Biological ScienceOrganism DiversityYear 5 Science

Sorting living things: plants, animals and keys

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What this lesson covers

Why scientists sort living things into groups
How a classification key works, and how to make one
The main groups of plants: flowering plants, cone-bearing plants, ferns and mosses
Why algae are a separate group from plants
Vertebrates and invertebrates, and the main groups of each
Microorganisms, which are too small to see without a microscope

Key idea

Why sort living things?

An organism is any living thing: a plant, an animal, a mushroom or a germ.
Classification means sorting organisms into groups by the features they share, such as having feathers or making seeds.
Small groups fit inside bigger groups, like books on shelves inside sections of a library.
Organisms in the same group are usually related to each other, the way cousins share the same grandparents. Over a very long time, groups of living things have changed and split into new groups.
Sorting this way helps scientists all over the world talk about the same organism and spot new ones.

Key idea

Groups of plants

Plants are sorted by their structures, which means their body parts, such as flowers, cones, roots and leaves.
They are not sorted by where they live. Seagrass grows under the sea in New Zealand estuaries, but it has flowers, so it belongs with the flowering plants.

Group	Key features	New Zealand examples
Flowering plants	Have flowers; seeds form inside a fruit	Kōwhai, pōhutukawa, grasses, seagrass
Cone-bearing plants	No flowers; seeds grow in cones	Kauri, pine trees
Ferns	No flowers or seeds; fronds with spores underneath	Ponga (silver fern), kiokio
Mosses	Tiny, soft, no true roots; spores, no seeds	Moss on damp rocks and logs

Key idea

Try it: which plant group?

Key idea

Algae are a group of their own

Algae (say "al-gee") are living things that make their own food from sunlight, like plants do.
Seaweeds such as kelp are algae, and so is the green slime that grows in a pond.
Algae do not have true roots, stems or leaves. A seaweed holds onto a rock with a holdfast, but it does not take in water through it like a root does.
Because their structures are so different, scientists put algae in a separate group from plants.

Key idea

Vertebrates and invertebrates

Animals are first sorted into two big groups by one feature: a backbone.
A vertebrate is an animal with a backbone. Fish, amphibians, reptiles, birds and mammals are vertebrates.
An invertebrate is an animal without a backbone. Molluscs, worms, spiders and insects are invertebrates.

Group	Backbone?	New Zealand example
Fish	Yes	Snapper
Amphibians	Yes	Archey's frog
Reptiles	Yes	Tuatara, geckos
Birds	Yes	Kiwi, tūī
Mammals	Yes	Long-tailed bat, people
Molluscs	No	Pāua, garden snail
Worms	No	Earthworm
Spiders	No	Kātipo
Insects	No	Wētā, monarch butterfly

A sorting tree. Animals split into vertebrates (with a backbone): fish, amphibians, reptiles, birds and mammals; and invertebrates (no backbone): molluscs, worms, spiders and insects.

Key idea

Try it: backbone or not?

Key idea

Microorganisms

A microorganism is a living thing so small that you need a microscope to see it. "Micro" means very small.
A microscope is a tool with lenses that makes tiny things look many times bigger.
Bacteria are microorganisms, and so are some algae and yeasts.
A single drop of pond water can hold hundreds of microorganisms that you cannot see with your eyes alone.

Key idea

Classification keys

A classification key is a tool for finding out what an organism is.
It is a list of questions about features you can see, each with two answers, such as "Does it have flowers? Yes or no."
Each answer sends you to the next question, until you reach the organism's name.
Good questions are about features anyone can check, such as legs, shells or flowers. Questions about colour or size can trick you, because these can change.

Worked example

Example: using a key on four plants

Tama finds four plants on a bush walk: a kōwhai, a kauri, a ponga and a patch of moss.
Use the key in the figure to name a plant that has no flowers, no cones and large fronds.

A key drawn as a flowchart. Has flowers? Yes: kōwhai. No: has cones? Yes: kauri. No: has large fronds? Yes: ponga. No: moss.

Has flowers? Nogo to the next question
Has cones? Nogo to the next question
Has large fronds? Yesfollow the yes arrow
The plant is a ponga

Worked example

Example: designing a key for four animals

Make a key that separates a kiwi, a tuatara, a wētā and a pāua.

1. Has a backbone? Yes: go to 2. No: go to 3.split vertebrates from invertebrates
2. Has feathers? Yes: kiwi. No: tuatara.a bird and a reptile
3. Has a shell? Yes: pāua. No: wētā.a mollusc and an insect
Three questions name all four animals

Common mistakes

Seaweed is a plant because it is green and lives in water.
Seaweed is an alga: it has no true roots, stems or leaves, so it is in a separate group from plants.
Plants that live in water all go in the same group.
Plants are grouped by their structures, not where they live; seagrass has flowers, so it is a flowering plant.
A spider is an insect.
Spiders have eight legs and two body parts; insects have six legs and three body parts, so they are different groups.
A key question can be "Is it big?"
Use features anyone can check the same way, such as "Does it have a shell?", because big means different things to different people.

Try it at home

Make a key for leaves from your garden

You need: 6 different leaves from a garden or park, a sheet of paper, a pencil, a family member to test your key

With an adult, collect six leaves that look different from each other.
Lay them out and find one feature that splits them into two groups, such as "Is the edge smooth or jagged?"
Keep splitting each group with a new yes or no question until every leaf is on its own.
Write your questions down as a key, then hand one leaf to a family member and ask them to name it using only your key.
If they get it wrong, look for the question that confused them and make it clearer.

Safety: Have an adult check each plant before you pick from it, because some garden plants are poisonous or prickly, and wash your hands afterwards.

Your turn

A kauri makes seeds in cones and has no flowers. Which plant group is it in?

A tuatara has a backbone. Is it a vertebrate or an invertebrate?

Why is kelp not classified as a plant?

An animal has eight legs, two body parts and no backbone. Is it an insect or a spider?

Which of these can only be seen with a microscope: a bacterium, a moss or an ant?

Show answer

1. Cone-bearing plants. 2. A vertebrate (it is a reptile). 3. It has no true roots, stems or leaves, so it is an alga, not a plant. 4. A spider, because insects have six legs and three body parts. 5. A bacterium, because it is a microorganism.

Summary

Recap

Classification sorts organisms into groups by shared features; related organisms end up together.
Plants are grouped by structure: flowering plants, cone-bearing plants, ferns and mosses.
Algae have no true roots, stems or leaves, so they are not plants.
Vertebrates (fish, amphibians, reptiles, birds, mammals) have a backbone; invertebrates (molluscs, worms, spiders, insects) do not.
Microorganisms can only be seen with a microscope.
A classification key uses yes or no questions about features you can see to name an organism.

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