VMBO Year 3 · Ecology · Section 6.1

Eating and being eaten

Photosynthesis: storing energy in glucose

Green plants make organic food substances through photosynthesis. They take in carbon dioxide from the air and water from the soil. In chloroplasts, light energy is used to produce glucose and oxygen. Glucose stores chemical energy derived from sunlight. Photosynthetic organisms therefore form the base of most food chains.

Carbon dioxide + water + light energy → glucose + oxygen

Cellular respiration and metabolism

During aerobic cellular respiration, cells release usable energy from substances such as glucose, using oxygen. Carbon dioxide and water are formed. The energy supports movement, growth, maintenance and, in some animals, temperature regulation. Plants as well as animals respire. Photosynthesis and respiration are both parts of metabolism, the chemical reactions changing substances into other substances within organisms.

Glucose + oxygen → carbon dioxide + water + released energy

Food chains and food webs

A food chain is a sequence of feeding relationships: one organism is eaten by the next. It begins with a producer, usually a plant or alga. Herbivores eat producers and are primary consumers. Carnivores eat animals and occupy higher feeding levels. Omnivores eat both plants and animals and can feed at several levels. Interconnected food chains form a food web. Arrows point from food to the organism eating it, showing the transfer of matter and energy.

Roles in an ecosystem

Producers make energy-rich organic substances from simple inorganic substances. Consumers obtain organic substances by feeding on other organisms or their products. Decomposers, especially bacteria and fungi, break down dead material and wastes from every feeding level. They release mineral nutrients that plants can take up again. Matter is therefore recycled. Energy flows through the system and is eventually dissipated as heat rather than recycled.

Glossary

Omnivores: Animals eating both plant and animal material, potentially feeding at several trophic levels.
Consumers: Organisms obtaining organic, energy-rich substances made by other organisms.
Energy-poor substances: In this course, simple inorganic substances such as carbon dioxide, water and mineral nutrients, which do not supply food energy to consumers.
Energy-rich substances: Organic substances such as carbohydrates, fats and proteins, containing chemical energy organisms can use.
Photosynthesis: The use of light energy to make glucose from carbon dioxide and water, releasing oxygen in plants and algae.
Nutrient cycle: Repeated movement and reuse of elements and substances through organisms and the environment.
Mineral nutrients: Inorganic substances such as nitrate taken up by plants, usually through their roots.
Herbivores: Animals feeding on plants or algae, acting as primary consumers in a grazing food chain.
Producers: Organisms making organic substances from inorganic substances, usually using light energy.
Decomposers: Organisms, especially bacteria and fungi, breaking down dead organic material and releasing mineral nutrients.
Metabolism: All chemical reactions changing substances into other substances in an organism.
Carnivores: Animals eating other animals and occupying higher consumer levels in a grazing food chain.
Food chain: A sequence showing feeding relationships from a producer through consumers.
Food web: The interconnected feeding relationships in an ecosystem.