Biology – Classification of Living Organisms

30 Question-and-Answer flashcards covering key facts on biological classification, kingdoms, vertebrates, binomial nomenclature, species concepts, and identification keys.

What is the main purpose of biological classification?

To organise and identify living organisms in an ordered, universal system.

What is meant by a species’ binomial name?

A two-part scientific name consisting of the genus followed by the species (e.g., Homo sapiens).

List the seven main taxonomic ranks in order, starting with kingdom.

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

Give the full classification of a lion from kingdom to species.

Kingdom Animalia, Phylum Vertebrata, Class Mammalia, Order Carnivora, Family Felidae, Genus Panthera (big cat), Species Panthera leo (lion).

Why is binomial classification important to conservationists?

It clearly identifies species, aids study, and allows targeted conservation efforts without confusion.

Which two robins are distinguished by the binomial names Turdus migratorius and Erithacus rubecula?

The American robin (Turdus migratorius) and the UK/European robin (Erithacus rubecula).

Name the five kingdoms used in modern classification.

Animalia, Plantae, Fungi, Protoctista (Protista), Prokaryotae (Monera/Bacteria).

State two key cellular characteristics of Kingdom Animalia.

Multicellular, no cell walls or chlorophyll; organisms are heterotrophic.

How do members of Kingdom Plantae obtain food and what cell feature supports this?

They are autotrophic via photosynthesis and possess cell walls containing chlorophyll.

What type of nutrition do fungi exhibit, and what key cellular feature do they lack compared with plants?

Saprophytic (decomposer) nutrition; they lack chlorophyll.

Why was Kingdom Protoctista (Protista) created?

To group mostly unicellular eukaryotes like Euglena that don’t fit well into plant, animal, or fungal kingdoms.

What distinguishes organisms in Kingdom Prokaryotae from the other four kingdoms?

They are unicellular and lack a true nucleus (e.g., bacteria, blue-green algae).

Which three conflicting traits make Euglena tricky to classify?

Presence of chloroplasts (plant-like), absence of a cell wall (animal-like), and possession of a flagellum (bacteria-like).

Give two reasons viruses are not classified as living organisms.

They do not perform all seven life processes on their own and must hijack host cells to replicate.

List three criteria scientists use to subdivide vertebrates.

Method of oxygen intake (lungs, gills, skin), thermoregulation (homeotherm vs. poikilotherm), and mode of reproduction (fertilisation type; oviparous vs. viviparous).

Which vertebrate group has gills, external fertilisation, and is oviparous and poikilothermic?

Fish.

Name a vertebrate class that may use lungs and/or gills, has external fertilisation, and is poikilothermic.

Amphibians.

Which vertebrate class is poikilothermic, has lungs, internal fertilisation, and lays eggs?

Reptiles.

Identify the vertebrate group that is homeothermic, has lungs, internal fertilisation, and lays eggs.

Birds.

What reproductive and thermal traits define mammals?

Internal fertilisation, viviparous (live birth), and homeothermic (warm-blooded).

Why are sharks challenging to classify strictly by vertebrate criteria?

They are fish but exhibit internal fertilisation and give birth to live young, traits typical of some other vertebrate classes.

Define a biological species.

A group of organisms that share many characteristics and can interbreed to produce fertile offspring.

Give an example showing large variation within a single species.

Different pedigree dog breeds (e.g., Beagle vs. Golden Retriever) are all Canis familiaris yet look very different.

What is hybridisation in classification, and why can it complicate species boundaries?

Breeding between closely related species, producing hybrids that share features of both parents and are often infertile.

Explain the concept of a ring species.

Adjacent populations can interbreed along a geographic chain, but the populations at the ends of the chain cannot interbreed directly.

What are the two main formats of identification keys used by biologists?

Branching keys and paired statement (dichotomous) keys.

In a dichotomous key, which question would distinguish a pig from a cow or horse?

"Does the animal have a curly tail?" – Yes identifies a pig.

Which question in the farm-animal key separates birds from humans?

"Does the animal have webbed feet?" – Yes identifies a duck; No identifies a human.

State two ways classification helps evolutionary studies.

By revealing relationships between species and tracing their shared ancestry.

Give the full kingdom-to-species classification for modern humans.

Kingdom Animalia; Phylum Chordata; Class Mammalia; Order Primates; Family Hominidae; Genus Homo; Species Homo sapiens.