BY2 Unofficial Markscheme

1)A: Capillaries
B: Epithelial Cells
C: Lacteal (3)

Extensive capillary network - products carried away and concentration gradient maintained

Projections. Microvilli and villi increase surface area for diffusion. (4) No clue on what they wanted...

Mucus (1)
Lubricated food for passage
Protects lining against digestive enzymes/acidic chyme (2)

Antagonistic pair of muscles; circular and longtitudinal, smooth as it isn't under conscious control
Co ordinate peristalis, with nervous coordination from sub mucosa (3)

NH2 removed, converted to urea and excreted. Converted to carbs. (2)

(15)

2) Transpiration is loss of water vapour through stomatal pores(2)

- causes tension so water pulled up for areas which need it (1)

- No leakage to displace air bubble further. Affects results (2)

- measure distance travelled in a specified time. Divide distance by time (2)

- xerophytes (1)

- sunken stomata, increases diffusion path. Creates humid layer in air chamber. Concentration gradient decreased. Less diffusion (3)

- thick cuticle to avoid excessive water loss
- hairs to trap air and decrease conc gradient
- rolled leaves to reduce surface area from which transpiration can occur (2)

(13)

3) adaptive radiation (1)

Population introduced into new area
Many vacant niches
No intraspecific competition
Organisms adapt to certain niche and pass off these alleles to offspring
Natural selection occurs so fittest survive
Speciation, can no longer interbreed to produce fertile offspring so new species (4)

Human and gorilla most closely related
Greater number of common amino acids
High number of common amino acids between all three so same class
Horse and human most distant as small number of common amino acids (3)

Protein Analysis (or DNA hybridization?) (1)

Can detect similarity in DNA, how closely related. Remove error if features are analogous. (1)

(10)

4) gill filament is a specialised internal respiratory surface as opposed to relying on diffusion across body (list features it has) (2)

Water in:
Mouth opens
Buccal cavity floor lowers
Operculum closes
Vol Inc
Pressure decrease
Water moves in

And reverse argument for water out (4)

Counter current flow: water moves in opposite direction to blood
O2 conc in water always higher
Diffusion occurs across entire length of lamellae, 80% efficient (3)

If diameter too big, diffusion path is too big. Which is a problem because muscles need O2 to meet metabolic demands. (2)

Less fluid during flight through abdominal ventilation, more air, decreased pressure, more O2 in for muscles (2)

OR shorter diffusion path for O2 maybe

(13)

5)
Parenchyma
Phloem Tissue (2)

- No organelles to obstruct movement
- cytoplasm to move through (4) (I wrote cytoplasmic filaments and pores to move through)

- mass flow is passive, mitochondria suggests active. Doesn't agree... Also affected by cyanide. Uses carrier proteins (3)

(9)

6) essay (10)

Unsure what the Marks are for that.

Open to corrections.

Phloem tissue and phloem fibres the same thing?

The question involving rate and transpiration...was saying divide by two necessary? I'm sure only the measurements were needed

Hey thanks so much for this I recently liked your post so can't give rep but,

for sunken stomata can you write less sun hits chloroplast less energy etc for active uptake of ions? I didn't really revise xerophytes and that point made a lot of sense to me

*so stomata opens less and less water is lost

Not too sure about the pressure argument for the tracheole fluid question.

Gel electrophoresis is what I put for the protein analysis one.

Other than that it seems like we put similar things.

i only wrote fibres and parenchyma do i get marks for that?

Where you put protein analysis, could you have put DNA fingerprinting instead? :/

Logic is right though?

Ah, don't know what'll be accepted.

Good to know.


Think so


Don't know sorry

Logic is right though?

Anyone want to suggest grade boundaries? I'm thinking pretty low as it was by a country mile the hardest by2 paper I've ever seen. I've been getting around 60ish for most past papers but that was something else. I doubt I managed to even get 50 marks

I don't think it will be as bad as BY1 but I'm expecting it to be around 57 for 120 ums

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1)A: Capillaries
B: Epithelial Cells
C: Lacteal (3)

Extensive capillary network - products carried away and concentration gradient maintained

Projections. Microvilli and villi increase surface area for diffusion. (4) No clue on what they wanted...

Mucus (1)
Lubricated food for passage
Protects lining against digestive enzymes/acidic chyme (2)

Antagonistic pair of muscles; circular and longtitudinal, smooth as it isn't under conscious control
Co ordinate peristalis, with nervous coordination from sub mucosa (3)

NH2 removed, converted to urea and excreted. Converted to carbs. (2)

(15)

2) Transpiration is loss of water vapour through stomatal pores(2)

- causes tension so water pulled up for areas which need it (1)

- No leakage to displace air bubble further. Affects results (2)

- measure distance travelled in a specified time. Divide distance by time (2)

- xerophytes (1)

- sunken stomata, increases diffusion path. Creates humid layer in air chamber. Concentration gradient decreased. Less diffusion (3)

- thick cuticle to avoid excessive water loss
- hairs to trap air and decrease conc gradient
- rolled leaves to reduce surface area from which transpiration can occur (2)

(13)

3) adaptive radiation (1)

Population introduced into new area
Many vacant niches
No intraspecific competition
Organisms adapt to certain niche and pass off these alleles to offspring
Natural selection occurs so fittest survive
Speciation, can no longer interbreed to produce fertile offspring so new species (4)

Human and gorilla most closely related
Greater number of common amino acids
High number of common amino acids between all three so same class
Horse and human most distant as small number of common amino acids (3)

Protein Analysis (or DNA hybridization?) (1)

Can detect similarity in DNA, how closely related. Remove error if features are analogous. (1)

(10)

4) gill filament is a specialised internal respiratory surface as opposed to relying on diffusion across body (list features it has) (2)

Water in:
Mouth opens
Buccal cavity floor lowers
Operculum closes
Vol Inc
Pressure decrease
Water moves in

And reverse argument for water out (4)

Counter current flow: water moves in opposite direction to blood
O2 conc in water always higher
Diffusion occurs across entire length of lamellae, 80% efficient (3)

If diameter too big, diffusion path is too big. Which is a problem because muscles need O2 to meet metabolic demands. (2)

Less fluid during flight through abdominal ventilation, more air, decreased pressure, more O2 in for muscles (2)

OR shorter diffusion path for O2 maybe

(13)

5)
Parenchyma
Phloem Fibres(2)

- No organelles to obstruct movement
- cytoplasm to move through (4) (I wrote cytoplasmic filaments and pores to move through)

- mass flow is passive, mitochondria suggests active. Doesn't agree... Also affected by cyanide. Uses carrier proteins (3)

(9)

6) essay (10)

Unsure what the Marks are for that.

Open to corrections.

Bearing in mind that you're a student, just like myself, you have no copy of the paper to hand.
What is to say that your answers are correct considering its from memory?
I'd suggest waiting until a teacher has looked at the paper for a more official mark scheme that is more likely to be correct.
Seems a rather stuck up thing to do posting what you consider to be the model answers.