17. Fossil Record & Biogeography

What is the principle of superposition used for in geology?

It states that in a series of stratified sedimentary rocks, the lowest stratum is the oldest, allowing for relative dating.

According to the geologic time scale, during which period did the first mammals appear?

The Triassic period.

What major evolutionary event occurred during the Quaternary period?

The evolution of humans.

The process of measuring the actual ages of rocks using the decay of unstable atoms is known as _.

radiometric dating

What is the definition of an isotope's 'half-life'?

The amount of time it takes for half of the parent radioactive material to decay into a daughter product.

What are the two fundamental assumptions made when using radioactive dating?

That radioactive decay rates are constant over time and are not affected by physical stresses.

How did counting daily growth rings in ancient corals help validate radiometric dating?

Corals dated to 380 mya showed approximately 400 daily growth rings per year, matching predictions of Earth's faster rotation at that time.

What is one of the four key predictions that evolutionary theory makes about the fossil record?

Complex adaptations should appear in later (younger) geological strata.

Evolutionary theory predicts that the youngest fossils we find should be the most similar to _ species.

living

What does evolutionary theory predict we should be able to see within fossil lineages over time?

Cases of evolutionary change within a single lineage.

What did Darwin identify as the primary reason for the 'extreme imperfection of the geological record'?

That geological formations are separated from each other by wide, unrecorded intervals of time.

Why is it a 'wholly false view' to look for fossils directly intermediate between two modern species like a horse and a tapir?

We should look for forms intermediate between each species and a common, unknown ancestor, not between the modern descendants.

What is one reason Darwin gave for the rarity of fossils?

Organisms with no hard parts cannot be preserved, or shells and bones often decay before they can be fossilised.

According to Darwin, why might a complete series of transitional fossils be rare even in a continuous rock formation?

The species undergoing modification would have had to live in the exact same area while the deposit accumulated, which is unlikely due to migration.

A species showing a mixture of traits from organisms that lived both before and after it is known as a _ species.

transitional

What creature is a key transitional fossil showing features of both reptiles and birds?

Archaeopteryx.

What reptilian features did the transitional fossil Archaeopteryx possess?

Reptilian teeth, a long bony tail, and a theropod-like pubis.

What is one of the key evolutionary changes seen in the fossil record of whales?

The shifting of the nasal opening backwards towards the position of a modern blowhole.

What are the three main lessons that the fossil record teaches us about evolution?

It confirms gradual change, lineage splitting, and the existence of transitional forms.

The fossil record shows that transitional forms are found precisely where they should be in the geological timeline. What famous example would falsify this pattern if found in Precambrian rocks?

A Precambrian rabbit.

The fossil record demonstrates that evolutionary change almost always involves the _ of old structures into new ones.

remodelling

What is the study of the geographical distribution of species on Earth called?

Biogeography.

What term describes species that are found in one specific geographic location and nowhere else?

Endemic.

What is a characteristic pattern of life on isolated oceanic islands?

They have many unique, endemic species but are missing entire major groups of animals like native land mammals or amphibians.

What was Darwin's 'first great fact' of biogeography?

That neither the similarity nor the dissimilarity of inhabitants of various regions can be explained by their physical conditions alone.

What was Darwin's 'second great fact' of biogeography concerning barriers?

That geographic barriers to free migration are closely related to the differences between the species of various regions.

What was Darwin's 'third great fact' of biogeography regarding continental species?

That species on the same continent show an affinity (are related), even if they live in very different habitats.

What imaginary line demarcates the distinct faunal realms of Asia (Oriental) and Australia?

Wallace's Line.

Why do distant deserts in the Americas and Africa have plants that look superficially similar but are fundamentally different?

This is due to convergent evolution, where similar selection pressures lead to similar adaptations in unrelated species.

What is the key difference between the spines of cacti (Americas) and the spines of euphorbs (Africa)?

Cacti spines are modified leaves, whereas euphorb spines are modified stipules.

The evolution of similar forms and ecological roles in different lineages, such as placental and marsupial mammals, is known as _.

convergent evolution

What geological theory, unknown to Darwin, provided a mechanism for explaining many biogeographic puzzles?

Plate tectonics (continental drift).

Around 245 million years ago, Earth's continents were united in a single supercontinent called _.

Pangea

Pangea split into two large landmasses: _ in the north and Gondwana in the south.

Laurasia

Term: Vicariance

The geographical separation of a population, typically by a physical barrier like an ocean or mountain range, which can lead to speciation.

How does continental drift explain why nearly all of Australia's native mammals are marsupials?

Marsupials evolved and spread across Gondwana, reaching Australia before it separated, where they then diversified in isolation from placental mammals.

Based on continental drift, where did scientists predict they would find marsupial fossils that linked South American and Australian populations?

Antarctica.

What prediction, based on the relatedness of humans to Old World monkeys and apes, did Darwin make about the location of early human fossils?

That our early progenitors lived on the African continent.

Why do oceanic islands often lack native freshwater fish, amphibians, reptiles, and land mammals?

These groups are poor at dispersing across large expanses of salt water, unlike plants, birds, and insects.

The profusion of many similar, related species that have evolved from a single colonising ancestor on an island is known as an _.

adaptive radiation

The diverse group of Hawaiian honeycreepers and Darwin's finches on the Galápagos are classic examples of what evolutionary phenomenon?

Adaptive radiation.

A key observation in island biogeography is that the animals and plants on oceanic islands are most similar to species found where?

On the nearest mainland.

What did Darwin's experiments, such as immersing seeds in seawater, demonstrate about life on oceanic islands?

They demonstrated that the types of organisms found on islands (plants, insects) were the ones capable of surviving long-distance dispersal.

The fossil record shows a gradual, though erratic, increase in the number of pygidial ribs in five groups of _ over three million years.

trilobites

The first photosynthetic bacterial fossils appear in the _ eon.

Precambrian

During which geologic era did dinosaurs diversify, followed by their extinction?

The Mesozoic Era.

The Cenozoic Era is often called the Age of _.

Mammals

What major extinction event marks the boundary between the Permian and Triassic periods?

Major extinctions (the Permian–Triassic extinction event).

According to the source, what happened during the Ordovician period?

A sudden diversification of metazoan families.

What key evolutionary step for plants occurred during the Silurian period?

The appearance of the first vascular land plants.

The first amphibians appeared in the _ period.

Devonian

The evolution of the first reptiles took place during the _ period.

Carboniferous (specifically, the Pennsylvanian subperiod).

Flowering plants first appeared in the fossil record during the _ period.

Cretaceous

What isotope is used for dating relatively recent organic remains, with a useful range of 100 to 30,000 years?

Carbon-14.

For dating very old rocks (100,000 - 4.5 billion years), what parent-daughter isotope pair is commonly used?

Potassium-40, which decays into Argon-40.

Why did Darwin believe the Earth had to be ancient?

He observed slow geological processes like erosion and reasoned that a vast amount of time was necessary for these changes and for gradual evolution by natural selection.

What was Darwin's crude estimate for the time it took for the denudation of the Weald in England?

Over 300 million years.

What common misunderstanding about transitional fossils is exemplified by the 'dog-cat' or 'cat-rat' argument?

The idea that evolution predicts chimeras directly linking two modern species, rather than species with traits of a common ancestor.

How does the co-occurrence of fossil ancestors and their descendants in the same geographic region support evolution?

It suggests species in an area are descendants of earlier species from that same place, such as fossil kangaroos being found in Australia.

What often happens to non-native species when introduced to oceanic islands by humans?

They often thrive and outcompete native species, showing the islands are perfectly suitable for the groups that were naturally absent.