SCSA Human Biology Evidence for evolution

Amino acid sequences accumulate mutations over time, making them highly useful for comparing genetic divergence and determining evolutionary relationships among different mammals.

Protein sequences provide valuable molecular data for constructing phylogenetic trees, as comparing their similarities and differences helps identify how closely related different species are.

Variations in bone structure (homologous structures) provide important morphological evidence that helps biologists distinguish and group different mammalian lineages.

This is incorrect because specimens should not be exposed to decomposers (II). Decomposers break down organic matter, which prevents fossilisation.

This is incorrect because both exposure to decomposers (II) and disturbance (V) would destroy the specimen before it has a chance to fossilise.

This is incorrect because exposure to decomposers (II) and physical disturbance (V) actively destroy remains, making fossilisation impossible.

Although Potassium-40 decays into both Argon-40 and Calcium-40, the potassium-argon dating method specifically measures the ratio of Argon-40 to Potassium-40, not Calcium-40.

The potassium-argon dating method relies on the radioactive decay of Potassium-40 into Argon-40, not the isotopes Potassium-41 and Argon-41.

This method involves the parent isotope Potassium-40, not Potassium-41, and specifically compares it to Argon-40 rather than a combination of Argon-40 and Calcium-40.

Measuring the depth of index fossils is a method of relative dating, not absolute dating using radioisotopes.

Carbon-14 dating is used for organic materials, not volcanic rocks, and its relatively short half-life makes it unsuitable for dating ancient geological formations.

Measuring the depth of rocks relies on the principles of stratigraphy for relative dating, which does not involve the use of radioisotopes.

While some surviving species will diverge, not all will recover. Many surviving lineages may still decline or remain marginalized due to severely disrupted ecosystems.

Mass extinctions are typically triggered by rapid, catastrophic changes to the global climate or environment, rather than constant or stable conditions.

Mass extinctions do not affect all species equally. Species with specific vulnerabilities, specialized diets, or limited habitats are much more likely to perish than adaptable generalists.

Index fossils must have existed for a relatively short period of geological time, not a long period, in order to accurately pinpoint the age of the rock layer they are found in.

This describes transitional fossils, which show evolutionary links between ancestors and descendants, rather than index fossils used for dating.

This describes trace fossils, such as footprints or burrows, which provide indirect evidence of life, rather than index fossils which are actual remains used for chronological dating.

This would be true after only one half-life (1.25 billion years), not 3.75 billion years.

This would be the amount remaining after two half-lives (2.5 billion years), where $(1/2)^2 = 1/4$.

Radioactive decay is an exponential process, meaning a fraction of the parent isotope will always remain; it never completely reaches zero.

While a clade is a subset of a larger group, 'subgroup' is a generic term and does not specifically define a lineage consisting of an ancestor and all its descendants.

A population refers to a group of individuals of the same species living in a specific geographic area at the same time, not a complete evolutionary lineage.

A community is an ecological term describing a group of interacting populations of different species in a shared environment, not a group defined by ancestry.

Incorrect. Fossils are specifically the remains or traces of previously living organisms, not just any inanimate object.

Incorrect. While preserved bones are a common type of fossil, this definition is too narrow because fossils also include shells, leaves, footprints, and other traces of life.

Incorrect. Human-made artefacts are archaeological items, not fossils. Fossils must be the remains or traces of the organisms themselves.

Incorrect. Green algae are simple aquatic organisms that evolved long before complex vertebrates like fish.

Incorrect. Mammals first appeared in the Triassic period, which predates the emergence of flowering plants (angiosperms) in the Cretaceous period.

Incorrect. Green algae evolved over a billion years ago, making them much older than the emergence of fish and mammals.

Potassium-argon dating is a radiometric dating technique, which means it provides an absolute date rather than a relative one.

This limitation applies to radiocarbon (Carbon-14) dating. Potassium-argon dating is used to date volcanic rocks, not organic material.

Potassium-argon dating does provide a reliable statistical measure of age, complete with a margin of error, for the volcanic rocks it dates.

Cladistics assumes that all organisms within a group are related by descent from a common ancestor, rather than having independent origins.

Cladistics relies on the assumption that characteristics change over time, allowing lineages to be distinguished by derived traits.

This describes phenetics; cladistics determines relatedness based specifically on shared derived characteristics (synapomorphies), not just the total number of shared traits.

Statement I describes a condition necessary for fossil formation, not a reason why existing fossils are difficult to locate.

Statement IV describes a condition required for a specimen to become a fossil, rather than a reason why they are hard to find once formed.

Statements IV and V describe the conditions necessary for fossil formation, not the challenges associated with locating them.

This is incorrect. After 10,000 years, exactly one half-life would have passed, leaving $1/2$ of the original isotope present, not $1/8$.

This is incorrect. After 20,000 years, two half-lives would have passed ($1/2 \times 1/2$), leaving $1/4$ of the original isotope present.

This is incorrect. After 40,000 years, four half-lives would have passed, which would leave only $1/16$ of the original isotope present.