Extinction

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Lesson notes

What is Extinction?

**Extinction** is the process where a species completely disappears from Earth.
It occurs when environmental changes make survival difficult for a species.
If a species cannot **adapt** quickly enough, it struggles to compete for resources like food and water.
Fewer individuals survive to reproduce, and over time the entire species becomes extinct.

Causes of Extinction

**Climate change** – if conditions become too hot, cold, dry or wet, some species cannot survive.
**Habitat loss** – deforestation or draining wetlands destroys homes for animals and plants.
**Pollution** – chemicals in air, water and soil can harm or kill sensitive species.
**Introduction of new species** – non-native species with no predators can outcompete native species for resources.

What is Biodiversity?

**Biodiversity** is the variety of all living things on Earth, including plants, animals and microorganisms.
High biodiversity means many different species live in an ecosystem.

Importance of Biodiversity

**Ecosystem stability** – species depend on each other; loss of one can affect many others.
**Resources** – food, medicine and clean water come from biodiversity; losing species reduces these resources.
**Resilience to change** – ecosystems with high biodiversity are more resilient to changes like climate change.

Gene Banks

**Gene banks** store genetic material such as seeds, sperm, eggs or embryos.
They help protect endangered species and could bring back extinct species.
**Preservation and research** – scientists study stored genetic material to learn how to protect species.
**Restoration** – gene banks can be used to breed new individuals and reintroduce species into the wild.

Causes of extinction: environmental changes lead to reduced survival and reproduction, eventually causing extinction.

Biodiversity includes many species; gene banks store genetic material to preserve and restore species.

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Practice questions

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1.What is extinction?
Easy
- AThe process where a species completely disappears from the Earth
- BThe process where a species evolves into a new species
- CThe process where a species migrates to a new habitat
- DThe process where a species becomes more numerous
2.Which of the following is NOT a cause of extinction mentioned in the source?
Easy
- AClimate change
- BHabitat loss
- CNatural selection
- DIntroduction of new species
3.What is biodiversity?
Easy
- AThe variety of all living things on Earth
- BThe number of individuals of a single species
- CThe total mass of all organisms in an area
- DThe genetic similarity within a population
4.Which of the following is a reason why maintaining biodiversity is important?
Medium
- AIt ensures that all species are the same
- BIt makes ecosystems more vulnerable to change
- CIt provides resources such as food and medicine
- DIt reduces the number of species in an ecosystem
5.How can the introduction of a new species lead to extinction?
Medium
- AThe new species provides food for native species
- BThe new species has no natural predators and outcompetes native species
- CThe new species increases the biodiversity of the ecosystem
- DThe new species helps native species adapt to changes
6.What is a gene bank?
Medium
- AA place where genetic material is stored
- BA bank that provides money for conservation
- CA list of all the genes in a species
- DA facility that breeds endangered animals
7.Which of the following statements about gene banks is correct?
Medium
- AGene banks can be used to reintroduce species into the wild
- BGene banks only store seeds from plants
- CGene banks are used to create new species
- DGene banks increase the rate of extinction
8.An ecosystem has high biodiversity. Which statement is most likely true?
Hard
- AIt is less resilient to environmental changes
- BIt is more resilient to environmental changes
- CIt has fewer species than an ecosystem with low biodiversity
- DIt is more likely to experience extinction events

