CHAPTER 4: SCIENCE SEMINAR

Transcription

1 CHAPTER 4: SCIENCE SEMINAR

2 4.1.1: WARM-UP Annotate a passage from the article about stickleback fish, which you read for homework. (5 min)

3 4.1.2: INTRODUCING STICKLEBACKS Introduce the new question about the stickleback fish and explain the change the population has undergone. (10 min)

4 This map shows where the stickleback population we are studying was found in a lake in Alaska. This population of sticklebacks has lived in this lake for approximately 13 generations : INTRODUCING STICKLEBACKS

5 Sticklebacks are tiny fish, no longer than your pinky. As you can see, there are spikes or stickles on its back. This is where the fish gets its name. Inside, these fish also have bony plates of armor : INTRODUCING STICKLEBACKS

6 4.1.2: INTRODUCING STICKLEBACKS Scientists can clearly see and count the plates of armor of a stickleback fish by using a special stain that colors the armor. In this photo, you can see the armor plates in red. The individuals in the stickleback population 13 generations ago had many plates of armor; they were considered to have high levels of armor. Over time, the individuals have developed less armor. As you can see, most of the individuals now have only four plates of armor. They are considered to have low levels of armor. Scientists found that sticklebacks with low levels of armor are faster swimmers than sticklebacks with high levels of armor.

7 4.1.2: INTRODUCING STICKLEBACKS As you can see in this histogram, most of the sticklebacks in the population were slow swimmers 13 generations ago. Now, most of the sticklebacks are fast swimmers.

8 4.1.2: INTRODUCING STICKLEBACKS What caused the stickleback population to have less armor and become faster? Scientists do not know why this drastic change occurred. However, they do know that when sticklebacks have less armor they are able to swim faster. There are a few reasons why swimming faster could be helpful for sticklebacks. When you looked at the sticklebacks in your Warm-Up, did you have any thoughts about what may have caused the change? What might we want to investigate in order to consider what caused this change?

9 4.1.2: INTRODUCING STICKLEBACKS Biologists have narrowed down the possible factors in the environment that led to the change in trait distribution, making your jobs easier. You will be getting some evidence to help support the claims.

10 Students read and annotate evidence cards. Then discuss them with their partners. (20 min) Before you can determine whether you think Claim 1 or 2 is correct, you will need to analyze evidence about the sticklebacks' previous and current environments This card shows the average life span of sticklebacks in the lake, their current environment : EXAMINING EVIDENCE ABOUT STICKLEBACKS

11 4.1.3: EXAMINING EVIDENCE ABOUT STICKLEBACKS How do they die? Are they killed by predators? Do they die due to starvation? Old age? something else?

12 I see that fish with lowarmor levels are fast and fish with higharmor levels are slow. Therefore, the table shows that the more armor a stickleback has, the slower it swims : EXAMINING EVIDENCE ABOUT STICKLEBACKS

13 The table also shows that fast swimmers live an average of four years, while slow swimmers live an average of one year. I wonder if that is because the fast swimmers can catch more food and eat more, or if it is because they can swim away from predators without being eaten : EXAMINING EVIDENCE ABOUT STICKLEBACKS

14 4.1.3: EXAMINING EVIDENCE ABOUT STICKLEBACKS Do fast sticklebacks live longer because they escape more predators or because they catch more prey? Sticklebacks reproduce once a year. If fast swimmers live four years, then these fast sticklebacks must reproduce about four times during their life span. Slow swimmers, however, only live for one year. Therefore, they most likely reproduce only once during their life span.

15 4.1.3: EXAMINING EVIDENCE ABOUT STICKLEBACKS Do fast sticklebacks live longer because they escape more predators or because they catch more prey? Sticklebacks reproduce once a year. If fast swimmers live four years, then these fast sticklebacks must reproduce about four times during their life span. Slow swimmers, however, only live for one year. Therefore, they most likely reproduce only once during their life span.

16 4.1.3: EXAMINING EVIDENCE ABOUT STICKLEBACKS Do fast sticklebacks live longer because they escape more predators or because they catch more prey? Sticklebacks reproduce once a year. If fast swimmers live four years, then these fast sticklebacks must reproduce about four times during their life span. Slow swimmers, however, only live for one year. Therefore, they most likely reproduce only once during their life span.

17 4.1.3: EXAMINING EVIDENCE ABOUT STICKLEBACKS

18 4.1.4: DISCUSSING EVIDENCE AND CLAIMS You will work with a partner to consider how the Stickleback Evidence Cards connect to the claims. Then decide which claim is best supported by the evidence. The question you are trying to answer. The Chapter 4 Question Do fast sticklebacks live longer because they escape more predators or because they catch more prey? You and your partner will be discussing ideas, but each student will sort their own evidence cards under the claim on the appropriate page of the Argument Organizer student sheets.

19 4.1.4: DISCUSSING EVIDENCE AND CLAIMS You should place each Stickleback Evidence Card under the claim it supports or goes against. If the evidence supports a claim, you should write "supports Claim 1 or supports Claim 2" on that card. If the evidence refutes a claim, you should write "goes against Claim 1 or goes against Claim 2" on that card. If the evidence on one card connects with another, you should write "connects with Evidence Card A (or B, C, D, E, F)" on that card.

20 4.1.4: DISCUSSING EVIDENCE AND CLAIMS Discuss each piece of evidence and then decide if it supports or goes against either of the two claims. You do not have to agree about the placement of the evidence cards. As you sort the cards discuss their reasoning.

21 4.1.4: DISCUSSING EVIDENCE AND CLAIMS Clip your Stickleback Evidence Cards to your Argument Organizer student sheets. Store them in your Science folder. You will need these again in Lessons 4.2 and 4.3.