A2 Biology OCR June 2015 Revision Thread

Rahhh did you get full ums?

This is the first im hearing of this

I thought they were two seperate things as well but we learned operant conditioning is where an animal can be trained to show a behaviour if it is offered a treat whereas classical conditioning is where an animal learns to associate two unrelated stimuli through repeated exposure together?

Is phototropism also an example of Taxis? I cant find an example of Taxis.

The ATP that is made in cyclic photophosphorylation is used in the calvin cycle to reduce and phosphorylate GP so it becomes Triose phosphate, in which carbohydrates and lipids are formed

Thank you! so what happens to the ATP thats made in cyclic photophosphorylation?

Woodlouse finding shade when subjected to intense light is taxis, surely?

It's used in the light independent stage to reduce gp to tp

your example of a woodlice is a kineses, as the movement is random an increases upon increased subjection to an unfavorable stimuli (the sun), and i think taxis is specific to animals and that tropisms are specific to plants, although there the same as one another? an example of a taxis is the movement of animals towards chemical signals, some worms display positive chemotaxis

Yeah but surely the otters associate the man coming to the otter area with the food being presented by the man? Hence making a large argument for it being classical conditioning. I've seen a similar example with a farming bringing food to sheep; sheep run over to trough. Apparently operant conditioning too but to me it's clearly classical?


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I was thinking the same. Hmm I think tropism is definitely for plants only but I dont think taxis is exclusively for animals.Im just going to go with the animal taxis just to be on the safe side.

Is phototropism also an example of Taxis? I cant find an example of Taxis.

Yeah I'd have called that example classical conditioning too. I only got the question right because it was the last one left in a multiple choice :')

I think I've worked it out, but not 100% sure!

So operant conditioning is when you have an animal initially performing a behaviour and then a reward/punishment, so the animal associates this particular behaviour with the reward/punishment.

Classical conditioning is when you start off with two different stimuli which then causes a conditioned response. I think the two stimuli must be quite distinct from one another for classical conditioning to be the case.

Basically operant: behaviour then consequence.
And classical is two different distinct stimuli.

So the emphasis on the initial behaviour by the otters in the given question indicates operant conditioning is the case!

Still an argument for both to be the case really but i think this is the logic behind it!😊


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Phototropism is for plants only and Taxis is for animal behaviour. The example my book gives for taxis is a shark is attracted to a source of blood in the water and so swims towards the source

Yeah I would use the word taxis in terms of animal innate responses and tropism in terms of plants. After looking this up on wikipedia, they distinguish between taxis and tropism in this way:

A taxis (plural taxes[1][2][3] /ˈtæksiːz/, from the Ancient Greek τάξις, meaning "arrangement"[4]) is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioral responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that the organism has motility and demonstrates guided movement towards or away from the stimulus source.[5][6] It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.

However saying taxis is a 'guided movement towards/away' doesn't really help, surely tropism a can be classified as guided movement? A turning response is still movement surely? Or is this not the case.

On the tropism page, it says the word is usually used when talking about plants but is not necessarily restricted to plants, just organisms that do not motility.


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Thank you! so when does cyclic photophosphorylation happen? Does there have to be certain conditions for it to hapen? or does it happen at the same time as non cyclic photophosphorylation? I thought that it would happen when theres no co2 but then surely the calvin cycle will stop?