The shape of the lesson
By the end of the lesson, learners can
- What makes a feature adaptive: Start with the arctic fox in the sim.
- Reading an organism from information: Exam questions often show a picture or table about an unfamiliar species and ask you to describe its adaptive features.
- Xerophytes and hydrophytes: Extended.
- Adaptive feature: inherited, helps survival and reproduction in the environment.
- Answer frame: name the feature, say what it does, say why that matters in this habitat.
- Xerophytes (Extended): reduce water loss (spines, thick cuticle, sunken stomata, rolled leaves, hairs) and store or find water.
- Hydrophytes (Extended): air spaces, stomata on the upper surface, large floating leaves, flexible stems.
One picture every idea returns to
An adaptive feature is an inherited feature that helps an organism to survive and reproduce in its environment. To describe one, name the feature and link it to a problem in the habitat: cold, drought, predators, too much water. Extended: xerophytes are plants adapted to dry places and reduce water loss; hydrophytes are plants adapted to living in water.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Built for the place it lives.. An arctic fox, a cactus and a water lily each look the way they do for a reason. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: What makes a feature adaptive | Start with the arctic fox in the sim. Project tab 4 of the lab (Adaptive features of the arctic fox and plants) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Reading an organism from information | Exam questions often show a picture or table about an unfamiliar species and ask you to describe its adaptive features. | Pairs |
| 21 to 30 min | Teach and check: Xerophytes and hydrophytes | Extended. Project tab 4 of the lab (Cactus, marram grass and water lily) and let a student drive it while the class predicts. | Corners |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 20 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Xerophytes and hydrophytes, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Corners
Put one answer or viewpoint in each corner of the room. Students move to the corner they agree with, justify the choice to a partner there, then hear one voice from each corner before the reveal.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Always link the feature to the environment. "It has thick fur" earns nothing on its own; "thick fur traps air, which insulates the fox against the cold" is an explanation. | Return to What makes a feature adaptive: ask a pair to state the correct version and show it on the lab before moving on. |
| Sunken stomata and hairs do not stop water loss completely. | They trap moist air, so the concentration gradient of water vapour is smaller and the rate of diffusion out of the leaf is lower. |
Adaptive features: worksheet
6 questions, 20 marks. Written in the style of the papers; no past paper question is reproduced.
Define the term adaptive feature.
The arctic fox lives in a cold, snowy habitat. Explain how two of its features help it to survive there.
The fennec fox lives in hot deserts. It has very large ears, pale sandy fur and furry soles on its feet. It hunts at night. Suggest how each feature helps it survive.
Extended. Explain how three features of a cactus help it survive in a desert.
Extended. A water lily is a hydrophyte. Explain the advantage of each of these features: (a) large air spaces in the stem, (b) stomata on the upper surface of the leaf, (c) large flat leaves, (d) flexible stems.
Extended. Marram grass grows on sand dunes. Its leaves roll up in dry weather, with hairs and sunken stomata on the inner surface. Explain how these features reduce water loss.
Answer key and marking notes
- An inherited feature,
- that helps an organism to survive and reproduce in its environment.
- Thick fur traps a layer of air, which insulates and reduces heat loss.
- White fur camouflages it against snow, so it can approach prey without being seen.
- Small ears have a small surface area, so less heat is lost.
- A layer of fat insulates and stores energy for when food is scarce. (Any two features, each with an explanation.)
- Large ears: a large surface area to lose heat (and to hear prey).
- Pale sandy fur: camouflage against sand, so it is hidden from predators and prey.
- Furry soles: insulate the feet from hot sand (and grip on loose sand); hunting at night avoids the heat of the day.
- Leaves reduced to spines: a very small surface area, so little water is lost by transpiration (and they deter animals).
- Thick waxy cuticle: reduces evaporation of water from the surface.
- Swollen stem: stores water and carries out photosynthesis in place of leaves.
- Few, sunken stomata (often open only at night) or wide shallow roots and a deep root. (Any three, each explained.)
- (a) Air spaces keep the leaves afloat and allow oxygen to diffuse to the submerged stems and roots.
- (b) The upper surface is in contact with the air, so gases can be exchanged through the stomata.
- (c) A large surface area spread on the water absorbs as much light as possible for photosynthesis.
- (d) Flexible stems bend with water currents without breaking; the water supports the plant.
- Rolling the leaf traps moist (humid) air inside the roll.
- Hairs trap a further layer of moist air, and sunken stomata sit in pits of humid air.
- The water vapour concentration gradient between the inside of the leaf and the air is reduced, so less water vapour diffuses out (and wind cannot blow the moist air away).
