AQA A Level Biology Unit 6 - Organisms respond to changes in their internal and external environments Questions & Answers 100% Correct

What kind of receptors are changes in blood pH and pressure detected by? - ANSWERchemoreceptors and pressure receptors in the aorta or carotid artery Two types of photoreceptors in the eye? - ANSWERrods and cones What colour do rods detect and why? - ANSWERBlack and white ONLY - because they can't distinguish between wavelengths of light What kind of light intensity do rods detect and why? - ANSWER- Rods detect low light intensity - because many rods connect to one sensory neurone (RETINAL CONVERGENCE) how do rods create generator potential? - ANSWER- Rhodopsin (pigments of rod cells) are broken down by light energy - Enough energy from low light intensity to cause this breakdown - enough rhodopsin must be broken for threshold to be met in bipolar cell Why can threshold still be met in low light intensity in rods? - ANSWERMany rod cells are connected to a singular bipolar cell (example of spatial summation) Do rods have low or high visual acuity and why? - ANSWER- Rods have low visual acuity - because RETINAL CONVERGENCE causes the brain to be unable to distinguish between the separate sources of light that stimulated it - therefore, two light sources cannot be seen as separate What are the 3 types of cone cells and what do they contain - ANSWER- Red, green, and blue - all contain different types of iodopsin pigment Where are most cones found in the eye? - ANSWERFovea In which light intensity can iodopsin be broken down? - ANSWERHigh light intensity so action potentials are only generated with enough light Do CONE cells have high or low visual acuity and why? - ANSWERCone cells have HIGH visual acuity - Each cone cell connects to a bipolar cell, allowing the brain to distinguish between two separate sources of light