IB Biology SL D4.1 Natural selection Question Bank

Mice (Mus musculus) have various defence systems against predators such as foxes (Vulpus vulpus) or stoats (Mustela erminea). The mice release specific alarm compounds when under threat that serve as danger signals for other mice. Predators also release scents that the mice can detect.

In one study, mice were exposed to paper soaked in compounds taken from other mice, foxes or stoats in a test chamber. The scientists then measured the reaction of three different groups of neurons used in smelling: G1, G2 and G3, as shown in the diagram.

The percentage of G1, G2 and G3 neurons responding to the mouse, fox and stoat compounds, as well as a control compound, are shown in the chart.

A group of nine semi-wild Asian elephants (Elephas maximus) from an elephant camp in Myanmar were trained to pull two ends of a single rope to get access to food in food trays located on a table behind a barrier. When both elephants pulled the rope, the table moved towards them making the food trays accessible. The task required two elephants to work together in cooperation for mutual benefit to obtain food.

The graph shows the rate of cooperation between pairs of elephants in pulling the rope when there were two food trays, one at each end of the table (as shown in the diagram), or when there was one food tray placed in the centre of the table. The cooperation rate was the number of successful cooperative attempts divided by the number of all attempts in one session. The experiment was repeated for many sessions on successive days.

Several studies have been undertaken to determine whether there is an evolutionary explanation for menopause, the time when reproductive capacity stops in women. Two contemporary hunter-gatherer societies were studied. The graph shows what percentage of women survive to each of the ages given.

Populations evolve by natural selection due to interactions with the environment and other species within the ecosystem.

Sickle-cell anemia is a disease caused by a base substitution mutation, where GAG has changed to GTG. The distribution of the sickle-cell allele is correlated with the incidence of malaria in many places, as shown by the map of Africa.

What is required for natural selection to occur?

I. Acquired characteristics
II. Advantageous characteristics
III. Genetic variation

By the end of the 19th century in England, the dark form of the moth Biston betularia formed up to 98 % of the total population in industrial areas. From 1970, the percentage of dark forms decreased significantly. What is an explanation for the decrease?

When might a favourable variation become unfavourable?