Biology Test - January '25

classification through to diffusion inclusive

What are the levels of classification in the Linnaean system?

Kingdom, Phylum, Class, Order, Family, Genus, Species.

Define a species.

A group of organisms that can interbreed and produce fertile offspring.

What is the binomial system?

A system that names organisms using two parts: the genus (capitalized) and species (lowercase), e.g., Homo sapiens.

What is an identification key?

A tool that helps identify organisms based on a series of paired statements about characteristics.

What is a dichotomous key?

An identification key that presents two contrasting options at each step to identify an organism.

What does an evolutionary tree (phylogeny) show?

The evolutionary relationships between species based on common ancestors.

What does a node represent on an evolutionary tree?

A common ancestor shared by the species that branch from it.

Name the five kingdoms.

Plants, Animals, Fungi, Protoctista, Prokaryotes.

Give one key characteristic of each kingdom.

• Plants: Photosynthetic

• Animals: Heterotrophic with internal digestion

• Fungi: Chitin cell walls, extracellular digestion

• Protoctista: Mostly unicellular, diverse traits

• Prokaryotes: No membrane-bound nucleus

Why are viruses not considered living organisms?

They are not made of cells, cannot carry out respiration, and can only reproduce by hijacking host cells.

What is the structure of a virus?

Genetic material (DNA/RNA) surrounded by a protein coat, sometimes with an additional membrane envelope.

Describe the lifecycle of a typical virus.

Entry into host → release of genetic material → replication → assembly of new viruses → host cell destruction.

What type of nutrition do animals have?

Heterotrophic nutrition (obtaining organic molecules from other organisms).

How do fungi obtain nutrients?

Through extracellular digestion—secreting enzymes onto food and absorbing nutrients.