Types of Nutrition: Autotrophic vs. Heterotrophic Processes
Nutrition is the process by which living organisms obtain and utilise food to carry out vital life processes. It supplies the energy needed for growth, repair, and daily activities, making it one of the most important biological functions. The energy obtained from food fuels various cellular functions and helps organisms stay healthy and alive.
Autotrophic Nutrition
Autotrophic nutrition refers to the ability of certain organisms to produce their own food using simple inorganic substances like water and carbon dioxide. This process usually takes place in the presence of sunlight and a green pigment called chlorophyll, making [photosynthesis] the main pathway for food production in autotrophic organisms. Examples include green plants, algae, and some bacteria.
Key Stages in Photosynthesis
Light Absorption: Chlorophyll in the leaves traps sunlight.
Conversion of Energy: The light energy absorbed is converted into chemical energy, and water molecules split into hydrogen and oxygen.
Reduction of Carbon Dioxide: Hydrogen from water combines with carbon dioxide to form carbohydrates (sugars), which are then stored as starch.
Although the above steps help in understanding photosynthesis clearly, they do not always occur one after another in a strict sequence. Some organisms open or close special leaf pores called stomata at different times of the day to control the exchange of gases and conserve water.
Did you know? Some bacteria, called chemoautotrophs, synthesise their food using chemical energy (from inorganic compounds) instead of sunlight.
Heterotrophic Nutrition
Heterotrophic nutrition is found in organisms that cannot make their own food. Instead, they depend on other organisms for their nourishment. All animals, fungi, and some bacteria follow this type of nutrition. They are called heterotrophs, and they rely directly or indirectly on autotrophs for their energy needs.
Modes of Heterotrophic Nutrition
Parasitic Nutrition: Organisms live on or inside a host and derive nutrients at the host’s expense. Examples include ticks, tapeworms, and leeches.
Saprophytic Nutrition: Organisms feed on dead and decaying matter, secreting digestive enzymes onto it and then absorbing the nutrients. Fungi, such as mushrooms, follow this type.
Holozoic Nutrition: Organisms ingest solid or liquid food and then carry out digestion, absorption, and assimilation. Amoeba and humans exhibit holozoic nutrition by taking in complex substances and breaking them down into simpler ones.
Mode of Nutrition in Plants
Most plants show an autotrophic nutrition pattern, using sunlight, water, and carbon dioxide to make glucose. However, a few plants have additional or modified methods:
Insectivorous Plants (e.g., Pitcher Plants, Venus Flytraps): They trap insects to supplement their nitrogen requirements.
Parasitic Plants (e.g., Cuscuta or Dodder): They absorb nutrients directly from the host plant’s tissues.
In general, the mode of nutrition in plants remains primarily autotrophic, as they possess chlorophyll and carry out photosynthesis to produce their food.
Blue-Green Algae (Cyanobacteria)
Blue-green algae can be autotrophs, heterotrophs, or a mix of both (mixotrophs). Some species perform photosynthesis like plants, whereas others can switch to a heterotrophic mode if conditions require.
Quiz Time!
Test your understanding of modes of nutrition class 10 with the following questions:
1. Which type of nutrition involves an organism producing its own food using sunlight?
Answer: Autotrophic nutrition.
2. Name a mode of heterotrophic nutrition where organisms feed on dead organic matter.
Answer: Saprophytic nutrition.
3. Which structure in plant leaves mainly controls the exchange of gases during photosynthesis?
Answer: Stomata.
4. Give one example of an organism that shows holozoic nutrition.
Answer: Amoeba (humans also exhibit holozoic nutrition).
Related Topics
FAQs on Nutrition in Living Organisms Explained for Class 10 Students
1. What is nutrition, and why is it considered an essential life process for all organisms?
Nutrition is the process by which an organism takes in food (nutrients), digests it, absorbs it, and utilises it to obtain energy for various life activities. It is essential because this energy is required for growth, development, repair of damaged tissues, and to maintain the body's metabolic functions. Without nutrition, no organism can sustain life.
