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1. UNIT
2
The nutrition function
THE NUTRITION
PROCESS
Natural Science 2. Secondary Education

2. UNIT
2
The nutrition process
NUTRITION
OBTAINING
NUTRIENTS
RESPIRATION
AUTOTROPHIC
NUTRITION
SUBSTANCE
DISTRIBUTION
HETEROTROPHIC
NUTRITION
EXCRETION
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Natural Science 2. Secondary Education

3. UNIT
2
The nutrition process
Obtaining nutrients
• Nutrients are the substances (organic or inorganic)
that living things ingest and that can be used by their
cells.
• There are two types of nutrition:
• Autotrophic
• Heterotrophic
Inorganic
substances
Energy
Organic
nutrients
Food
Organic
nutrients
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Natural Science 2. Secondary Education

4. UNIT
2
The nutrition process
Autotrophic nutrition
• Autotrophic organisms produce organic nutrients
from inorganic substances, such as:
• Water
• Mineral salts
• Carbon dioxide
Natural Science 2. Secondary Education

5. UNIT
2
The nutrition process
Autotrophic nutrition
• One example is photosynthesis. Plants and algae
make organic nutrients using the energy from
sunlight.
ENERGY
Natural Science 2. Secondary Education
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6. UNIT
2
The nutrition process
Heterotrophic nutrition
• Heterotrophic organisms cannot make organic
matter from inorganic matter. Therefore, they obtain
nutrients from other organisms or their derivatives.
• Animals are an example of heterotrophic
organisms.
Natural Science 2. Secondary Education
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7. UNIT
2
The nutrition process
Respiration
• Respiration is the process where a living organism takes
in oxygen and expels carbon dioxide.
• This process also takes place in cells, which use oxygen
to generate energy from nutrients. Mitochondria are the
organelles that carry out cellular respiration.
Carbon
dioxide
Oxygen
Natural Science 2. Secondary Education

8. UNIT
2
The nutrition process
Cellular respiration
• In this process, the mitochondrion takes in
oxygen, obtains energy from nutrients and expels
carbon dioxide and water.
Oxygen
Carbon
dioxide
Energy
Carbohydrates
Water
Respiration in a
mitochondrion
Natural Science 2. Secondary Education
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9. UNIT
2
The nutrition process
Substance distribution in unicellular organisms
• In unicellular organisms, the cell exchanges
substances directly with the environment through
the membrane.
The exchange of
substances in a
protozoan
Nutrients
Waste
Natural Science 2. Secondary Education

10. UNIT
2
The nutrition process
Substance distribution in multicellular organisms
• In multicellular organisms, different parts of the
body specialise in:
• Taking in or expelling substances.
• Transporting substances.
The digestive
system
of a bird
Natural Science 2. Secondary Education
The circulatory
system
of a fish
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11. UNIT
2
The nutrition process
Excretion
• This is the process by where living beings expel
the waste products generated by their activity.
The excretory system
of a reptile
Natural Science 2. Secondary Education
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