Campbell Biology Chapter 19: Descent with Modification

Comprehensive review flashcards covering Chapter 19: Descent with Modification, including historical context, Darwin's observations and inferences, artificial selection, direct observations of natural selection, homologies, convergent evolution, the fossil record of cetaceans, and biogeography.

How is evolution defined both broadly and at the population genetic level?

Broadly, evolution is defined as descent with modification (the accumulation of differences from ancestors over time). At the population level, it is defined as a change in the genetic composition of a population across generations.

What is the distinction between evolution as a pattern and evolution as a process?

The pattern of evolution is revealed through scientific data showing how species have been modified over time, whereas the process consists of the mechanisms that produce that pattern, such as natural selection, genetic drift, and gene flow.

How did Aristotle view the stability of species and their place in the natural order?

Aristotle ($384$-$322\text{ BCE}$) viewed species as fixed (unchanging) and arranged them on a ladder of increasing complexity known as the scala naturae ("scale of nature"), consistent with the concept that each life-form is perfect and permanent.

How did Carolus Linnaeus's interpretation of species relationships differ from Darwin's?

Carolus Linnaeus ($1707$-$1778$) developed the binomial naming system and a nested classification hierarchy (grouping species into genera, families, etc.), but attributed structural similarities to a divine pattern of creation rather than evolutionary kinship.

According to the principle of rock stratification depicted here, how do sedimentary strata document past life?

Sediment compresses over time into distinct layers called strata; older strata lie beneath younger ones, and the fossils in deeper, older layers are more dissimilar to modern living forms than those in more recent layers.

How did Georges Cuvier explain the sudden appearance and disappearance of species between fossil strata?

Georges Cuvier ($1769$-$1832$) opposed evolution and proposed that boundaries between strata represented localized catastrophic extinction events, after which new species migrated into the area from elsewhere.

How did the geological theories of James Hutton and Charles Lyell influence Darwin's perspective on Earth's age and biology?

Hutton ($1795$) proposed gradualism (geological features form via slow, continuous mechanisms) and Lyell ($1830$) argued these processes operate at uniform rates; this convinced Darwin that Earth was far older than a few thousand years, providing ample time for slow biological change to accumulate.

What were the two core principles of Jean-Baptiste de Lamarck's evolutionary hypothesis, and why was it refuted?

Lamarck ($1809$) proposed 'use and disuse' (body parts strengthen or deteriorate with use during an individual's lifetime) and 'inheritance of acquired characteristics' (such modifications pass to offspring); experimental genetics refuted it because phenotypic traits acquired during an organism's lifetime cannot alter heritable gametic DNA.

What critical observation did Darwin make during the $1831$-$1836$ voyage of HMS Beagle regarding South American fossils and modern organisms?

Fossils Darwin collected across different South American environments resembled living South American species far more closely than they resembled organisms or fossils from similar environments in Europe.

What geological observation did Darwin make in Chile that reinforced Lyell's Principles of Geology?

Darwin witnessed an earthquake in Chile that lifted coastal rock several meters out of the water; later finding marine fossils high in the Andes Mountains confirmed that gradual, repeated upward thrusts could build mountain chains over immense periods.

What did Darwin conclude about the origin of unique species found on the Galápagos Islands?

Located $900\,\text{km}$ west of South America, the islands were colonized by stray mainland organisms that gradually diverged and accumulated adaptations, giving rise to distinct species suited to specific island niches.

What is the biological definition of an adaptation?

An adaptation is an inherited characteristic of an organism that enhances its survival and reproductive success in a specific environment.

Who independently conceived the hypothesis of natural selection in $1858$, prompting the presentation of joint papers to the Linnean Society of London?

Alfred Russel Wallace ($1823$-$1913$), who developed his hypothesis while studying the biogeography of species in the Malay Archipelago.

In Darwin's tree metaphor of descent with modification, what do the trunk, forks, and branch tips represent?

The common trunk represents common ancestry, each fork represents the most recent common ancestor of all branching lineages, branch tips represent living species, and unlabeled ending branches represent extinct groups.

What crops were developed through the artificial selection of the wild mustard plant (Brassica oleracea), and which plant parts were modified?

Artificial selection on wild mustard generated: cabbage (selection for apical/tip bud), Brussels sprouts (axillary/side buds), broccoli (flowers and stems), kohlrabi (stems), and kale (leaves).

What are Darwin's two fundamental observations regarding populations in nature?

Observation 1: Members of a population often vary in their heritable characteristics. Observation 2: All species produce more offspring than their environment can support, leading many to fail to survive and reproduce.