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which of these is an adaptive feature?
- AThe thick inherited fur of a polar bear
- BA scar on a lion's leg from a fight
- CA dog that has learned to sit on command
- DLarge muscles a horse gained from training
A snowshoe hare has white fur in winter and brown fur in summer. How does this help it to survive?
- AIt is camouflaged from predators in both seasons
- BWhite fur absorbs more heat from the sun in winter
- CBrown fur reflects heat and keeps the hare cool
- DChanging colour attracts more mates all year
Camels can go without drinking for days and have long eyelashes and nostrils they can close. Which habitat are they adapted to?
- AHot, dry, sandy desert
- BCold, snowy mountain slopes
- CShallow freshwater lakes
- DWet tropical rainforest
Two fox species are compared. The arctic fox has small ears and a short muzzle; the desert fennec fox has very large ears. What explains the difference in ear size?
- ALarge ears lose more heat, which suits a hot habitat
- BLarge ears keep the body warmer in a hot habitat
- CSmall ears lose more heat, which suits a cold habitat
- DEar size has no effect on heat loss in foxes
A cheetah has long legs, a flexible spine and sharp eyesight. Which statement best explains how these features help it survive and reproduce?
- AThey help it see and chase down fast prey, so it gets enough food
- BThey help it hide from larger predators by staying still
- CThey reduce water loss in its hot grassland habitat
- DThey help it keep warm during cold nights on the grassland
Extended: the diagram shows a leaf cut across. Which label points to a feature that reduces water loss by trapping moist air next to the stomata?
- AB, the hairs on the inner surface
- BA, the thick waxy cuticle on the outer surface
- CC, the open edge of the rolled leaf
- DD, the green photosynthetic tissue
Extended: which combination of features would you expect in a hydrophyte such as a water lily?
- ALarge air spaces, stomata on the upper leaf surface, little xylem
- BThick waxy cuticle, sunken stomata, deep roots
- CLeaves reduced to spines, swollen stem, wide roots
- DRolled leaves, hairs around the stomata, thick cuticle
Extended: many cacti open their stomata only at night. Why does this help them survive in a desert?
- ALess water is lost because the air is cooler and more humid at night
- BPhotosynthesis is faster at night when it is cooler
- CCarbon dioxide can only enter a cactus in the dark
- DWater vapour diffuses into the cactus at night
Quiz key
Thick fur is inherited and helps the polar bear survive the cold, so it is an adaptive feature. A scar, a learned trick and muscles built by training are all acquired during the animal's life; they are not inherited, so they are not adaptive features.
White fur matches snow in winter and brown fur matches soil and dead leaves in summer, so the hare is camouflaged from predators all year and more likely to survive. White surfaces reflect rather than absorb heat. Brown fur is darker, so it would absorb more heat, not reflect it. Colour change here is about hiding, not attracting mates.
Surviving without water suits a dry habitat, and long eyelashes and closable nostrils keep out blowing sand: a hot, sandy desert. Snowy slopes have water as snow and need insulation. A lake has plenty of water. A rainforest is wet, with no shortage of drinking water and little blowing sand.
Large ears have a large surface area, so they lose more heat, which helps the fennec fox stay cool in the desert. Small ears lose less heat, helping the arctic fox keep warm. Large ears do not keep the body warmer, and small ears lose less heat, not more. Surface area does affect heat loss, so ear size matters.
Sharp eyesight spots prey and long legs with a flexible spine give speed to catch it, so the cheetah gets food, survives and can reproduce. These features are for chasing, not hiding. They do nothing to reduce water loss or keep the animal warm.
The hairs on the inner surface (B) trap a layer of moist air around the sunken stomata, reducing the water vapour gradient so less water diffuses out. The cuticle (A) also reduces water loss, but by stopping evaporation from the outer surface, not by trapping air. The open edge (C) is where humid air could escape, so it does not trap it. The green tissue (D) photosynthesises; it does not trap air.
Hydrophytes have large air spaces for buoyancy and to get oxygen to submerged parts, stomata on the upper surface in contact with the air, and little xylem because water supports them. The other three combinations are xerophyte features that reduce water loss or store water: cuticle and sunken stomata, spines and swollen stems, rolled leaves and hairs.
At night the air is cooler and more humid, so the water vapour gradient out of the stomata is smaller and less water is lost by transpiration. Photosynthesis needs light, so it does not happen at night (the cactus stores the carbon dioxide until day). Carbon dioxide can enter whenever stomata are open; it is not limited to the dark. Water vapour still diffuses out of the leaf, not in.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.