Principles of Classification

Classification

What is biodiversity?

A measure of the variety of living organisms and their genetic differences.

Why is biodiversity important?

It provides a wide variety of organisms and genetic variation and helps ecosystems remain stable and adaptable.

What is classification?

The organisation of living organisms into groups based on their similarities, differences and evolutionary relationships.

Why do biologists classify organisms?

To identify organisms accurately, organise biodiversity, monitor populations and understand evolutionary relationships.

Why is an internationally recognised classification system important?

It allows scientists worldwide to refer to the same organisms despite differences in common names and languages.

What is taxonomy?

The science of describing, classifying and naming living organisms.

What is the aim of a classification system?

To group organisms accurately and show their relationships and common ancestry.

What is evolution?

The process by which natural selection acts on variation, producing adaptations and potentially leading to new species.

Why has evolution produced such a large variety of organisms?

Millions of years of evolution and adaptation to different environments have produced extensive biodiversity.

What is morphology?

The study of the form and structure of organisms.

What are analogous features?

Features that look similar or perform similar functions but do not have the same evolutionary origin.

Why can analogous features cause problems in classification?

They can make unrelated organisms appear closely related.

What are homologous structures?

Structures that show genuine common ancestry, even if they now have different functions.

Why are homologous structures useful in classification?

They provide evidence of evolutionary relationships and common ancestry.

Who developed the first scientifically based classification system?

Carolus Linnaeus.

What did Linnaeus contribute to classification?

He developed a hierarchical classification system and the binomial system of naming organisms.

What are the three domains?

Archaea, Bacteria and Eukaryota.

What is the largest taxonomic group?

Domain.

What is the correct order of the main taxonomic groups from largest to smallest?

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

What taxonomic group is used instead of phylum in plants?

Division.

What is a domain?

One of the three largest classification categories: Archaea, Bacteria and Eukaryota.

What is a kingdom?

A classification category below domain containing related phyla or divisions.

What is a phylum?

A group of related classes that share common characteristics.

What is a class?

A group of related orders that share common characteristics.

What is an order?

A group of related families that share common characteristics.

What is a family?

A group of related genera that share common characteristics.

What is a genus?

A group of closely related species that share common characteristics.

What is a species?

A group of closely related organisms that are potentially capable of interbreeding to produce fertile offspring.

Which kingdom is found in the Archaea domain?

Archaebacteria.

What are Archaea?

Bacteria-like prokaryotic organisms that are thought to be early relatives of eukaryotes and can occur in extreme and ordinary environments.

What are Archaebacteria?

Ancient types of bacteria found in many different environments.

Which kingdom is found in the Bacteria domain?

Eubacteria.

What are Eubacteria?

True bacteria; prokaryotic organisms including disease-causing bacteria and many useful bacteria.

What are some important roles of Eubacteria?

Some cause disease, while others aid digestion and recycle nutrients in ecosystems.

Which kingdoms belong to the Eukaryota domain?

Protista, Fungi, Plantae and Animalia.

What are Protista?

A diverse kingdom of mainly microscopic eukaryotic organisms, including both autotrophs and heterotrophs.

What are examples of protists?

Amoeba, Chlamydomonas, green and brown algae and slime moulds.

What is an autotroph?

An organism that makes its own organic food, usually by photosynthesis.

What is a heterotroph?

An organism that obtains organic nutrients by consuming or absorbing material from other organisms.

What are the main characteristics of fungi?

They are eukaryotic heterotrophs, most are saprophytic, some are parasitic, and their cell walls contain chitin.

What does saprophytic mean?

Obtaining nutrients from dead or decaying organic matter.

What are the main characteristics of plants?

They are mainly autotrophic eukaryotes that make their own food by photosynthesis using chlorophyll.

What groups are included in the plant kingdom?

Mosses, liverworts, ferns, gymnosperms and angiosperms.

What are the main characteristics of animals?

They are mainly heterotrophic eukaryotes that can move their whole bodies during at least one stage of their life cycle.

What groups are included in the animal kingdom?

Invertebrates and vertebrates, including insects, molluscs, worms, fish, amphibians, reptiles, birds and mammals.

What is the binomial system?

A system in which every organism is given a two-part scientific name consisting of its genus and species.

What does binomial mean?

Two names.

What are the two parts of a binomial name?

The genus name followed by the species name.

How should a scientific binomial name be written?

The genus begins with a capital letter, the species begins with a lower-case letter, and both are written in italics.

Give an example of a correctly written binomial name.

Homo sapiens.

How can a binomial name be abbreviated?

The genus can be shortened to its initial followed by the full species name, e.g. H. sapiens.

Why are binomial names useful?

They provide a universal and precise way of identifying organisms.

What do organisms in the same genus have in common?

They are closely related and share many characteristics.

Do organisms with the same species name necessarily belong to the same genus?

No. The same species name can occur in different genera and the organisms may be unrelated.

What does the classification of organisms increasingly aim to represent?

Evolutionary relationships and common ancestry.

Why can classification systems change over time?

New scientific evidence can reveal previously unknown evolutionary relationships between organisms.

What type of evidence was traditionally used to classify organisms?

Observable physical characteristics and morphology.

Why is classification useful for monitoring biodiversity?

It allows scientists to identify organisms and track changes in the numbers and distribution of different species.

What is the relationship between classification and common ancestry?

A good classification system groups organisms according to their evolutionary relationships, so closely related groups share more recent common ancestors.