Phototropism (Biology) · LearnViz STEM

Lesson notes

Overview

Auxin moves to the shaded side of a shoot and makes it grow toward the light. This topic is rated intermediate and is number 44 of 110 in Biology. Builds on the basics with relationships, methods and trade-offs.

What you are seeing

The panel above shows the steps of a process, laid out in order. Click a step to see what happens next. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.

In depth

Phototropism is the growth of a plant towards light. The hormone auxin, made at the shoot tip, moves to the shaded side, where it makes the cells elongate more, so the shoot bends towards the light. Charles Darwin and his son demonstrated that the tip senses the light, and later experiments identified auxin. The response lets leaves capture more light for photosynthesis. Roots show the opposite behaviour, growing away from light.

Reading the relationship

The expression "auxin gradient" is a compact summary of the idea. It uses the symbols a, u, x, i, n, g; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.

A guided exploration

1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.

Try this

Predict the outcome first, then test extreme slider values to find where the pattern changes or breaks.

Common pitfalls

Biological processes are rarely all-or-nothing. Look for the feedback, the timing and the exceptions, rather than learning a single fixed sequence by heart.

How it connects

It builds on “Plant Transpiration”, the topic before it in Biology. Once you are comfortable, continue with “Pollination and Seed Formation”.

Why it matters

Biology shows how living things are built and how they work, grow, inherit traits and adapt.

Where you might use it

Revising “Phototropism” before a class, exam or certification
Understanding inherited conditions, medicines and how the body responds to disease
Working in farming, conservation and food production, where populations and genes matter
Following news about vaccines, genetic testing and climate effects on wildlife

Frequently asked questions

What is Phototropism?

Auxin moves to the shaded side of a shoot and makes it grow toward the light. It is an intermediate topic in Biology.

How do I use the Phototropism simulation?

The panel at the top shows the steps of a process, laid out in order. Click a step to see what happens next. Move the sliders one at a time, then press Space to pause the animation and look closer.

What does the formula mean?

The expression auxin gradient packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.

Who is this topic for?

Builds on the basics with relationships, methods and trade-offs. If the quiz feels hard, reread the lesson notes and try the previous topic first.

What should I learn before this?

Start with “Plant Transpiration”, the previous topic in Biology. Each topic in a subject builds on the ones before it.

How do I track my progress?

Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.