A2 Biology OCR June 2015 Revision Thread

Reply 3880

tewas

2

i don't know the sand dune example for succession, is that okay?

Reply 3881

buxtonarmy

6

Original post by wanna get laid

Alright fam, lemme clear the air for ya on this one

Basically, the animal learns to associate a pair of events, so that it produces a response to the first stimulus in anticipation for the second

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Teach me the whole course pls x

Reply 3882

Shanahey

8

Why can gene therapy be used to treat recessive conditions but not dominant conditions?

Reply 3883

peanutcracker20

2

what are advantages and disadvantages of animal cloning for a 4 mark question

Reply 3884

loperdoper

15

Original post by Shanahey

Why can gene therapy be used to treat recessive conditions but not dominant conditions?

Because you can only add genes in gene therapy, so you can't "overpower" dominant alleles, but you can with recessive.

Reply 3885

corey7695

11

what are there reasons for using micro-organisms in bio tech? my textbook said some but i remember the mark scheme not crediting them i think

Reply 3886

molly788

Original post by Shanahey

Can someone please explain pollarding and coppicing?
Thanks

They are both small-scale timber production techniques:

Coppicing: cutting the trunk of a decideous tree close to the ground. Several new shoots will grow from the cut surface, and these will mature into stems (with a narrow diameter.) These stems can be cut and used for fencing, firewood etc. After cutting, the shoots will grow again, and so a cycle continues.

Pollarding: the same thing expect the trunk is cut higher up, to stop Deer eating the emerging shoots

Reply 3887

tewas

2

Original post by Shanahey

Can someone please explain pollarding and coppicing?
Thanks

Coppicing is basically cutting the tree trunk close to the ground to encourage new shoot growth and pollarding is basically the same as coppicing but the trunk is cut a little higher so deer can't eat the new shoots ha!
there is rotational coppicing which is basically sectioning the woodland and only cutting one section per year or something since it depends on the type of tree/demand for timber etc. This maintains biodiversity. Standards are trees left for a long time before being cut down so large pieces of timber can be made

Reply 3888

loperdoper

15

Original post by domcandrews

What are the ratios we should know for genetics?

12:3:1/13:3 - dominant epistasis
9:3:4 - recessive epistasis
9:7 - complementary epistasis

Original post by tewas

i don't know the sand dune example for succession, is that okay?

You need to know at least one example for succession, so provided you know another one that's fine.

Reply 3889

HeyThereHarry

16

Original post by Shanahey

Why can gene therapy be used to treat recessive conditions but not dominant conditions?

So you can insert just one allele, the dominant one, to mask the effect of the recessive. No alleles need removing.

However, I think you can insert an allele so as to disrupt the sequence of a dominant allele, therefore being able to treat a dominant condition, but that may cause mutation/disease etc and won't work if its polygenic.

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Reply 3890

Shanahey

8

Original post by loperdoper

Because you can only add genes in gene therapy, so you can't "overpower" dominant alleles, but you can with recessive.

Thanks!

Original post by molly788

They are both small-scale timber production techniques:

Coppicing: cutting the trunk of a decideous tree close to the ground. Several new shoots will grow from the cut surface, and these will mature into stems (with a narrow diameter.) These stems can be cut and used for fencing, firewood etc. After cutting, the shoots will grow again, and so a cycle continues.

Pollarding: the same thing expect the trunk is cut higher up, to stop Deer eating the emerging shoots

Thank you!

Reply 3891

tewas

2

Original post by peanutcracker20

what are advantages and disadvantages of animal cloning for a 4 mark question

Adv: -animals with desirable characteristics can be produced eg high milk yield
- rare species on the verge on extinction can be preserved
- genetically engineered organisms can be produced quickly

Dis: - little genetic variation - more susceptible to environmental conditions/disease
- nobody knows long term health implications
- animal welfare issues hardly ever taken into account

Reply 3892

molly788

Original post by peanutcracker20

what are advantages and disadvantages of animal cloning for a 4 mark question

Advantages:
-high value animals can be cloned in large numbers
-rare animals can be cloned to preserve species
-genetically modified animals can be quickly reproduced

Disadvantages:
-can be produced without welfare in mind
-excessive genetic uniformity makes it unable to adapt to changes in environment (disease etc)
-still unclear whether cloned animals will remain healthy in long term

Reply 3893

HeyThereHarry

16

Original post by corey7695

what are there reasons for using micro-organisms in bio tech? my textbook said some but i remember the mark scheme not crediting them i think

Can grown rapidly at optimum temp
Optimum temp may be relatively low and therefore cheap
May grow on toxic or useless substances
Products fairly pure so few costly downstream processes needed
Genetically modified easily for specific products

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Reply 3894

bakedbeans247

20

Original post by ooxbridge

Predictions guys?

This is what i've heard people have been saying and what i think hasn't come up for a while:

galapagos,
something out of the topic about pcr/genome sequencing/insulin/rice etc,
something out of the pages 232, 236-237 (muscles topic),
brain
shedding leaves (pg 223)
how auxins stimulate shoot growth (pg 222)
meiosis
apoptosis
epistasis
something out of the topic animal behaviors (social behavior in primates i think)
Chi squared
Nitrogen cycle
Aseptic techniques/Asepsis - that table on the bottom of pg 163
Timber management

but anything could come up

even repeated topics

Reply 3895

wanna get laid

2

Is anyone actually bothering with the synoptic stuff

I really cba to have a quick look over AS units and f214 ---____---

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Reply 3896

HeyThereHarry

16

Original post by wanna get laid

Is anyone actually bothering with the synoptic stuff

I really cba to have a quick look over AS units and f214 ---____---

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I was just about to post this lol! Nope, I'm just going to use my natural instinct for synoptic qs..............(so help me god)

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Reply 3897

domcandrews

2

Original post by bakedbeans247

This is what i've heard people have been saying and what i think hasn't come up for a while:

galapagos,
something out of the topic about pcr/genome sequencing/insulin/rice etc,
something out of the pages 232, 236-237 (muscles topic),
brain
shedding leaves (pg 223)
how auxins stimulate shoot growth (pg 222)
meiosis
apoptosis
epistasis
something out of the topic animal behaviors (social behavior in primates i think)
Chi squared
Nitrogen cycle
Aseptic techniques/Asepsis - that table on the bottom of pg 163
Timber management

but anything could come up

even repeated topics

Looks quite accurate to me, apoptosis and meiosis QWC would be ideal, labelling/functions of brain looks likely too

Reply 3898

domcandrews

2

Original post by loperdoper

12:3:1/13:3 - dominant epistasis
9:3:4 - recessive epistasis
9:7 - complementary epistasis

You need to know at least one example for succession, so provided you know another one that's fine.