HKDSE Biology 2019 Paper 2A & C

Paper 2A – 1(a)(i)(1)(2)

Event Change

Paper 2A – 1(a)(i)(1)(2)

• (1) Yellow body degenerates

Decrease in estrogen production (hence level decrease)

• (2) Follicles developing (not accept only follicles)

Increase in estrogen secretion (hence level increase)

Paper 2A – 1(a)(ii)(1)(2)

Paper 2A – 1(a)(ii)(1)

• (1) Graph 1 : FSH increase as estrogen decrease during later

period of first cycle (must refer to the corresponding

period of injection)

Graph 2 : FSH remains low (not accept decrease) during

period of injection

Graph 2 : FSH level rises again after estrogen treatment

stopped

(must relate to estrogen injection, not just description of

FSH level change)

Estrogen inhibits (negative feedback on) FSH

(release/production)

• (2) No follicle development

No ovulation / No mature eggs for ovulation

Paper 2A – 1(a)(ii)

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Paper 2A – 1(a)(ii)

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Paper 2A – 1(b)(i)

Paper 2A – 1(b)(i)

• Hydrated group : cardiac output remained more or less the

same / slightly increase

Dehydrated group : dropped

• Cardiac output oxygen/nutrients supply to skeletal muscles

• Respiration, release energy

• For skeletal muscle contractions

• Hydrated group : constant energy supply maintain cycling

speed

Dehydrated group : decreased energy supply slowed speed

(Must mention both groups, can be separated paragraph)

Paper 2A – 1(b)(i)

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Paper 2A – 1(b)(i)

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Paper 2A – 1(b)(ii)(1)(2)

• (1) Stroke volume

• (2) (Net) water loss by sweating/breathing

Drop in (total) blood volume

P P

Paper 2A – 1(b)(iii)

• SV : Dehydrated group < Hydrated group

• HR increase to compensate for decrease in SV / HR increase to

keep a high Cardiac Output for exercise

Paper 2C – 3(a)(i)

• A : 2 hrs

• B : 20 hrs

(Calculation step not necessary)

(Correct unit is required)

Paper 2C – 3(a)(ii)

• Pathogen C

• Shortest doubling time (comparison among 3 pathogens)

• in pH 4 at 37oC

• which are conditions in the stomach

37oC

Shortest doubling time

Paper 2C – 3(a)(ii)

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Paper 2C – 3(a)(iii)

• Food poisoning

• B has shorter doubling time growth under refrigeration

• Toxin accumulation in food

• Doubling time at 37oC > 4oC

• B is heat-sensitive / probably killed by cooking illness not cause

by bacteria but by toxin produced

Paper 2C – 3(a)(iii)

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Paper 2C – 3(b)(i)

• X : hyphae

• Y : spores / sporangium / spore-forming bodies

Paper 2C – 3(b)(ii)

• Fungus secret enzymes

• Digest layer of dead cells

• Digested products absorbed for growth

• X penetrate skin / grow deeper reach sensory nerve endings

hyphae

mode of nutrition of fungi,

not physical/mechanical

features of X

Paper 2C – 3(b)(ii)

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Paper 2C – 3(b)(iii)

• (1) Any one : warm / hot / wet / humid / with skin debris

• (2) X (hyphae) had been lysed/destroyed no itchy feeling

Some spores (Y) left in the skin

Spores are resistant to cream / not killed by cream

Spores germinated and re-infected the skin

(Must address different effects of cream on hyphae and spores)

(Not accept explanation by cream potency / natural selection)

Only first answer

Paper 2C – 3(b)(iii)

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