Zadanie 8, Paper 2, maj 2025, TZ3, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2025, TZ3, pytanie 8. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Zadanie
Polecenie
A flowering plant can reproduce sexually or form new individuals by vegetative growth.
(a) Explain why both meiosis and gamete fusion are needed in a sexual life cycle.
(b) Describe how interphase and mitosis preserve chromosome number during vegetative reproduction.
(c) Discuss reproductive barriers between species and how polyploidy can restore fertility in some hybrids.
One holistic mark is available for clear, concise communication across the response.
Korepetytor AI
Nie wiesz, jak ruszyć? Korepetytor zna to zadanie i poprowadzi Cię krok po kroku, bez gotowca.
3 rozmowy · bez karty · Zaloguj się
Sprawdź się
Odpowiedz i oceń, jak poszło. Klucz odsłoń dopiero, gdy masz swoją odpowiedź.
Jak poszło Ci z tym zadaniem?
Wybierz ocenę: zapamięta ją ta przeglądarka, a z darmowym kontem zobaczysz ją na każdym urządzeniu.
Pokaż rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(a) Meiosis halves chromosome number, producing haploid cells. ✔
Fusion of two haploid gametes restores the diploid chromosome number. ✔
Together these processes prevent progressive chromosome-number doubling across generations. ✔
Gamete fusion combines alleles from two parents. ✔
Meiosis reshuffles alleles through segregation, independent assortment and crossing over. ✔
The resulting genetic variation supplies material for natural selection and population resilience. ✔
(b) DNA is replicated before mitosis. ✔
Replication occurs in S phase, with DNA polymerases synthesizing new strands. ✔
Each replicated chromosome consists of sister chromatids. ✔
Cyclins and checkpoints coordinate cell-cycle progression. ✔
Chromatin condenses into visible chromosomes in prophase. ✔
Spindle microtubules attach to kinetochores, or chromosomes align at the metaphase equator. ✔
Microtubule depolymerization contributes to chromosome movement. ✔
Cohesin is cleaved so sister chromatids can separate. ✔
Sister chromatids move to opposite poles during anaphase. ✔
Nuclear envelopes re-form in telophase. ✔
Cytokinesis divides the cytoplasm. ✔
Daughter cells retain the parental chromosome number. ✔
(c) Species-specific mating behaviour can prevent mating between species. ✔
Different reproductive seasons or times can isolate species. ✔
Physical or geographical separation can prevent mating. ✔
Incompatible reproductive anatomy can block gamete transfer. ✔
Interspecific hybrids may be sterile. ✔
Meiosis may fail in a hybrid. ✔
Parental chromosome sets may differ in number or structure. ✔
Without homologous partners, chromosomes cannot pair normally during meiosis. ✔
Polyploidy adds complete chromosome sets, for example through whole-genome doubling. ✔
Doubling a sterile hybrid’s genome can provide homologous partners and restore fertility. ✔
A tetraploid can produce diploid gametes. ✔
Polyploid hybridization can establish a reproductively distinct new species. ✔
Communication: the complete answer is coherent, concise and easy to follow. ✔
Schemat punktowania
(a) Any 4, maximum 4. (b) Any 7, maximum 7; S phase OR DNA-polymerase synthesis suffices for the second point, and spindle attachment OR equatorial alignment suffices for the spindle point. (c) Any 4, maximum 4; general animal behavioural/anatomical examples are acceptable despite the plant context. Polyploidy concerns complete sets, not aneuploidy. Add 1 holistic clarity mark independently of content. Total 16. In (a), segregation OR independent assortment OR crossing over earns the reshuffling point. In (b), cyclin control alone suffices; cohesin cleavage OR centromere division suffices for chromatid release. In (c), species usually not mating with one another OR a behavioural isolation mechanism earns the first point.