Species & Taxonomy (AQA A Level Biology)

The domestic dog, Canis familiaris, and wolves belong to the family Canidae. Complete Table 1 below to show the classification of the domestic dog.

 Table 1

It is still debated as to whether dogs and wolves are entirely different species or subspecies. It has been suggested that some wolves have bred with domestic dogs to produce fertile offspring. Suggest three different methods that scientists could use determine if the two animals are different species.

The classification seen in Table 1 is described as a hierarchical system. Explain what is meant by this.

The scientist decided to compare the DNA of domestic dogs and wolves. Name two other types of sequence data they could have used.

Taxonomists use specific principles when classifying organisms into different groups.

Explain what these are.

Cytochrome c is a respiratory protein consisting of roughly 100 amino acids. Haemoglobin is a quaternary protein found in red blood cells consisting of over 400 amino acids. Explain which protein is a better choice for use in the construction of a phylogenetic tree that spreads across plantae, fungi and animalia.

Scientists studied the amino acid sequence of cytochrome c in five different animals.
The number of differences in the amino acid sequence were recorded and compared with human cytochrome c.

Table 1 below shows their results.

Table 1

Explain how these results suggest that the monkey is the most closely related to humans.

An assistant who looked at the results in Table 1 suggested that dogs were more closely related to ducks than to any of the other animals. Is this conclusion credible? Justify your answer.

Figure 1 below shows how some animals with antlers and horns have been classified.

Figure 1

State how many different orders are present in Figure 1?

Describe one similarity and one difference between a phylogenetic system and a simple hierarchy.

According to Figure 1 to which family and genus do the red deer belong to?

The offspring produced from breeding a horse with a donkey is known as a mule. The body cells of a horse contain 64 chromosomes while the body cells of a donkey contain 62 chromosomes. Predict whether mules are fertile or infertile. Explain your answer.

Specimen A and specimen B are small rodents.

Scientists wanted to determine whether specimen A and B are different species of rodent, or different forms of the same species.

In order to do this, they caught large numbers of each specimen type. For each rodent they recorded its sex, mass, tail length and took a sample of blood.

Table 1 shows some of the results.

Table 1

Explain how the standard deviation can help with the interpretation of this data.

Evaluate if the data in Table 1 supports the hypothesis that the two specimens are different forms of the same rodent species.

The scientists analysed the amino acid sequences of the blood protein samples that were taken from the different specimens. Explain how these sequences could provide evidence to determine if specimen A and specimen B are different species.

When looking at a specific protein 13, the scientists noticed that specimen A and specimen B both had the same amino acid sequence for protein 13. However, upon further investigation they discovered they had different DNA sequences for protein 13.Explain how this is possible. 

The scientific names of three great apes are shown in Table 1 below.

Table 1

Explain what the scientific names suggest about how the great apes are related to each other.

Describe what Figure 1 below represents. Explain your answer.

Figure 1

The orangutan also belongs to the Hominidae family. Use the information provided in Table 1 to sketch out Figure 1 and add the orangutan. The orangutan can be represented by the letter X.

Name the highest-ranking taxonomic group in the biological classification system.

Explain how courtship behaviour prevents mating between different species. 

Figure 1 shows the courtship behaviour of the brown widow spider, Latrodectus geometricus. When the female drives the male away, he will resume courting from an earlier stage of the sequence. 

Figure 1

Suggest why males who have been driven away by the female may resume courtship from an earlier stage. 

The courtship sequence displayed by males is an energetically costly display that can last for several hours before the females decide to mate. Explain why the female brown widow spider might drive the male brown widow spiders away during a courtship sequence.

The brown widow spider population has a disproportionately larger female population. Use the information from Figure 1 and the question to suggest why. 

Ailuropoda melanoleuca, the giant panda, and Ailurus fulgens, the red panda, are both native to China. The following evolutionary evidence suggests that these two panda species are closely related.

