key area 7: mass extinction, regaining biodiversity and measuring biodiversity
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Key area 7: Mass extinction, regaining
biodiversity and measuring biodiversity
CFE Higher BiologySustainability
and interdependenc
e
Learning Intentions• Understand what is meant by mass extinction and how these events occur.
• Be able to name two of the 5 mass extinction periods caused by catastrophic events.
• Be able to explain recovery of biodiversity after a period of mass extinction
• Understand that we are heading for a sixth mass extinction due to Human impact on the world which have led to an increasing extinction rate
CFE Higher BiologySustainability
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What is extinction?Extinction is the complete demise of a group of organism.
This is a natural process – where by organisms not best adapted to the environment do not survive to reproduce.
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Mass extinction events
Fossil evidence suggests that the Earth has experienced several mass extinction events – where large numbers of species have been wiped out in a relatively short time span.
These are usually related to dramatic changes in the global climate.
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The Big 5•Five main extinction events have been recognized, these are known as the BIG 5.• Late Ordovician event 438 million years ago, when 100 families went extinct• Late Devonian 360 million years ago, when 30% of families went extinct• End Permian 245 million years ago, the biggest extinction of all time when over 50% of all families were lost.• Late Triassic 35% of families died out• The Cretaceous Tertiary (K-T) 65 Million years ago, which ended the reign of the dinosaurs
(*A family consists of a few thousand species.)
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Mass extinction researchWith in the class divide into 5 groups (1 per extinction event). Using available resources produce a wall display (or class summary sheet) on each extinction event.-What caused the event?-Who were the big winners?-Who were the big losers?
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Regaining biodiversity after an extinction event
After any extinction event there are winners and losers. Organisms that survive the mass extinction can now exploit niches left by the extinct species. Natural selection favours those best suited to the new environment and adaptive radiation occurs.
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Common ancestor of mammals
Adaptation to jungle
Adaptation to oceans
Adap
tatio
n to
flig
ht
Adaptation to g
rassland
Adaptive radiation in mammals
Monkeys
WhalesBats
Lions
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Estimating the extinction rate
The extinction rate is the number of species becoming extinction in an area per unit of time.
Past extinction rates are estimated by looking at the fossil records. Modern extinction rates can be used by estimating the numbers of organisms.
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The effect of humans…
Megafauna were hunted to extinction by humans.
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Modern habitat destructionSatisfying the needs of an ever growing population has led to:•Over hunting•Habitat destructionLeading to species extinction much higher than would occur naturally – leading to many species becoming endangered.
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Biodiversity
Biodiversity has three main measurable components:•genetic diversity•species diversity•ecosystem diversity Watch this video https://youtu.be/GK_vRtHJZu4 (4 min)
CFE Higher BiologySustainability
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Measuring genetic diversityGenetic diversity can be measured by counting the total number of different alleles that exist in a population and how frequently they occur.
If a population loses some of its genetic diversity (e.g. due to human activities) then it may not be able to adapt to future environmental conditions.
CFE Higher BiologySustainability
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Measuring species diversity
Species diversity depends on:•The richness of species (the number of different species)•The relative abundance of each species.
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Measuring ecosystem diversity
Ecosystem biodiversity is the number of distinct ecosystems within a defined area.
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Why maintain biodiversity?
Watch this video on why we should maintain biodiversity https://youtu.be/7tgNamjTRkk (7.5 minutes)It refers to examples in Australia – but the message is the same the world over.List the five reasons we should maintain biodiversity.