2. What is the main difference between autotrophic and heterotrophic nutrition?
The main difference lies in how organisms obtain their food. Autotrophic nutrition is the process where organisms produce their own food from simple inorganic raw materials like carbon dioxide and water, using sunlight (e.g., green plants). In contrast, heterotrophic nutrition is the mode where organisms cannot synthesise their own food and depend directly or indirectly on other organisms for their nutrients (e.g., animals, fungi).
3. How does photosynthesis in plants work? Explain the key components involved.
Photosynthesis is the process used by green plants to convert light energy into chemical energy. The key components and steps are:
- Chlorophyll: The green pigment in chloroplasts that traps sunlight.
- Sunlight: Provides the energy to drive the chemical reaction.
- Carbon Dioxide: Taken from the atmosphere through small pores called stomata.
- Water: Absorbed from the soil by the roots.
During the process, water is split to release oxygen, and carbon dioxide is reduced to form glucose (food).
4. What are the different types of heterotrophic nutrition as per the CBSE Class 10 syllabus?
Heterotrophic nutrition is mainly divided into three types:
- Saprotrophic Nutrition: Organisms feed on dead and decaying organic matter. They secrete digestive enzymes externally and absorb the nutrients. Example: Fungi like mushrooms and yeast.
- Parasitic Nutrition: Organisms live inside or on another living organism (the host) and derive nutrients from it, often causing harm. Example: Cuscuta (Amarbel), tapeworms.
- Holozoic Nutrition: Organisms ingest complex solid food particles. The process involves ingestion, digestion, absorption, assimilation, and egestion. Example: Humans, Amoeba.
5. How is the small intestine specially designed for the efficient absorption of digested food?
The small intestine is exceptionally well-adapted for absorption due to several key features. Firstly, it is very long, providing a large surface area and sufficient time for absorption. Secondly, its inner lining has millions of tiny, finger-like projections called villi. These villi further increase the surface area enormously. Each villus has a rich network of thin-walled blood capillaries, which allows the digested nutrients to be quickly and efficiently absorbed into the bloodstream.
6. Why do desert plants often open their stomata only at night?
This is a crucial adaptation to conserve water in arid environments. During the day, the intense heat would cause significant water loss through transpiration if the stomata were open. By opening their stomata at night, desert plants take in carbon dioxide when temperatures are cooler and water loss is minimal. They convert this CO₂ into an intermediate acid, which is then used during the day to perform photosynthesis using sunlight.
7. What is the role of hydrochloric acid (HCl) in the human stomach, besides killing germs?
While killing harmful bacteria is a vital function, the primary role of hydrochloric acid (HCl) in the stomach is to create an acidic medium. This acidic environment is necessary to activate the protein-digesting enzyme pepsin. Pepsin can only function effectively in a low pH, and HCl provides this optimal condition, initiating the breakdown of proteins into smaller peptides.
8. Explain the process of nutrition in Amoeba.
Amoeba exhibits holozoic nutrition. The process occurs in these steps:
- Ingestion: Amoeba senses food and extends finger-like projections called pseudopodia to engulf the food particle, forming a food vacuole.
- Digestion: Digestive enzymes are secreted into the food vacuole, breaking down the complex food into simpler, soluble molecules.
- Absorption: The digested food diffuses from the food vacuole into the cytoplasm.
- Assimilation: The absorbed nutrients are used for energy, growth, and repair.
- Egestion: The undigested waste is moved to the cell surface and expelled from the body.
9. What are mixotrophs? Give a common example.
Mixotrophs are unique organisms that can switch between autotrophic and heterotrophic modes of nutrition based on environmental conditions. A common example is Euglena. In the presence of sunlight, Euglena can perform photosynthesis like a plant. However, in the absence of light, it can ingest food particles from its surroundings, behaving like a heterotroph.
