Last chance for the northern white rhino
350 words over 33 numbered lines, then 7 parts worth 14 marks (Linear Paper 2 (4BI1/2B) style, 14–18 marks). Read the article, answer each part, then open its mark scheme and set your mark.
Illustrative article written for Scholar Lab, not a Pearson text. The biology is real; the studies, people and figures are invented or rounded for practice.
Last chance for the northern white rhino
In a guarded enclosure in Kenya live the last two northern white
rhinos on Earth. Both are female, and neither can carry a pregnancy.
The last male died in 2018. For most species, that would be the end of
the story. For this one, scientists are trying to use reproductive
technology to bring it back.
Before the last males died, their sperm was collected and frozen in
liquid nitrogen. Every few months, vets give one of the females an
anaesthetic and collect egg cells from her ovaries. The eggs are flown
to a laboratory in Europe, where each egg is injected with a single
sperm cell. If fertilisation happens, the zygote divides to form an
embryo, which is frozen until it can be used.
In an illustrative count, 220 eggs had been collected by the end of
one year and 33 embryos had been produced. Because neither female can
carry a pregnancy, the embryos will be placed in the uterus of a
female southern white rhino, a closely related subspecies.
There is another problem. All the embryos come from just two females
and a few males, so the new population would have very little genetic
variation. Scientists have therefore stored skin cells from twelve
northern white rhinos that died in zoos over the past forty years.
They hope to use these cells to make new gametes in the laboratory, or
to produce cloned rhinos.
Cloning a large mammal is difficult. Sheep, cattle and horses have
been cloned successfully, but most cloned embryos fail to develop. A
cloned rhino would also be genetically identical to the animal that
provided the skin cell, so cloning alone cannot add new variation. It
can, however, bring back alleles that were lost when the zoo animals
died.
Not everyone supports the project, which has cost many millions of
dollars. Critics say that the money would protect more animals if it
were spent on stopping poaching and protecting the habitats of rhinos
that still survive in the wild. Supporters reply that the techniques
they develop could also help to save other endangered mammals in the
future.
Read the article. Use the information in the article and your own knowledge to answer the questions. The lines in brackets show where to look; select them to highlight the text.
Use the information in the article and your own knowledge to answer the questions. The lines in brackets show you where to look; select them to highlight the text.
State what is meant by the term fertilisation.
(1)Which describes the number of chromosomes in a cell of the embryo compared with the number in an egg cell?
(1)Calculate the percentage of collected eggs that produced embryos.
(2)Explain why the embryos must be placed in the uterus of a female southern white rhino.
(2)Describe how a skin cell from a northern white rhino could be used to produce a cloned rhino.
(3)Explain why a population with very little genetic variation is at risk.
(3)Suggest why the critics think the money should be spent on protecting habitats and stopping poaching.
(2)Total for this question: 14 marks
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