Plant Classification
You'll be able to sort a plant into one of the four main groups using simple features.
In 1994, botanist David Noble absailed into a hidden canyon 150 km from Sydney and found a living Wollemi pine, a tree scientists thought had been extinct for 2 million years.
Printable Worksheets
Print or save as PDF, or build a custom worksheet from any module's questions.
Q1 · Name three plants you'd see around your area. What do they have in common, and how do they differ?
Q2 · A moss never grows very tall (only a few cm). A gum tree can be 40 m tall. What do you think a gum tree has that a moss doesn't, that lets it grow so tall?
● Know
- The four main plant groups: mosses, ferns, gymnosperms, angiosperms
- What "vascular" means in a plant
- The difference between a monocot and a dicot
● Understand
- Why mosses must stay small and damp
- Why flowers and fruits gave angiosperms a huge advantage
- How seed leaves, veins and roots reliably split monocots from dicots
● Can do
- Sort a plant into one of the four main groups using simple features
- Decide if a flowering plant is a monocot or a dicot
- Give an Australian example of each group
- Vascular tissue
- Spore
- Gymnosperm
- Angiosperm
- Cotyledon
- A flowering plant, seeds in fruit
- Tubes that carry water and food inside the plant
- A "seed leaf", first leaf inside a seed
- A plant that makes seeds in cones
- A tiny one-celled reproductive unit (no seed)
Pull apart a celery stalk and you can see the stringy tubes running up the inside, those are the vascular channels that carry water from roots to leaves, and whether a plant has them or not is the first big yes/no question for sorting plants. and (2) Do they make seeds, or just spores? Combining those gives four neat groups:
| Group | Vascular? | Reproduces by | Flowers? | Examples |
|---|---|---|---|---|
| Mosses | No | Spores | No | The green mat on a damp rock or log |
| Ferns | Yes | Spores | No | Tree fern, bracken fern |
| Gymnosperms | Yes | Seeds (in cones) | No | Pine, cycad, Wollemi pine |
| Angiosperms | Yes | Seeds (in fruit) | YES | Gum tree, wattle, grass, rose, apple |
Roughly 90% of all plants on Earth are angiosperms. Flowers and fruit turned out to be a winning combination, flowers attract pollinators (insects, birds, bats) and fruit helps spread the seeds.
Text description
- Plants split into non-vascular and vascular.
- Non-vascular: mosses, liverworts.
- Vascular splits into seedless and seeds.
- Seedless (reproduce by spores): ferns, horsetails.
- Seeds split into gymnosperms (conifers, cycads; seeds in cones) and angiosperms (flowering plants; seeds in fruit).
Mosses are some of the oldest land plants, about 470 million years old. They are small, soft and live in damp shady spots (a rock by a creek, the side of a tree trunk).
Two big features set them apart:
- No vascular tissue. They can't pipe water up from the ground, so they can only grow a few centimetres tall. Every cell has to be close to water.
- Reproduce by spores. The little stalks you can sometimes see sticking up from a mossy patch are spore capsules. Spores need wet conditions to grow.
Put those two features together and you can say exactly which habitat a moss is suited to, and why. With no vascular tissue there are no tubes to lift water from the ground, so every cell has to sit within a fraction of a millimetre of water it can soak up directly from its surroundings. A moss can therefore only be a few centimetres tall, and it can only survive in a place where the air and the surface stay damp: the shaded side of a creek rock, the base of a tree trunk, a gap between pavers that never gets full sun. Its spores need the same thing. A moss spore has to land in a film of water before it can grow, and in dry open ground it never gets one. So a moss is not a failed tree. It is a plant adapted to damp shade, doing well in exactly the conditions that would be no use to something taller.
Even though mosses are tiny, they are important: they slow water flow, hold soil together and are some of the first plants to colonise bare rock.
Ferns were the next big jump, they evolved vascular tissue, so they can grow much taller than mosses (some Aussie tree ferns are 10 m tall). But they still reproduce by spores. Look on the back of a fern leaf and you'll often see brown dots, those are spore-producing structures.
Gymnosperms were the next jump again, they make seeds, not spores. A seed is a tough little package that contains an embryo plant plus food, so it doesn't need a damp environment to germinate. Gymnosperm seeds are made inside cones, not flowers. "Gymno-sperm" literally means "naked seed".
Watch what the tree fern shows you, because it separates two things that are easy to run together. A tree fern is 10 metres tall, so it clearly solved the water-transport problem that keeps a moss at three centimetres. And yet you will only find one in a damp gully, never on an exposed western slope, because it still reproduces by spores and a spore still needs a film of water. Growing tall and escaping the need for water are two separate problems, and vascular tissue only solved the first. It was the seed that solved the second, and that is why the seed makes a bigger difference to where a plant can live than height ever did.
Two Australian gymnosperms are worth knowing. The Wollemi pine is a "living fossil", thought extinct for two million years until a park ranger found about a hundred of them in a Blue Mountains canyon in 1994. A canyon, not a ridge, because these trees need shelter and reliable moisture. Macrozamia cycads, the palm-like plants common through eastern Australia, went the other way: their thick waxy leaves and underground stem let them survive in dry sclerophyll forest, and let them come back after a fire that kills almost everything around them.
Ferns have tissue but reproduce by . Gymnosperms reproduce by made inside they do not make .
