The Variety of Living Organisms in Biology

Eukaryotic Organisms

Organisms whose cells contain a nucleus enclosed within membranes, usually more complex with membrane-bound organelles.

Plants

Multicellular organisms with a nucleus, cell wall made of cellulose, chloroplasts for photosynthesis, and vacuoles.

Photosynthesis

The process by which plants carry out for energy.

Carbon dioxide + water + light energy → glucose + oxygen.

Animals

Multicellular organisms with a nucleus, no cell wall or chloroplasts, that gain nutrition by feeding on other organisms.

Heterotrophic

Organisms that cannot photosynthesise and gain nutrition by feeding on other organisms.

Fungi

Organisms that can be unicellular or multicellular, have a nucleus and cell walls made of chitin, and do not photosynthesise.

Saprotrophic Nutrition

Nutrition obtained by secreting enzymes onto organic material and absorbing the products.

Protoctists (Protists)

Microscopic single-celled organisms that all have a nucleus, some can photosynthesise, and some are pathogenic.

Prokaryotic Organisms

Organisms made of cells without a nucleus, with DNA free in the cytoplasm, often in a single circular chromosome.

Binary Fission

The asexual reproduction method used by prokaryotic organisms.

Viruses

Non-living particles made of a protein coat surrounding genetic material, can only reproduce inside living cells.

Pathogen

A microorganism that causes disease.

Types of Pathogens

Include fungi (e.g. athlete's foot), bacteria (e.g. Pneumococcus), protoctists (e.g. Plasmodium), and viruses (e.g. HIV).

Influenza Virus

A virus that causes flu.

HIV

A virus that causes AIDS.

Tobacco Mosaic Virus (TMV)

A virus that affects plants and causes discoloration of leaves.

Lactobacillus

A bacterium used in the production of yoghurt.

Pneumococcus

A bacterium that causes pneumonia.

Salmonella

A bacterium that causes food poisoning.

Key Points Summary

Eukaryotic organisms include plants, animals, fungi, and protoctists. Prokaryotic organisms like bacteria lack a nucleus. Viruses must infect living cells to reproduce.