Forces and Responses How do living things respond

Forces and Responses How do living things respond to forces?

• TEKS 7. 7 C Demonstrate and illustrate forces that affect motion in everyday life, such as emergence of seedlings, turgor pressure, and geotropism • TEKS 7. 13 A Investigate how organisms respond to external stimuli found in the environment such as phototropism and fight or flight

Forces • A Force is a push or a pull on an object in a specific direction

Forces can be used by living organisms to perform basic functions.

Forces are used in many ways by humans.

For example, interactions between the muscular & skeletal systems allow the body to apply forces needed for movement.

Humans use the force of their heart muscles contracting to keep blood flowing through their bodies.

The roots of plants use force to push through the soil.

• Plants use force in other ways by changing their growth in response to their environment.

The way a plant responds to stimuli is called a tropism.

Geotropism • Geotropism occurs when a plant grows or bends in response to gravity.

A plant’s shoots will grow up and its roots will grow down.

Phototropism • The way a plant grows or bends in response to light is called phototropism.

The plant will grow toward light, even if it must grow sideways.

When a plant takes in water, the vacuole fills up and exerts pressure on the plant’s cell wall.

This pressure is called turgor pressure.

Turgor pressure allows a plant to become rigid causing the plant to stand upright.