What you need to know
- 4.15The variety of life has become extensive over time, but is now threatened by human activity.
- 4.16Meanings of biodiversityThe variety of life in an area, including species richness and genetic diversity. and endemicDescribes a species found naturally in only one geographical area..
Historical diversification is evolutionary. The current threat is human activity. Global assessment numbers in Beyond the classroom are enrichment, not extra specification recall. Measuring richness, heterozygosity and D is 4C 2. Conservation methods are 4C 6.
By the end, you should be able to…
- Define biodiversity and endemism.
- Distinguish evolutionary increase in variety from current human-driven loss.
- Explain why losing an endemic speciesA group of organisms that can interbreed to produce fertile offspring. is a global loss.
Build your understanding
What biodiversity means
biodiversityThe variety of life in an area, including species richness and genetic diversity. is the variety of living organisms. Treat it at more than one level: genetic variation within a speciesA group of organisms that can interbreed to produce fertile offspring., the number and variety of species in a habitat, and the range of habitatThe place where an organism lives. or ecosystemA community together with the non-living (abiotic) parts of its environment, interacting.. A coral reef and a wheat field can both contain living things; they are not equally diverse.
species richnessThe number of different species in an area. (how many species) is one part of that idea. It is not the whole of biodiversity. A habitat of ten common weeds and a habitat of ten rare endemics can share a richness of ten and still differ in conservationProtecting and managing species and habitats to maintain biodiversity. importance.
Endemism is about natural range
An endemicDescribes a species found naturally in only one geographical area. species (or other taxon) occurs naturally only in one defined place and nowhere else. An island plant known only from that island is endemic. A garden cultivar bred in a country is not endemic there. A migrant bird that winters in many countries is not endemic to any one of them.
If an endemic is lost from its only place, it is lost from Earth. That is why endemism raises the stakes of habitat destruction. A widespread weed can be locally wiped out and still survive elsewhere; an endemic cannot.
Extensive, then threatened
Over evolutionary time, speciationThe formation of a new species, when populations become reproductively isolated and their gene pools change. has produced a huge variety of lineages. That is not a human achievement. Specification 4.15 then asks you to know that this variety is now threatened by human activity: habitat destruction and fragmentation, overexploitation, pollution, climate change and introduced species.
Background extinction has always occurred. The present concern is a faster, human-linked decline. Habitat loss removes niches, shrinks populationAll the individuals of one species living in one area at the same time., and can cut genetic diversityThe variety of alleles in a population or species. before the last individual dies. Those links are the biology; they are not a claim that every past extinction was human-caused.
NOT: endemic does not mean endangered, and richness does not include how even the numbers are.
- Biodiversity is variety at more than one scale, including species
- Endemism is about geographic range
- Human activity is the current threat emphasised here
- Measuring D is the next lesson
Two traps this diagram blocks
- Do not define endemic as “dangerous” or “extinct”.
- Do not treat two habitats with the same richness as equally diverse if one is dominated by a single species. That comparison needs abundance.
From the diagram alone
Question
Distinguish species richness from endemism, and explain why habitat loss is a greater extinction risk for an endemic species. [3]
Show a model answer
Species richness is the number of species in a place. Endemism means a species lives only in one place. If that place is destroyed, an endemic species has no other population, whereas a widespread species may survive elsewhere.
| Idea | What it captures | What it misses |
|---|---|---|
| Biodiversity | Variety of life at genetic, species and habitat levels | A single count of species in one visit |
| Endemism | Natural occurrence only in one defined place | How common the species is inside that place |
| Local disappearance of a widespread species | Loss from one site | The lineage may still exist elsewhere |
Make your reasoning visible
Keep the two time scales
Variety became extensive through evolution. The threat now is human activity. Do not merge those sentences.
Endemic ≠ rare automatically
A speciesA group of organisms that can interbreed to produce fertile offspring. can be endemicDescribes a species found naturally in only one geographical area. and still locally abundant. The conservationProtecting and managing species and habitats to maintain biodiversity. issue is that there is no second homeland.
Key explanations
- species richnessThe number of different species in an area. is the number of species in a habitatThe place where an organism lives. or sample. It ignores how many individuals each species has.
- Human activity, including habitat destruction, is the main current threat described in this lesson.
Avoid this misconception
The claim: biodiversityThe variety of life in an area, including species richness and genetic diversity. just means “lots of animals in a zoo”.
The correction: Biodiversity includes genetic variation, wild species and habitats. Captive collections can hold some diversity, but they are not a habitat’s biodiversity.
