Zadanie 8, Paper 2, specimen 2025, Biologia IB HL
Wzorowane na: Biology HL Paper 2, Specimen 2025, pytanie 8. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
Specific molecular interactions occur in several biological systems.
(a) Explain how a vaccine can produce specific immunity against a viral infection.
(b) Outline how membrane proteins control movement of particular ions at different stages of a nerve impulse.
(c) Describe barriers that prevent hybridization between species.
One additional mark is available for clear, concise construction of the complete response.
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Odpowiedź z klucza
(a) Maximum 7:
Immunity elicited by vaccination targets particular pathogens or antigens. ✔
A vaccine presents or leads to production of pathogen-associated antigens. ✔
Some vaccines use an attenuated virus or a harmless related viral preparation. ✔
Vaccination elicits a primary immune response (without the usual disease). ✔
Antigen-specific lymphocytes generate memory cells (following activation). ✔
On later exposure, memory responses lead to more rapid antibody production. ✔
Memory cells can provide long-lasting protection. ✔
(b) Maximum 4:
Sodium channels open (during depolarization). ✔
Sodium enters the axon through those channels. ✔
Potassium channels open (during repolarization). ✔
Potassium leaves the axon. ✔
The sodium–potassium pump maintains and restores ion gradients supporting the resting state. ✔
It exports three sodium ions while importing two potassium ions (per ATP cycle). ✔
(c) Maximum 4:
Species can have distinct courtship displays. ✔
Failure to perform the expected courtship sequence can lead to rejection. ✔
Gamete recognition can be species-specific. ✔
Interactions of the acrosome with egg coverings can be incompatible across species. ✔
A sperm from another species may attach but fail to fuse with the egg membrane. ✔
Hybrids may be sterile. ✔
Differences in chromosome number can cause hybrid sterility (by interfering with meiotic pairing). ✔
Construction: 1 mark for clear, concise communication across the response.
Schemat punktowania
Award any N listed points within each part, where N is its cap. Part caps: 7, 4, 4. Maximum 15 content marks plus 1 independent construction mark, total 16. In (b), rapid repolarization is due mainly to potassium conductance; do not require the incorrect claim that pumping alone causes it.