Key area 7: Mass extinction, regaining biodiversity and measuring biodiversity

CFE Higher Biology Sustainability and interdependence 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 Biology Sustainability and interdependence 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.

CFE Higher Biology Sustainability and interdependence 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.

CFE Higher Biology Sustainability and interdependence 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.)

CFE Higher Biology Sustainability and interdependence Mass extinction research With 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?

CFE Higher Biology Sustainability and interdependence 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.

CFE Higher Biology Sustainability and interdependence Common ancestor of mammals Adaptation to jungle Adaptation to oceans Adaptation to flight Adaptation to grassland Adaptive radiation in mammals Monkeys Whales Bats Lions

CFE Higher Biology Sustainability and interdependence 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.

CFE Higher Biology Sustainability and interdependence The effect of humans… Megafauna were hunted to extinction by humans.

CFE Higher Biology Sustainability and interdependence Modern habitat destruction Satisfying the needs of an ever growing population has led to: Over hunting Habitat destruction Leading to species extinction much higher than would occur naturally – leading to many species becoming endangered.

CFE Higher Biology Sustainability and interdependence Biodiversity Biodiversity has three main measurable components: genetic diversity species diversity ecosystem diversity Watch this video (4 min)

CFE Higher Biology Sustainability and interdependence Measuring genetic diversity Genetic 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 Biology Sustainability and interdependence Measuring species diversity Species diversity depends on: The richness of species (the number of different species) The relative abundance of each species.

CFE Higher Biology Sustainability and interdependence Measuring ecosystem diversity Ecosystem biodiversity is the number of distinct ecosystems within a defined area.

CFE Higher Biology Sustainability and interdependence Why maintain biodiversity? Watch this video on why we should maintain biodiversity (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.