Seed Dispersal – physics and biology at Key Stage 3

This collection of resources for 11-14 students uses the topic of plants to address important scientific ideas in biology and physics.

While investigating how plants have evolved to disperse their seeds in different environments, the students can cover topics about forces, pressure in fluids, and forces and motion.

The resources involve a mixture of independent investigations, engaging and hands-on practicals, and activities to identify misconceptions and strengthen understanding. Teachers can opt to include as many or as few of the resources from the collection as they like.

Seed dispersal is an important aspect of plant reproduction. If not suitably dispersed, seeds will germinate very close to their parent plant. This means that the seedlings must compete with one another and, of course, the parent plant for space, light, water and nutrients.

Studying wind dispersal can bring together important scientific ideas in biology and physics.

These include forces, motion and evolution.

Evolution of seed dispersal

Plants have evolved clever ways of having their seed-containing fruits carried away, sometimes over long distances. They produce fruit that, for example

• are attractive to animals who eat them, carry them away and release the seeds in their droppings
• have hooks or barbs that can attach to the fur or wool of an animal
• explode and burst open when ripe, propelling the seeds away from the plant
• have structures that allow them to be carried by the wind away from the plan.

This group of sheets is about wind dispersal:

• Falling from trees
• Coconuts
• Parachuting fruits
• Gliding fruits
• Spinning fruits
• One-winged fruits
• Two-winged fruits

Key scientific ideas

Studying wind dispersal can bring together important scientific ideas in biology and physics. These are summarised by statements in the National curriculum for science in England at key stage 3:

In biology pupils should be taught about Reproduction

• reproduction in plants, including flower structure, wind and insect pollination, fertilisation, seed and fruit formation and dispersal, including quantitative investigation of some dispersal mechanisms

In physics pupils should be taught about Forces, Pressure in fluids and Forces and motion

• forces as pushes or pulls, arising from the interaction between two objects
• using force arrows in diagrams, adding forces in one dimension, balanced and unbalanced forces
• moment as the turning effect of a force
• forces: with pushing things out of the way; resistance to motion of air and water
• non-contact forces: gravity forces acting at a distance on Earth and in space
• atmospheric pressure, decreases with increase of height as weight of air above decreases with height
• pressure in liquids, increasing with depth; upthrust effects, floating and sinking
• pressure measured by ratio of force over area – acting normal to any surface
• forces being needed to cause objects to stop or start moving, or to change their speed or direction of motion (qualitative only)
• change depending on direction of force and its size

Tackling common misconceptions

The activities described in the sheets also provide an opportunity to tackle some of the common misconceptions, including

• Gravity = ‘downness’;
• When an object is stationary, no forces are acting on it;
• Heavy objects fall faster than light objects;
• Something stops moving because the force has run out;
• Air doesn’t weigh anything;
• Particles are the same as visible grains as in rocks, for example;
• Microbes, cells and particles are much the same.

This resource links to and follows from the KS2 resource: Fruits, seeds and their dispersal