The Flower
ICSE Class 6 · Biology · Chapter 2
What this chapter covers
- Parts of a flower
- Pollination
- Fertilisation and the formation of fruit
- Fruits
- Seed
- Germination
Key points
- A flower is the part of a plant that makes seeds.
- A complete flower has four whorls: calyx (sepals), corolla (petals), androecium (stamens) and gynoecium (pistil).
- Sepals protect the bud, petals attract insects, stamens make pollen and the pistil receives pollen and makes seeds.
- A stamen has a filament and an anther; a pistil has a stigma, a style and an ovary with ovules.
- Pollination is the transfer of pollen from an anther to a stigma; it can be self-pollination or cross-pollination.
- Wind, water and insects carry pollen in cross-pollination.
- Fertilisation is the joining of the male cell from pollen with the egg cell in an ovule.
- After fertilisation the ovary becomes the fruit, the ovules become seeds, and the sepals, petals, stamens, style and stigma usually fall off.
- Fruits are dry (pea, bean) or fleshy (mango, tomato).
- The pericarp of a fleshy fruit has three layers: epicarp, mesocarp and endocarp.
- A seed has a seed coat, one or two cotyledons and an embryo with a radicle and a plumule.
- Dicot seeds have two cotyledons; monocot seeds have one.
- Seeds need moisture and warmth to germinate.
Questions answered
Name the four whorls of a complete flower, from the outside in.
Calyx, corolla, androecium and gynoecium.
What is the main job of the petals?
Petals attract insects with their bright colour, smell and nectar.
Name the two parts of a stamen and the three parts of a pistil.
A stamen has a filament and an anther. A pistil has a stigma, a style and an ovary.
What is the difference between self-pollination and cross-pollination?
In self-pollination, pollen reaches the stigma of the same flower or another flower on the same plant. In cross-pollination, pollen reaches the stigma of a flower on another plant of the same kind.
Give one example each of a plant pollinated by wind, by water and by insects.
Wind: maize. Water: Vallisneria. Insects: mustard.
After fertilisation, what do the ovary and the ovules become?
The ovary becomes the fruit and the ovules become the seeds.
Name the three layers of the pericarp of a mango and say which one you eat.
Epicarp, mesocarp and endocarp. You eat the mesocarp, the juicy pulp.
Which two conditions does a seed need to germinate? Is a maize grain a monocot or a dicot seed?
Moisture and warmth. A maize grain is a monocot seed, because it has one cotyledon.