Amoeba, Paramoecium, Euglena and Diatom

BIOLOGY CLASSIFICATION OF PLANTS

Kingdom Protista

Introduction to Kingdom Protista

 Kingdom Protista consists of unicellular organisms.  They contain a well-defined nucleus and a nucleolus enclosed in a nuclear membrane.  The protoplasm is surrounded by the plasma membrane.  The cytoplasm contains various cell organelles.  Nuclear material is organised in the form of a linear, double-stranded and helical DNA, along with proteins.  The mode of nutrition is either autotrophic or heterotrophic.  Examples: Amoeba, Paramoecium, Euglena and diatom

Amoeba Paramoecium Euglena Diatom

Amoeba

 Amoeba is microscopic and one of the simplest organisms made of just one cell.  It is found in ponds, ditches, mud or on submerged water plants in freshwater bodies.  The body of Amoeba is irregular in shape.  The outer membrane called cell membrane or plasmalemma encloses the cytoplasm.  A prominent nucleus, several food vacuoles, a contractile vacuole and reserve food granules are present.  Amoeba uses pseudopodia for feeding and locomotion.  It reproduces by binary fission.  During unfavourable conditions (e.g. drying up of pond), it forms a protective cyst within which it reproduces by multiple fission, producing several offspring.

Structure of Amoeba www.topperlearning.com 2

BIOLOGY CLASSIFICATION OF PLANTS

Movement in Amoeba

 Movement in Amoeba occurs with the help of temporary or false feet called pseudopodia.  Pseudopodia are finger-like projections formed by the flowing of cytoplasm into these extensions.  At a time, several pseudopodia can be seen projecting out from the body of an Amoeba.  However, only one of them extends longer than the others towards the direction it wants to move.  This type of movement is called amoeboid movement.

Movement in Amoeba

Feeding in Amoeba

Amoeba senses food in its vicinity, projects out pseudopodia and moves towards the food particle

It extends two of its pseudopodia and surrounds the food particle

The tips of the pseudopodia fuse together to form a food vacuole

The cytoplasm secretes digestive juices into the food vacuole which breaks it down into simple soluble form

This soluble food is absorbed into the cytoplasm where it is stored or utilised for growth and release of energy

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BIOLOGY CLASSIFICATION OF PLANTS

Feeding in Amoeba

Excretion in Amoeba

 Excretion in Amoeba occurs with the help of contractile vacuole.  Ammonia is the major waste product formed in the body of an Amoeba.  Excess of water from the body of Amoeba gets collected in the contractile vacuole.  Ammonia is soluble in water and hence, gets absorbed into the contractile vacuole along with water.  The contractile vacuole gradually expands as it gets filled with water and moves towards the cell surface.  Suddenly, the contractile vacuole collapses or bursts and releases water through a small opening in the cell membrane.  As a result, the nitrogenous waste is also eliminated from the body of Amoeba through general body surface by the process of simple diffusion.  Later, the contractile vacuole shrinks when the water is released into the surroundings.

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BIOLOGY CLASSIFICATION OF PLANTS

Respiration in Amoeba

 Respiration or exchange of gases in Amoeba takes place through the cell membrane by the process of simple diffusion.  Amoeba lives in water which has oxygen dissolved in it.  The oxygen from the surrounding water diffuses into the cell cytoplasm of Amoeba through its cell membrane.  Because Amoeba is very small in size, the oxygen spreads quickly into its entire body by the process of diffusion. This oxygen is used for respiration inside the cell.  The process of respiration produces carbon dioxide continuously. This carbon dioxide gas from the cell cytoplasm diffuses through the cell membrane into the surrounding water.

Respiration in Amoeba

Reproduction in Amoeba

 Under normal conditions, Amoeba reproduces by splitting into two parts. This process is called binary fission.  Binary fission is a method of asexual reproduction in which the parent organism divides and gives rise to two identical daughter organisms.  However, when the environmental conditions are unfavourable, Amoeba reproduces by a method called multiple fission.  Multiple fission is a method of asexual reproduction in which a parent cell divides to produce many identical new individuals.

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BIOLOGY CLASSIFICATION OF PLANTS

Binary Fission in Amoeba

Parent Amoeba grows upto a certain size

Two daughter Pseudopodia are Amoebae are formed pulled in

Cytoplasm divides Nucleus lengthens in into two parts size

Nucleus divides into two daughter nuclei

Binary fission in Amoeba

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BIOLOGY CLASSIFICATION OF PLANTS

Multiple Fission in Amoeba

Inside the cyst, the Amoeba withdraws its It secretes a thick hard nucleus undergoes pseudopodia and turns covering called cyst repeated divisions to into a small rounded around itself. form several daughter speck. nuclei.

On return of favourabe Each daughter nucleus Nuclear division is conditions, the cyst burst gets surrounded by followed by cytoplasmic opens to release the some cytoplasm to form division. daughter amoebulae. daughter amoebulae.

Multiple fission in Amoeba