Past questions Flashcards
What is the PTSC
The ongoing cycle of formation and breakup of supercontinents
In the fossil record, terrestrial vertebrates first appeared in the Devonian Period. What advantages did the terrestrial environment offer these vertebrates?
Less competition for resources
Account for the change in both the abundance and distribution of stromatolites over time
Stromatolites have decreased in abundance over time due to the greater number of predators. They have decreased in distribution over time due to changes in the environmental conditions, resulting in fewer locations where they can survive.
Explain the role of photosynthetic organisms in the development of the ozone layer
When cyanobacteria photosynthesise one of the products is oxygen. As oxygen levels increased, UV rays in the upper atmosphere split some oxygen molecules. The free oxygen atoms bonded with oxygen molecules, forming ozone. As oxygen levels in the atmosphere increased, this process continued over time and the ozone layer was formed.
Outline 2 features of land plants that have enabled them to survive in terrestrial environments
Terrestrial plants have a thin coating on their leaves called the cuticle. This waxy layer helps to prevent the desiccation of plants on land. Terrestrial plants have vascular tissue which allows the plant to transport water, minerals and food around the plant to where it is needed.
A critical evolutionary development that allowed animals to survive in terrestrial environments was:
An ability to minimise water loss
Q26 2010
How are BIFs evidence of life that existed in Archean oceans?
BIFs only form when there is oxygen available to combine with the iron. Earth’s early atmosphere and oceans did not contain oxygen. The first oxygen had to be produced by oxygen-producing organisms such as cyanobacteria.
Compare the causes and effects of mass extinctions and smaller extinctions. In your answer, give examples of both types of extinctions.
Mass extinctions are caused by large-scale catastrophic events, such as the meteor event that was thought to have caused the mass extinction at the end of the Cretaceous period, large-scale glaciations or massive volcanic eruptions. Mass extinctions occur on a global scale and affect both terrestrial or marine environments.
Smaller extinction events are regional rather than global. Climatic change and human intervention are causes and the effects are the extinction of target groups such as the Australian megafauna, and sometimes, entire ecosystems.
Account for the differences in the occurrence of modern stromatolites compared to that of the fossil forms.
Compared to the fossil forms, modern stromatolites are rare and live in restricted shallow environment such as at Shark Bay. This is because in modern times, there are many grazing invertebrates that feed on the cyanobacteria and larger organisms that can physically disrupt the bacterial mats. In the Archean and Proterozoic, advanced organisms were not present so cyanobacteria could flourish in many different locations.
Name one evolutionary advance made by early plants and explain how it helped them to spread into the terrestrial environment.
The development of vascular tissue by some early plants gave them an advantage in that they could grow taller and thus gain more light to photosynthesise. The vascular tissue enabled water to be absorbed by roots from deeper in the soil and be transported to all parts of the plant. The plants were also able to spread away from permanent water.
What combination of structures, in addition to support tissue, was essential for terrestrial plants to evolve from simple aquatic plants.
Transport tissue, stomates and seeds
Describe one advantage a terrestrial environment offered for the first land plants that evolved from ancestors that lived in an aquatic environment.
They could colonise more easily. Movement of spores in water is restricted by the current movement. In the drier terrestrial environment, wind is an agent of dispersal and this allows a wider ranger for the dispersal of seeds and pollen, thus allowing new habitats to be colonised.
Why are BIFs no longer forming?
The formation of BIFs removed all of the iron from the ancient oceans and excess oxygen escaped to the atmosphere. In modern environments atmospheric oxygen reacts with iron on the land and thus the formation of iron oxide no longer occurs in the oceans.
