Evolutionary theories

Explain what fixism or creationism claimed about the origin and the permanence of species, and why fossils of animals that no longer exist were a problem for that idea.

During his voyage on the Beagle, Darwin made observations that made him doubt fixism. Name two of them (for example, fossils of extinct species similar to present-day ones, or different species on each Galápagos island) and explain what each one suggested to him.

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.

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.

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

Define adaptation and give two examples of adaptations of living things to their environment, explaining what the advantage of each one consists of.

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.

Explain what a fossil is, how it usually forms and what two kinds of information it provides about evolution: what living things of the past were like and how old the rocks containing them are.

Distinguish between homologous organs and analogous organs using the wing of a bird, the wing of a bat, the human arm and the wing of a butterfly, and explain which of the two cases is evidence of evolutionary kinship and why.

Explain what vestigial organs are and give two examples (for example, the human appendix or the remains of a pelvis in whales), reasoning why they constitute evidence of evolution.

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.

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.

When studying a series of marine strata spanning 12 million years, a paleontology team discovers that a mollusk species maintains exactly the same morphology for 10 million years. However, in a layer representing an abrupt change of barely 40 000 years, the species disappears and two very distinct derived species emerge, remaining stable for the rest of the time. A) Compare how Darwinian phyletic gradualism and Gould and Eldredge's punctuated equilibrium theory would explain this fossil record. B) Justify why the "rapid" pace supported by punctuated equilibrium does not contradict natural selection or imply instantaneous changes.