survive on the original island?
They are adapted to grip larger seeds better than small seeds
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
6. Did those who were successful in Round One survive equally well when other were
competing for food at the same dish during Round Two?
No. Fewer species survived when many species competed for food at the
same dish.
7. Why were there fewer survivors at the end of Round Three
There were fewer survivors due to increased competition
8. At the end of Round Three, were the types of “beaks that were successful on the
new island the same as the types of beaks that were successful on the original
island?
No, some beaks were better adapted to pick up small seeds whereas other
beaks did better job at picking up large seeds.
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
9. Explain how this activity simulates each of the concepts listed below as they are
involved in the process of natural selection.
a. Environment: Students = birds, seeds = food, tools = beaks; tables = islands,
cups = nests
b. Variation Different types of beaks, and different sizes of seeds: large and small
seeds
c. Struggle for survival Each bird trying to get enough seeds to survive
d. Competition More than one bird feeding at one bowl
e. Survival of the fit Those birds with beaks better adapted to the seeds survive
f. Adaptation Some beaks are better than others at picking up smalls seeds
g. Differential Reproduction
Those birds with better adaptation produce more
offspring
h. Accumulation of Traits After many generation all birds in the population got
beaks adapted to the seeds present in the environment
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
10. Predict which species of finch would be most likely to survive if the weather on the
Galapagos Islands gradually changed and the seeds available to the finches
became larger with heavier coverings.
Large Ground Finches, because they have big, thick beaks to break the seed
heavy coverings.
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
11. One island is populated by two species Small
Ground Finches and Small Tree Finches
a. What two types of food would you expect to be
available on this island?
Animal food (such as insects) and
plant food (such as seeds)
b. Would you expect the two species to compete for
food on this island?
No, they would not compete because they feed on
different kind of food.
c. How might the two native finch populations be affected if several dozen Sharp-billed
Ground Finches were to migrate to the island and survive?
The Small Ground Finches might have to compete with the new Sharp billed
Ground Finches, since they have similar food preferences and beaks.
Therefore, Small Ground Finch population will decrease.
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
12. a. Explain how an island could support large populations of both Large Ground
Finches and Small Ground Finches
The island would need to have both large and small seeds available
b. How could you use the materials provided in this lab to test your explanation?
I would put many large and small seeds
in separate dishes.
Then, I would run trials using tools
from the “large-seed survivors”
and tools from the “small-seed
survivors” to compete for the
seeds in the dishes
Beaks that were
Present at the beginning of the activity
Successful at feeding in Round One on
the original island – fed on small seeds,
did not need to migrate
Not successful at feeding in Round One
on the original island – fed on small
seeds, had to migrate to the new island
Successful at feeding in Round Two on
the original island- fed on small seeds
Successful at feeding in Round Two on
the new island – fed on large seeds
Not successful at feeding in Round Two
on either island – species dies out
Successful at feeding in Round Three
on the original island – fed on small
seeds
Successful at feeding in Round Three
on the new island – fed on large seeds
Not successful at feeding in Round
Three on either island – species
eliminated
# of beak
types
Characteristics of Beaks
(Size and shape)
Objective: Understand How Natural Selection Works
Key Words: adaptation, environment, struggle for survival, survival of fit,
differential reproduction, accumulation of traits, natural selection
9. Explain how this activity simulates each of the concepts listed below as they
are involved in the process of natural selection.
Variation
Different types of beaks,
Different sizes of seeds: large and small seeds
Competition More than one bird feeding at one bowl
Struggle for survival
Adaptation
Environment
Each bird trying to get enough seeds to survive
Some beaks are better than others at picking up smalls seeds
Students = birds, seeds = food, tools = beaks
tables = islands, cups = nests
Selecting agent
The type of seed available in the environment