Explain what is meant by the term 'species' and describe how the five-kingdom classification system organises living organisms.

A species is a group of organisms that can interbreed and produce fertile offspring.
The five‑kingdom system classifies organisms into:
1. Animals – multicellular, heterotrophic, lack cell walls.
2. Plants – multicellular, autotrophic, have cell walls.
3. Fungi – multicellular or unicellular, heterotrophic, have cell walls.
4. Protists – mostly unicellular eukaryotes, diverse.
5. Prokaryotes – unicellular, lack a nucleus and membrane‑bound organelles.
Organisms are grouped according to shared characteristics such as cell type, nutrition, and presence or absence of a nucleus.