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Flashcards · 5090 · Topic 2

Classification flashcards

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Topic 2: Classification

Species
A group of organisms that can reproduce to produce fertile offspring.
Binomial system
An internationally agreed system in which the scientific name of an organism has two parts showing the genus and species, e.g. Panthera leo. Genus has a capital letter; species is lower case; italics in print, underlined by hand.
Dichotomous key: what it is, and how many couplets for n organisms?
A key in which each step splits the organisms into two groups using one identifiable feature. n organisms need n − 1 couplets.
Why should colour or size not be used in a dichotomous key?
They vary between individuals of the same species, so they are not reliable. Use clear features such as number of legs, wings present or absent, or leaf veins parallel or branching.
Prokaryote kingdom: main features
Single cells with no nucleus; circular DNA free in the cytoplasm, plasmids, ribosomes and a cell wall.
Fungus kingdom: main features
Nucleus; cell wall not made of cellulose; no chloroplasts; body of hyphae (yeast is single-celled); secrete enzymes and absorb the food.
Insects vs arachnids
Insects: 3 body sections, 3 pairs of legs, 1 pair of antennae. Arachnids: 2 body sections, 4 pairs of legs, no antennae.
Crustaceans vs myriapods
Crustaceans: more than 4 pairs of legs, 2 pairs of antennae. Myriapods: many segments with 1 or 2 pairs of legs per segment, 1 pair of antennae.
Reptiles vs amphibians
Reptiles: dry scales; rubbery or leathery-shelled eggs laid on land. Amphibians: moist skin with no scales; soft eggs without shells laid in water; larvae with gills.
Mammals vs birds: identifying features
Mammals: hair or fur, external ears (pinnae), mammary glands; most give birth to live young. Birds: feathers, beak, wings, hard-shelled eggs.
Ferns vs flowering plants; monocots vs dicots
Ferns: fronds, reproduce by spores, no flowers. Flowering plants: reproduce by seeds. Monocots: 1 cotyledon, parallel veins, flower parts in threes. Dicots: 2 cotyledons, branching veins, parts in fours or fives.
Features of viruses
Only a protein coat and genetic material. Not cells and in none of the five kingdoms; they can only replicate inside living cells.

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