Question 23M.2.HL.TZ2.4
| Date | May 2023 | Marks available | [Maximum mark: 7] | Reference code | 23M.2.HL.TZ2.4 |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain, State | Question number | 4 | Adapted from | N/A |
The Chinese pangolin (Manis pentadactyla) is a critically endangered species that has declined in numbers by 80 % since 2000. It inhabits both forest and grassland, where it uses long, powerful claws to open ant and termite nests and ingests the insects using a long, sticky tongue.
[Source: By U.S. Fish and Wildlife Service Headquarters - Manis pentadactyla, CC BY 2.0,
https://commons.wikimedia.org/w/index.php?curid=56589200.
Photo credit to Ms. Sarita Jnawali of NTNC – Central Zoo The United States is
cosponsoring four separate proposals to increase CITES protections for pangolins
from Appendix II to Appendix I, U.S. Fish and Wildlife Service Headquarters -
Manis pentadactyla. CC BY 2.0. File:Manis pentadactyla (29054818144).jpg.
Created: 14 September 2016.]
State with a reason whether pangolins are autotrophic or heterotrophic.
[1]
heterotrophic because it feeds on/eats food/other organisms /eats ants/termites/ doesn’t photosynthesise/does not produce its own food;
Do not accept “it is not autotrophic” as it is part of the stem question.
The identification that pangolins are heterotrophic as they need to feed on other organisms because they cannot produce their own food was done effectively. However, every now and again scripts were observed with the answer "autotrophs", or candidates not getting the marking point as they omitted the reason for stating that pangolins are heterotrophic.
Explain what information is needed to find the trophic level of pangolins.
[2]
- what (prey) it eats/feeds on/ stomach content;
- the trophic level of what (prey) it eats/feeds on/the trophic level of ants/termites;
- trophic level is the position an organism occupies in the food chain/web;
Do not award points for indicating that predator information is needed.
Many candidates were aware that to find the trophic level of the pangolins, it was necessary to know what the pangolin eats. Few went further to indicate that the trophic level of the ants and termites (or what these feed on) was also necessary. Many students incorrectly assumed that to find the trophic level of the pangolin, information about the predators of the pangolin was necessary. The trophic level is determined from the start of a food chain.
Pangolins are unique among mammals in having evolved scales, which are a recognition feature of reptiles. Explain which features you expect pangolins to have, which would show that they are mammals, not reptiles.
[2]
- hair;
- mammary glands/milk secretion;
- alveoli in lungs;
- lower mandible/jaw consisting of just one bone;
- giving birth to live young/are placental (apart from duck-billed platypus/echidna);
- external ears/ pinna;
- warm-blooded/endothermic/constant body temperature;
Mpa: pangolin underside may be covered with sparse fur.
Do not accept double circulation. Mpe: accept “do not lay eggs” as WTTE Do not accept internal fertilization.
Many earned full marks as they were able to identify 2 features that would help determine that pangolins are mammals. However, there were quite several answers referring to sexual reproduction and internal fertilization, not realizing that these are common to both reptiles and mammals.
The Chinese pangolin, Manis pentadactyla, has a diploid chromosome number of 40.
The Chinese pangolin, Manis pentadactyla, has a diploid chromosome number of 40.
State how many chromosomes there would be in gametes of this species.
[1]
20;
In general, no major problems were observed in this question, as many candidates were able to remember that gametes are haploid and therefore 20 chromosomes would be present in gametes of the Chinese pangolin species.
Sex is determined in the same way in pangolins as in humans. State how many autosomes there are in somatic cells of M. pentadactyla.
[1]
38
OR
19 pairs;
Even though many students referred to 38 chromosomes, several stated "19" but omitted the word "pairs" (of chromosomes). many candidates seemed to have been confused while quickly reading the question that asked for the number of chromosomes in somatic cells of the pangolin, and instead answered "2" as if referring to the number of sex chromosomes.