The five groups of plants differ in the dominant generation, in vascular tissue, in their need for water at fertilisation, and in seeds and fruits. A short key of four questions places any plant. Read in order, the groups show clear trends from water to land.
This is the first lesson of Plant Kingdom: Deep Dive and NEET Practice, free for everyone to read.
Five groups, one story
The free courses met the five groups one by one. This lesson puts them side by side. Exam questions often ask you to compare two groups, or to place a plant that you have never seen. Both are easy once the differences are in one place.
Five boxes, one for each group of plants, joined by arrows from water to land. Algae: the body is a thallus with no embryo, no xylem or phloem, water is needed for fertilisation, no seeds; for example Volvox, Fucus and Gelidium. Bryophytes: the gametophyte is dominant, the embryo is kept on the plant, no xylem or phloem, water is needed for fertilisation; for example Marchantia and Funaria. Pteridophytes: the sporophyte is dominant, the first xylem and phloem, water is needed for fertilisation, no seeds and some are heterosporous; for example Selaginella and Dryopteris. Gymnosperms: the sporophyte is dominant, xylem and phloem, a pollen tube so no free water is needed, naked seeds and no fruit; for example Cycas and Pinus. Angiosperms: the sporophyte is dominant, xylem and phloem, a pollen tube and double fertilisation, seeds inside fruits; for example mustard and wheat.
The five features that matter
Five features separate the groups. Learn them as questions.
Which generation is dominant? In bryophytes the green plant you see is the gametophyte (n). In pteridophytes, gymnosperms and angiosperms it is the sporophyte (2n). Most algae spend most of their life as haploid plants.
Is there vascular tissue? Xylem and phloem appear first in the pteridophytes. Algae and bryophytes have none.
Is there an embryo? Bryophytes and all later groups keep the young sporophyte on the parent. Algae do not.
Does fertilisation need free water? It does in algae, bryophytes and pteridophytes, because their male gametes swim. Gymnosperms and angiosperms use a pollen tube.
Are there seeds, and are they enclosed? Gymnosperms have naked seeds. Angiosperms enclose their seeds inside fruits.
A key that places any plant
A key asks one question at a time. Each answer cuts the choice in two.
Has it xylem and phloem? If no: does it keep an embryo on the parent? Yes means a bryophyte, no means an alga.
If yes: does it make seeds? No means a pteridophyte.
If it makes seeds: are they inside a fruit? Yes means an angiosperm, no means a gymnosperm.
The key needs the right questions, asked in the right order. Asking about flowers first would fail for every group without flowers.
Trends from water to land
Read the groups in order and the same changes keep appearing.
The sporophyte grows, the gametophyte shrinks. In mosses the gametophyte feeds the sporophyte. In ferns the gametophyte is a tiny prothallus. In seed plants it is only a few cells inside the sporophyte.
Vascular tissue appears. It carries water up and allows tall plants.
Independence from water. The pollen tube frees fertilisation from rain and dew.
Heterospory leads to seeds. Two kinds of spores, kept on the parent, are the first step towards an ovule.
Seeds, then fruits. The seed protects and feeds the embryo. The fruit protects the seed and helps it spread.
Move the slider from 1 to 5. The gametophyte bar falls and the sporophyte bar rises. Bryophytes are the only group where the gametophyte still wins.
Try it in Python
The program turns the key into a function with four questions, and places six plants.
Practise with new numbers
Common mistakes
Calling the moss plant a sporophyte. The leafy moss is the gametophyte. Only its capsule on a stalk is the sporophyte.
Saying pteridophytes have seeds. They have spores only. Selaginella is heterosporous, but it still forms no seed.
Thinking gymnosperms have fruits. Their ovules and seeds are naked. Fruits come from an ovary, which they lack.
Placing a plant by its size or habitat. A tiny Wolffia is still an angiosperm. Use the features of the key.
First vascular tissue: pteridophytes. First embryo kept on the parent: bryophytes.
Free water for fertilisation: algae, bryophytes, pteridophytes. Pollen tube: seed plants.
Naked seeds: gymnosperms. Seeds in fruits: angiosperms.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
A plant has no xylem or phloem, but it keeps its young sporophyte on itself. Which group is it in?
Name the first group in which the sporophyte is the dominant, independent plant.
Why do gymnosperms not need free water at fertilisation?
Which trend leads from heterospory to the seed?
In the key, why must the question about vascular tissue come before the question about fruits?
Liked this lesson? There is more
Plant Kingdom: Deep Dive and NEET Practice is a Standard course. It adds 2 more lessons, practice and tests on top of the free chapter.
11Problems2Python Labs1Question Set1Mock Test
Plants that matter to people: Plants feed, house and heal people. Red algae give agar and carrageen, brown algae give algin, and Chlorella and Spirulina are protein-rich foods. Sphagnum gives peat and holds water. Gymnosperms give timber and resins, and angiosperms give most food, fibres and medicines.
Tricky points the exams test: Exams return to the same confusions. They include the gametes of Chlamydomonas, gemmae, Selaginella and Salvinia, and the roots of Cycas and Pinus. Others are the embryo sac, triple fusion and the endosperm, and which plants have which life cycle. Each is worked here as a NEET-style question.