Part 3-Lesson 1

Extinctions and RadiationsPart 3-Lesson 1ClassificationLife forms are constantly undergoing changes and evolving. Scientists have created a classification system to keep track of this and show how organisms are related.

ClassificationClassificationThis classification system sorts and groups similar organisms to show where an organism fits with the entire scheme of living things. This is called taxonomy (the practice and science of classification) .

ClassificationKingdom is the broadest of all groups in the classification system and species is the narrowest. The kingdom group contains organisms that are not very closely related while the species group contains organisms which are very closely related.

ClassificationThe groups in between kingdom and species show a gradual decrease in difference between organisms within each level. As you go from Kingdom to species, the similarity of organisms increase. Gradual or explosive?The rate of evolution has not been constant. There were times of both gradual and explosive periods of evolution. The rate of evolution depends on the rate of mutation and environmental change.

Gradual or explosive?As discussed before, mutations are random changes in an organisms genetics. During periods of frequent or large environmental change, evolution occurs explosively or rapidly as organisms try to keep up with the changes. When there is little environmental change, evolution is not necessary for organisms to survive. Gradual or explosive?Extinctions can also be gradual or explosive. They too have occurred regularly throughout geologic time. Extinctions and evolutionary radiation are often linked.

Gradual or explosive?If the rate of extinction is low, it is likely the rate of evolutionary radiation that follows will be low. If the rate of extinction is high the rate of evolutionary radiation that follows will be high. Gradual or explosive?After a mass extinction, environments become less populated therefore allowing surviving organisms to colonise and evolve in the empty environment. The rate of evolution can be recorded and graphed by looking at the number of new organisms appearing over time. Homework Read pages 93-95 HCS Spotlight TextUpdate electronic vocabularyComplete activity 2.11 page 56Complete DOT Point 5.2Mass Extinctions Part 3-Lesson 2Mass ExtinctionsTwo of the most studies mass extinctions occurred at the end of both the Permian and Cretaceous.

Activity:-Add these to your timeline

Mass extinctionsThe Permian extinction was the most devastating in geologic history as almost 95% of all marine species and a large number of terrestrial species died out.

Mass extinctionsThere are many theories to try and explain the causes for mass extinctions including glaciations, volcanic eruptions and meteorite impacts. Its thought that the cause of the Permian extinction was due to large scale glaciations. Global temperatures would have lowered and sea levels would have also lowered as water would have been locked up in ice.

Mass extinctionsThe mass extinction at the end of the Cretaceous resulted in the extinction of the dinosaurs and approximately 40% of all known species of the time. The most popular theory which explains this extinction is a meteorite impact.

Mass extinctionsSuch a meteorite impact would force tonnes of materials into the atmosphere blocking out large amounts of solar radiation. This would have caused global temperatures to decline.

HomeworkRead page 95-96 HSC Spotlight TextUpdate electronic vocabularyComplete DOT Points 5.4, 5.5Small ExtinctionsPart 3-Lesson 3Small extinctionsExtinctions are not always caused by natural environmental factors. Humans and other large predators have also caused extinctions.

Small extinctionsFor example, the extinction of the Australian megafauna is believed to be largely because of human intervention. Megafauna were slow movers which made them easy prey for humans. It is suggested that the arrival of humans to Australia coincided with the extinction of the megafauna.

Small extinctionsThis type of extinction directly targets a group of animals and is therefore termed as small. A mass extinction impacts on a wide range of organisms in a geologically small period of time. Small extinctionsThe extinction of Australias megafauna targeted mostly large marsupials but a significant amount of smaller marsupials were able to survive. Climate change may have also played a part in the extinction of megafauna and survival of smaller marsupials in Australia.ActivityComplete activity 2.14 page 97 HSC Spotlight Text together.HomeworkUpdate electronic vocabularyComplete DOT Point 5.6-5.8Current rate of extinctionPart 3-Lesson 4Current rate of extinctionWhy is Australia unique? We are an island continent and have been so for a very long time. This has allowed large amounts of Australia flora and fauna to become endemic and diverse.

Current rate of extinctionHowever this has also made Australia sensitive to extinctions. At present the entire world is experiencing a very high extinction rate. Current estimates suggest it is between 1000 and 10000 times greater than is would naturally be. Australia has the highest rate in the world.Current rate of extinctionThis is because of the destruction of natural habitats and unsustainable management of the country. This has ALL been caused by humans.

Current rate of extinctionIn the last 200 years, since European settlement, 18 species of mammals and approximately 100 species of plants have become extinct. 40 species of mammals and hundreds of species of plants are today endangered.

Current rate of extinctionWe need to address and take action now to stop this rate and bring it under control. What do you think the future of the biodiversity of Australia is? What can you do to reduce the extinction rate?Science SkillsComplete Science Skills Activity pg 98 HSC Spotlight Text together.HomeworkUpdate electronic vocabularyComplete To Think About set 1 and 2 pages 98-100 HSC Spotlight Text