• They live in similar environments;
• They both digest bamboo as a primary source of food;
• They both have a pseudo-thumb (a sixth digit) used to grip and shred food such as bamboo.

Table 1 shows the differences between a comparable sequence of mitochondrial DNA of four different mammals. 

Table 1

A group of students concluded that the raccoon is most closely related to the black bear. Use Table 1 to evaluate this conclusion. 

The base sequences of a different section of mitochondrial DNA (not those shown in Table 1) were analysed and the number of differences was counted between the giant panda DNA and the DNA of the other mammals, as shown in Table 2. 

Table 2

Mitochondrial DNA is estimated to mutate 1.87 x 10^-7 mutations site^-1 yr^-1. Use the data from Table 2 to calculate how long ago the giant panda and the red panda evolved from a common ancestor. Give your answer in standard form and to three significant figures. 

The red panda has 36 chromosomes per somatic cell whereas the giant panda has 42 chromosomes. Offspring born when these two species mate are infertile. Suggest why. 

Explain how genome sequencing can be used to deduce evolutionary relationships between organisms, such as the giant panda and red panda. 

Dolphins and whales belong to the Cetaceans, an order of carnivorous aquatic mammals. There are two proposals put forward regarding the closest living relative of the cetaceans, as shown by R and S, in Figure 1. 

Figure 1

Describe the differences and similarities between the information in diagram R and S. 

Casein is a protein found in the milk of most mammals. Scientists investigated the differences in the DNA base sequence of the gene coding for casein in the mammals shown in question 3a). Figure 2 shows their results. 

Figure 2

Using the information in Figure 2, debate whether Diagram R or S, from Figure 1, represents the current accepted theory regarding the evolutionary origin of the cetacean. 

More recently, scientists decided to merge the orders Cetacea and Artiodactyla into a single order called Cetartiodactyla. Opinion is divided in the scientific literature about whether this change should have been made. Explain how this provides evidence for the tentative nature of taxonomy. 

Use the information from part a) to identify the four taxonomic group headings to which dolphins and whales both belong. 

The point in time when a species diverged from its most recent ancestor can be measured by measuring the percentage difference in DNA bases as these two features are proportional when measured over long periods of time. 

There is a 0.7% difference between the DNA of the pygmy chimpanzee and common chimpanzee, which diverged 3 million years ago. Human DNA differs from both the pygmy chimpanzee and common chimpanzee by 1.6%. 

Calculate how long ago humans diverged from the chimpanzee. State your answer to an appropriate number of significant figures. 

Describe how immunological comparisons can be used to identify the closest living relative of humans. 

Humans have a binomial name of Homo sapiens. Fossil evidence shows that, at one time, there were other species, Homo habilis and Homo erectus, living concurrently with humans. Some of the Homo species mated with other Homo species and produced children, but scientists still considered them as separate species. Suggest why.

There are no other living members of the Homo genus, yet scientists are able to create authentic structures and models that represent how they probably looked. Explain how scientists are able to do this. 

There are 18 different species of penguin, living almost exclusively in the Southern hemisphere. They feed on fish, squid, krill and other sea animals. 

A group of scientists wanted to find how closely related a group of different species of penguin (surviving and extinct) were and used the method of DNA hybridisation. This is a process where a single strand of DNA is taken from each species and mixed with the opposite strand from another species. Time is allowed to form a hybrid, double stranded DNA molecule by complementary base pairing. 

Table 1 shows the results of the scientists' investigation. 

Table 1

The scientists measured the temperatures at which each sample of hybrid DNA separated into single strands. Explain how the information obtained could be used to find the percentage of hybridisation. 

Explain what the data in Table 1 shows about the evolutionary relationships between the different species of penguin. 

Explain why, in Table 1, two members of P. antarcticus (chinstrap penguin) did not have 100% DNA hybridisation. Do not include sources of measurement error in your answer.  

The data in Table 1 includes DNA analysis from an extinct species, Aptenodytes ridgeni (Ridgen’s penguin). Suggest how the scientists managed to gather data from an extinct species.