Bio 115, Lecture Quiz 3: Macroevolution, Ontogeny, and Extinction

Comprehensive review flashcards covering macroevolutionary patterns, speciation modes, tempos, ontogeny, allometry, heterochrony, phylogenetic analysis, and extinction dynamics.

How do microevolution and macroevolution differ in terms of scale and focus?

Microevolution occurs on a smaller scale over shorter timeframes, focusing on processes from populations to species. Macroevolution occurs on a larger scale over longer periods, considering evolutionary patterns and processes at or above the species level.

What are the four primary geographic pathways to speciation illustrated in this diagram?

Allopatric (barrier formation resulting in reproductive isolation in isolation), Peripatric (a new isolated niche is entered), Parapatric (a new adjacent niche is entered), and Sympatric (genetic polymorphism arising within the same population).

What is the key difference between anagenesis and cladogenesis?

Anagenesis is evolutionary change within a single unbranched lineage over time without splitting, whereas cladogenesis is the splitting of an ancestral lineage into two or more distinct descendant lineages through speciation.

What is the theory of Punctuated Equilibrium proposed by Eldredge and Gould in $1972$?

It proposes that species experience long periods of morphological stasis (little or no evolutionary change) punctuated by brief, rapid intervals of speciation and change, typically associated with allopatric speciation.

How do phyletic gradualism and punctuated equilibrium differ in where the majority of morphological change occurs?

In phyletic gradualism, most morphological change occurs steadily within species lineages over time with little change during speciation. In punctuated equilibrium, there is almost no change within established lineages (stasis), and large morphological changes occur rapidly during speciation events.

What characterizes a random walk model of morphological evolution in the fossil record?

A pattern where the direction of change has an equal probability in either direction for each time interval, resulting in no sustained net directionality (as documented in shell diameter changes in the Jurassic ammonite Zugokosmoceras).

What is reticulate evolution (reticulation)?

The evolutionary process where two distinct lineages unite to form a single lineage through hybridization or polyploidy, such as seen in the ancestry of the cultivated potato.

Why is the combination of 'punctuated gradualism' or 'anagenetic cladogenesis' considered biologically impossible?

Because punctuated implies rapid episodic change whereas gradualism requires slow continuous change; similarly, anagenesis by definition is change within a single unbranched lineage, whereas cladogenesis by definition requires lineage branching.

What is a 'living fossil'?

An organism exhibiting very little obvious morphological change over an extraordinarily long span of geological time, such as onychophorans and the coelacanth.

What is Cope's Rule, and what selective advantages may drive it?

The evolutionary pattern where lineages tend to evolve larger body size over geological time. Selective advantages include reduced predation, longer lifespan, increased capacity to capture and retain nutrition, and increased resistance to starvation.

What is the Lilliput Effect in macroevolution?

A phenomenon where the surviving organisms immediately following a mass extinction event are significantly smaller in body size, often due to collapse to lower trophic levels, reduced nutrient availability, or shortened growth periods.

How does the Red Queen Hypothesis contrast with the Court Jester Hypothesis?

The Red Queen Hypothesis posits that biotic interactions (competition, predation) drive constant co-adaptation just to maintain fitness without net directional change, whereas the Court Jester Hypothesis proposes that abiotic factors (climate, tectonic events) drive major speciation and extinction events across larger spatio-temporal scales.

What is an adaptive radiation, and what factors typically trigger it?

A burst of rapid cladogenesis over a short geological timeframe where many new species evolve to exploit diverse ecological niches. Triggers include key innovations, colonization of competitor-free habitats, and ecological opportunities following mass extinctions.

What ecological and biological changes marked the Cambrian Explosion?

The widespread appearance of animals with mineralized skeletons, an increase in large body sizes, and diversification into complex new ecological niches (such as active burrowing and swimming macrophagous predators), recorded in lagerstätten like the Burgess Shale.

In macroevolution, how do tempo and mode combine to define evolutionary pathways?

Tempo refers to the speed of change (gradual vs. punctuational), while mode refers to the lineage structure (anagenesis vs. cladogenesis), creating four distinct combinations: gradual anagenesis, punctuational anagenesis, gradual cladogenesis, and punctuational cladogenesis.

What distinguishes convergent evolution from parallel evolution?