More questions

9.How does habitat loss lead to extinction?
Hard
- AIt creates new habitats for species to colonize
- BIt removes the environment where species live and find resources
- CIt increases the genetic diversity of populations
- DIt allows species to adapt more quickly
10.Which of the following is an example of pollution that can lead to extinction?
Easy
- APlanting trees in a forest
- BChemicals released into rivers killing fish
- CBuilding a nature reserve
- DIntroducing a predator to control pests
11.Why might a species fail to adapt to climate change?
Medium
- AClimate change happens too quickly for evolution to keep up
- BClimate change only affects animals, not plants
- CSpecies always adapt to any change
- DClimate change increases the availability of resources
12.A scientist collects seeds from a rare plant and stores them in a freezer. This is an example of:
Hard
- AHabitat restoration
- BA gene bank
- CPollution control
- DClimate change mitigation
13.A small island has a unique species of bird that feeds only on a particular type of insect. If a new predator that eats the insect is introduced to the island, what is the most likely outcome for the bird species?
Medium
- AThe bird population will increase because there are more insects.
- BThe bird population will decrease because its food source is reduced.
- CThe bird will adapt by eating other insects immediately.
- DThe bird will migrate to a different island.
14.A gene bank stores seeds from a rare plant species. The stored seeds have a germination rate of 40%. If 500 seeds are planted, how many are expected to germinate?
Medium
- A200
- B250
- C300
- D400
15.The table shows the number of species in four ecosystems before and after a drought. Which ecosystem was most resilient to the drought? | Ecosystem | Number of species before drought | Number of species after drought | |-----------|----------------------------------|---------------------------------| | W | 10 | 8 | | X | 20 | 18 | | Y | 30 | 15 | | Z | 40 | 20 |
Hard
- AW
- BX
- CY
- DZ
16.Which of the following is an example of habitat loss leading to extinction?
Easy
- AA forest is cut down, and a bird species loses its nesting sites.
- BA new predator is introduced that eats the eggs of a turtle species.
- CA chemical spill kills all the fish in a river.
- DA drought makes a desert even drier, killing many plants.
17.A scientist claims that an ecosystem with high biodiversity is more stable. Which piece of evidence best supports this claim?
Medium
- AIn a high-biodiversity forest, when one tree species dies, other tree species can fill the gap.
- BIn a low-biodiversity grassland, a drought kills all the grass, and the ecosystem collapses.
- CIn a high-biodiversity coral reef, a disease kills one fish species, but other fish species continue to thrive.
- DAll of the above.
18.A gene bank stores genetic material from an endangered frog species. The stored material includes eggs and sperm. What is the main purpose of storing both eggs and sperm?
Hard
- ATo study the genetic differences between eggs and sperm.
- BTo allow breeding of new individuals in the future.
- CTo prevent the eggs from being eaten by predators.
- DTo keep the genetic material at the correct temperature.
19.Over 50 years, the population of a plant species decreased from 10,000 to 500 individuals. What is the percentage decrease in the population?
Medium
- A5%
- B50%
- C95%
- D99%
20.Which of the following is the most likely reason that an ecosystem with low biodiversity is less resilient to change?
Medium
- AThere are fewer species to perform different roles.
- BThe species are all very similar to each other.
- CThe ecosystem has more predators.
- DThe climate is more variable.
21.Which of the following is NOT a way that the environment can change to cause extinction, according to the source?
Easy
- AClimate change
- BHabitat loss
- CNatural selection
- DIntroduction of new species
22.A researcher compares two islands: Island A has 50 plant species and 20 animal species; Island B has 30 plant species and 15 animal species. A disease kills half the plant species on both islands. Which island's animal community is likely to be more affected?
Hard
- AIsland A, because it has more animals.
- BIsland B, because it has fewer plant species remaining.
- CBoth islands will be affected equally.
- DNeither island will be affected because animals can eat other food.
23.Why might storing seeds in a gene bank help protect a plant species from extinction?
Medium
- AThe seeds can be planted to grow new plants if the wild population is lost.
- BThe seeds can be used to study the plant's DNA.
- CThe seeds can be sold for money to fund conservation.
- DThe seeds can be eaten by animals to spread the plant.
24.What is the definition of extinction?
Easy
- AWhen a species moves to a new habitat.
- BWhen a species completely disappears from the Earth.
- CWhen a species evolves into a new species.
- DWhen the number of individuals in a species decreases.
25.A scientist wants to test the effect of pollution on the germination of seeds from a rare plant species. She places 50 seeds on damp filter paper in a petri dish and adds a measured volume of polluted water. She places another 50 seeds on damp filter paper with the same volume of distilled water. After 7 days, she counts the number of seeds that have germinated in each dish. What is the control variable in this experiment?
Medium
- AThe number of seeds that germinate
- BThe type of water used
- CThe temperature at which the dishes are kept
