Dispersal of Seeeds

Dispersal of Seeds

Middle School

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Learning Objectives

• Define seed dispersal and learn why it is important for plant survival.

• Identify the four main ways seeds are spread: by wind, water, animals, and explosions.

• Describe the special features of seeds that help them travel in different ways.

• Explain how fruits help to protect seeds and also help them to spread.

Key Vocabulary

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Seed

A seed is a plant ovule with an embryo, storing food for the young plant's growth.

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Seed Dispersal

This is the scattering of seeds away from the parent plant to reduce competition for resources.

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Dormant

A dormant seed is in a resting state, waiting for the right conditions to start growing.

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Wind Dispersal

Light seeds with wings or parachutes are carried over long distances by the blowing wind.

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Water Dispersal

Waterproof seeds that can float are transported by currents to new areas for future growth.

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Animal Dispersal

Animals help spread seeds by eating fruits or when seeds attach to their fur or feathers.

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What is a Seed and Why Disperse?

What is a Seed?

• A seed is a part of a plant that holds a tiny, undeveloped plant called an embryo.

• It can stay dormant, or resting, to survive harsh conditions like cold winters or lack of water.

• The seed also stores food that the young plant will use for energy when it starts to grow.

Why Disperse Seeds?

• Seed dispersal is the scattering of seeds, which is necessary for a plant species to be successful.

• It prevents overcrowding so seedlings don’t have to compete for resources like water and sunlight.

• A fruit's main jobs are to protect the seeds inside it and help spread them to new areas.

Multiple Choice

What are the primary reasons for seed dispersal?

• To make sure all seeds land directly under the parent plant.

• To ensure seeds have enough food and can stay dormant.

• To protect the seeds from harsh weather conditions.

• To avoid overcrowding and reduce competition for light and water.

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Dispersal by Wind and Water

Dispersal by Wind

• ​Seeds that use wind dispersal are very light in weight.

• ​​They often have special features like parachutes or wings to catch the wind.

• ​These features help them travel long distances away from the parent plant.

Dispersal by Water

• ​Many plants that grow near water use this method for seed dispersal.

• ​​The seeds are waterproof and have the ability to float on the water.

• ​Examples include coconuts, which have hollow coverings, and also mangrove seeds.

Multiple Choice

What is a key difference between seeds dispersed by wind and those dispersed by water?

• Wind-dispersed seeds explode, while water-dispersed seeds are eaten by animals.

• Wind-dispersed seeds are heavy, while water-dispersed seeds are light.

• Wind-dispersed seeds have wings or parachutes, while water-dispersed seeds are adapted to float.

• Wind-dispersed seeds are sweet, while water-dispersed seeds are spiky.

Dispersal by Animals

• Animals eat colorful fruits, and seeds exit in their droppings.

• Some seeds have hooks that stick to an animal's fur or feathers.

• Squirrels may bury seeds like acorns and forget where they are.

Multiple Choice

How do burrs typically disperse their seeds?

• By being light enough to be carried by the wind.

• By exploding and shooting the seeds out.

• By having hooks or spines that attach to an animal's fur.

• By being eaten by animals and passing through their digestive tract.

Explosion and Other Methods of Seed Dispersal

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Explosion or Bursting

• ​Some plants like peas have seedpods that dry out when ripe.

• ​​The dry pods split open suddenly, shooting out all the seeds.

• ​This method is also known as mechanical dispersal.

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Gravity

• ​Some heavy and round fruits simply use gravity to spread seeds.

• ​​For example, horse chestnuts drop and roll away when ripe.

• ​This happens because of their round shape and heavy weight.

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Shaking

• ​Other plants, such as poppies, act like shakers to disperse seeds.

• ​​They have long stems with seed pods that have small holes.

• ​When the wind blows, it shakes the stem, scattering the seeds.

Multiple Choice

What is mechanical dispersal?

• When animals eat fruits and disperse the seeds in their droppings.

• When seeds are transported by water.

• When seeds are carried by wind.

• When seedpods dry out and burst, shooting the seeds away.

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Common Misconceptions

Misconception	Correction
All seeds are planted by people.	Most plants use wind, water, or animals to disperse their seeds.
A fruit's only purpose is to be food.	A fruit's main jobs are to protect and disperse its seeds.
Seeds need to be planted right away to grow.	Many seeds can stay dormant, waiting for the right conditions to grow.
It is best for seeds to grow next to the parent plant.	Seeds move away from the parent to avoid competition for resources.

Multiple Choice

Based on the adaptations of seeds, which method of dispersal is used by a seed with feathery bristles?

• Wind dispersal

• Explosion

• Water dispersal

• Animal dispersal

Multiple Choice

Explain the primary advantage a plant gains by having its seeds dispersed far away rather than dropping them nearby.

• It makes it easier for animals to find all the seeds in one place.

• It ensures the seeds stay in the same type of soil.

• It reduces competition between the new seedlings and the parent plant for resources.

• It allows the parent plant to have more sunlight.

Multiple Choice

A plant produces a bright, sweet-tasting berry. How does this adaptation help the plant effectively disperse its seeds to a new location?

• The berry attracts an animal to eat it, and the seeds are later deposited in the animal's droppings elsewhere.

• The bright color scares away animals that might eat the seeds.

• The sweetness of the berry makes it float better in water.

• The berry attaches to animal fur and drops off later.

Multiple Choice

Imagine a mangrove tree, which normally disperses its seeds by water, is now growing in an area far from any water source. What is the most likely outcome for this tree's ability to reproduce?

• The seeds will develop the ability to explode from the tree.

• The seeds will adapt to be dispersed by wind instead.

• Animals will start eating the seeds and dispersing them.

• The tree will not be able to disperse its seeds effectively, and new trees will be overcrowded near the parent.

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Summary

• Seed dispersal scatters seeds to new locations, preventing overcrowding and competition for resources.

• The main methods of seed dispersal are wind, water, animals, and explosion.

• Seeds and fruits have special adaptations that help them travel.

• Some seeds can stay dormant until conditions are right for them to grow.

Poll

On a scale of 1-4, how confident are you about the different methods of seed dispersal?

• 1

• 2

• 3

• 4