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Life Processes and Living Things - Pollination and fertilization

Grade 5IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The flower is the reproductive organ of many plants, containing male and female parts.

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The male part is the stamen, consisting of the anther and the filament. The anther produces pollen grains which contain the male gametes.

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The female part is the carpel (or pistil), consisting of the stigma, style, and ovary. The ovary contains ovules, which hold the female gametes.

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Pollination is the transfer of pollen from the anther to the stigma of a flower. This can occur via wind, insects, or other animals.

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Insect-pollinated flowers usually have brightly colored petals, NectarNectar, and a scent to attract pollinators.

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Wind-pollinated flowers often have small, dull petals, long filaments with hanging anthers, and feathery stigmas to catch drifting pollen.

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Fertilization is the fusion of the male gamete nucleus with the female gamete (ovule) nucleus to form a zygote.

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After fertilization, the ovary develops into the fruit, and the ovules develop into seeds containing the embryo.

📐Formulae

Stamen=Anther+Filament\text{Stamen} = \text{Anther} + \text{Filament}

Carpel=Stigma+Style+Ovary\text{Carpel} = \text{Stigma} + \text{Style} + \text{Ovary}

Pollination:Anther→Pollen TransferStigma\text{Pollination}: \text{Anther} \xrightarrow{\text{Pollen Transfer}} \text{Stigma}

Fertilization:Male Nucleus+Female Nucleus→Zygote\text{Fertilization}: \text{Male Nucleus} + \text{Female Nucleus} \rightarrow \text{Zygote}

Seed Development:Ovule→Seed\text{Seed Development}: \text{Ovule} \rightarrow \text{Seed}

Fruit Development:Ovary→Fruit\text{Fruit Development}: \text{Ovary} \rightarrow \text{Fruit}

💡Examples

Problem 1:

A flower has very light, smooth pollen and its anthers hang outside the flower. Identify the method of pollination and explain why.

Solution:

The method is wind-pollination.

Explanation:

Wind-pollinated plants produce light, smooth pollen so it can be easily carried by the air. Anthers hang outside the flower (ExertedExerted) to ensure the wind can catch the pollen as it passes.

Problem 2:

Describe the journey of a male gamete from the moment it lands on the stigma until fertilization occurs.

Solution:

Stigma→Pollen Tube→Style→Ovary→Ovule\text{Stigma} \rightarrow \text{Pollen Tube} \rightarrow \text{Style} \rightarrow \text{Ovary} \rightarrow \text{Ovule}

Explanation:

Once a pollen grain lands on the stigma, it grows a pollen tube down through the style into the ovary. The male nucleus travels down this tube to reach the ovule, where fertilization takes place.

Problem 3:

In an experiment, the petals of a flower are removed before it blooms. How will this affect the plant if it is usually pollinated by bees?

Solution:

Pollination will likely fail because bees will not be attracted to the flower.

Explanation:

Bees are attracted to flowers by bright colors and scents. Removing the petals removes the visual signal, meaning the bees will not visit to transfer pollen from the Anther\text{Anther} to the Stigma\text{Stigma}.