- DThe volume of water added
26.A gene bank stores seeds from an endangered plant species. The seeds have an average germination rate of 30% when planted immediately. However, after being stored for 5 years, the germination rate drops to 15%. If 200 seeds from the same batch are planted after 5 years of storage, how many are expected to germinate?
Hard
- A60
- B30
- C15
- D45
27.Which of the following is an example of habitat loss that could lead to extinction?
Medium
- AA forest fire that kills many trees but the forest regrows over time
- BA wetland being drained to build a housing estate
- CA cold winter that reduces the population of insects
- DA new predator being introduced to an island
28.What is the term for the variety of all living things on Earth, including plants, animals and microorganisms?
Easy
- AExtinction
- BBiodiversity
- CGene bank
- DEcosystem stability
29.A student is investigating the effect of temperature on the survival of a species of water flea. She places 10 water fleas in each of three beakers containing the same volume of pond water. One beaker is kept at 10°C, one at 20°C, and one at 30°C. After 24 hours, she counts the number of water fleas still alive in each beaker. What is the independent variable in this experiment?
Medium
- AThe number of water fleas alive
- BThe temperature of the water
- CThe volume of pond water
- DThe type of pond water
30.A conservationist is comparing two ecosystems: Ecosystem X has 40 plant species and 25 animal species; Ecosystem Y has 60 plant species and 40 animal species. A disease kills half of the plant species in both ecosystems. Which ecosystem is likely to be more resilient to this change, and why?
Hard
- AEcosystem X, because it has fewer species so the remaining species are stronger
- BEcosystem Y, because it has higher biodiversity and more species can fill the roles of lost species
- CEcosystem X, because it has fewer animal species so less competition
- DEcosystem Y, because it has more animal species that can eat any plant
31.A scientist is studying the impact of a new predator on a native bird species. She collects data on the number of birds before and after the predator is introduced. The following table shows the results: | Year | Number of birds | |------|-----------------| | 1 | 200 | | 2 | 180 | | 3 | 150 | | 4 | 120 | | 5 | 90 | What is the percentage decrease in the bird population from year 1 to year 5?
Hard
- A45%
- B55%
- C110%
- D90%
32.A researcher is investigating the effect of pollution on the growth of a plant. She grows 20 plants in clean soil and 20 plants in soil contaminated with a chemical. She measures the height of each plant after 4 weeks. The results are shown in the table: | Soil type | Mean height (cm) | Standard deviation | |-----------|------------------|-------------------| | Clean | 12.5 | 1.2 | | Contaminated | 8.3 | 1.5 | What conclusion can be drawn from these results?
Hard
- AThe chemical has no effect on plant growth
- BThe chemical reduces plant growth
- CThe chemical increases plant growth
- DThe results are not reliable because the standard deviations overlap
33.Which of the following is a cause of extinction mentioned in the source?
Easy
- AClimate change
- BIncreased reproduction
- CNatural selection
- DGenetic mutation
34.Why is maintaining biodiversity important?
Medium
- AIt ensures ecosystem stability and resilience to change.
- BIt increases the number of predators in an ecosystem.
- CIt reduces the need for gene banks.
- DIt prevents all species from becoming extinct.
35.How can gene banks help in preserving species?
Hard
- ABy storing genetic material that can be used to breed new individuals.
- BBy providing a natural habitat for endangered species.
- CBy increasing the population of predators.
- DBy removing all threats to the species.
36.Which of the following is NOT a way the environment can change leading to extinction?
Medium
- AIncreased genetic diversity
- BClimate change
- CPollution
- DIntroduction of new species
37.A species cannot adapt quickly enough to environmental changes. What is the most likely outcome?
Hard
- AThe species may become extinct.
- BThe species will evolve rapidly.
- CThe species will migrate to a new habitat.
- DThe species will increase in number.
38.Which statement best describes how the introduction of a new species can lead to extinction?
Hard
- AThe new species outcompetes native species for resources.
- BThe new species increases biodiversity.
- CThe new species provides food for native predators.
- DThe new species helps native species adapt.
39.A small island has a unique species of bird that feeds only on a particular type of insect. If a new predator that eats the insect is introduced to the island, what is the most likely long-term effect on the bird species?
Medium
- AThe bird population will increase because the predator reduces competition.
- BThe bird population will decrease because its food source is reduced.
- CThe bird will adapt to eat other insects and its population will remain stable.
- DThe bird will prey on the new predator and its population will increase.
40.The table shows the number of species in four ecosystems before and after a drought. Which ecosystem was most resilient to the drought? | Ecosystem | Number of species before drought | Number of species after drought | |-----------|----------------------------------|---------------------------------| | W | 20 | 18 | | X | 30 | 15 | | Y | 40 | 36 | | Z | 50 | 25 |
Medium
- AW
- BX
- CY
- DZ