Angiosperms are the flowering plants. They are by far the most diverse and successful plant group, about 90% of all plant species. The two big innovations:
- Flowers attract pollinators (insects, birds, bats), making reproduction much more efficient than just dumping pollen into the wind.
- Fruit is a tasty package around the seed. Animals eat the fruit and "deposit" the seed somewhere new, free transport!
Why those innovations let angiosperms live almost anywhere. Take the three features one at a time and ask what each one does for a plant trying to survive in a new place.
A flower hands pollen to an animal that carries it to another flower of the same species. Wind pollination works too, and wind-blown pollen can travel a long way, but it is a numbers game: the pollen goes in every direction and only a tiny share of it lands on the right species, so a plant relying on wind has to make enormous quantities and does best where its own kind grow thickly together. That is why wind-pollinated pines tend to form forests of pines. An animal delivers a far larger share of what it carries to the right flower, and it will cross open ground to do it, so a flowering plant can grow much more thinly scattered and still set seed reliably.
Fruit then moves the seed away from the parent. This matters more than it sounds, because a seedling that germinates in its parent's shade is competing with a much larger plant for the same light and water. A currawong that eats a lilly pilly fruit and lands three valleys away has put that seed somewhere with no competition at all, and possibly in a habitat the parent could not have reached.
And the seed itself, which angiosperms share with gymnosperms, carries a food store inside a tough coat, so it can sit in dry ground for months or years and only germinate once there is enough water to finish the job. In most of Australia that is the feature that decides everything, because rain here is unreliable. A plant that can wait out a drought inside a seed is suited to country a spore-producing plant simply cannot survive in.
Angiosperms include almost all crops (wheat, rice, apple, banana, tomato), grasses, gum trees, wattles, roses and orchids. They are split into two big sub-groups, monocots and dicots which we'll cover next.
Angiosperms split into two big groups based on the number of "seed leaves" (cotyledons) inside the seed. You can tell them apart without ever cutting a seed open, just look at the leaves, veins and roots.
| Feature | Monocot | Dicot |
|---|---|---|
| Seed leaves (cotyledons) | One | Two |
| Leaf veins | Parallel (run side by side) | Net-like (branching) |
| Roots | Fibrous (lots of thin roots) | Taproot (one main root + side roots) |
| Flower parts | In multiples of 3 | In multiples of 4 or 5 |
| Examples | Grass, wheat, lily, palm, banana | Rose, gum tree, wattle, sunflower, oak |
The lazy rule: a blade of grass has parallel veins (monocot). A rose leaf has branching net veins (dicot). Most things you'll see are dicots.
You pull up a banana plant and notice: it has long parallel veins running down each leaf, the roots are a bunch of thin roots (no big main root), and it has small flowers in threes. Predict: is it a monocot or a dicot? Use the features as evidence.
How close was your prediction?
Nice, you spotted that all three features point the same way.
Good, remembering that bananas are in the grass/lily/palm group catches a lot of students.
At the start of the lesson you were asked: a pine tree never makes flowers, so how does it make baby pine trees?
Now that you know the four plant groups, write your full answer. Name the pine's group, explain how seeds inside cones work, and say how this is different from what a gum tree does.
Q1. Name the four main groups of plants and write one key feature of each. (3 marks)
Q2. A plant has leaves with branching net-like veins, a single big main root, and small five-petalled flowers. Is it a monocot or a dicot? Give all three reasons. (4 marks)
Q3. Explain why angiosperms are now the most common plant group on Earth, while mosses are stuck small. Use at least three terms from the lesson. (4 marks)
Answers
▾MCQ 1
A Mosses are the only group without vascular tissue. That's why they have to stay small and damp. Ferns, gymnosperms and angiosperms all have it.
MCQ 2
C Pines make seeds inside cones (no flowers, no fruit). "Gymnosperm" means "naked seed".
MCQ 3
B Monocots have ONE seed leaf, PARALLEL veins, and FIBROUS roots. Dicots are the opposite (two seed leaves, net veins, taproot).
MCQ 4
D Angiosperms make up about 90% of all plant species. Flowers and fruit gave them a huge reproductive advantage.
MCQ 5
A Ferns have vascular tissue (water-carrying tubes), which is why they can grow much taller than mosses. They still reproduce by spores, like mosses do.
Short Answer 1
Model answer: Mosses, no vascular tissue, reproduce by spores, stay small and damp. Ferns, vascular tissue but still reproduce by spores. Gymnosperms, make seeds inside cones, no flowers (e.g. pine, Wollemi pine). Angiosperms, flowering plants, make seeds inside fruit (e.g. gum tree, wattle).
Short Answer 2
Model answer: The plant is a dicot. Three reasons: (1) the leaves have net-like (branching) veins, monocots have parallel veins. (2) It has a single big main root (a taproot), monocots have fibrous root systems. (3) The flowers have five petals, monocot flower parts come in threes, dicots in 4s or 5s.
Short Answer 3
Model answer: Angiosperms have two big advantages: flowers attract pollinators like bees and birds, which makes pollination far more efficient than just dumping pollen into the wind, and fruit surrounds the seeds so animals carry them to new places. They also have vascular tissue, so they can grow as tall as gum trees. Mosses, by contrast, have no vascular tissue, so water cannot be carried up the plant, they are stuck a few cm tall. They also reproduce by spores, which need a damp environment. That's why mosses are limited to small damp spots while angiosperms have spread to almost every land habitat on Earth.