bio paper 2

Suggest and explain how the interaction between the muscles labelled could cause the pupil to constrict / narrow.

• one muscle contracts, the other relaxes

• antagonistic pairs

The eagle’s fovea has many cones. Explain how this enables an eagle to see its prey in detail.

• more cones = high visual acuity

• 1 cone connects to 1 neurone

• sends separate sets of impulses to the brain

The owl’s retina has many rod cells. Explain how this enables an owl to see at night.

• high visual sensitivity

• many rods to 1 neurone

• enough neurotransmitter to exceed threshold

• spatial summation of rod cells

Suggest how AR could stimulate gene expression.

• is a transcription factor

• binds to promoter

• stimulates RNA polymerase

State three features of the calorimeter that allow a valid measurement of heat energy released.

• stirrer to distribute heat energy

• insulation prevents heat loss

• water has high SHC

In natural ecosystems, most of the light falling on producers is not used in photosynthesis. Explain why.

• light reflected

• wrong wavelength

• missed chlorophyll

• other limiting factor: co2 or temperature

Describe how to produce a calibration curve.

• specified volumes

• water + pigment dilution series

• absorbance recorded on colorimeter

• absorbance vs dilution graph

Describe transmission at the cholinergic synapse.

• presynaptic depolarises

• calcium channels open

• enters knob

• synaptic vessels fuse with presynaptic membrane

• release Ach, diffuses, attach to postsynaptic receptors

• Na+ caused to enter, depolarisation