Revision notes

## Extinction **Extinction** is when a species completely disappears from Earth. It happens when the environment changes and the species cannot adapt quickly enough to survive and reproduce. ### Causes of Extinction - **Climate change** – too hot, cold, dry, or wet. - **Habitat loss** – e.g., deforestation, draining wetlands. - **Pollution** – chemicals in air, water, soil. - **Introduction of new species** – non-native species outcompete natives. ### Biodiversity **Biodiversity** is the variety of all living things (plants, animals, microorganisms). High biodiversity means many different species in an ecosystem. ### Importance of Biodiversity - **Ecosystem stability** – species depend on each other; loss of one affects others. - **Resources** – food, medicine, clean water come from biodiversity. - **Resilience to change** – high biodiversity helps ecosystems cope with changes like climate change. ### Gene Banks **Gene banks** store genetic material (seeds, sperm, eggs, embryos). They help by: - **Preservation and research** – scientists study genetic material to protect endangered species. - **Restoration** – breeding new individuals from stored material to reintroduce species into the wild.

Extinction: The process where a species completely disappears from the Earth.
Biodiversity: The variety of all living things on Earth, including plants, animals and microorganisms.
Gene bank: A place where genetic material (like seeds, sperm, eggs or embryos) is stored to help protect endangered species or bring back extinct species.

Flashcards

What is extinction?

Extinction is the process where a species completely disappears from the Earth.

What happens when a species can't adapt to environmental changes?

They may struggle to compete for resources like food and water, fewer individuals survive to reproduce, and over time the species can become extinct.

List four ways the environment can change leading to extinction.

Climate change, habitat loss, pollution, and introduction of new species.

How does climate change cause extinction?

If the climate becomes too hot, too cold, too dry or too wet, some species might not be able to survive in the new conditions.

How does habitat loss lead to extinction?

When forests are cut down or wetlands are drained, the animals and plants that lived there may have nowhere to go.

How does pollution cause extinction?

Chemicals released into the air, water and soil can harm or kill species that are sensitive to these pollutants.

How can the introduction of new species lead to extinction?

New species introduced to an environment with no natural predators can outcompete native species for resources, leading to extinction of the native species.

What is biodiversity?

Biodiversity refers to the variety of all living things on Earth, including plants, animals and microorganisms.

What does high biodiversity mean?

High biodiversity means that there are many different species living in an ecosystem.

Why is maintaining biodiversity important for ecosystem stability?

Different species often depend on each other; if one species goes extinct, it can affect many other species in the ecosystem.

Why is biodiversity important for resources?

Many resources we rely on, such as food, medicine and clean water, come from biodiversity. Losing species can reduce their availability.

Why does high biodiversity make ecosystems more resilient to change?

Ecosystems with high biodiversity have more species that can fill different roles if some species are lost, making them more resilient to changes like climate change.

What is a gene bank?

A gene bank is a place where genetic material (like seeds, sperm, eggs or embryos) is stored.

How can gene banks help protect endangered species?

Gene banks store genetic material that can be used to help protect endangered species or bring back species that have become extinct.

How do gene banks aid in preservation and research?

By storing genetic material, scientists can preserve and study it to learn more about how to protect endangered species.

How can gene banks be used for restoration?

Gene banks can be used to reintroduce species into the wild by breeding new individuals from the stored genetic material.

True or false: Ecosystems with high biodiversity are often less resistant to change.

False. Ecosystems with high biodiversity are often more resilient to change.

True or false: If one species in an ecosystem goes extinct, it won’t affect any other species.

False. Different species often depend on each other, so extinction of one species can affect many others.

True or false: One way to help prevent extinction is to use gene banks.

True.

What is the definition of extinction?

Extinction is the process where a species completely disappears from the Earth.

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