Science notes, unit 4

Plants

Textbook Science Year 5 (DLP), pages 93–114

What this chapter covers

You can state the specific characteristics of plants that protect them from enemies, such as sharp thorns, latex, fine hairs, poison and bad smell (4.1.1)
You can describe how plants adapt to strong seasonal wind, hot climate and dry season, and cold climate (4.1.2)
You can explain why these characteristics help plant species survive (4.1.3)
You can state the ways seeds and fruits are dispersed, by wind, water, animals and humans, and explosive mechanism (4.2.1)
You can relate the characteristics of seeds and fruits to their way of dispersal and predict how a seed is dispersed (4.2.2, 4.2.3)
You can explain how living things depend on each other to keep the balance of nature (4.2.4)

A plant cannot run away from danger or move to a cooler place. Yet plant species survive for a very long time. How? Plants have specific characteristics that protect them, help them live through weather changes and spread their seeds. In this unit you will study all three.

4.1Characteristics of plants for survival

Protection from enemies

An enemy of a plant is any animal or person that eats or harms it. A plant protects itself with specific characteristics so that its species can survive.

The textbook describes five of these characteristics. Learn each one with its example.

Characteristic	How it protects the plant	Examples
Sharp thorns	The thorns hurt animals that want to eat the plant or its fruit.	Durian, pineapple
Produce latex	The latex is sticky, so enemies are put off eating the fruit.	Jackfruit tree, papaya tree
Fine hairs	The hairs make the skin itchy when touched.	Bamboo, pumpkin plant
Poisonous	Eating or touching the plant causes poisoning, even death.	Allamanda, pong pong tree
Bad smell	The strong smell makes enemies go away.	Citronella, lantana

A girl touching a durian and getting hurt by its sharp thorns, with a durian and a pineapple shown — Sharp thorns hurt enemies that want to eat the durian.

A girl and her grandfather looking at sticky latex on a jackfruit tree, with a papaya tree beside it — The sticky latex of the jackfruit tree puts enemies off.

A girl scratching her hand after touching bamboo leaves, with a bamboo plant and a pumpkin plant — The fine hairs on bamboo leaves make the skin itch.

A girl about to pick yellow flowers of the allamanda plant, with an allamanda plant and a pong pong tree — Every part of the allamanda is poisonous. Do not pick the flowers.

A girl holding her nose beside citronella plants, with a citronella plant and a lantana plant — The citronella plant produces a strong bad smell.

Did you know? Citronella is also called the mosquito repellent plant. It is often planted around the house because mosquitoes do not like the smell of its leaves.

Do not touch or taste a plant just because it looks pretty. Allamanda has bright flowers but all its parts are poisonous.

Name the characteristic that protects each plant: (a) pineapple, (b) papaya tree, (c) pong pong tree.

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(a) Sharp thorns. (b) Produces latex. (c) Poisonous.

Adapting to climate and seasonal changes

Plants adapt to climate and seasonal changes: strong seasonal wind, hot climate and dry season, and cold climate. Each has its own set of specific characteristics.

Strong seasonal wind. The plant must not be broken or blown over.

A coconut tree with a flexible trunk and split leaves, and a casuarina tree with needle-shaped leaves — Coconut tree and casuarina tree.

Hot climate and dry season. The main danger is losing too much water.

A cactus plant with spikes for leaves and a close-up of its stem — The cactus has leaves modified as spikes, a stem that stores water and long roots.

A tomato plant with a close-up of the fine hairs on its stem and leaves — Fine hairs on the tomato plant's stem and leaves.

A turmeric plant that rolls its leaves and a yam plant with waxy leaves — The turmeric plant rolls its leaves. The yam plant has waxy leaves.

A rubber tree with leaves on the left and the same tree with bare branches on the right — The rubber tree sheds its leaves in hot weather and in the dry season.

Cold climate. The plant must be protected from the cold.

A maple tree with a close-up of the thick bark on its trunk — Thick bark covers the trunk of the maple tree.

Situation	Characteristic	What it does	Example
Strong seasonal wind	Flexible trunk and branches	Bends instead of breaking	Coconut tree, casuarina
	Split leaves	Reduce the force of the wind	Coconut tree
	Needle-shaped leaves	Reduce the force of the wind	Casuarina, pine
Hot climate and dry season	Leaves modified as spikes	Prevent water loss	Cactus
	Stem stores water; long roots	Keeps water; absorbs water deep in the soil	Cactus
	Fine hairs on stem and leaves	Prevent water loss	Tomato plant
	Rolling leaves	Prevent water loss	Turmeric
	Waxy leaves	Avoid too much water loss	Yam
	Shedding leaves	Avoid water loss	Rubber tree, bougainvillea
Cold climate	Thick bark	Protects the trunk from the cold	Maple tree, pine
Cold climate	Needle-shaped leaves	Help the tree live through the cold	Pine

Example: the pine tree

A pine tree has needle-shaped leaves that reduce the force of strong winds, and thick bark that protects the trunk from the cold. One tree uses different characteristics to survive different kinds of weather.

