Inheritance Variation and Evolution

Maple syrup urine disease (MSUD) is a rare inherited human condition. The allele for MSUD is recessive. What is a recessive allele?

Figure 1 shows the inheritance of MSUD in one family. The symbol for a male with MSUD is not in the key. What would this symbol represent?

Persons 1 and 2 in Figure 1 have a child with MSUD and some children without MSUD. Complete the Punnett square (Figure 2) to show the possible genotypes of the children. Use the following symbols: N = allele for not having MSUD n = allele for MSUD

What is the phenotype of a person with the genotype Nn?

What percentage of the offspring in the Punnett square will have MSUD?

Which scientific term describes the allele N?

Alleles are found in the nucleus of a cell. What chemical substance are alleles made from?

Living organisms can be classified into groups. Trilobites are animals that lived in the sea 400 to 500 million years ago. Table 3 gives the classification of two species of trilobite. Complete the table by choosing the correct classification group that comes before Phylum.

Complete Table 3 by choosing the correct classification group that comes between Family and Species.

Which scientist invented the classification system given in Table 3?

What is the binomial name of trilobite A? Use information from Table 3.

A scientist made the hypothesis: 'Organism B may have evolved from organism A.' A scientist studies two fossils, Fossil A and Fossil B. Fossil A is found in a rock layer 50 metres deep. Fossil B is found in a rock layer 20 metres deep. Both fossils have similar body structures, but Fossil B has a more complex skeleton. What two pieces of evidence support the scientist's hypothesis?

Trilobites are animals that lived in the sea. Complete the sentences about how the fossils of trilobites A and B were formed. The animal dies and falls to the sea bed. The animal is buried in __________.

The __________ of the animal decay.

The remains which do not decay are replaced by __________.

Trilobites A and B are now extinct. Give three possible causes of extinction.

Evolution of new species occurs by mutation and natural selection. What is a mutation?

Describe the process of natural selection.

Which scientists suggested the theory of evolution by natural selection?

The hoverfly and the wasp are insects with bright yellow and black markings. The wasp has a sting to defend itself against predators, but the hoverfly does not have a sting. Hoverflies and wasps live in the same habitat. Explain how having yellow and black markings helps the hoverfly survive.

Some human disorders are inherited. Polydactyly is an inherited disorder where a person has extra fingers or toes. Polydactyly is caused by a dominant allele. What is a dominant allele?

Cystic fibrosis (CF) is another inherited disorder caused by a mutation. The mutation occurs in a gene called CFTR. For the CFTR gene, one allele in every 50 in the UK population is the cystic fibrosis allele. Explain why only one person in 2500 in the UK population has cystic fibrosis.

Glyphosate is a herbicide used in agriculture. Soya bean plants have been genetically modified (GM) to be resistant to glyphosate. A farmer can increase the yield of soya beans by: - growing GM soya bean plants - spraying glyphosate on the field. Explain how the use of GM soya bean plants and glyphosate can increase the yield of soya beans.

Suggest two reasons why some people are concerned about the use of GM soya bean plants. Do not refer to ethical concerns or religion in your answer.