Natural sciences Year 5: Plants and animals facing water, light and temperature
Natural sciences, Year 5 (Portugal): Plants need suitable water, light and temperature to develop; animals respond to changes in them with body features and behaviour.
What a plant needs to grow
Plants need suitable water, light and temperature. A seed absorbs water to germinate. Light is needed for photosynthesis, which makes the plant's food: without it the plant grows tall, thin and pale. Each plant has a range of temperatures that suits it: strong cold slows or stops growth and frost can damage it. Too little water makes a plant wilt, and too much can rot the roots, which also need air.
How animals respond
Animals also respond to changes in water, light and temperature, with morphological adaptations (of the body) and behavioural ones (of what they do). Morphological: a thicker coat in winter, big eyes in animals active at night. Behavioural: many hedgehogs hibernate in winter, swallows migrate to Africa when it gets colder, and many desert animals come out at night, avoiding the heat of the day.
Reading a plant experiment
Example results (made up): four bean pots. A: light, water, 20 °C: 12 cm, green. B: dark, water, 20 °C: 15 cm, pale, thin stem. C: light, no water, 20 °C: 3 cm, wilted. D: light, water, cold place (5 °C): 1 cm. Step 1: compared with A, each pot changes only one condition. Step 2: B grows tall and pale without light. Step 3: C wilts without water. Step 4: D barely grows in the cold. Conclusion: a plant needs all three, in suitable amounts.
The camel's hump is not a water tank
A common idea is «the camel keeps water in its hump». The hump holds fat, an energy reserve. The camel copes with lack of water in other ways: it loses little water, it can stand losing a large share of the water in its body and it can drink a lot at once. In the desert, an animal's adaptations are usually several working together, not a single trick.
The seasons, seen as science
The year shows all of this. Deciduous trees lose their leaves in autumn, when the days get shorter and colder. Swallows arrive in spring and many hedgehogs sleep through winter. A plant on a windowsill leans towards the light. In a garden, note down on one day: which plants are in flower, which animals you saw, and the temperature. That is how field science begins.
Test what you learned
A bean plant grown in the dark is tall, thin and pale. Which condition was missing?
- a) Water
- b) Light
- c) A suitable temperature
Correct answer: b) Light — Right: without light there is no photosynthesis, and the plant grows tall, thin and pale.
Pots A and C are the same in every way except water: A is watered, C is not. C wilts and stays small. What can you conclude?
- a) The lack of water made C wilt, because it is the only difference
- b) Light made C wilt
- c) Nothing, because two pots cannot be compared
Correct answer: a) The lack of water made C wilt, because it is the only difference — Right: with one difference only, the result can be linked to that condition.
What does a camel's hump mainly store?
- a) Water
- b) Air
- c) Fat, an energy reserve
Correct answer: c) Fat, an energy reserve — Right: the camel copes with lack of water by losing little and drinking a lot at once.
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