The shape of the lesson
By the end of the lesson, learners can
- Four routes to extinction: Start with no threat, then pick climate change, competition, hunting and habitat loss in turn.
- Keeping endangered species safe: Click through the conservation methods: zoos, botanic gardens, national and marine parks, frozen zoos and seed banks.
- Assisted reproduction, aliens and international law: The last chips in the conservation tab cover IVF, embryo transfer and surrogacy, invasive species, and the IUCN and CITES.
- Four threats: climate change, competition, hunting, habitat loss; explain the effect on numbers.
- In the habitat: national and marine parks. Away: zoos, botanic gardens, frozen zoos, seed banks.
- IVF, embryo transfer, surrogacy multiply offspring from rare mammals.
- IUCN = Red List; CITES = trade rules.
One picture every idea returns to
Populations and species become extinct when climate change shifts conditions faster than they can move or adapt, when a competitor uses their resources more efficiently, when hunting by humans removes individuals faster than they reproduce, and when habitats are degraded or lost. Small populations also lose genetic diversity. Biodiversity is worth maintaining for ecosystem stability and services, for food, medicines and genes, for economic value such as ecotourism, and for ethical reasons. Conservation protects species in national and marine parks, and away from their habitat in zoos, botanic gardens, frozen zoos and seed banks. Rare mammals can be bred by IVF, embryo transfer and surrogacy. Invasive alien species are controlled to protect native species, and internationally the IUCN assesses threat (the Red List) while CITES regulates trade.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Why species vanish, and how we keep them.. Populations shrink when their climate shifts, when competitors arrive, when they are hunted or when their habitat is cleared. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: Four routes to extinction | Start with no threat, then pick climate change, competition, hunting and habitat loss in turn. Project tab 7 of the lab (Biodiversity lab, threats to species) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Keeping endangered species safe | Click through the conservation methods: zoos, botanic gardens, national and marine parks, frozen zoos and seed banks. Project tab 8 of the lab (Biodiversity lab, conservation) and let a student drive it while the class predicts. | Pairs |
| 21 to 30 min | Teach and check: Assisted reproduction, aliens and international law | The last chips in the conservation tab cover IVF, embryo transfer and surrogacy, invasive species, and the IUCN and CITES. | Connect-Extend-Challenge |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 19 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Assisted reproduction, aliens and international law, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Connect-Extend-Challenge
After the new idea, each student writes three lines: how it connects to what they knew, how it extends their thinking, and what still challenges them. Pairs compare, then the challenges become the plenary.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Do not just name the threat: explain the effect on the population. | For example, habitat loss reduces the food and breeding sites available, so the carrying capacity falls and fewer individuals survive and reproduce. |
| Seed banks and frozen zoos do not stop a species declining in the wild on their own. | They store genetic diversity; the habitat must still be protected for any reintroduced organisms to survive. |
Extinction and conservation: worksheet
6 questions, 19 marks. Written in the style of the papers; no past paper question is reproduced.
Explain how climate change and the degradation of habitats can each cause a species to become extinct.
Outline three reasons for the need to maintain biodiversity.
Outline the roles of frozen zoos and seed banks in the conservation of endangered species.
Describe how IVF, embryo transfer and surrogacy can be used to increase the number of offspring of an endangered mammal.
Explain reasons for controlling invasive alien species.
Outline the roles of the IUCN and CITES in conservation.
Answer key and marking notes
- Climate change: temperature and rainfall patterns shift, so the conditions the species is adapted to are found in a smaller area or elsewhere.
- If the species cannot migrate or adapt quickly enough, survival and reproduction fall and the population declines.
- Habitat degradation / loss: clearing or pollution removes food, shelter and breeding sites, lowering the number of individuals the area can support.
- Fragmentation leaves small isolated populations with low genetic diversity, vulnerable to inbreeding and chance events.
- Ecological: diverse ecosystems are more stable and provide services such as pollination, nutrient cycling and clean water.
- Economic / practical: wild species provide food, medicines, timber and genes for improving crops and livestock; ecotourism brings income.
- Ethical / aesthetic: people have a responsibility to protect other species for their own sake and for future generations.
- Frozen zoos store sperm, eggs, embryos and tissue samples in liquid nitrogen at −196 °C.
- These keep genetic diversity and can be used in IVF / embryo transfer, even after the donor has died.
- Seed banks store dried seeds at low temperature (about −20 °C) for long periods, conserving the genetic diversity of wild plants and crops; seeds are germinated periodically to test viability and renew stocks.
- A female of the endangered species is treated with hormones so that several eggs mature; the eggs are collected.
- The eggs are fertilised with sperm (fresh or from a frozen zoo) in the laboratory: IVF.
- The embryos are grown for a few days, then transferred into the uterus of a female: embryo transfer; spare embryos can be frozen.
- A surrogate mother, possibly of a closely related common species, carries the pregnancy, so the rare female can produce many more offspring.
- Invasive species often have no natural predators, parasites or competitors in their new area, so their populations increase rapidly.
