Summary of Environments Through Time This summary has been taken directly from the HSC Spotlight Earth and Environmental Science Text pages Review

Evidence from early Earth indicates the first life forms survived in changing habitats during the Archaean and Proterozoic eons. Lesson 1

Summary Geologic time is divided into eons: Hadean Archaean Proterozoic Phanerozoic It is divided using fossil evidence of various life forms

Summary Cyanobacteria are simple photosynthetic organisms. Western Australia has some of the world’s most significant fossil evidence of cyanobacteria. Both fossil and modern stromatolites are similar in structure. The distribution of stromatolites has changed over time Banded iron formations give us evidence of environmental conditions when they were formed.

Dot Points Discuss DOT Points

Summary Fossilisation is a rare process because certain conditions must be present. There are three major types of fossilisation: Moulds Casts Carbonisation Isotopes can give evidence for the presence of life

DOT Point Discuss DOT Points

Environments of the Phanerozoic & The Cambrian event Lesson 2

Summary The formation of the ozone layer could only take place once the concentration of oxygen had built up in the atmosphere A chemical reaction (photolysis) takes place in the stratosphere to change oxygen into ozone Ozone filters out ultraviolet radiation. This made the terrestrial environment much less harmful and enabled evolution onto land

DOT Point Discuss DOT Points

Summary The age of a fossil can be determined by interpreting its position in a stratigraphical sequence Relative dating is carried out by interpreting the position of a rock/fossil in a stratigraphic section to determine its age in relation to other rocks/fossils. It gives the age as a geological period. Absolute age is determined by radiometric dating with isotopes. It gives a numerical value of age

Summary The numerous fossils of hard-bodied organisms in the Cambrian show both the explosion of new life forms and higher rates of preservation Hard-bodied organisms have many advantages over soft-bodied organisms Evolution occurs via the mechanisms of mutation and natural selection

DOT Point Discuss DOT Points 3.1, 3.4, 3.5

Exploiting new environments Lesson 3

Summary Many lines of evidence show how organisms in the past have evolved into modern-day organisms Organisms faced with environmental pressures when they made the transition from the marine to the terrestrial environment Significant organisms that were initiators in the transition were liverworts, arthropods/insects, crossopterygians/lungfish and amphibians

DOT Points Discuss DOT Points 4.1, 4.3, 4.6, 4.7

Past extinction and mass extinction events Lesson 4

Summary The first land dwellers were able to gain certain advantages over their marine relatives There are times throughout geological history when evolution moves at either a gradual of an explosive rate. The latter often follows a mass extinction A mass extinction is different from a small extinction as it affects entire groups of organisms on a global scale

DOT Points Discuss DOT Points 5.2, 5.4, 5.5

Summary Australia has undergone in the past a small extinction of megafauna. The cause is likely to be because of wither climate change as the continent moved or human impact. The mass extinction at the end of the Permian is thought to have resulted from global climate change caused by large scale glaciation The mass extinction at the end of the Cretaceous is thought to have resulted from global climate change by a meteorite impact

Summary Australia is not experiencing an increased rate of extinction compared with and in the last 60 million years owing to human influences

DOT Points Discuss DOT Points