CHAPTER 3 MUTATION AND ADAPTIVE TRAITS

Transcription

1 CHAPTER 3 MUTATION AND ADAPTIVE TRAITS

2 3.3.1 WARM-UP Reread the story below and then respond to the question. Why did the mutation that resulted in a long-hair trait in these rabbits become more common in the population? The mutant trait became more common because the cold environment made long hair an adaptive trait. The rabbits with longer hair were able to live long enough to reproduce, while the rabbits with shorter hair were more likely to die before reproducing. The long-haired rabbits had offspring with long hair, so it became a common trait in the population.

3 3.3.2 WRITE AND SHARE: DISCUSSING MUTATIONS You will participate in the Write and Share routine to support one another s understanding of mutations and mutant traits. (20 min) Write and Share routine. Antarctic eelpout. Today, you will participate in the Write and Share routine to analyze data about mutations in a population and explain why some mutations become more common and others do not. This will help you to review key concepts so that you are prepared to create a final argument for Alex Young, Head Biologist at Oregon State Park, explaining why the newt population has changed so much.

4 Discussing How Mutations Change Trait Distribution Antarctic eelpout WRITE AND SHARE: DISCUSSING MUTATIONS The Arctic eelpout (Lycodes reticulatus) looks very similar to the Antarctic eelpout. Antarctic eelpouts are a type of fish that can be up to three-feet long and that look like eels. They can range in color from yellow to brown. They are found in very cold water, such as in the water near Antarctica.

5 Discussing How Mutations Change Trait Distribution WRITE AND SHARE: DISCUSSING MUTATIONS There are three histograms on your sheet. At Time 1, Antarctic eelpouts used to live in warmer water. When land masses moved millions of years ago, the water became much colder. Each student in your group will consider a different data set that shows possible changes in a population, given these conditions. Time 2 represents some time after the environment changed. Time 3 represents many generations after the environment changed.

6 3.3.2 WRITE AND SHARE: DISCUSSING MUTATIONS Assign students in groups of 3 (and number yourselves 1-3) Locate the sheet that corresponds to your assigned number.

7 3.3.2 WRITE AND SHARE: DISCUSSING MUTATIONS Did mutations affect which trait was the most common at Time 3? Why or why not? I am looking at data about the population, which in this case is a series of histograms. If I want to describe the population, I need to carefully think about what the data tells me and use what I already know about the vocabulary words to see if I can use any of them in my description.

8 3.3.2 WRITE AND SHARE: DISCUSSING MUTATIONS Did mutations affect which trait was the most common at Time 3? Why or why not? Be ready to share your ideas with the class.

9 Student #1: Non-adaptive mutation WRITE AND SHARE: DISCUSSING MUTATIONS Mutations did not affect the distribution of traits in this population very much. The trait for Cold Resistance Level 1 is a mutant trait. I know this because it was not present in the first population, but it showed up in the population after many generations. Since individuals get their traits from their parents, and no parents had this trait, a mutation must have occurred. This mutation was random, and it resulted in a non-adaptive trait in an environment with very cold water. This mutant trait was not helpful for survival in this environment and, therefore, did not become more common because individuals with this mutation did not survive long enough to pass their traits onto very many offspring.

10 Student #2: Adaptive mutation WRITE AND SHARE: DISCUSSING MUTATIONS Mutations changed the distributions of traits in this population a lot. The trait for Cold Resistance Level 6 is a mutant trait. I know this because it was not present in the first population, but it showed up in the population after many generations. Since individuals get their traits from their parents, and no parents had this trait, a mutation must have occurred. This mutation was random, but it resulted in an adaptive trait in an environment with very cold water. This mutant trait was helpful for survival in this environment and, therefore, it become more common because individuals with the mutant trait were able to live long enough to reproduce and pass their traits onto the most offspring.

11 Student #3: Neutral mutation Mutations did not affect the distribution of traits in this population very much. The trait for Brown Color Level 6 is a mutant trait. I know this because it was not present in the first population, but it showed up in the population after many generations. Since individuals get their traits from their parents, and no parents had this trait, a mutation must have occurred. This mutation was random, but it is not an adaptive trait or a non-adaptive trait in an environment with very cold water WRITE AND SHARE: DISCUSSING MUTATIONS Since it didn t help individuals survive or stop them from surviving, it didn t die out or became more common because individuals with this mutation lived normal lives and passed their traits onto their offspring.

12 Investigation Question: WRITE AND SHARE: DISCUSSING MUTATIONS What determines whether a new trait will become more common in the population? In the previous lesson, we realized this question requires a two-part answer. We already know that mutations can sometimes introduce new traits into a population. When do mutated traits become common in a population? Discuss with a partner. Mutations can produce adaptive or non-adaptive traits, but the traits mutations produce only become more common in a population if they are adaptive to a particular environment.

13 Preparing Your Final Report to Alex Young MODELING TOOL Goal: Show what caused there to be some extremely poisonous newts in the newt population when there were none in the population 200 generations ago. You have now learned everything you need to know in order to explain why the roughskinned newts became so poisonous. Your explanation you wrote in Lesson 2.4 is still accurate, it is just incomplete given the new information about the newt population from 200 generations ago, specifically the new evidence we received in Lesson 3.1 about the absence of Poison Level 10 in the original population. Remember you can look back at your work from previous lessons and utilize the glossary.

14 Do: Analyze all four histograms and environment descriptions. Label Histogram 3 with any Trait labels that apply. Tips: You can add multiple Trait labels to a single trait. You can use Trait labels more than once, and you do not have to use all of them MODELING TOOL Explain how your model answers the question: How did a poison-level trait that wasn t always present in the newt population become the most common trait?

15 3.3.3 MODELING TOOL A possible proficient model should include at least two traits labeled in Histogram 3 but might include labeling for all traits. Only Poison Level 10 should be labeled with M. Explain how your model answers the question: How did a poison-level trait that wasn t always present in the newt population become the most common trait? There were no snakes in the rough-skinned newts environment 200 generations ago, and the trait for Poison Level 10 was not present in the population. A mutation happened 50 generations ago and a mutant trait for Poison Level 10 was introduced into the population. Snakes became part of the newts environment 40 generations ago. This made high-poison levels adaptive traits because the snakes could not eat them. This is why Poison Level 10 is the most common trait in the population today.

16 3.3.4 HOMEWORK You will read the articles The Stickleback Fish in Its Environment and Why the Corpse Flower Smells So Bad and annotate them with your questions and connections. Reading "The Stickleback Fish and Its Environment" Read and annotate the article, answer the reflection question, and then press NEXT.

17 3.3.4 HOMEWORK You will read the articles The Stickleback Fish in Its Environment and Why the Corpse Flower Smells So Bad and annotate them with your questions and connections. Reading Why the Corpse Flower Smells So Bad You have been learning about natural selection in animal populations, but what about plants? Open the "Why the Corpse Flower Smells So Bad article in the Amplify Library. Read the article to learn more about a unique organism called the corpse flower, and answer the question below. Then, press HAND IN to submit your article.

18 3.3.5 HOMEWORK SELF-ASSESSMENT This optional homework provides a chance for you to reflect on your learning. Check Your Understanding This is a chance for you to reflect on your learning so far. This is not a test. Be open and truthful when you respond to the questions below.