Seed dispersal

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Lesson notes

Why Seed Dispersal is Important

Seeds need to be dispersed away from the parent plant to **spread to new areas**.
Dispersal promotes **genetic diversity**.
It **reduces competition** for resources like water and light.

Wind Dispersal

Seeds are **light** and have structures to catch the wind.
**Dandelion seeds** have feathery bristles.
**Maple seeds** have wings that allow them to be carried by the wind.

Water Dispersal

Seeds have **waterproof coverings** that enable them to float.
**Coconuts** can travel long distances across oceans and still germinate.

Animal Dispersal

Seeds with **hooks or spines** (e.g., burrs) attach to animal fur or feathers.
Seeds can be **eaten by animals** and later excreted in different areas.

Explosive Dispersal

Some plants have seed pods that **dry out and burst open**.
The pods fling seeds in all directions (e.g., **pea pods**).

Gravity Dispersal

Fruit simply **falls from the plant** and relies on gravity to roll away.
This is especially effective if the plant is on a **slope**.

Investigating Wind Dispersal

In a clear, open area, use a **fan or hairdryer** to create a steady breeze.
Drop a seed from a marked starting point and let the wind carry it.
**Measure the distance** the seed travels and record the result.
Repeat with different types of seeds and compare which travel furthest.

Illustration of different seed dispersal methods: wind, water, animal, explosive, and gravity.

Slides

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Practice questions

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1.Which of the following is an example of a seed dispersed by water?
Easy
- ACoconut
- BDandelion
- CBurr
- DPea pod
2.Dandelion seeds have feathery bristles. This adaptation is for which method of seed dispersal?
Easy
- AWind
- BWater
- CAnimal
- DExplosive
3.Which of the following is NOT a reason why seed dispersal is important?
Easy
- ATo reduce competition for resources
- BTo help plants spread to new areas
- CTo increase genetic diversity
- DTo ensure seeds remain near the parent plant
4.Which seed dispersal method relies on seeds being eaten by animals and later excreted?
Medium
- AWind dispersal
- BWater dispersal
- CAnimal dispersal via ingestion
- DExplosive dispersal
5.Maple seeds have wings. This adaptation helps them to be dispersed by:
Medium
- AWind
- BWater
- CAnimals
- DExplosive force
6.In an experiment to test wind dispersal, a student drops seeds in front of a fan and measures the distance they travel. Which variable should be kept constant?
Medium
- AType of seed
- BFan speed
- CDistance traveled
- DNumber of seeds dropped
7.Which of the following is an example of explosive seed dispersal?
Medium
- ACoconut floating in the sea
- BDandelion seed blowing in the wind
- CPea pod bursting open
- DBurr attaching to animal fur
8.A student investigates wind dispersal using a fan. Which of the following would improve the reliability of the results?
Hard
- AUsing only one type of seed
- BRepeating each measurement three times
- CChanging the fan speed for each seed type
- DDropping seeds from different heights

