IB Biology SL A3.1 Diversity of organisms Questions

The land snail Cepaea nemoralis is very common in North America and in Europe.

The base colour of its shell varies between brown, pink and yellow, and also in its intensity. Some shells are unbanded, but most show one to five bands of different width on top of the shell base colour.

In the early 1950s, scientists studied the proportion of colours and banding of C. nemoralis in woods and fields near Oxford, UK, which differed in the type of plants and background colour. Each data point on the graph represents the percentage of yellow base colour shells and unbanded shells in a sample from either one type of wood or field, although other snail colours were present.

Using the data in the graph, distinguish between the distribution of C. nemoralis shells in woods and fields.

Orangutans are closely related to humans.

Outline two recognition features that would show that orangutans are mammals.

The karyogram shows the chromosomes of an orangutan that did not have any chromosome abnormalities.

According to the biological species concept, which of the following indicates that two organisms belong to the same species?

I. They occupy the same ecological niche.
II. They share morphological features.
III. They can crossbreed and produce fertile offspring.

On the islands of the St Kilda chain, off the coast of Scotland, there are small birds called St Kilda wrens (Troglodytes troglodytes hirtensis). They look similar to wrens on the mainland of Scotland (Troglodytes troglodytes indigenus), but they are larger and there are differences in the colour of their feathers.

What is the most likely explanation for these differences?

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells. What can be deduced from this information?

There can be much variation within a single species, such as dogs (Canis familiaris).

Describe how karyotyping can be used to decide if all these dogs are of the same species or not.

What helps make the genome of each human unique?

Analysis of the genome of primates reveals many DNA segments that have been duplicated. It is possible to deduce the stage in evolution at which segmental duplications (SDs) occurred by comparing human and other primate genomes. Human-specific SDs occurred after humans and chimpanzees diverged. Human-chimpanzee shared SDs occurred after the common human-chimpanzee ancestor diverged from gorillas and so on. It is possible to estimate the rates at which SDs occurred during evolution using knowledge of when the primates changed. In the chart the bars indicate numbers of shared SDs and the line shows estimates of the rate of SDs per millions of years (Myr).

Aequorea victoria is a jellyfish that produces green fluorescent protein (GFP) which glows in blue light. The gene for GFP has been isolated and can be used as a marker gene. Plants with the gene incorporated glow when exposed to blue light.

Describe how an open reading frame (ORF) can be identified.