Adaptations of Plants in Different Habitats: Biology questions

Section A: objective questions

12 marks

Choose the best answer for each question.

Which type of plant lives in a habitat that is neither too dry nor too wet?

Xerophyte
Mesophyte
Halophyte
Hydrophyte

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Mesophytes have an adequate water supply. Most plants, such as the mango tree, are mesophytes.

For the teacher: Remembering, low difficulty, standard 7.1.1

Textbook p. 135

Which plant is a halophyte?

Cactus
Lotus
Mangrove tree
Hibiscus

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The mangrove tree lives in the salty swamp at the river mouth.

For the teacher: Remembering, low difficulty, standard 7.1.1

Textbook p. 135

What are the breathing roots of mangrove trees called?

Pneumatophores
Aerenchyma
Hydathodes
Lenticels

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Pneumatophores grow upwards above the mud. Lenticels are the pores on them.

For the teacher: Remembering, low difficulty, standard 7.1.2

Textbook p. 136

What is the function of the lenticels on mangrove roots?

To remove excess salt
To store water
To allow gaseous exchange with the atmosphere
To anchor the plant in mud

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Lenticels are pores that let gases be exchanged with the air because the mud has little oxygen.

For the teacher: Understanding, medium difficulty, standard 7.1.2

Textbook p. 136

Why do mangrove roots not lose water to the sea water by osmosis?

The cell sap has a higher salt content than sea water
The roots have a thick cuticle
The roots have no cells
The cell sap has a lower salt content than sea water

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The salt concentration inside is higher, so water moves into the roots.

For the teacher: Understanding, medium difficulty, standard 7.1.2

Textbook p. 136

What is the function of aerenchyma tissue in the stem of a lotus?

To transport sugars
To make the stem light and buoyant
To reduce transpiration
To store salt

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Aerenchyma has large air spaces, which give buoyancy and store air.

For the teacher: Understanding, medium difficulty, standard 7.1.2

Textbook p. 137

Where are most stomata found on the leaves of a floating hydrophyte?

Lower epidermis
Both surfaces equally
Upper epidermis
They have none

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The stomata are on the upper epidermis, which is exposed to the air and covered by a waxy cuticle.

For the teacher: Remembering, low difficulty, standard 7.1.2

Textbook p. 137

Why does Elodea have thin and small leaves with no stomata?

To reduce the loss of water
To allow direct diffusion of water, mineral salts and gases through the epidermis
To collect dew
To store food

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A submerged plant takes in dissolved substances directly through the epidermis.

For the teacher: Applying, medium difficulty, standard 7.1.2

Textbook p. 137

Which is an adaptive feature of a cactus to reduce water loss?

Broad flat leaves
Many stomata on the upper surface
Leaves modified into thorns
Air spaces in the stem

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Thorns reduce the surface area exposed to the sun and thus reduce water loss.

For the teacher: Understanding, low difficulty, standard 7.1.2

Textbook p. 137

A plant has fibrous roots that trap air bubbles. What is the advantage?

It absorbs salt
It reduces transpiration
It stores water in the roots
It makes the plant lighter and more stable in water

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Trapped air makes hydrophytes lighter and helps them float or stand upright.

For the teacher: Applying, medium difficulty, standard 7.1.2

Textbook p. 136

Which feature of mangrove leaves helps to remove excess salt?

Sunken stomata
Succulent tissue
Thick cuticle
Hydathodes

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Leaves have hydathodes that eliminate excess salt; old leaves also store salt and fall off.

For the teacher: Remembering, low difficulty, standard 7.1.2

Textbook p. 136

A plant lives in the Arctic where the ground is frozen for long periods. It is classified as a xerophyte because it

is surrounded by sea water
has aerenchyma tissue
lives in water
cannot absorb water from frozen ground

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Frozen ground makes water unavailable, as in a desert, so Arctic plants are xerophytes.

