EasyBiologyHigh School (11–12)Diversity of Living Organisms › Bryophytes and PteridophytesConceptual
After the rains, Farhan sees a soft green coat on the shaded side of a brick wall.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
After the rains, Farhan sees a soft green coat on the shaded side of a brick wall. Under a hand lens, the tiny plants have small leaf-like parts and thin threads holding them to the brick, but no flowers. On some of them, short stalks end in small brown capsules. (a) To which group do these plants belong? (b) Why do they grow on the shaded, damp side of the wall?
Need a reminder? The key ideaShow
Bryophytes (liverworts and mosses) live in damp places and need water for fertilisation. The main plant body is the haploid gametophyte, held by rhizoids, with no vascular tissue. Antheridia make biflagellate antherozoids; archegonia make one egg. The zygote grows into a sporophyte (foot, seta, capsule) that depends on the gametophyte and makes spores by meiosis. Liverworts make gemmae in gemma cups; mosses grow from a protonema. Sphagnum holds much water and forms peat.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The group. Leaf-like parts, rhizoids instead of roots, no flowers, and capsules on stalks: these are mosses, which are bryophytes. The capsules on stalks are the sporophytes.
Step 2. Why the damp side. Bryophytes have no vascular tissue, so they cannot carry water far. They dry out easily. Their antherozoids also need a film of water to swim to the egg. The shaded side of the wall stays damp for longer.
Answer: (a) bryophytes (mosses); (b) they need moisture to stay alive and water for fertilisation, and the shaded side stays damp.
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