Leaves for extreme climates

Leaves for extreme climates

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about identifying features of adaptation.

Read the information in the box below about the jobs leaves do for plants. 

Leaves do three main important jobs for plants:
  • Leaves use sunlight to make food.
  • Leaves help plants "breathe".
  • Water travels up from the roots and passes out of the leaves, which keeps water supplies moving through the plant.
 
Now for each picture of leaves:
  • Read the information about the leaves and the plant that they come from;
  • Describe how the special features of the leaves help that plant survive in its environment

(The first one is done for you.)  

a) Where the plant is adapted to grow: In cold snowy places.
Description of the leaves: The leaves are long and thin with a waxy coating. There are a lot of them.
How the special features of the leaves help the plant grow in cold snowy places:

  • There are lots of leaves so the tree can “make food” even though the leaves are small and there is not a lot of sunlight.
  • The waxy coating helps save water when the tree can't get water from the frozen ground.

Question 1Change answer

b) Where the plant is adapted to grow: In shady places under bigger trees.
Description of the leaves: Its leaves are quite large.
How the special features of the leaves help the plant grow in shady places:

Question 1Change answer

c) Where the plant is adapted to grow: In water.
Description of the leaves: Its leaf has a waxy coating and many air spaces. When you look at it through a microscope you can see lots of little holes on top.
How the special features of the leaves help the plant grow in water:

Question 1Change answer

d) Where the plant is adapted to grow: In very hot, dry places.
Description of the leaves: The leaves look more like a prickle than a leaf.
How the special features of the leaves help the plant grow in very hot dry places:
Task administration: 
This task can be completed with pen and paper or online (with NO auto marking).
This task is not suitable for students who do not have some knowledge of structure of plants and functions of the main parts such as leaves, roots, stems, and possibly flowers.
A resource that relates solely to identifying students' knowledge about structure and function of parts of a plant is:
Copyright: 
Picture source: Wikipedia
 
Picture source: www.virtualoceania.net
 
Picture source: Wikipedia
 
Picture source: Wikipedia
Level:
3
Curriculum info: 
Science, Understanding about science, Living World
Keywords: 
ecology, adaptation, climate, plants, leaves, key competencies, thinking
Description of task: 
Task: Use evidence to make inferences about how leaves help plants survive in particular environments. Assessment focus: leaf adaptations.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Use evidence
This resource provides opportunities to discuss using evidence to support an explanation. 
Science capabilities: 
Use evidence
Making Better Sense: 
Adaptation
Answers/responses: 
Y6 (08/2006)  
a)

(Answer provided)

There are lots of leaves so the tree can make food even though the leaves are small and there is not a lot of sunlight.

or

The waxy coating helps save water when the tree can't get water from the frozen ground.
b)

Best answer (very difficult)

Answer includes reference to both sun/light and making food.

  • The big leaves help the plant "catch" enough sunlight to make enough food for the plant.
Partial answer acceptable at this level  (difficult)
  • Reference to light or sun only
c)

Best answer  (very difficult)

Answer includes being on top of the water so it can catch enough sunlight to make food and/or breathe.

  • Because the leaf can float on top of the water, it can "catch" sunlight for making food.
  • The plant can "breathe" because the leaves sit on top of the water.
Partial answers acceptable at this level  (moderate)
Answer makes reference to sunlight or breathing only.
  • The little holes on top of the leaf allow it to "breathe."
or
Answer makes reference to floating.orAnswer makes reference to waterproofing.
  • The waxy coating stops the leaf getting "waterlogged".
d)
Best answers  (very difficult)
Relates function of the leaf to surface area and/or water retention
  • The small surface of the leaf/spine keeps the plant from losing water through evaporation.
or
Answer includes reference to protection and water stored in the plant.
  • The leaves/spines protect the plant from animals that are attracted to water stored in its stems.
Partial answers acceptable at this level  (difficult)
Answer makes reference to protection only.
or
Answer mentions water without reference to leaves.
or
Answer implies preventing dehydration, but either does not explain how, or explanation includes a misconception.
or
Answer makes reference to the sun (beginning to explain the relationship between too much sun and the reduced leaf area).
Based on a representative sample of 179 Year 6 students, August 2006. 
NOTE: Two levels of answers are provided. "Best answers" provide a model for teaching points. Few of the trial students could answer at this level, but, because it was a random sample, it is likely that many had not had explicit teaching in this area. "Partial answers" provide important clues to students' current thinking, and therefore what their next learning steps might be.
Teaching and learning: 
Adaptation is an important "big idea" in science. In the context of plants this is important when we are selecting plants to grow in gardens or as a crop, or when considering what plants are likely to become pests (weeds) in particular environments. It is also important for ensuring survival of native plants, which in turn is important for the survival of native birds and insects.  NEMP research and ARB trials have shown that students have difficulty with identifying how adaptations help a  plant or animal survive in a particular environment.