For the teacher: Understanding, medium difficulty, standard 7.1.2

Textbook p. 137

Section B: structured questions

27 marks

Answer all questions. Write your answers in the spaces provided.

Classify the plants by habitat.

[1 mark] (a)Cactus

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Xerophyte1

Tick each point you got.

[1 mark] (b)Elodea sp.

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Hydrophyte1

Tick each point you got.

[1 mark] (c)Rubber tree

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Mesophyte1

Tick each point you got.

For the teacher: Remembering, low difficulty, standard 7.1.1

Textbook p. 135

Mangrove trees live in soft, muddy and salty soil with low oxygen.

[2 marks] (a)State two adaptive features of the roots that support the tree.

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Roots branch widely in various shapes and sizes [1]1
Prevents uprooting by strong wind / supports in soft mud [1]1

Tick each point you got.

[2 marks] (b)How do the roots obtain oxygen?

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Pneumatophores grow upwards above the mud [1]1
Lenticels allow gaseous exchange with the atmosphere [1]1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 7.1.2

Textbook p. 136

A lotus floats on the surface of a lake.

[2 marks] (a)Explain how the leaf shape helps photosynthesis.

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Broad, thin and flat [1]1
Absorbs maximum sunlight [1]1

Tick each point you got.

[2 marks] (b)Name the tissue in the stem that has many air spaces and state its function.

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Aerenchyma tissue [1]1
Makes the stem light and buoyant so it floats [1]1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 7.1.2

Textbook p. 137

A cactus grows in a desert.

[2 marks] (a)State two features of the cactus that reduce water loss.

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Any 2 points

Leaves modified into thorns / small leaves [1]1
Thick waxy cuticle [1]1
Embedded stomata [1]1

Tick each point you got.

[1 mark] (b)State another function of the thorns.

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Collect dew / protect from being eaten by animals [1]1

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[1 mark] (c)Why can the cactus stem carry out photosynthesis?

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The stem is green and has chloroplasts, as the leaves are reduced [1]1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 7.1.2

Textbook p. 137

A tree has dense leaves that shade its stem, thorns, and roots that spread close to the surface and also go deep into the soil. State its type and support with two facts.

[1 mark] (a)Type of plant

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Xerophyte [1]1

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[2 marks] (b)Facts

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Any 2 points

Thorns reduce surface area / water loss [1]1
Roots spread widely and go deep to absorb water [1]1
Shade from leaves lowers the stem temperature [1]1

Tick each point you got.

For the teacher: Analysing, high difficulty, standard 7.1.2

Textbook p. 138

Oil spills cover the roots of mangrove trees. Predict what happens to the trees and explain.

[1 mark] (a)Prediction

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The trees will die / growth reduced [1]1

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[2 marks] (b)Explanation

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Oil blocks the lenticels of the pneumatophores [1]1
No gaseous exchange, so roots cannot respire / lack oxygen [1]1

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For the teacher: Evaluating, medium difficulty, standard 7.1.2

Textbook p. 140

Can a mangrove tree grow in a freshwater habitat? Give two reasons.

[3 marks] (a)Answer and reasons

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Unlikely / cannot grow well [1]1
Mangrove root sap has high salt concentration, so too much water would enter the roots by osmosis [1]1
Adapted to salty, low-oxygen mud; features not suited for fresh water [1]1

Tick each point you got.

For the teacher: Evaluating, medium difficulty, standard 7.1.2

Textbook p. 140

A landscape architect plans to plant at a hotel near the beach. Suggest one suitable plant and justify.

[3 marks] (a)Plant and reasons

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Plant suited to salty, windy, sunny beach e.g. mangrove or a plant with succulent leaves [1]1
Thick cuticle / sunken stomata reduce water loss [1]1
Wide root system holds plant in loose soil against wind [1]1

Tick each point you got.

For the teacher: Creating, high difficulty, standard 7.1.2

Textbook p. 140

Section A: objective questions

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Section B: structured questions

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20