6.1 Evidence of evolution – Questions and answers
Bk Ch6 S6.1 Q1
Outline, using a named example, how changes in the physical or chemical conditions in the environment can lead to changes in a species.
Bk Ch6 S6.1 A1
Example (peppered moth):
The peppered moth represents an example of how physical change in the environment has led to a change in a population. In unpolluted forests light-coloured moths have the advantage because they are camouflaged against the light-coloured bark of the trees. Any dark-coloured moths in the population would be easy prey for birds. However, in polluted forests close to cities the bark of trees is darker in colour and the dark-coloured moths have the advantage of camouflage, so the light-coloured moths are more likely to be eaten. This change in the physical environment has led to an increase in the number of dark-coloured moths and a decrease in the number of light-coloured moths in the populations that inhabit these forests.
Bk Ch6 S6.1 Q2
Explain how transitional forms of organisms in the fossil record support the theory of evolution. Outline two animal examples and one plant example.
Bk Ch6 S6.1 A2
Transitional or intermediate forms of organisms have structural similarities with organisms that preceded them on Earth as well as with more recent forms. This suggests that one group of organisms evolved from another or from a common ancestor. For example, Archaeopteryx was a flying dinosaur that lived during the Jurassic Period. The presence of feathers on Archaeopteryx along with other characteristics shared by birds and reptiles leads scientists to believe that modern birds evolved from the reptiles. Crossopterygian fish that lived about 400 million years ago are another example. These fish could obtain oxygen from the air and had bones in their fins, suggesting that they were mobile on the land. The existence of this transitional form supports the theory that amphibians evolved from fish through this line. The now-extinct seed ferns are an example of a transitional form of plants. Although their general structure resembled modern ferns they produced seeds attached to leaves and along with other features are now thought to be more closely related to gymnosperms.
Bk Ch6 S6.1 Q3
aExplain what is meant by biogeography.
bOutline how the biogeography of the waratah lends support to the theory of evolution suggested by Alfred Wallace.
cIs the evolution of the waratah an example of divergent or convergent evolution? Explain your answer.
Bk Ch6 S6.1 A3
aBiogeography is the study of the distribution of living organisms.
bAccording to Alfred Wallace the plants and animals of Asia evolved along separate lines from those of Australia and New Guinea. His theory is supported by the biogeography of the waratah. The three different genera of the waratah are distributed in New Guinea and along the eastern coast of Australia as well as in forests in South America, but none occur in Asia.
cDivergent evolution. The presence of a number of closely related genera on landmasses in close proximity to one another suggests that at some time in history the landmasses were connected and that the different genera represented today evolved from a common ancestor.
Bk Ch6 S6.1 Q4
Use Figure 6.10 to explain how the embryology of organisms provides important information in our understanding of evolution.
Bk Ch6 S6.1 A4
Similarities in the embryology of different organisms can provide important information about the relationships between the organisms. For example, in the diagram shown, the presence of aortic arches in sharks, amphibians and humans is quite different in the adult form of each kind of organism. However, they all show a basic pattern of six pairs of aortic arches in the embryonic stage. Different numbers of these paired arches are lost during development in each of the different kinds of organisms. This and other similarities in embryology suggest that these organisms are related by a common ancestry.
Bk Ch6 S6.1 Q5
Study the forelimbs of the vertebrates shown in Figure 6.11. Explain what your observations suggest about the relationship between the different organisms.
Bk Ch6 S6.1 A5
The forelimbs of each of the animals shown have five digits in each limb. This comparative anatomy suggests that the organisms are related to one another and probably shared a common ancestor.
Bk Ch6 S6.1 Q6
aExplain how biochemistry is used to analyse evolutionary relationships.
bOutline how biochemical studies suggest a relationship between humans and other mammals.
Bk Ch6 S6.1 A6
aBiochemistry can be used to analyse evolutionary relationships by comparing the degree of molecular similarity. The greater the degree of similarity of certain molecules between species the closer the evolutionary relationship.
bAnalysis of amino acid sequences between humans and other primates reveals a greater degree of similarity between humans and chimpanzees than between humans and gorillas, gibbons, monkeys and other mammals. This suggests that humans are more closely related to chimpanzees than to these other organisms.
Bk Ch6 S6.1 Q7
Explain the difference between evolutionary convergence and evolutionary divergence. Use examples to illustrate your answer.
Bk Ch6 S6.1 A7
Convergent evolution is the term used to account for the presence of similar adaptations to similar environmental pressures in unrelated species. For example, the flippers of dolphins and seals are similar in appearance and function but these organisms are not closely related. The presence of similar modified limbs is an adaptation to a similar environment. Divergent evolution begins with a single ancestral species that has been geographically dispersed and the different populations have been subject to different environmental pressures, resulting in the evolution of different but related species. Darwin’s finches are an example. Different species of finch inhabit the different islands of the Galapagos archipelago. The different environmental pressures on the different islands account for the differences between these closely related species.
6.1 Evidence for evolution QApage 1 of 2
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