Nutrition of Animals and Plants
Problem — How do living beings, animals and plants, feed themselves to live, grow, and reproduce?
- Understand the concept of nutrition and its fundamental role in living beings.
- Identify the main differences between animal nutrition and plant nutrition.
- Know the structures and processes involved in the nutrition of plants and animals.
- Describe concrete examples of various nutrition modes in both groups.
- Understand the importance of nutrition for the maintenance of life and organism function.
Part 1: Nutrition, a vital function for all living beings
Nutrition is the set of processes by which a living being takes substances from its environment necessary for its function, growth, maintenance, and reproduction.
All living beings need to feed, that is, to obtain matter and energy. These resources allow cells to function, produce new molecules, repair certain structures, and enable growth. Although all living beings perform nutrition, animals and plants do not feed in the same way.
Main functions related to nutrition
- Feeding: intake of substances from the environment.
- Digestion: transformation of food into simpler molecules usable by the organism, mainly in animals.
- Absorption: passage of nutrients into the organism.
- Transport: movement of substances to the cells.
- Use by cells: energy production, material synthesis, and maintenance of the organism.
Nutrition is an essential function for life. It allows organisms to acquire the energy and matter needed for their functioning and growth. Both animals and plants perform this function but use different sources of matter and different mechanisms.
Part 2: Nutrition in animals
Animals are heterotrophic living beings: they must consume organic matter from other living beings to feed.
Animals do not produce their own organic matter from minerals. They must feed on other living beings or organic matter. Their nutrition is called heterotrophic. Depending on the species, their diet can be very varied: some are herbivores, others carnivores, omnivores, or detritivores when consuming dead organic matter.
Stages of animal nutrition
- Ingestion: food enters the body, often through the mouth.
- Digestion: transformation of food into simpler nutrients by mechanical and chemical actions, notably digestive enzymes.
- Absorption: passing nutrients through the intestinal wall into the blood or lymph.
- Transport: distributing nutrients to all cells of the organism.
- Assimilation: use of nutrients by cells to produce energy and build matter.
- Elimination: rejection of undigested waste as feces.
Concrete example: digestion in humans
In humans, food is first chewed in the mouth. It then travels to the stomach where it is mixed with digestive juices. In the small intestine, digestive enzymes break down food into simple nutrients like glucose, amino acids, fatty acids, and glycerol. These nutrients can then pass into the blood and be transported to cells. Undigested waste is expelled as stool.
Animals are consumers: they rely on other organisms for matter and energy. Their nutrition involves ingestion, digestion, absorption, transport, and use of nutrients by cells. The variety of diets shows animals are adapted to diverse environments and resources.
Part 3: Nutrition in plants
Chlorophyllous plants are autotrophic living beings: they produce their own organic matter from minerals and light energy.
Unlike animals, chlorophyllous plants do not consume other living beings to produce their organic matter. Their nutrition is called autotrophic. Thanks to photosynthesis, they use light energy to transform mineral matter into organic matter, mainly sugars.
Nutritional needs of chlorophyllous plants
- Water and minerals, absorbed by roots from the soil.
- Carbon dioxide (CO2), taken from the air through leaves.
- Light energy, captured by chlorophyll in leaf cells.
The role of photosynthesis
Photosynthesis is a biological reaction occurring in chloroplasts of chlorophyll cells. It allows plants to make glucose from carbon dioxide and water using light energy. It also releases oxygen into the air:
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Concrete example: nutrition of a green plant
A plant like the bean absorbs water and minerals through its roots. Its leaves capture sunlight and absorb carbon dioxide from the air. Thanks to photosynthesis, the plant makes glucose. This glucose can be used to produce energy, make other organic molecules, or build plant tissues. The oxygen produced during photosynthesis is released into the air.
Plants perform photosynthesis, but they also perform cellular respiration. During respiration, like animals, their cells consume oxygen and release carbon dioxide. Photosynthesis only happens in light, whereas respiration happens all the time.
Chlorophyllous plants have a special nutrition: they produce their own organic matter thanks to photosynthesis. They take water, minerals, and carbon dioxide from their environment, then use light energy to produce glucose and other organic molecules needed for growth.
Part 4: Comparison and interaction between animal and plant nutrition
Animals and plants have different nutrition modes but are linked in ecosystems. Chlorophyllous plants produce organic matter that forms the base of food chains. Animals use this organic matter by feeding on plants, other animals, or dead organic matter. Decomposers like bacteria and fungi recycle organic matter into mineral elements reusable by plants.
| Aspect | Animal nutrition | Plant nutrition |
|---|---|---|
| Type of nutrition | Heterotrophic: consumes organic matter from other living beings. | Autotrophic: produces its own organic matter from minerals. |
| Matter used | Food containing organic matter: carbohydrates, lipids, proteins. | Water, minerals, and carbon dioxide (CO2). |
| Energy source | Chemical energy in food. | Light energy captured by chlorophyll. |
| Main process | Ingestion, digestion, absorption, and assimilation. | Photosynthesis, then use of produced organic matter. |
| Gas exchange | Consumes oxygen (O2) during respiration and releases carbon dioxide (CO2). | Absorbs CO2 and releases O2 during photosynthesis; also breathes oxygen (O2) and releases CO2. |
| Role in food chains | Consumers. | Primary producers. |
An essential interaction
In an ecosystem, chlorophyllous plants are primary producers: they make organic matter that directly or indirectly feeds other living beings. Animals consume this organic matter and release carbon dioxide during respiration. Decomposers transform remains and waste into mineral elements that plants can reuse. Thus, matter circulates between living beings and their environment.
Animal and plant nutrition modes differ but complement each other. Chlorophyllous plants produce organic matter via photosynthesis. Animals consume this matter by feeding. Decomposers then recycle organic matter into minerals. These relations ensure matter circulation in ecosystems and contribute to their balance.
Nutrition is an essential function for all living beings. Animals are heterotrophic: they consume organic matter, digest it, and use nutrients to produce energy and build their own matter. Chlorophyllous plants are autotrophic: they make their own organic matter through photosynthesis from water, minerals, carbon dioxide, and light energy. These two nutrition modes complement each other in ecosystems. Plants are the base of food chains, animals consume organic matter, and decomposers recycle matter. Understanding nutrition helps better understand relationships between living beings and their environment.