Biology IGCSE Edexcel - Characteristics Of Living Organisms

For Biology IGCSE Edexcel

What seven characteristics define living organisms?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition

What are the main key features of plants?

Multicellular

They have cell walls (cellulose) chloroplast, and carry out photosynthesis.

They store carbohydrates as starch or sucrose.

What are the main key features of animals?

They are multicellular

No cell walls or chloroplasts

Often move and have nervous coordination.

They often store carbohydrates as glycogen

What are the main key features of fungi?

Can be multicellular or unicellular.

Their cell walls are made of chitin.

Feed by saprophytic nutrition using extracellular enzymes.

They store carbohydrates as glycogen.

Mushrooms, yeasts are examples

What are the main key features of protoctists?

Mostly microscopic and single-celled

Their cells have a nucleus, they are eukaryotic

Some represent animal cells, some plant cells

They do not have nervous coordination

What are the main key features of bacteria?

They are unicellular

Their cells are prokaryotic, they do not contain a nucleus

Their cell wall is made of peptidoglycan

Some bacteria photosynthesise, some feed on decaying matter or organic material.

Why aren’t viruses considered living organisms?

They have no cellular structure (no cell wall, no nucleus, no cytoplasm)

They are particles (not cells)

They consist of a protein coat and carry out genetic material (DNA or RNA)

All are parasites

What is mitochondria?

Carries out the reactions for aerobic respiration

Releases energy for cell functions like active transport, growth, division.

What are chloroplasts?

Contain chlorophyll, for photosynthesis

Converts light energy into chemical energy (glucose) for the plant

What is the cytoplasm?

Watery jelly like liquid which contains all of the organelles and enzymes.

Many of the cell’s chemical reactions take place in

the cytoplasm.

These are called metabolic reactions.

What are ribosomes?

Very very small particles found in the cytoplasm.

They make proteins (protein synthesis).

These are determined by the genes in the nucleus.