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Plant Life - Dispersal of seeds (Wind, Water, Animals, Explosion)

Grade 5ICSE

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

🔑Concepts

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Seed dispersal is the process of scattering seeds away from the parent plant to prevent overcrowding and reduce competition for H2OH_2O, sunlight, and minerals.

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Wind Dispersal: Seeds are typically small, light, and may possess wing-like structures (e.g., Maple) or hair-like structures (e.g., Dandelion) to be carried by air currents.

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Water Dispersal: Plants growing near water bodies produce seeds/fruits with fibrous or spongy outer coats (e.g., Coconut, Lotus) that allow them to float on H2OH_2O.

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Animal Dispersal: Seeds may have hooks or spines (e.g., XanthiumXanthium) to stick to animal fur, or they may be contained within fleshy fruits (e.g., Mango, Guava) which are eaten, and the seeds are excreted elsewhere.

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Explosion (Self-mechanism): Some plants have pods that dry up and burst open with a sudden force, shooting the seeds out in different directions (e.g., Pea, Balsam, Geranium).

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Without dispersal, seedlings would compete for CO2CO_2, nutrients like NN (Nitrogen), PP (Phosphorus), and KK (Potassium), leading to poor growth.

📐Formulae

Success of Germination∝1Competition for H2O and Light\text{Success of Germination} \propto \frac{1}{\text{Competition for } H_2O \text{ and Light}}

6CO2+6H2O→Sunlight/ChlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{Sunlight/Chlorophyll}} C_6H_{12}O_6 + 6O_2

Growth Factors={Sunlight,H2O,Minerals,Space}\text{Growth Factors} = \{ \text{Sunlight}, H_2O, \text{Minerals}, \text{Space} \}

💡Examples

Problem 1:

A fruit is found floating in a river. It has a thick, fibrous husk. Identify the agent of dispersal and give an example of such a plant.

Solution:

Agent: Water (H2OH_2O). Example: Coconut.

Explanation:

The fibrous husk traps air, making the fruit buoyant so it can float on H2OH_2O to reach distant shores.

Problem 2:

How does the structure of a Dandelion seed assist in its dispersal?

Solution:

It uses Wind dispersal through its 'parachute' of hairs.

Explanation:

Dandelion seeds are very light and have a tuft of fine hairs that act like a parachute, allowing them to be carried long distances by the wind.

Problem 3:

Explain why XanthiumXanthium seeds are often found stuck to the wool of sheep.

Solution:

Dispersal by Animals.

Explanation:

Seeds of XanthiumXanthium have stiff hooks or spines that latch onto the fur (or wool) of passing animals, ensuring the seed is transported away from the parent plant.