Key Area 7 (a) : Mass extinction Unit 3: Sustainability and Interdependence

Extinction What does extinct means? – That not one member of the species is alive. What does mass extinction mean? – That a large percentage of species has become extinct over a short geological period. Where is the evidence for mass extinctions found? – In the fossil records CfE Higher Biology Sustainability and Interdependence

Fossil record CfE Higher Biology Sustainability and Interdependence The fossil record opens a window into the world of long ago, It provides glimpses of the evolution of life over billions of years. The fossil record is based primarily on the sequence in which fossils have accumulated in sedimentary rocks. The fossil record is substantial and significant but is an incomplete chronicle of evolutionary change.

Fossil record CfE Higher Biology Sustainability and Interdependence The fossil record shows that the overwhelming majority of species that ever lived are now extinct. Extinction occurs regularly and a species may become extinct for a variety of reasons. Where disruptive changes to the global environment cause the rate of extinction to increase dramatically this is called mass extinction. Five mass extinctions are documented in the fossil record over the past 500 million years.

Mass Extinction CfE Higher Biology Sustainability and Interdependence The first 5 mass extinctions occurred in the: – Cretaceous – Triassic – Permian – Devonian – Ordovician periods

Mass Extinction CfE Higher Biology Sustainability and Interdependence Collect the card sorting task. Write the information in to your jotter.

Mass Extinction CfE Higher Biology Sustainability and Interdependence Mass extinctions have significant and long term effects. Large number of species can be eliminated, reducing thriving and complex communities. The fossil record shows that it takes about 5-10 million years for the diversity of life to recover, sometimes longer.

Fossil record Width represents number of living families Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovidan Cambrian Period animal families lost in extinction Millions of years ago (mya) 50% 33% 60% 30% 50% Explain the following observations; Biodiversity regains slowly after an event. Survivors radiate/speciation occurs as they spread into open niches. It is difficult to state precise extinction rates for past mass extinction. Fossil record is incomplete, you do not always know how long a species was around for, or its numbers It is difficult to state current extinction rates Many species are not recorded/ identified Human activity (in particular ecosystem degradation) has increased the rate of species extinction from the background rate. Naturally some species will become extinct, but changes in the ecosystem mean that there are changes in most ‘fit’ species and so change chances of extinction

After the Mass Extinctions CfE Higher Biology Sustainability and Interdependence After each Mass Extinction, because so many species have been eliminated, adaptive radiation can take place. This means that new groups of organisms can proliferate and form new species. These new species form adaptations allowing them to fill different ecological roles, or niches, in their communities.

Adaptive Radiation CfE Higher Biology Sustainability and Interdependence Common ancestor camel zebra dolphin Polar bear monkey Adaptation to jungle Adaptation to desert Adaptation to grassland Adaptation to ocean Adaptation to icy environment

The 6 th mass extinction CfE Higher Biology Sustainability and Interdependence What is the Holocene mass extinction? – It is the one currently occurring – in this epoch. Why would a 6 th mass extinction be occurring? – Human activities