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Nutmeg is dispersed by birds. Photo credit: russolab.unl.edu |
1. Wind-dispersed seeds
- Fruits contain seeds, and usually have a parachute or a wing to help them be carried away from the parent plant by the wind.
- Examples: dandelion, sycamore
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZ0R0Z4mXntUxa0j3Pbg3e733aEefHdUHX0ax9I8i0OfthazROr6FJ7QA5vAjy2WpAyWyVj_XVGhe6a1XD1ZIhpPOx2tnL-UEmCCMwNWMY52iDc5twKpbA7OGXC_scQ91_OvbLddMzn5ji/s280/wind-disersed+fruits.jpg)
The dandelion fruit has a group of fine hairs called a pappus, which catches the wind and acts like a parachute. The fruit counterbalances the pappus.
The sycamore
has a wing with a large surface area. When the fruit drops off the tree it
spins, slowing down in descent. If caught by the wind the seed will be carried
away from the parent plant, reducing competition for nutrients, water and light.
2. Animal-dispersed seeds
Succulent
fruits attract animals because they are brightly coloured, juicy and nutritious.
When eaten, the seed pass through
animal’s faeces, which may be a
long way from the parent plant. The faeces provides nutrients when the seeds germinate.
Hooked fruits
catch on to an animal’s fur as it
brushes past the parent plant. Eventually the seeds drops off, or the animal
grooms itself to remove them. This disperses the seeds away from the parent
plant.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-58QpGKUdhcE-d6EyBNWx6J4VIiLX63O1EbB2RVgenTpHd-b5A9CDOg5n8c4Qf1EGu7L1Ppb5do1QAXWpBB3P6gDfEjDeYy1koLOez3bPeY7CFJ3mGEImzlXxFXctL3JdhXoHw_gNfY8M/s280/Seeds+dispersal+by+animals+vs+by+wind.png)
Try this
Figure below shows a section through a bean seed.
1. i) Name the parts labeled A, B and C. [3 marks]
ii) Copy the diagram and label with an X the part that contains the seed’s food reserves. [1 mark]
2. Seeds and fruits are dispersed away from the parents plant.
i)Sketch a seed or fruit that is adapted for dispersal by wind. Label with a Y the special feature of the seed or fruit that helps in wind dispersal. [1 mark]
ii) Suggest how this feature helps in wind dispersal. [2 marks]
iii) Suggest another way in which wind assist in the reproduction of plants. [1 mark]
Answer
1. i) A plumule; B cotyledon, C testa (seed coat)
ii) X on any part of the cotyledon.
2. i) Sketch of dandelion, sycamore…
Y on the part that catches the wind (parachute, wing…).
ii) Two points from:
- description of how the feature catches the wind
- and slows down the descent of the seed or fruit
- so the seed or fruit is carried away from the parent plant.
iii) Wind pollination
Video: Seeds - An amazing video taken from BBC's The Private Life of Plants documentary series (MUST SEE).
This has been removed from the IGCSE syllabus :)
ReplyDeleteBut it is included in the O level syllabus :)
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ReplyDeleteThanks
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ReplyDelete