Paleobiology and Macroevolution - Flashcards

Flashcards covering core concepts from paleobiology and macroevolution, including fossilization, dating, continental drift, biogeography, evolution patterns, and development.

What is paleobiology and macroevolution in one sentence?

Paleobiology studies life in the past and macroevolution examines large-scale evolutionary patterns and processes over long timescales.

Why is the fossil record considered an incomplete portrait of life's history?

Because soft-bodied organisms fossilize poorly, many species are rare or locally distributed, some habitats don’t accumulate sediments, and fossils don’t last forever.

Where do most fossils form and why?

Most fossils form in sedimentary rocks where sediments bury and preserve remains over long timescales.

What are strata in geology?

Strata are successive layers of sedimentary rock deposited over millions of years, with younger layers on top of older ones.

What is the process by which minerals replace organic tissue to form a fossil?

Permineralization (mineral replacement) forms fossilized hard structures; other fossils are molds, casts, or impressions.

Why is oxygen-poor (anoxic) environment important for fossil preservation?

Anoxic conditions slow decay and promote preservation of certain organisms and structures.

What percentage of described fossil species represents the total species that have ever lived?

Less than 1% of all species that have ever lived are described as fossils.

List four primary reasons the fossil record is incomplete.

Soft-bodied organisms fossilize poorly; rare or locally distributed species are underrepresented; lack of sediments in some habitats; and fossils do not last forever.

What is radiometric dating?

Dating rocks by measuring decay of unstable isotopes to stable daughter isotopes at a constant rate.

Which rock type is best for radiometric dating and why?

Volcanic rocks, because they contain rocks with easily datable radiometric isotopes and can be reset by melting.

What is the half-life of carbon-14 (14C)?

5,730 years.

Why can't most fossils be dated directly by radiometric dating?

Most fossils are in sedimentary rocks, whereas radiometric dating works best on volcanic/igneous rocks; dating relies on surrounding or associated volcanic layers.

What information can fossils provide beyond morphology?

Data on when lineages proliferated or went extinct, geographical distribution, and indirect data on behavior, physiology, and ecology.

What is the difference between relative dating and absolute dating?

Relative dating orders events in time using strata; absolute dating provides actual numerical ages via radiometric methods.

What is geologic time scale composed of (from largest to smaller units)?

Eon > Era > Period > Epoch.

What are the major units of the Phanerozoic timeline shown in the notes?

Hadean, Archean, Proterozoic, then Phanerozoic with eras and periods.

What is continental drift?

The movement of Earth's continents due to plate tectonics driven by mantle convection.

What is Pangaea?

A supercontinent that existed and later split into the landmasses Laurasia and Gondwana.

What two major landmasses did Pangaea split into around 170 million years ago?

Laurasia and Gondwana.

What are vicariance and dispersal in biogeography?

Vicariance is range fragmentation by external barriers; dispersal is movement away from the origin.

How can we determine whether a disjunct distribution is due to dispersal or vicariance?

By examining lineage history, fossil records, and geological history to see if distributions align with continental breakup (vicariance) or recent colonization (dispersal).

What is a biogeographic realm?

A large geographic region with a distinct assemblage of species sharing a history, e.g., Nearctic, Palearctic, Neotropical, etc.

Why are Australian marsupials so dominant and diverse in Australia?

Because Australia has been geographically isolated for a long time, limiting placental mammals.

What is convergent evolution?

The independent evolution of similar traits in distantly related groups due to similar environments.

Give an example of convergent evolution.

Cacti in the Americas and spurges in Africa that look alike due to similar ecological roles.

What is the ‘genetic toolkit’ in animal development?

A set of conserved homeobox genes (including Hox genes and Pax-6) that regulate body plan development across animals.

What is exaptation?

A trait that evolved for one function but was co-opted for a new function (e.g., feathers evolving for insulation/display then for flight).

What is allometric growth?

Different parts of an organism grow at different rates, leading to changes in form among related species.

What is heterochrony?

Changes in the timing of developmental events, such as paedomorphosis where reproductive maturity occurs while retaining juvenile characteristics.

What is the concept of transiting fossils into new functions via modification of existing structures?

Exaptation: existing features are co-opted for new uses (e.g., forelimbs/feathers evolving for flight).

What is Archaeopteryx and why is it important?

A transitional fossil showing both dinosaur and bird features, supporting feather/flight evolution from dinosaur ancestors.

What evidence supports exaptive origins of feathers and wings in birds?

Fossil feathers across various dinosaurs, filamentous structures, and β-keratin; forelimbs showing feathered features preceding flight.

What is adaptive radiation?

Rapid speciation to occupy multiple ecological niches after a lineage enters an unfilled adaptive zone.

What is background extinction?

The steady, low rate of extinction associated with ongoing environmental change.

What is mass extinction?

A period when a large number of species die out in a geologic short time; examples include Permian and Cretaceous (K-T).

What is the Permian mass extinction?

The most severe extinction event, with >85% of species lost and many major groups affected.

What is the Cretaceous (K-T) extinction hypothesis and evidence?

An asteroid impact likely caused a global dust cloud blocking sunlight; supported by an iridium-rich layer and the Chicxulub crater.

What is the Chicxulub crater?

A large impact crater (~180 km) on the Yucatán Peninsula associated with the K-T extinction.

What role do volcanic eruptions and asteroid impacts play in climate change?

They can inject ash and dust into the atmosphere or molten rock, altering temperature and climate, potentially driving extinctions.

What is the Great Oxidation Event and when did it occur?

A major rise in atmospheric oxygen roughly 2.4 to 2.2 billion years ago, enabling aerobic respiration.

What is the relationship between continental drift and climate change?

Continental drift changes latitude and sea level, which alters climate and glaciation patterns over millions of years.

How can mass extinctions create evolutionary opportunities?

Survivors with adaptive traits or large populations can radiate into vacated niches, increasing biodiversity.

What is the concept of species selection?

Differential replication of species due to their traits, leading to changes in biodiversity patterns.

What is the significance of the horse fossil lineage (Hyracotherium to Equus)?

A classic example of gradual, directional evolution with increasing body size and limb modernization for faster running.

What is peopling of the genetic toolkit and its significance for evolution?

Despite diverse morphologies, many animals share the same core regulatory genes that guide development, enabling diverse body plans.

Why are transitional fossils important?

They support the idea of gradual or punctuated change and illuminate the steps between major groups.

What is the role of the Pax-6 gene?

A key gene in the genetic toolkit that influences eye development and sensory organ formation across animals.