More questions

9.Seeds with hooks or spines are most likely to be dispersed by:
Hard
- AWind
- BWater
- CAnimals
- DGravity
10.Which of the following best explains why seed dispersal reduces competition?
Hard
- ASeeds are spread out over a larger area
- BSeeds are eaten by animals
- CSeeds are buried underground
- DSeeds germinate faster
11.Gravity dispersal is most effective when:
Hard
- AThe plant is on a slope
- BThe seeds are very light
- CThe seeds have hooks
- DThe fruit floats
12.Which of the following is NOT a method of seed dispersal?
Medium
- AWind
- BWater
- CPhotosynthesis
- DExplosive
13.A student drops a seed from a height of 1 m in front of a fan. The seed travels 2.5 m horizontally before hitting the ground. If the fan speed is increased, what would be the most likely effect on the distance travelled?
Medium
- AIt would increase because stronger wind pushes the seed further.
- BIt would decrease because stronger wind pushes the seed down.
- CIt would stay the same because height is constant.
- DIt would increase because the seed falls more slowly.
14.In an experiment to compare wind dispersal of three seed types (A, B, C), a student drops each seed from the same height in front of a fan and measures the distance travelled. The results are: A: 1.2 m, B: 0.8 m, C: 2.5 m. Which seed is most likely to have a wing-like structure?
Hard
- ASeed C, because it travelled the furthest.
- BSeed A, because it travelled a medium distance.
- CSeed B, because it travelled the shortest distance.
- DSeed A, because it has the largest mass.
15.A student counts the number of seedlings growing at different distances from a parent plant. The results are shown in the table: Distance (m) | Number of seedlings 0-1 | 2 1-2 | 5 2-3 | 12 3-4 | 8 4-5 | 3 What conclusion can be drawn about seed dispersal?
Medium
- AMost seeds are dispersed between 2 and 3 metres from the parent.
- BMost seeds fall directly under the parent plant.
- CSeed dispersal is uniform in all directions.
- DNo seeds are dispersed beyond 5 metres.
16.Which of the following is an example of a seed dispersed by explosive mechanism?
Easy
- APea pod
- BCoconut
- CDandelion
- DBurr
17.A student wants to test whether seeds with hooks travel further on animal fur than smooth seeds. Which of the following is the independent variable?
Medium
- AThe type of seed (hooked or smooth)
- BThe distance the seeds travel
- CThe type of animal fur
- DThe number of seeds used
18.In an investigation, a student places a seed in a stream of water and measures the time it takes to travel 1 metre. The seed has a waterproof covering. Which of the following would most likely increase the time taken to travel 1 m?
Hard
- AIncreasing the water flow speed
- BUsing a seed with a less waterproof covering
- CDecreasing the water flow speed
- DUsing a heavier seed
19.What is the main advantage of seed dispersal for a plant species?
Easy
- AReduces competition for resources
- BIncreases the size of the seeds
- CMakes seeds germinate faster
- DProtects seeds from being eaten
20.A graph shows the number of seeds germinating at different distances from a parent tree. The highest number germinates at 10 m, with numbers decreasing at greater distances. Which dispersal method is most likely responsible?
Hard
- AExplosive dispersal
- BWind dispersal
- CAnimal dispersal
- DGravity dispersal
21.Which adaptation would be most useful for a seed that is dispersed by water?
Medium
- AWaterproof covering
- BFeathery bristles
- CHooks and spines
- DWings
22.Which method of seed dispersal relies on seeds being eaten by animals and later excreted?
Easy
- AAnimal dispersal
- BWind dispersal
- CExplosive dispersal
- DWater dispersal
23.A student measures the distance travelled by five seeds of the same type dropped from the same height in front of a fan. The distances are: 1.5 m, 1.7 m, 1.6 m, 1.5 m, 1.7 m. What is the mean distance?
Medium
- A1.6 m
- B1.5 m
- C1.7 m
- D1.65 m
24.Which of the following is a reason why seed dispersal is important?
Easy
- ATo reduce competition for resources
- BTo keep seeds close to the parent plant
- CTo ensure all seeds germinate at the same time
- DTo increase the size of the seeds
25.Coconuts are dispersed by water. Which adaptation helps them to float?
Medium
- AFeathery bristles
- BWaterproof covering
- CHooks and spines
- DWings
26.Which of the following seeds is most likely to be dispersed by explosive mechanism?
Medium
- ADandelion
- BCoconut
- CPea
- DMaple
27.A student drops a seed from a height of 1 m in front of a fan set at medium speed. The seed travels 2.0 m horizontally. If the fan speed is increased to high, what would you expect to happen to the distance travelled?
Hard
- AIt would decrease
- BIt would stay the same
- CIt would increase
- DIt would become zero
28.In an experiment to compare wind dispersal of three seed types (A, B, C), a student drops each seed from the same height in front of a fan and measures the distance travelled. Which variable should be kept constant?
Medium
- AType of seed
- BDistance travelled
- CFan speed
- DNumber of seeds dropped
29.A student investigates wind dispersal using a fan. They drop a seed and measure the distance it travels. They repeat the test five times with the same seed type. Which of the following would improve the reliability of the results?
Hard
- AUsing different fan speeds each time
- BDropping the seed from different heights
- CCalculating the mean distance from the five trials
- DUsing a different seed type for each trial
30.A student places a seed in a stream of water and measures the time it takes to travel 1 metre. The seed has a waterproof covering. Which of the following is a conclusion that can be drawn from this observation?
Hard
- AThe seed is dispersed by wind
- BThe seed is adapted for water dispersal
- CThe seed is dispersed by animals
- DThe seed is dispersed by explosion
31.A graph shows the number of seeds germinating at different distances from a parent tree. The highest number germinates at 10 m, with numbers decreasing at greater distances. What does this suggest about seed dispersal?
Hard
- AMost seeds fall directly under the tree
- BSeeds are dispersed away from the parent
- CSeeds are not dispersed at all
- DSeeds germinate best in shade
32.Which of the following is an example of a seed dispersed by gravity?
Easy
- ADandelion
- BCoconut
- CApple falling from a tree
- DBurr attached to fur
33.Which of the following is an example of a seed dispersed by wind?
Easy
- ACoconut
- BDandelion
- CBurr
- DPea pod
34.Which of the following is a method of seed dispersal?
Easy
- APhotosynthesis
- BGermination
- CExplosive dispersal
- DPollination
35.True or false: Coconuts are an example of seeds dispersed by wind.
Easy
- ATrue
- BFalse
- CNeither true nor false
- DBoth true and false
36.Which of the following adaptations helps a seed to be dispersed by wind?
Easy
- AWaterproof covering
- BHooks or spines
- CFeathery bristles
- DFleshy fruit
37.A student investigates the effect of seed mass on wind dispersal distance. They drop seeds of three different masses from the same height in front of a fan at a fixed speed. The results are shown in the table: Seed mass (g) | Distance travelled (m) 0.2 | 3.5 0.5 | 2.1 0.8 | 1.3 Which conclusion is best supported by the data?
Medium
- ASeeds with lower mass travel further in the wind.
- BSeed mass does not affect wind dispersal distance.
- CHeavier seeds are better adapted for wind dispersal.
- DThe fan speed was not kept constant.
38.A student drops a seed from a height of 1.5 m in front of a fan. The seed takes 2 seconds to hit the ground and travels 3.0 m horizontally. What is the average horizontal speed of the seed?
Medium
- A1.5 m/s
- B2.0 m/s
- C3.0 m/s
- D0.75 m/s
39.A student counts the number of seedlings at different distances from a parent tree. The results are: Distance (m) | Number of seedlings 0-5 | 2 5-10 | 15 10-15 | 25 15-20 | 8 Which statement is correct?
Hard
- AMost seeds germinate far from the parent tree, reducing competition.
- BMost seeds fall directly under the tree.
- CSeed dispersal is not effective for this tree.
- DThe tree produces very few seeds.
40.Which of the following is a reason why seed dispersal is important for plants?
Easy
- AIt reduces competition for resources like water and light.
- BIt helps seeds to germinate faster.
- CIt increases the size of the seeds.
- DIt prevents seeds from being eaten by animals.

