We have populated ten commonly asked questions with brief solutions in order to guide you through Module 3: Biological Diversity.
Tackling as many questions as possible will prepare you better for your exams.
You can see how you went with the answers at the bottom of the page.
List THREE biotic and THREE abiotic selection pressures.
Outline Charles Darwin’s conclusions about evolution that were based on the observations he made aboard the Beagle.
Explain the difference between convergent and divergent evolution.
In 1935, cane toads were introduced to Australia to hunt insect pests in cane fields. Explain how the toads have acted as a selection pressure on native species.
Darwin concluded that the 13 different species of finch he collected from the Galapagos Islands evolved from a common ancestor that arrived from the mainland.
What type of evolution is this?
a) Divergent evolution
(c) Convergent evolution
(d) Punctuated equilibrium
Explain microevolution using an example.
Describe ONE type of evidence that supports the theory of evolution by natural selection and provide an example.
Black bears can store extra body fat and have the ability to undergo hibernation to preserve energy when food is unavailable. What type of adaptation is this?
(a) Behavioural adaptation
(b) Convergent evolution
(c) Structural adaptation
(d) Physiological adaptation
Outline the difference between punctuated equilibrium and gradualism.
Describe a modern example of evolutionary change.
Biotic factors include:
- Sexual selection
Abiotic factors include:
- Light availability
- Water availability
- Species change (evolve) over time.
- Evolutionary change is very slow.
- Variation in species occurs randomly.
- The survival of species depends on their ability to cope in a changing environment in response to natural selection.
- All living species evolved from a common ancestor through speciation.
Convergent evolution is the process where unrelated species evolve to become more similar structurally and behaviourally as a result of exposure to similar selection pressures such as food availability.
Divergent evolution is the process where two or more closely related populations of a species become less similar over time. Divergence can occur to a point where related populations evolve into different species in a process known as speciation. Divergent evolution can occur when the different populations are exposed to different selection pressures such as climate.
Cane toads are poisonous throughout their lifecycle and thus have few predators. For the predatory snakes that eat them, the toads have acted as a selection pressure. Snakes with small heads are less likely to attempt to eat the large toads and so more likely to survive and reproduce. As a result, there has been a decrease in head size in some predatory snake populations.
Some populations of small predatory mammals have also become more tolerant of cane toad toxin over time, as those most sensitive to the toxin are less likely to survive and reproduce.
(a) Divergent evolution
One species has become many species over time. Based on the information provided in the question it is not possible to tell if the divergence occurred gradually or whether punctuated equilibrium has occurred.
Microevolution is the accumulation of small evolutionary changes in species over millions of years. An example is microevolution in the horse which has undergone structural changes due to selection pressures such as food availability and predation.
Modern day horses run on a single toe instead of multiple toes as it is more efficient allowing them to run faster away from predators. Fossils reveal that the extra toes shrunk and were lost very gradually over time.
Horses molars also became gradually larger and flatter over time to efficiently breakdown the tough grasses that became more abundant.
These microevolutionary changes in the anatomy of the horse teeth and toes have allowed the modern-day horse to survive selection pressures and adapt better to their environment.
The evidence that supports the theory of evolution includes: palaeontology, comparative anatomy, comparative embryology, biogeography and biochemical evidence.
Palaeontology refers to the study of fossils – the preserved remains or traces of animals, plants and other organisms that lived in the past.
Transition fossils are fossils with characteristics from two different groups of organisms. Archaeopteryx is a transition fossil that has features of both birds and reptiles.
This supports the theory of evolution by natural selection as it suggests that birds and reptiles once shared a common ancestor before diverging into separate groups.
(d) Physiological adaptation
Charles Darwin assumed that evolution by natural selection occurs very gradually and at a steady rate.
Punctuated equilibrium is the theory that evolution in species occurs rapidly as a result of a sudden environmental change, which is then followed by a period of stability. The species change relatively quickly at first and then there is little change when the environment is stable.
A modern example is the evolution of antibiotic-resistant strains of bacteria.
- When an antibiotic is applied to a population of bacteria it acts as a selection pressure
- There is natural variation in the population of bacteria where some bacteria are resistant to the antibiotic while others are not.
- The bacteria with the favourable antibiotic-resistant trait will survive and reproduce, the others will die.
- The result is a new strain of antibiotic-resistant bacteria.
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