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Nutrition in Plants and Animals - Feeding and Digestion in Amoeba

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Amoeba is a microscopic, single-celled organism found in pond water that lacks a fixed shape and possesses a cell membrane, a dense nucleus, and many small bubble-like vacuoles in its cytoplasm.

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The organism moves and captures food using finger-like projections called pseudopodia (false feet\text{false feet}).

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Nutrition in Amoeba is holozoic, meaning it ingests solid organic matter which is then digested and absorbed internally.

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The process of feeding begins with Ingestion: Amoeba senses food, pushes out pseudopodia to encircle the particle, and engulfs it into a food vacuole.

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Digestion occurs inside the food vacuole where digestive enzymes are secreted to break down complex food into simpler, soluble substances: Complex Food→EnzymesSimple Substances\text{Complex Food} \xrightarrow{\text{Enzymes}} \text{Simple Substances}.

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Absorption and Assimilation: The digested food is absorbed directly into the cytoplasm. These nutrients are used for growth, maintenance, and multiplication (2n2^n cell division).

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Egestion: The undigested residue of the food is expelled outside by the vacuole at any point of the cell membrane.

📐Formulae

Ingestion→Digestion→Absorption→Assimilation→Egestion\text{Ingestion} \rightarrow \text{Digestion} \rightarrow \text{Absorption} \rightarrow \text{Assimilation} \rightarrow \text{Egestion}

Food Vacuole=Food Particle+Water Droplet\text{Food Vacuole} = \text{Food Particle} + \text{Water Droplet}

Complex Nutrients+Digestive Juices→Simple Soluble Nutrients\text{Complex Nutrients} + \text{Digestive Juices} \rightarrow \text{Simple Soluble Nutrients}

💡Examples

Problem 1:

Explain how the pseudopodia assist in the nutrition of Amoeba.

Solution:

Pseudopodia are temporary extensions of the cell membrane. When Amoeba senses a food particle, it extends two pseudopodia around it. These join together to trap the food in a 'food vacuole'.

Explanation:

This process is a type of endocytosis specifically known as phagocytosis, where the membrane wraps around the solid particle to bring it inside the cell.

Problem 2:

What is the destination of the absorbed nutrients in an Amoeba?

Solution:

The absorbed nutrients diffuse into the cytoplasm and are used for growth, repair, and reproduction through binary fission.

Explanation:

Since Amoeba is unicellular, it does not have a complex circulatory system; hence, substances move via simple diffusion across the cytoplasm\text{cytoplasm}.

Problem 3:

Compare the 'stomach' of a human to the 'food vacuole' of an Amoeba.

Solution:

The food vacuole in Amoeba acts as a temporary stomach where enzymes break down food, similar to how the human stomach uses HClHCl and pepsin for digestion.

Explanation:

Both structures serve the purpose of chemical digestion using specialized secretions to convert complex matter into simple forms.

Feeding and Digestion in Amoeba - Revision Notes & Key Formulas | CBSE Class 7 Science