Past Ecosystems M4.2

Reconstructing a timeline of Earth’s history can be likened to forensic analysis in that:

• every change in the environment involves an exchange of materials that may remain behind.

• scientists can prove which organisms existed and interacted with the environment.

• there is always evidence of changes in biotic and abiotic factors in the rock record.

• we can be certain that all organisms that existed in the past have left trace of their activity.

In terms of evolution, changes in the biotic and abiotic environment act on living things as:

• adaptations.

• variation.

• selective pressures.

• random factors.

Human historical records can be used to reconstruct past events in Earth’s history. Examples of this include:

• fossil evidence

• Aboriginal rock art

• banded iron formations

• stromatolites

The Law of Superposition states that:

• the oldest rock layers are found at the top of any sequence of rocks that are undisturbed.

• any rock layers that cross through or intrude into another must be older than those layers.

• rock layers always continue sideways without being disturbed by erosion of tectonic forces.

• the oldest rock layers are found at the bottom of any sequence of undisturbed rocks.

Banded iron formations are an important piece of evidence for:

• a cooling of Earth’s oceans and atmosphere due to volcanic eruptions.

• catastrophic climate change resulting from an asteroid strike on Earth.

• the development of the ozone layer, which allowed photosynthesis to develop.

• an increase in the oxygen concentration of the oceans and atmosphere.

Molecular biomarkers are most likely to be found in:

• sedimentary rocks.

• igneous rocks.

• metamorphic rocks.

• a combination of the above.

Ice cores are particularly useful for reconstructing past Earth climates because:

• they contain trapped bubbles of atmospheric gas from the time they formed.

• they often trap dust and pollen that settles from the atmosphere onto the ice.

• isotopic analysis of gases in bubbles allow scientists to infer average global temperatures of the time.

• All are correct.

Carbon-14, used for dating biological material, is not as useful for most geological samples because:

• it does not decay to a more stable element.

• its half-life is too short.

• it can only be used for samples greater than 50 000 years old.

• its half-life is too long.

Convergent evolution would explain the similarities between:

• whales and dolphins.

• horses and zebras.

• echidnas and hedgehogs.

• kangaroos and wallabies.

Which of the following is an example of a fossil?

• Organic remains of living things, such as trace chemicals

• Impressions of organisms in sedimentary rocks

• Moulds and casts of hard parts of organisms

• All are correct.