- They out-compete native species for food, light or space, prey on them, or spread disease / hybridise with them.
- This reduces native biodiversity and can disrupt food webs and ecosystems (and damage crops or the economy), so controlling them protects native species.
- IUCN: assesses the conservation status of species and publishes the Red List of threatened species, helping set priorities and supporting conservation projects.
- CITES: an international agreement that bans trade in the most endangered species and controls trade in others by permits (for example ivory, rhino horn, live animals and plants).
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
What is the main conservation role of a seed bank?
- Astoring dried seeds at low temperature to conserve the genetic diversity of plants
- Bgrowing endangered plants in glasshouses for public display
- Cstoring frozen embryos of endangered plants in liquid nitrogen
- Dprotecting rare plants in their natural habitat
What is the role of the IUCN in conservation?
- Aassessing the threat to species and publishing the Red List
- Bbanning the international trade in ivory and rhino horn
- Crunning the captive breeding programmes of all zoos
- Dstoring seeds of every plant species in one seed bank
Why do zoos keep stud books for endangered animals in captive breeding programmes?
- Ato choose unrelated parents and so avoid inbreeding
- Bto record which animals have been released into the wild
- Cto prove to CITES that the animals were bought legally
- Dto make sure every animal breeds as often as possible
How does a marine park help conserve an endangered species of reef fish?
- Ait limits fishing and damage, protecting the fish in its own habitat with its natural interactions
- Bit keeps the fish in tanks, away from predators, until numbers recover
- Cit bans international trade in all species of fish
- Dit stores eggs and sperm of the fish in liquid nitrogen
Which is a valid reason for maintaining biodiversity?
- Awild species are a source of new medicines and of genes for crop improvement
- Becosystems with fewer species are always more stable
- Cevery species is a source of food for humans
- Dbiodiversity prevents all natural extinctions
The graph shows a ground-nesting bird on an island. Which explanation of the trend after 2010 is best?
- Aremoving the invasive rats ended predation on eggs and chicks, so more young survived to breed
- Bthe rats had become a food source for the birds, so the population grew
- Cthe birds evolved resistance to the rats after 2010
- Dthe island habitat grew larger once the rats had gone
Only three females of a rare wild cat remain in zoos. Why might embryos be transferred into females of a common domestic cat species?
- Athe surrogates can carry many embryos, so the few rare females produce far more offspring
- Bthe offspring will be hybrids with greater genetic diversity
- Cthe domestic cats pass on their own alleles to strengthen the rare species
- Dit avoids the need for IVF to produce the embryos
A species of mountain hare lives only in the coldest zone near a summit. Over 30 years its lowest altitude has risen by 300 m. Why is it at high risk of extinction?
- Aas climate warms its suitable zone moves uphill and shrinks, and there is no higher land to move to
- Bhares at high altitude are hunted more often than those lower down
- Cthe hares are moving up to compete with a new predator at the summit
- Dwarmer temperatures directly denature the enzymes of all hares
Quiz key
Seed banks dry seeds and store them cold (about −20 °C) so they stay viable for decades, conserving genetic diversity. Growing plants for display is a botanic garden; embryos in liquid nitrogen describes a frozen zoo for animals; protecting plants in their habitat is a conserved area.
The IUCN assesses the conservation status of species and publishes the Red List, which guides priorities. Trade bans are the role of CITES. Captive breeding is run by zoos and their associations, and seed storage by seed banks.
A stud book records the ancestry of every animal, so breeders can pair unrelated individuals and keep genetic diversity high, avoiding the harmful effects of inbreeding. Recording releases or legal trade is not its purpose, and breeding every animal as often as possible would let a few genotypes dominate.
A marine park restricts fishing, anchoring and other damage, so the whole reef ecosystem is protected and the fish stays in its natural habitat. Tanks describe an aquarium or zoo; trade bans are CITES; storing gametes is a frozen zoo.
Many medicines come from wild organisms, and wild relatives of crops carry useful genes such as disease resistance. Diverse ecosystems are more stable, not less. Not every species is human food, and extinctions happen naturally whatever the biodiversity.
Invasive rats eat eggs and chicks of ground-nesting birds that evolved without them, so numbers fell after they arrived. Eradicating them removed the predation, so breeding success and the population rose: the reason for controlling invasive alien species. The birds do not eat rats, evolution would not act this quickly or in this way, and the island did not change size.
In surrogacy the embryo comes from the rare species (via IVF), so the kittens are fully the rare species, and using common surrogates lets each rare female supply many eggs rather than carrying every pregnancy. The surrogate contributes no alleles, so the young are not hybrids, and IVF is still needed to make the embryos.
Climate change shifts the conditions the hare is adapted to uphill, so its range moves up and becomes smaller; once the zone reaches the summit there is nowhere else to go, the population becomes small and vulnerable, and it may become extinct. Hunting and predators are not indicated by the data, and a few degrees of warming does not denature enzymes.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.