Tuesday, June 2, 2015 HOMEWORK: Evolution Test June 10,11,15,16 OBJECTIVE: I will be able to create a model that shows the change in a species over time/natural

Tuesday, June 2, 2015• HOMEWORK: Evolution Test June

10,11,15,16• OBJECTIVE: I will be able to create a model that

shows the change in a species over time/natural selection by using evidence and including topics such as populations, individual, traits, versions of traits, advantageous, and environmental change.

• DO NOW: Turn in Red Bellied Snake packet(Doc#12)Which topic (big horn sheep, peppered moths, or snakes) was most helpful in helping you understand evolution? Why?

Developing a general model

• We have studied three evolutionary cases in detail.

• Now we’ll use what we have learned to develop a general model.

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I will be able to create a model that shows the change in a species over time/natural selection by using evidence and including topics such as populations, individual, traits, versions of traits, advantageous, and environmental change.

Natural Selection• The evolutionary models that we have been developing are called

“natural selection” models. Natural selection means that some animals survive and have more offspring because they have a trait that is advantageous in the environment. For example:

– Mountain sheep with small horns survive better and have more offspring when hunters are around because hunters don’t shoot them. We say that sheep with small horns are naturally selected, because in their environment, they are the ones that survive better and have offspring.

– Moths that are light-colored survive better and have more offspring when they rest on light-colored trees, because they are better camouflaged on light-colored trees. We say that the light moths are naturally selected because in this environment, they are the ones that survive and have more offspring.

• We are going to make a general model of natural selection.

3I will be able to create a model that shows the change in a species over time/natural selection by using evidence and including topics such as populations, individual, traits, versions of traits, advantageous, and environmental change.

Words that may be helpful as you think about what the modelshave in common

• A population is a collection of animals or plants in a species. – Example: All the moths living in forests in New England

are a population of moths.– Example: All the red-bellied black snakes living in

Australia are a population of red-bellied black snakes.• An individual is one animal or plant in a

population.– An individual moth is one moth.– An individual red-belled black snake is one snake.

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Words that may be helpful as you think about what the models have in common

• Traits. Here are some examples.– Wing color in moths.– Weight of moths.– Ear size of rabbits.– Hair color of humans.

• Versions of traits. Here are examples:– Wing color in moths is the trait: one version of the trait is dark;

another version is light.– Weight of moths: One version of the trait is 3 grams. Another

version of the trait is 2 grams.– Ear size of rabbits: One version of the trait is large. Another

version of the trait is short.– Hair color of humans. One version of the trait is blonde. Another

version is brown. Another version is black. Another is red.

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Trait versus Version of Trait

• In each group, which is the trait, and which are versions of the trait?– color of hair, red, brown– thick, thin, width of tail– 22 inches, 12 inches, length of horn– fast, speed, slow– Length of dance, 25 minutes, 15 minutes

• For human hair, what are some traits? What are versions of each trait?

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• The advantageous version of a trait is the version of a trait that helps individuals in a particular environment.– Example: Lighter wing color is an advantageous

version of the wing color trait for moths when the trees have light bark.

– Example: Small heads are an advantage trait for snakes when there are poisonous toads around, because then they cannot eat the toads and die from the poison. 7


Check understanding

• When there are lots of hunters, what is the advantageous version of the trait horn size for male mountain sheep?

• When trees have dark bark, what is the advantageous version of the trait wing color for peppered moths?

• When mice live on a beach with gray sand and want to hide from birds looking for them from above, what is an advantageous version of the trait fur color for mice?

• When rabbits live in a hot desert, what is the advantageous version of the trait ear size for the rabbits?

8I will be able to create a model that shows the change in a species over time/natural selection by using evidence and including topics such as populations, individual, traits, versions of traits, advantageous, and environmental change.


• An environmental change is a change in the environment. – If hunters start hunting in an area, that is an

environmental change.– If tadpoles are living in a quiet pond, and

dragonfly larvae move to the pond, that is an environmental change.

– If the color of trees that moths rest on changes, that is an environmental change.

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Check understanding

• What was the environmental change that caused snakes’ heads to get smaller over time in Australia?

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What parts do the two models have in common?

• You will receive models of two of the natural selection changes you have studied: peppered moths and red-bellied snakes. Each of these models fits the evidence you have seen. Discuss in your groups: What parts of these models are similar or the same? Write down everything you can think of that you see that is common to both models.

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Useful words• As you think about what the models have in

common, these words may be helpful:– Population – Individual– Trait– Version of a trait– Advantageous version of a trait– Environmental change

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Begin working on #1 on page 1.


Sharing ideas

• Now we’ll share everyone’s ideas as a class.

• Generate list on board

• Anything else to add?

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Closure

• Using our list on the board:

• Look at the list and determine what happens in Step #1 in both models.


What does each step have in common?

We can take all the things that the models have in common to make a general model of what happens. We call these models of natural selection. Look at the list we have.

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What does each step have in common?

What happens first in both models?

Use general language that applies to both models.

•What does it say in both cases about variation? •In one case, most of the moths start out light colored, and in the other, it looks like a lot of the snakes start out with big heads. •How could we make a general statement that covers both of these ideas?

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What did you come up with1. The initial population varies in many traits.

Individuals have one version of some traits.


Continue with Steps 2 through 5

• Now work in groups to write what happens, step by step, in Steps 2 to 5.

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What did you come up with1. The initial population varies in many traits.

Individuals have one version of some traits. 2. An environmental change occurs.3. Individuals with one version of a trait are more likely

to survive after the environmental change. The trait is advantageous in the new environment.

4. The individuals that survive more reproduce more. Their offspring vary but are similar to them. So more offspring have the advantageous version of the trait.

5. After many generations, the population still varies, but most individuals have the advantageous version of the trait.

Closure

• What is natural selection?


Documents

Tuesday, June 2, 2015 HOMEWORK: Evolution Test June 10,11,15,16 OBJECTIVE: I will be able to create a model that shows the change in a species over time/natural