GRADE 7
Name:
THINK ABOUT THIS:
What are the things that are necessary for a planet to sustain life?
Solar energy and the production of food
You learned in Grade 6 that green plants produce their own food by the process of
photosynthesis. Can you remember what the inputs and outputs of photosynthesis
are? Complete the diagram below:
PHOTOSYNTHESIS
IS
In the plant’s leaves, the chlorophyll in the chloroplasts absorb the solar energy from
the Sun. This starts the chemical reaction which combines Carbon dioxide (CO2)
from the air and water (H2O) from the soil. The product of this reaction is glucose
(C6H1206) – a simple sugar that can either be used by the plant or stored as starch in
the plant for later use. Another product, or by-product, of the reaction is Oxygen (O2)
which is released into the atmosphere.
All other creatures that live on the Earth need to get their energy from other sources.
Unlike plants, they cannot produce their own food. Herbivores eat plants, omnivores
eat plants and other animals and carnivores eat other animals in order to survive.
Ultimately, all animals rely on the ability of plants to produce their own food and
ultimately, plants rely on the Sun to create their own food. Therefore, all organisms
rely on the Sun’s energy to provide them with the energy they need to survive.
Solar energy and warmth
The Earth is surrounded by an atmosphere which is an important feature in the
sustenance of life. It is particularly important when it comes to warmth.
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Grade 7 Natural Science: Planet Earth and Beyond: Relationship of the Sun to the Earth: Solar energy and life on Earth
Solar energy and life on Earth
GRADE 7
The Sun’s light and heat radiate from it into space, encountering different objects
in space, including the planets. Some of these rays penetrate (come through) the
atmosphere and warm our Earth. The atmosphere traps some of these rays and some
bounce off the surface of the Earth and travel back out the atmosphere into space.
Those that stay in the atmosphere, help to keep it warm and maintain a constant
temperature. This is known as the ‘Greenhouse Effect’ and is necessary for our
survival on Earth.
One of the major reasons other planets cannot sustain life is because they are either
too hot or too cold. Without the heat energy from the Sun, the Earth would not be
able to sustain life.
sun
UV rays
ozone layer
Earth
A NOTE ABOUT THE GREENHOUSE EFFECT
The Greenhouse Effect happens as a result of the gases and particles in
our atmosphere that prevent the UV rays from escaping. This phenomenon
is necessary to keep the Earth’s surface warm.
A problem arises when this is enhanced (called the “Enhanced Greenhouse
Effect”). If more UV rays are trapped than should be, the atmosphere’s
average temperature increases and causes Global Warming. The Greenhouse
Effect is enhanced by an increase in gases and pollution in the atmosphere.
Solar energy and the water cycle
Another reason there is no life on other planets, is because there is no water. Water is
essential to life.
Water is not created by the Earth, instead, it is recycled through the water cycle.
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Grade 7 Natural Science: Planet Earth and Beyond: Relationship of the Sun to the Earth: Solar energy and life on Earth
Can you remember what the average temperature of the Earth is?
Condensation
Precipitation
Transpiration
Evaporation
Snowmelt runoff
Surface runoff
Stage 1: The solar energy warms up the water on the Earth’s surface and causes it to evaporate, changing from a liquid into a gas (water vapour).
Stage 2: The water vapour is warm and rises. As it travels further away from the Earth’s surface, it cools down and forms liquid droplets which form clouds.
Stage 3: Rain (liquid water) falls from the clouds back to the surface of the Earth.
(Rain is not the only form of precipitation; snow, dew and hail are also examples of
precipitation.)
Water that is not used, runs into lakes, rivers and dams, and the process begins again.
Without the energy the Sun provides, the surface water would not be able to
evaporate and go through this cycle. Thus, solar energy is crucial to the water cycle.
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GRADE 7
Grade 7 Natural Science: Planet Earth and Beyond: Relationship of the Sun to the Earth: Solar energy and life on Earth
Give the correct term for the process that takes place at each of these stages:
GRADE 7
What are the things that are necessary for a planet to sustain life?
Water, Light, Warmth, Food, Air/Oxygen, Protection from extreme cold and
heat, etc.
Solar energy and the production of food
Can you remember what the inputs and outputs of photosynthesis are?
carbon dioxide
water
PHOTOSYNTHESIS
IS
glucose (food)
oxygen
solar energy
Solar energy and warmth
Can you remember what the average temperature of the Earth was?
15°C
Solar energy and the water cycle
Stage 1: EVAPORATION
Stage 2: CONDENSATION
Stage 3: PRECIPITATION
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Grade 7 Natural Science: Planet Earth and Beyond: Relationship of the Sun to the Earth: Solar energy and life on Earth
Answer sheet