Living processes in unicellular organisms

• Eg. Of living processes:

Feed , respire, excrete, move, respond to stimuli, reproduce and grow.

Unicellular organisms?

• Simple organisms – consisting of only one cell.

• Each cell is a complete unit of life.

• Able to carry out all living processes in order to survive.

Examples of unicellular microorganisms.

• Amoeba sp .

• Paramecium sp.

• They’re called protozoa.

Amoeba sp.

Pseudopodium

(False feet)

Contractile vacuole

Food vacuole

Nucleus

General features

Contractile vacuole

• Water continually enters the Amoeba sp. By osmosis. This is collected by contractile vacoule which swells up. When full, its expels the water from the cell- OSMOREGULATION.

• It enables Amoeba sp. To survive in its habitat.

Membrane

• Respiration - gaseous exchange by simple diffusion.

• Being so small, the oxygen that they need diffuse into the cell through the membrane.

• Similarly, carbon dioxide and any dissolved waste diffuses out of the cell into the water.

Cytoplasm

• Clear on the outside(Ectoplasm)

• Grainy on the inside (Endoplasm)

Movement

• An extension of cytoplasm - called pseudopodium (false foot).

• The rest of cytoplasm slowly flows into extension, hence moving the organisms along.

• Pseudopodia can be extended out into any direction.

Reproduction of Amoeba sp.

Fully grown Amoeba sp.

Two daughter cellTwo daughter cell

Fully grown Amoeba sp

(parent)

Reproduction

• Grown to a certain size

• Its nucleus divides to form two daughter nuclei

• The cytoplasm then divides and two daughter Amoeba sp. are formed

• This is called Binary fission

• During drought – can divide by spore formation

Feeding of Amoeba sp.

Feeding of Amoeba sp.

• By process of PHAGOSITOSIS.

• It simply moves round a food particle and take into cytoplasm.

• Then it form food vacuole.

• Enzyme digest the food

• Nutrient diffuse through cytoplasm

• Any waste left behind as it moves away

Cell specialisation in multicellular organisms