Classifying living things into species

Biology · Classification

Follow a lion down the tree

A simplified route: it names the kingdom, family, genus and species steps and leaves the levels in between unlabelled. Five kingdoms is the model used in this lesson; other classification schemes exist.

Biology · Sorting animals

Same six animals, three different rules

Place each animal under the rule shown. Then switch the rule and sort the same animals again. Who ends up together?

Does it have a backbone?

6 of 6 still to sort.

Predict, then check

Here’s a real case to test a big idea on. ‘Fertile’ means able to have young of its own.

A horse and a donkey have a foal. It's called a mule. Now two mules are bred together. What do you predict?

What you need to know

• Classification means sorting organisms into groups, using features they share, such as having a backbone.
• Scientists don't group by names or habitat, so fish and jellyfish aren't grouped just because the names look alike.
• Have a goMaya says a goldfish and a jellyfish must be in the same group because 'it's literally in the name'. What should she check instead?

  Their features, such as whether each has a backbone.

  Scientists group by shared features. Names and habitat can put very different animals together.

• The levels run from largest to smallest: kingdom, phylum, class, order, family, genus, species.
• Big groups such as kingdoms hold lots of organisms that share only a few features.
• Lower down, in a genus or a species, there are fewer organisms and they share many more features.
• Have a goA family and a genus are both levels on the list. Which one holds more organisms, and which one's members share more features?

  A family holds more organisms. A genus's members share more features.

  Going down the list the groups get smaller, but the organisms in them get more alike.

• This lesson's model has five kingdoms: animals, plants, fungi, protists and bacteria.
• Vertebrates are animals with a backbone, and invertebrates are animals without one.
• A species is a group of very similar organisms that can reproduce together to produce fertile offspring.
• Every species has a binomial name made of its genus then its species, like Homo sapiens.
• Write the genus with a capital, the species all lowercase, and the whole name in italics or underlined.
• Have a goThe domestic cat's genus is Felis and its species is catus. Write its binomial name the right way.

  Felis catus (in italics, or underlined if handwritten)

  The genus takes the capital letter, the species stays all lowercase, and the whole name is italicised or underlined.

The big picture

Scientists classify organisms into groups within larger groups using the features they share, not their names or where they live. The levels run from kingdom down to species, and every step down leaves fewer organisms that share more features. A species is a group that can reproduce together to produce fertile offspring, and each species has a two-part binomial name.

⚠ Watch out

Grouping animals by what they're called or where they live. A goldfish and a jellyfish both live in water and both have 'fish' in the name, but scientists group by features such as a backbone, not by names or habitat.

Memory hook

King Philip Came Over For Good Soup: Kingdom, Phylum, Class, Order, Family, Genus, Species. Biggest crowd first, smallest crowd last.

Check yourself

Order these from MOST organisms to FEWEST: genus Panthera, the animal kingdom, the cat family. Which group's members share the most features? Answer: kingdom, family, genus Panthera; the genus.