Convergent evolution is the independent evolution of similar analogous features (homoplasies) in distantly related lineages via different pathways, whereas parallel evolution involves closely related sister lineages independently evolving similar structures via similar developmental or genetic mechanisms.

What is coevolution?

A process where two or more interacting species reciprocally exert selective pressures that affect each other's evolutionary trajectories through natural selection, such as hawk moths (Xanthopan morgani) and long-spurred orchids.

What is allometry, and what are its three scaling relationships?

Allometry is the differential growth rate of body parts relative to each other or to overall body size. Its forms are positive allometry ($b > 1$, part grows faster than the body), negative allometry ($b < 1$, part grows slower than the body), and isometry ($b = 1$, proportional growth at the same rate).

What is heterochrony, and what are its two primary categories?

An evolutionary change in the rate or timing of developmental events. Its two categories are Paedomorphosis (the adult descendant retains ancestral juvenile traits) and Peramorphosis (the adult descendant develops beyond the ancestral adult stage).

What are the three developmental mechanisms that lead to paedomorphosis?

Progenesis/Hypomorphosis (earlier offset/cessation of growth), Neoteny/Deceleration (reduced rate of morphological development), and Postdisplacement (delayed onset of growth).

What are the three developmental mechanisms that lead to peramorphosis?

Hypermorphosis (delayed offset/extended duration of growth), Acceleration (increased rate of development over time), and Predisplacement (earlier onset of development).

What is mosaic evolution?

The evolutionary pattern where different physiological systems, organs, or morphological structures within an organism evolve at distinct rates and by different modes.

What is phylogenetic bracketing?

A comparative method predicting that unpreserved or unknown biological traits shared by two closely related extant clades (such as crocodiles and birds sharing four-chambered hearts and nest-brooding) were also present in their common ancestor and extinct intermediate descendants (like non-avian dinosaurs).

What dietary transition explains the extraordinary species richness of beetles (Coleoptera)?

Cladistic analyses show that clades of beetles that switched from feeding on non-angiosperm plants to feeding on angiosperms (flowering plants) diversified into far higher numbers of species than their sister groups.

Which structural form of spider web represents the ancestral state: cob webs or orb webs?

Phylogenetic character mapping demonstrates that cob webs are the ancestral state from which orb webs later evolved.

What is local extinction (extirpation), and what are examples from the lecture?

The loss of all individuals of a species within a restricted geographic area while populations survive elsewhere. Examples include American bison and pronghorn antelope in Grayson County, and the ostrich on the Arabian Peninsula.

How did the Black Death create a genetic bottleneck in European human populations with implications for modern HIV resistance?

The bubonic plague killed approximately $50\%$ of Europeans, acting as a selective filter that enriched the frequency of the CCR5-delta 32 mutation, which prevents HIV entry into CD4 cells in homozygous individuals.

What percentage of all species that have ever lived on Earth are estimated to be extinct, and what is typical species longevity?

Approximately $99.9\%$ of all species that have ever lived are extinct, and species have a typical duration of up to $1\text{--}10\text{ million years}$.

Why can abiotic natural catastrophes bypass normal reproductive fitness in causing species extinction?

Severe cataclysmic events (such as the $1883$ explosion of Krakatoa) occur too rapidly for natural selection and adaptive evolutionary changes to occur, meaning even high reproductive fitness provides no protection if an entire habitat is obliterated.

What ecological devastation was caused by the introduction of the brown tree snake to Guam?

As an invasive predatory species, its unchecked spread caused the extinction of $13$ native bird species and $2$ bat species.

What is the Allee effect in extinction biology?

A phenomenon where a population drops to such low numbers or density that individuals can no longer successfully locate mates, communicate, or cooperate, causing reproductive collapse prior to the loss of the last individual.

What is linked extinction (coextinction)?

The secondary loss of a dependent species following the extinction of an organism upon which it relies, such as host-specific parasites, mutualistic plants and pollinators, or specialized predators losing their sole prey.

What is functional extinction?

A state occurring before the death of a taxon's last member when the population has declined beyond the point where it retains the demographic or genetic capacity to reproduce and recover.

What is background extinction, and how does its cumulative toll compare to mass extinctions?

The constant, 'normal' rate of species loss operating in the absence of catastrophic global events (estimated at $5\text{--}10\%$ of species per million years). Cumulatively, background extinction has eliminated far more species throughout Earth history than mass extinctions.