WEEK FOUR 10/6/08

In the past four weeks, you have used the concept of adaptation as a lens for deeper understanding of various grass features. Scrutinizing plants through the "lens" of adaptation may be a new approach for you. But given the relevance of this concept for everything from the anatomy of an individual seed to the global distribution of vegetation, it's certainly a robust idea that helps us make sense of the evidence we are gathering! This week you continue to use this "lens" as you deepen your understanding in three investigations.

Here is a plan for what is coming up:

Scientists use the term "abiotic" to refer to factors related to the nonliving (physical) environment. The term "biotic" is used when environmental factors relate to a living (biological) entity.

In previous sessions, you've investigated the ways in which grasses are adapted to withstand common abiotic factors, such as shade. But to understand the whole, complex context in which grasses grow, it makes sense to consider the impact of living things on these plants. This week you will investigate adaptive features that help grasses survive biotic pressures, such as grazing.

In addition, you will report on your Germination Investigation and you'll take a closer look at the data you've collected from your Sun/Shade Investigation.

Although you'll be juggling three different investigations—Sun/Shade, Germination and Grazing—you will only report on your Sun/Shade Investigation.

Sun/Shade: When you planted your sun and shade grasses in light and in shade, you made some predictions about grass features that would help these plants to cope with these two very different sets of environmental challenges.

Are the growth patterns in your sun and shade plantings what you expected?

Do the two species look and/or grow the same?

What do your observations tell you about adaptation—and, conversely,how does the concept of adaptation help you interpret your sun/shade planting results?

This week, you'll share observations with your peers and, through further investigation, explore in more depth what it means to be adapted to sun or shade.

Germination: This week you implemented your refined investigation plan and collected data to learn more about adaptations in grass plants at this early stage in their life cycle.

Grazing: Grasses have more adaptation surprises in store for you. The environmental challenges you've investigated so far involved the "abiotic environment," that is, the nonliving aspects of the grass plants' environment.

Challenges are also presented to grasses by elements in the "biotic environment," that is, the living environment around them. For example, large mammals (such as bison or wildebeest) are historically associated with all major grasslands of the world. How is it possible for grasslands to sustain huge herds of grazing animals year after year? Why doesn't the vegetation run out? Could adaptation be key to the answer?

Plan for this week:

I.Sun/Shade Investigation

Referring to your journal, report your Sun/Shade Investigation experiences and results so far.

Use the following questions as a guide:

• What have you observed? Were there surprises, puzzles?

• What were all the possible environmental differences between sun and shade environments you thought of and your rationale for these differences?

• What challenges does each environment apparently present for grass plants? How do you imagine the two species might be adapted to these conditions?

• How do you explain your observations?

In week 1, I asked you to set up the sun and shade plantings in controlled environments where only the levels of light were different. But was it only light that was different? Might there be other factors that vary along with light? Brainstorm a list in your journal.

As you continue to collect data, think more closely about the relationship between the plant and its environment in your experimental setup. How are the environmental conditions in the "sun" and the "shade" plantings the same? How are they different?

II. Germination Investigation

As your experiment progresses, continue to record data in your journal. How does the environmental factor you are investigating affect germination? How do you think the plants might be adapted to cope with this factor? Note any new questions your investigation raises.

You will report your finding next week.

III. Grazing Investigation

We know that grasses survive continuous grazing by cows, or buffalo, or zebras. Take some time to speculate about this. What features of grasses make it possible for grasslands to support large herds of grazers? Why doesn't the grass run out in the face of such heavy grazing pressure?

Think about grazing in terms of our two familiar questions:

• What kinds of (environmental) pressures do we think that grazers might impose on grasses?

What would we expect from grasses in terms of being adapted to this kind of pressure?

In this investigation, you employ modeling, an investigative technique often used by scientists. You will model or simulate grazing by using scissors to "graze" your plants.

But first, think about what kind of grazer you want to model—for example, a cow, an antelope, a buffalo. What grazing action does this animal use? What effect will it have on the grass as it grazes? How far down will it bite?

Use these questions to decide where and how to cut your plants, then cut the radish and grass in your grazing planting.

During the rest of the week, spend a few minutes each day to observe the plants closely with the magnifying glass. What patterns do you see as the plants regrow? For example, where does new growth occur? Do the cut leaves change with time? What happens to the damaged edges?

Optional, yet encouraged—if you do several observational drawings periodically over the course of the week, you may be rewarded with more nuanced insights about grazing!

In your journal:

• Make an annotated drawing to show exactly where you cut the plants, and why.

• Predict what will happen to both the grass and the radish plants. Will the plants grow back? If so, how? Justify your prediction in terms of what you know now about adaptation.

• Record your observations.

WEEK THREE: 9/29/08

Part A. Choosing a question

Do germinating seedlings need light? Does temperature affect germination rate?

These are some of the questions you've been considering. Each of these questions can be viewed through the lens of adaptation. For example, you might ask whether, given the New England environment, a group of grass seeds that germinates at 32°C (90°F) is better adapted to New England conditions than a group that germinates at 10°C (50°F).

Your germination investigation spans several weeks. This week, you choose a question to investigate.

From the list of questions you and your colleagues compiled and refined last week, choose a question that seems compelling to you. Your investigation should give you data within about 10 days from start to finish, and should further your understanding of adaptation in some way.

Part B. Designing your investigation

In your journal: Begin to design your Germination Investigation using the following questions to guide you:

• What is your key question? Are there any other secondary questions associated with it?
• What evidence will you need to collect to answer the question?
• How will you set up an investigation to collect this evidence?
• What do you predict will happen and why?
• What are your questions and concerns about your design?

WEEK TWO: 9/22/08

By now your seeds have ben germinating for at least five days, and hopefully your germination plate is filled with a healthy crop of seedlings. Take a few minutes each day to continue your observations of these plants.

WEEK ONE : 9/15/08

What happens when grass germinates?

Part A. Speculate and predict: Consider a single grass seed, carried by the wind

Where will it land? How will it survive until it finds itself in the right place to germinate? Before you set seeds to germinate, spend some time thinking about germination and adaptation.

In your journal: Consider our two key questions, drawing on your everyday experience with growing plants to help you think about them:

• What environmental challenges do seeds/seedlings face as they germinate and start to grow?

• What adaptations would ensure survival during this time?

Generate a list. Note your speculations and your rationale for them. Also note any other questions you may have.

Part B. Germinate and record observations

Now, begin to germinate your seeds following our Instructions for Germination. Plan to spend about 15 minutes each day this week observing the seeds as they germinate—try not to miss a day. Observe and document at least seven days of seed growth. After day seven you can discard the germination plate if you wish.

In your journal: Make observational drawings to record seedling features you notice (use colored pencils to record colors accurately), annotate your drawings, and record your questions. As you make observations, keep considering what features of each germinating seedling might help ensure plant survival.