Revision notes

## Seed Dispersal Seeds need to be dispersed away from the parent plant to: - Spread to new areas - Promote genetic diversity - Reduce competition for resources (water, light) ### Mechanisms - **Wind dispersal**: Light seeds with structures like feathery bristles (dandelion) or wings (maple). - **Water dispersal**: Waterproof coverings allow floating; e.g., coconuts travel oceans. - **Animal dispersal**: Hooks/spines attach to fur/feathers (burrs); seeds eaten and excreted elsewhere. - **Explosive dispersal**: Pods dry and burst, flinging seeds (pea pods). - **Gravity dispersal**: Fruit falls and rolls away, especially on slopes. ### Experiment: Wind dispersal effectiveness 1. Use a fan/hairdryer to create steady breeze. 2. Drop seed from a marked point. 3. Measure distance traveled. 4. Repeat with different seeds and compare. ### Key Points - Coconuts are water-dispersed, not wind. - Animal fur can carry seeds. - Many plants in one location compete for resources.

Seed dispersal: The movement of seeds away from the parent plant to reduce competition and promote spread.
Wind dispersal: Dispersal using light seeds with structures like wings or bristles to catch the wind.
Water dispersal: Dispersal using waterproof coverings that allow seeds to float, e.g., coconuts.
Animal dispersal: Dispersal via hooks/spines attaching to animals or seeds being eaten and excreted.
Explosive dispersal: Dispersal when seed pods dry and burst open, flinging seeds.
Gravity dispersal: Dispersal when fruit falls and rolls away due to gravity.

Flashcards

What is seed dispersal?

Seed dispersal is the movement of seeds away from the parent plant to new locations.

Why is seed dispersal important?

It helps plants spread to new areas, promotes genetic diversity, and reduces competition for resources like water and light.

Name three benefits of seed dispersal.

Spreading to new areas, promoting genetic diversity, and reducing competition for resources.

What are the five seed dispersal mechanisms?

Wind, water, animal, explosive, and gravity dispersal.

How are dandelion seeds adapted for wind dispersal?

They have feathery bristles that help them catch the wind.

How are maple seeds adapted for wind dispersal?

They have wings that allow them to be carried by the wind.

Give an example of a seed dispersed by water.

Coconuts, which have waterproof coverings that enable them to float.

How do seeds with hooks or spines get dispersed?

They attach to the fur or feathers of animals and are carried to new locations.

How can animals disperse seeds through ingestion?

Seeds are eaten by animals and later excreted in different areas.

What is explosive dispersal?

Seed pods dry out and burst open, flinging seeds in all directions.

Give an example of a plant that uses explosive dispersal.

Pea pods.

What is gravity dispersal?

Fruit falls from the plant and relies on gravity to roll away, especially on a slope.

True or false: Coconuts are dispersed by wind.

False. Coconuts are dispersed by water.

True or false: Animal fur can carry seeds to new locations.

True.

True or false: If many plants grow in the same location, they compete for resources.

True.

Describe an experiment to test wind dispersal effectiveness.

In a clear, open area, use a fan or hairdryer to create a steady breeze. Drop a seed from a marked starting point, let the wind carry it, and measure the distance traveled. Repeat with different seeds and compare.

What adaptation do water-dispersed seeds have?

They often have waterproof coverings that enable them to float.

How do burrs disperse?

Burrs have hooks or spines that attach to animal fur or feathers.

Why might a seed dispersed by gravity travel further on a slope?

Gravity helps the seed roll away from the parent plant more easily on a slope.

What is the purpose of a seed's feathery bristles or wings?

To help the seed catch the wind and be carried away.

How does seed dispersal reduce competition?

By moving seeds away from the parent plant, they have access to their own resources without competing with the parent or siblings.

What is the role of the waterproof covering in coconut dispersal?

It allows the coconut to float and travel long distances across water.

Name two types of animal dispersal.

Seeds attaching to fur/feathers (e.g., burrs) and seeds being eaten and excreted.

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