Investigating Reaction Time

Ever wondered why you're slower to catch something when you're tired? Reaction time is the gap between seeing something happen and your body responding to it. Your eyes spot the stimulus, send a message through your sensory neurone to your brain, then your brain fires back through a motor neurone to make your muscles move.

The classic setup uses a metre stick that someone drops whilst you try to catch it. The distance it falls before you grab it shows how quick your reactions are. You could also use online reaction tests for more precise measurements.

Your reaction time changes based on loads of factors. Practice makes you faster, and so does proper concentration. But distractions, alcohol, certain medicines, or even just being knackered will slow you right down.

Quick Tip: In exam questions, they'll often ask about control variables (what you kept the same) and why repeating the experiment matters for getting reliable results.

Measuring Population Size

Imagine you're a wildlife researcher trying to work out how many different species live in a forest. Population means all the individuals of one species in a particular area, whilst distribution is how they're spread out across that space.

You've got two main techniques here. Random sampling uses quadrats (square frames) placed randomly across an area to get a general picture of what's living there. It's brilliant for understanding overall species distribution patterns.

Line transects work differently - you lay out a measuring tape in a straight line and take samples at regular intervals along it. This method's perfect when you want to see how something specific (like a lake or road) affects the wildlife nearby.

Remember: Quadrats are your square sampling frames that help you count organisms in a set area, making it easier to estimate total populations.

The tricky bit is making sure your sample represents the whole area fairly. You'll need to think about abiotic factors $non-living things like temperature$ and biotic factors (living influences like predators) that might affect where organisms choose to live.