Strategies to assist students experiencing language difficulties

The task includes two specialist science words that may cause problems for some students:

i) Feature – something that you notice. In this resource that can be something about the structure of a leaf such as its shape or size.
ii) Survive – to stay alive. This is linked to basic needs such as food, water, and protection from enemies. (Reproduction is another need, but is related to survival of the species rather than survival of the individual, and is not dealt with in this resource.)

Particular attention should be paid to discussing these words, especially with ESOL learners, or learners with limited vocabulary, but it is worth checking that all students are familiar with their meaning in this context.

Diagnostic and formative information: 
This task is challenging for Level 3 students because they have to apply their knowledge about the functions of leaves to explain how leaves are adapted to meet the needs of plants growing in extreme situations. The challenges involved make this a useful task for uncovering students' misconceptions about the functions of leaves, therefore providing information for decisions about next learning.

 

Common misconceptions

Common response Likely misconception Science view
Water is gained through the leaves (37 students). Confusion about which part of the plant absorbs water Roots absorb water and nutrients.
Leaves suck up water (3 students) The misconception could be the same as above. Water rises through the roots, up the stem and out through the leaves.
Large leaves provide shade for the plant (12 students). Consider that the leaves protect the plant from the sun. Sunlight is scarce so the leaves need to have a larger surface area to take advantage of what sun does reach them.

(The cactus) does not need much/any water (8 students).

(The fern) does not need sun (1 student).

Interprets the adaptation as meaning that the plant does not need water/sun, rather than an adaptation to overcome a lack of water/sun.

NOTE:  Because of these adaptations, plants may not do well in opposite conditions such as very wet (cactus) or very sunny (fern).

 All plants need sunlight to make food, and water to transport food and minerals around the plant. Some plants have adaptations to ensure the plant has strategies for gathering more sunlight or conserving water.

Functions of leaves

More students used the information that leaves use sunlight to make food than the other functions of respiration and transpiration.  

Next steps: 

Addressing misconceptions about functions of leaves

At this level students are not expected to know the mechanics of the functions of plants in great detail. Much of the information can be accessed from books, but some practical activities will help to demonstrate the functions.

Important understandings for Levels 3 and 4 Activities
Green plants use sunlight to make their food, and this mostly happens in the leaves. (Students do not need to be able to explain photosynthesis.)
  • Under fair testing conditions, grow a plant in a position of light and a similar plant in a dark position (both plants should be watered.) Compare the two plants. This investigation does not show that plants make food, but it does show that without light the plant will not grow well and eventually die. Encourage students to link to food and their growth, e.g., what do you need to grow?
  • Grow a bean plant in a box with a small hole. Observe how the bean grows towards the light.

Refer to BSC Book 63, Growing plants indoors, Activity 2, pages 9 and 10 for more details.
Water is taken up through the roots, and is lost through the leaves. This can be demonstrated by tying a plastic bag over a leaf, and observing the water collected.
Plants "breathe" through little holes in their leaves. (Roots also take in air from the soil.) Use a magnifying glass to look for the stomata (holes).
 
Assisting students to make links between functions of the leaf and special adaptations
Once students are clear about what functions a leaf carries out, share ideas about the purpose of various special adaptations. Ask questions that help them to think about the adaptation being a response to particular conditions, and to link this to the plant's survival,  e.g.:
  • If there is not much sun where a plant is growing, what might it need so it is able to make enough food?
  • Why do you think the size of some trees' leaves change as they get taller?
  • Investigate leaves of plants growing in the lower canopy. Is there a pattern? What other strategies do plants use to get sunlight (e.g., tendrils for climbing)?
  • Ask students to think about how all the parts of a plant work together, e.g., a cactus has long roots to collect water deep underground, stores water in its stems, and has reduced leaves to prevent losing too much water. All the parts work together to overcome the lack of water in dry conditions.

Ministry of Education (2004). Building Science Concepts Book 63. Growing plants indoors. Wellington: Learning Media.