Check your understanding
Try each question before opening the suggested answer.
Practice question
Retrieval and explanation · suggested answer
Define biodiversity.
Show suggested answer
The variety of living organisms, including genetic variation within species, the variety of species, and the variety of habitats or ecosystems.
Practice question
Retrieval and explanation · suggested answer
Define endemism.
Show suggested answer
A taxon that occurs naturally only in one defined place and nowhere else.
Practice question
Retrieval and explanation · suggested answer
Why does losing an endemic species reduce global variety more than losing one local population of a widespread weed?
Show suggested answer
The endemic exists only there, so extinction is global. The weed may still survive in other places.
Take the idea further
Apply the same specification knowledge to an unfamiliar problem. Any extra assumptions are supplied in the question.
Stretch question
A peninsula has high species richness but few endemics. A nearby island has lower richness but several endemics. Why might both still be conservation priorities, for different reasons?
Show a hint
Separate “many species” from “species that exist only here”.
Explore the reasoning
The peninsula may support many species and ecological roles. The island’s endemics cannot be replaced elsewhere, so habitat loss there is a global extinction risk. Priority is not a single richness ranking.
Recall this lesson
Lesson recall questions
Question 1 of 5: How can habitat loss reduce the variety of life?
Variety of life under threat
Practice question
Retrieval and explanation · suggested answer
How can habitat loss reduce the variety of life?
Lesson: 4C 1: Biodiversity and Endemism
Build the sequence from memory first. Then reveal the model order.
Tap the steps in the order you recall. Tap a placed step to send it back.
- 01Next step
- 02Waiting
- 03Waiting
Tap to place
Put your biology to work
Explore where these ideas appear in the world. Enrichment, not extra required recall.
An intergovernmental snapshot, not a mark scheme
4C · Biodiversity and EndemismThe 2019 IPBES Global Assessment concluded that nature is declining at rates unprecedented in human history, with human activity as the direct driver. It estimated that around one…Specification 4.15 · 4.16Read & use the scienceClose article
Why this matters
The 2019 IPBES Global Assessment concluded that nature is declining at rates unprecedented in human history, with human activity as the direct driver. It estimated that around one million animal and plant species are threatened with extinction. Those figures are a reviewed scientific synthesis. They are enrichment context for 4.15, not extra numbers you must recall as specification facts. Threatened species are not distributed evenly. Some are endemic to a limited region, so loss of that habitat can remove an entire lineage. Assessments combine many kinds of evidence and contain uncertainty; they are not a count made by visiting every organism. For the specification, define biodiversity and endemism clearly before discussing human pressures. The IPBES synthesis gives scale to the question, while a specific local survey would be needed to calculate richness or diversity in one habitat.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 2, pp. 21–24. The application extends beyond required recall.
- 4.15 know that, over time, the variety of life has become extensive but is now being threatened by human activity
- 4.16 understand what is meant by the terms biodiversity and endemism
Use the science
Why is “around one million species threatened” not the same statement as “one million species have already gone extinct this century”?
Explore a possible response
Threatened means at risk, using assessment criteria. Extinct means none remain. Mixing the two overstates what the evidence shows.
Explore the source
Why island endemics are vulnerable
4C · Biodiversity and EndemismThe Natural History Museum reports that invasive species threaten island plants and birds, many of which occur nowhere else. An endemic species has a restricted natural range; losing…Specification 4.15 · 4.16Read & use the scienceClose article
Why this matters
The Natural History Museum reports that invasive species threaten island plants and birds, many of which occur nowhere else. An endemic species has a restricted natural range; losing its only habitat can remove the species globally. But not every island species is endemic, and not every endemic species is already endangered. Conservation biologists have to map distributions and pressures before setting priorities. This real example gives meaning to the specification definitions of biodiversity and endemism. It also shows why human activity can reduce variety of life even when a local area still looks green. A wildlife documentary may show a dramatic predator, while the conservation decision still needs evidence about range and population.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 2, pp. 21–24. The application extends beyond required recall.
- 4.15 know that, over time, the variety of life has become extensive but is now being threatened by human activity
- 4.16 understand what is meant by the terms biodiversity and endemism
Use the science
If an introduced predator removes an endemic bird from its only island, why is the consequence different from a local loss of a widespread bird?
Explore a possible response
For the endemic, the island may hold the entire natural population, so local extinction could mean global extinction. A widespread species has other populations.
Explore the source
- Invasive species and island birds and plantsNatural History Museum