How did Thomas Malthus's $1798$ essay contribute to Darwin's second observation of natural selection?

Malthus observed that human population growth tends to outstrip food supplies and resources, leading to inevitable famine and conflict; Darwin applied this concept of overproduction and resource limitation to all natural populations.

What are the two key inferences Darwin drew from his observations on natural selection?

Inference 1: Individuals possessing heritable traits that fit them best to their environment tend to leave more surviving offspring. Inference 2: This unequal reproductive success leads to the accumulation of favorable traits in the population over generations.

Do individual organisms evolve during their lifetimes through natural selection?

No; natural selection acts on individuals by affecting their survival and reproductive success, but evolutionary change is measured only by shifts in allele and trait frequencies within a population over generations.

What are the four primary lines of scientific evidence that document the pattern of evolution?

The four main types of evidence are: direct observations of evolutionary change, homology, the fossil record, and biogeography.

How did Florida soapberry bugs provide direct observation of rapid natural selection when feeding on native vs. introduced plants?

Bugs feeding on large native balloon vine fruit evolved long beaks (around $8.5$-$9.5\,\text{mm}$), whereas those feeding on smaller, introduced flat-podded goldenrain tree fruit in central Florida evolved shorter beaks ($\approx 6.5$-$7.5\,\text{mm}$) in less than $35\,\text{years}$.

In John Endler's $1980$ guppy field experiment, what occurred when guppies were transplanted from pike-cichlid pools to killifish pools?

Predation was reduced because killifish prey mostly on juvenile guppies, allowing female mate preference (sexual selection) to drive the evolution of adult male guppies toward a significantly higher number and greater total area of brightly colored spots.

What biochemical mechanism allows MRSA (methicillin-resistant Staphylococcus aureus) to survive methicillin treatment?

Methicillin acts by disabling an enzyme used by standard S. aureus to synthesize cell walls, but MRSA variants utilize a structurally distinct cell-wall synthesis protein that methicillin cannot bind.

What anatomical bone pattern demonstrated across these mammalian forelimbs serves as evidence of homologous structures?

Human, cat, whale, and bat forelimbs all share the same developmental arrangement of skeletal elements—a single proximal humerus, paired radius and ulna, a cluster of carpals, metacarpals, and five digits (phalanges)—inherited from a common tetrapod ancestor despite divergent adaptations.

What embryonic structures shared between chick and human embryos reflect their shared vertebrate ancestry?

Comparative embryology reveals that all vertebrate embryos possess pharyngeal (throat) arches (which develop into gills in fish or parts of the ear/throat in humans) and a post-anal tail at some stage of early development.

What is a vestigial structure, and what are two prominent anatomical examples?

A vestigial structure is a remnant of an anatomical feature that had an important function in an organism's ancestors but serves little or no current purpose; examples include pelvis and leg bone remnants in modern pythons and rudimentary pelvic bones in cetaceans.

Why is the phenotypic similarity between the Australian sugar glider and the North American flying squirrel classified as convergent evolution rather than homology?

They independently evolved gliding adaptations (flaps of skin) in response to similar arboreal niches; sugar gliders are marsupials while flying squirrels are placental (eutherian) mammals whose common ancestor did not possess gliding membranes.

What distinctive astragalus (ankle bone) feature links fossil cetaceans like Pakicetus to even-toed ungulates (such as pigs and deer)?

Cetaceans and even-toed ungulates both possess a unique 'double-pulley' astragalus with distinct grooves at both ends (indicated by paired red arrows), absent in other mammals such as dogs (Canis).

What transitional fossil sequence illustrates the evolution of modern cetaceans from terrestrial four-legged ancestors over the past $50\,\text{million years}$?

The sequence progresses from the terrestrial/semi-aquatic Pakicetus ($\approx 50\,\text{Ma}$) to the semi-aquatic swimmer Rodhocetus, to the marine Dorudon ($\approx 40\,\text{Ma}$) showing progressive reduction of the pelvis and hind limbs, culminating in fully aquatic modern whales with rudimentary internal pelvic vestiges.

What is an endemic species, and how does biogeography account for high rates of endemism on isolated islands?

An endemic species is one found naturally nowhere else in the world; island endemism arises because mainland colonizing ancestors become geographically isolated, adapting and diversifying independently across local habitats (e.g., Hawaiian honeycreepers and Madagascar lemurs).

How does the scientific meaning of the word 'theory' differ from its common, colloquial usage?

In common parlance, 'theory' implies a mere guess or unproven speculation (equivalent to a hypothesis); in science, a theory is a broad, comprehensive framework supported by extensive, rigorous empirical evidence that unifies and explains diverse natural phenomena.