Differences between living and non-living things.

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1. Why do living things need nutrients?

Living things need nutrients to synthesize their body molecules and also to get energy for doing work.

2. What are nutrients?

Nutrients are the inorganic and organic substances that living things obtain from their surroundings in order to build their body constituents. Nutrients also act as a source of energy for living things.

3. Define inorganic and organic nutrients.

Inorganic nutrients are inorganic substances like water, carbon dioxide and minerals like iron, copper, sodium and zinc. Green plants obtain these inorganic substances from the soil and the atmosphere to synthesize organic nutrients. For example, green plants absorb carbon dioxide from the atmosphere and water from the soil and convert it into the organic nutrient starch in the presence of sunlight.

Organic nutrients are those nutrients obtained from plants or animals. Examples are: carbohydrates, fats, proteins etc. Human beings obtain organic nutrients from both plants (vegetables, fruits, cereals) and animals (milk, meat, eggs).

4. What are the two types of heterotrophic nutrition?

The two types of heterotrophic nutrition are: saprophytic nutrition and parasitic nutrition

5. Define saprophytic nutrition and parasitic nutrition

Saprophytic nutrition refers to that kind of nutrition in which organisms obtain their nutrients from dead and decaying matter such as rotten leaves, vegetables, dead animals etc present in the soil. Organisms that depend on saprophytic nutrition are called saprophytes. Examples of saprophytes are many fungi and bacteria.

In parasitic nutrition organisms or parasites obtain their nutrition from other living organisms. The organism that provides sustenance to the parasite is called the host. The host can be a plant or animal and it is not benefitted by the parasite. Examples of parasites are bacteria, many forms of fungi, round worms, pin worms, tape worms and some flowering plants (cuscuta) and some animals.

1.3 Autotrophic nutrition in green plants

Most green plants are autotrophic because with the help of the inorganic substances obtained from the surroundings they synthesize organic food. This process is called photosynthesis.

1. What is photosynthesis?

Photosynthesis is the process by which green plants produce complex carbohydrates from simple inorganic substances like water and carbon dioxide in the presence of sunlight. During photosynthesis plants also release oxygen into the atmosphere.

Photosynthesis is by far the most important process in the world because it not only supplies organic food to organisms that depend on it but also purifies the air by absorbing carbon dioxide and releasing oxygen. Photosynthesis can only occur in green plants because it requires the presence of green-coloured pigment called chlorophyll.

2. What are photosynthetic pigments?

Pigments are the coloured organic substances which absorb white or visible light. It is important to absorb white light because photosynthesis can only occur in the presence of visible light. The visible light is composed of seven different colours. Chlorophylls are the most important photosynthetic pigments. They are present in green plants.