A pine tree with a close-up of its thick bark — The pine tree: needle-shaped leaves and thick bark.

A bougainvillea tree with a close-up of its red leaves — Bougainvillea trees shed their leaves when it is hot and dry. This saves water.

Did you know? Thick bark stops the water that the tree has absorbed from freezing in extremely cold climates.

In hot weather, shedding leaves, rolling leaves, waxy leaves and fine hairs all have one purpose: to prevent water loss. Do not write that the plant "wants to make food faster".

Which characteristic helps a plant in (a) strong wind, (b) a dry season, (c) a cold climate? Give one for each.

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(a) Flexible trunk / split leaves / needle-shaped leaves. (b) Rolling leaves / waxy leaves / shedding leaves / fine hairs / water-storing stem (any one). (c) Thick bark (or needle-shaped leaves).

4.2Dispersal of seeds or fruits

Dispersal means moving seeds or fruits away from the parent plant. Plants need to disperse them far away so that the new plants have enough space, water and sunlight to grow, and the species survives.

There are four main ways. The shape and parts of a seed or fruit tell you its way of dispersal.

Way of dispersal	Characteristics of the seed or fruit	Example
Wind	Small, thin, lightweight, fine hairs, wing-like structure	Angsana fruit, dandelion
Water	Waxy skin, husk with air cavities	Coconut, nipa palm fruit
Animals and humans	Edible flesh, attractive colour, pleasant smell; or small, lightweight, with hooks	Rambutan; burr mallow
Explosive mechanism	Seed pods dry out and split open	Garden balsam, rubber fruit

An angsana fruit with its thin wing — Angsana fruit: a thin, lightweight wing lets the wind carry it far.

A coconut and a coconut cut open to show its husk — Coconut: waxy skin and a husk with air cavities, so it floats.

A rambutan with red hairy skin and white flesh — Rambutan (edible flesh, attractive colour) and burr mallow (hooks stick to fur).

Burr mallow seeds with small hooks — Rambutan (edible flesh, attractive colour) and burr mallow (hooks stick to fur).

Garden balsam seeds inside a seed pod — Garden balsam: the dry pod splits open and throws the seeds out.

Two kinds of animal dispersal. Fruits with edible flesh are eaten, and the animal drops or passes out the seeds somewhere else. Seeds with hooks stick to the fur of animals and fall off later.

Example: predicting the way of dispersal

Mangosteen has sweet flesh and an attractive colour, so animals and humans disperse it. Dandelion seeds have fine hairs, so the wind disperses them.

A dandelion, a nipa palm fruit, a mangosteen and a rubber fruit — Predict how each is dispersed from its characteristics.

Did you know? The durian has sharp thorns to protect itself, but animals and humans still disperse it. They eat the flesh and throw away the seeds.

Do not write "the fruit is eaten by animals" for hooks. Hooked seeds are not eaten. They stick to the fur and are carried away.

Name the way of dispersal: (a) a light seed with fine hairs, (b) a fruit with a husk full of air, (c) a pod that dries and splits.

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(a) Wind. (b) Water. (c) Explosive mechanism.

Why survival of species matters

Living things depend on each other to keep the balance of nature.

Plants are food for animals and humans. They also give oxygen during photosynthesis and materials for animals' nests.
Animals and humans give fertilisers and nutrients to plants when waste decays.
Animals and humans disperse the seeds and fruits of plants.

If plants could not ensure the survival of their species, the animals that depend on them would lose food, shelter and oxygen, and the balance of nature would be upset.

Pictures: Science Year 5 (DLP) textbook, pp. 94–112 (thorns and latex p. 94, hairs and poison p. 95, smell p. 96, wind and cactus p. 99, tomato, turmeric and yam p. 100, rubber and maple p. 101, pine and bougainvillea p. 102, angsana and coconut p. 105, rambutan and burr mallow p. 106, balsam p. 107, seeds p. 108).

Summary

Topic	Key points
Protection from enemies	Sharp thorns, produce latex, fine hairs, poisonous, bad smell
Strong seasonal wind	Flexible trunk, split leaves, needle-shaped leaves
Hot climate and dry season	Spikes, water-storing stem, long roots, fine hairs, rolling, waxy or shedding leaves: prevent water loss
Cold climate	Thick bark, needle-shaped leaves
Dispersal	Wind, water, animals and humans, explosive mechanism
Balance of nature	Plants, animals and humans depend on each other