Exercises: Evolutionary theories

Explain what biological evolution is and what it means to state that present-day species descend from other species of the past.

Summarise Lamarck's two main ideas (use and disuse of organs and inheritance of acquired characteristics) and explain how he interpreted the long neck of giraffes.

Summarise the key ideas of Darwinism: variation among individuals, the struggle for existence and natural selection of the best adapted.

Look at the diagram, which shows two different explanations (A and B) of how giraffes came to have long necks. State which corresponds to Lamarck and which to Darwin, and point out the fundamental difference between the two regarding what is inherited.

What does Neo-Darwinism or the synthetic theory add to Darwin's ideas? Explain how genetics (mutations and inheritance) completed the theory of natural selection.

Name and briefly describe three lines of evidence for evolution: fossils, comparative anatomy (homologous bones) and biogeography.

On a small island, a prolonged drought wipes out soft-seeded plants, and only those with large, hard seeds survive. A team of biologists measures beak depth in a finch population before the drought (mean of 8.8 mm) and one year later among the survivors (mean of 9.8 mm). A) Justify using the synthetic theory what has happened in the population at the phenotypic and genotypic levels. B) A student comments: "The finches had to strive to crack the hard seeds, which caused their beaks to grow 1 mm during their lifetime, and that is why their offspring were born with larger beaks." Refute their statement by pointing out why it falls into Lamarckism and how natural selection actually operates.

In an English industrial region, the proportion of dark (carbonaria) and light (typica) peppered moths (Biston betularia) was measured. After anti-coal pollution laws were passed in 1960, records showed: in 1960, 90% dark moths; in 1980, 50%; and in 2000, only 10%. A) Interpret these data by identifying the natural selection factor and explaining why the allele frequencies changed. B) Predict with reasoned arguments what would happen to the proportion of both varieties if a new nocturnal predator were introduced that locates its prey exclusively by smell and not by sight.

Analyze the following two situations: 1) If the tails of mice are surgically amputated for several successive generations, all offspring in subsequent litters continue to be born with intact tails. 2) If the testes of male mice are irradiated with X-rays, many of their offspring are born with tail malformations. A) Justify these results based on the difference between somatic cells and germline cells. B) If a bodybuilder were to use gene therapy to modify the DNA of their arm muscle fibers to induce hypertrophy, would their descendants inherit that muscle mass? Justify your answer.