Exam 34: Mechanisms of Evolution

Two closely related orchid species inhabit the same region of rainforest and have mature pollen at the same time. Both orchids are pollinated by wasps, and in the same manner. The flower of the orchid mimics the shape of a female wasp and releases a chemical scent that imitates the pheromone of a female wasp. Male wasps are attracted by the pheromone and, while attempting to mate with the flower, are doused with pollen that they will deposit on another orchid flower the next time they are similarly deceived. However, one orchid species imitates, and is pollinated by, one species of wasp and the other orchid species imitates, and is pollinated by, a different species of wasp. The male wasps are very particular in their preferences and are never attracted to the 'wrong' orchid. Which of the following types of reproductive barrier separates the two orchid species?

The Hardy-Weinberg principle states that

Which of the following reproductive isolating mechanisms acts after fertilisation?

In a chorus of male frogs of one species, which would be considered by evolutionary biologists to be the fittest?

A small population of wallabies lives on an island that was once connected to the mainland. Over many generations, several alleles have completely disappeared from the island population, although they are still present on the mainland. If the gene locus we were investigating contributed to the wallabies' efficient use of a particular food resource, the alleles may have disappeared from the island population due to

Jean-Baptiste Lamarck published the first modern theory of evolution. He theorised that

A tropical palm tree population is identified on an isolated atoll that appears to be Areca triandra. However, they are much shorter than other members of this species and have a broader stem. Scientists speculate that this morphology is due to sea spray stunting the trees growth. If controlled experiments reveal this is NOT the case, what does this suggest?

Which of the following is NOT consistent with the theory of natural selection?

The biological species concept defines species as potentially interbreeding populations. One complication of such a definition is that

The ultimate source of all genetic variation is

Persistent use of a drug against disease-causing bacteria can result in populations that are resistant to the drug. Which of the following is the best explanation for the appearance of these drug-resistant bacterial strains?

Cryptic species are

A particular species of frog has a broad geographic distribution across southern Australia. In the breeding season, males congregate at marshy areas and call to attract females. Young frogs do not disperse widely from their natal marsh. Through time, the mating call of male frogs in the north-western region of the distribution gradually diverges from the 'normal' call, until females from the rest of the species range no longer recognise and respond to the call. Similarly, females from the north-western region no longer recognise male frogs from other parts of the species distribution as potential mates. This would be considered an example of

Most random mutations

In adaptive evolution, selection

Mutation

Using 'Insecticide A' to control insect pests can lead to selection for alleles that convey resistance. Agricultural scientists have discovered that the development of resistance, in a population of insect pests, can be hindered by rotating the use of 'Insecticide A' with other pesticides. A reasonable explanation for the effectiveness of this strategy is that

In sexual selection, why do males often compete for female reproductive resources?

X and Y are two species of grasses, each with a diploid number of 20. A new sexually reproducing species, Z, arises as a polyploid following hybridisation between X and Y. The diploid number of Z would be

According to the biological species concept, the study of speciation is equivalent to