Evolution - Questions

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*What is biology as a science?

Biology is the systematic study of living organisms using observations and experiments in the natural world.

*What is methodological naturalism?

Methodological naturalism is the scientific approach that restricts inquiry to natural, observable phenomena.

What is philosophical naturalism?

Philosophical naturalism is the belief that only the natural world exists; it is a philosophical claim outside the scope of science.

Why did early science invoke supernatural explanations?

Early science lacked systematic natural explanations, so many phenomena were attributed to supernatural causes.

How were solar eclipses explained in ancient cultures?

Ancient cultures often interpreted solar eclipses as supernatural signs (e.g., dragons devouring the sun) before predictive astronomy.

How did Babylonian and Greek astronomers change eclipse interpretation?

They recorded and analyzed eclipse patterns, enabling predictions and shifting understanding toward natural causes.

What is the role of senses in science?

Science relies on observations accessible to the senses (sight, hearing, taste, touch, smell) or instruments extending them.

What is adaptation?

An adaptation is a trait or integrated suite of traits that increases the fitness of its possessor.

How is fitness measured?

Fitness is measured as reproductive success (number of surviving offspring or relative genetic contribution to future generations).

What is “descent with modification”?

Descent with modification describes how species change over generations from common ancestors.

What is the unifying theory of biology as quoted by Dobzhansky?

“Nothing makes sense in biology except in the light of evolution.”

How does natural selection operate?

Natural selection acts on existing variation: individuals with favorable heritable traits leave more offspring, shifting allele frequencies.

What idea did Malthus contribute to Darwin’s thinking?

Malthus described limits to population growth, highlighting a struggle for existence that influences selection.

What is a testable hypothesis in evolutionary biology?

A hypothesis that makes predictions that can be evaluated with empirical data (e.g., giraffe necks evolved for foraging).

Why are adaptive traits not always perfect?

Historical constraints, pleiotropy, trade-offs, and limited variation can prevent perfect adaptation.

What is a historical constraint?

A historical constraint is a limitation on adaptation resulting from an organism’s ancestry or past developmental pathways.

What is the Law of Succession (biogeography)?

The Law of Succession states that fossil species in an area are often similar to living species in the same region, indicating shared ancestry.

How did Lyell’s uniformitarianism influence evolutionary thought?

Lyell’s uniformitarianism (slow, consistent processes over deep time) provided the temporal framework for gradual evolution.

What was Paley’s “argument from design”?

Paley argued organisms’ complexity implies a designer (analogy: watchmaker), a teleological argument for divine creation.

What objections did Hume raise to Paley’s argument?

Hume argued the analogy is weak, that empiricism limits conclusions about a divine designer, and that a designer need not be God.

Who independently proposed natural selection alongside Darwin?

Alfred Russel Wallace independently developed the concept of natural selection and corresponded with Darwin.

What is artificial selection?

Artificial selection is human-directed breeding that selects for desirable traits, demonstrating selection’s power.

How can artificial selection illustrate natural selection?

Artificial selection shows how differential reproduction based on heritable traits changes populations over generations, analogous to natural selection.

What evidence supports common ancestry (homology)?

Structural, developmental, and molecular similarities (homologies) among diverse taxa indicate common ancestry.

What is structural homology?

Structural homology refers to similar anatomical features in different species due to shared ancestry (e.g., limb bones).

What is molecular homology?

Molecular homology refers to similarity in DNA, RNA, or protein sequences due to shared ancestry.

What are transitional fossils and why are they important?

Transitional fossils show intermediate features linking ancestral and derived forms, supporting evolutionary transitions (e.g., early cetaceans).

How does embryology support cetacean tetrapod ancestry?

Embryos of cetaceans show hind-limb buds and tetrapod developmental patterns before reduction, supporting a tetrapod ancestry.

What is biogeography and how does it support evolution?

Biogeography studies species distributions; patterns like endemic radiation and succession match historical diversification and vicariance.

What is the Hardy-Weinberg principle?

The Hardy-Weinberg principle describes allele and genotype frequencies in a non-evolving population under specific assumptions, providing a null model.

What is the Hardy-Weinberg equation for allele frequencies?

p

What is the genotype frequency equation in Hardy-Weinberg?

p²

What are the Hardy-Weinberg equilibrium assumptions?

Large population size, random mating, no selection, no mutation, no migration (no gene flow).

How can Hardy-Weinberg be used in practice?

It can test whether a population is evolving by comparing observed genotype frequencies to expected H-W frequencies.

What causes evolution (changes in allele frequency)?

Genetic drift, non-random mating, natural selection, mutation, and migration (gene flow).

What is genetic drift?

Genetic drift is random change in allele frequencies due to sampling error in small populations.

What is the founder effect?

The founder effect occurs when a new population is established by a small number of individuals, carrying only a subset of genetic variation.

What is a population bottleneck?

A bottleneck is a sharp reduction in population size that reduces genetic diversity and alters allele frequencies by chance.

How does non-random mating affect genotype frequencies?

Non-random mating changes genotype frequencies (e.g., increased homozygosity in inbreeding) but does not directly change allele frequencies unless coupled with selection.

What is assortative mating?

Assortative mating occurs when individuals preferentially mate with similar phenotypes (likes attract likes) or dissimilar (opposites attract).

What is inbreeding and its evolutionary consequence?

Inbreeding is mating between relatives; it increases homozygosity and can expose deleterious recessive alleles, reducing fitness.

What is natural selection (population-level definition)?

Natural selection is differential reproductive success of genotypes due to heritable variation in traits affecting survival or reproduction.

What is directional selection?

Directional selection favors one extreme phenotype, shifting the population mean in one direction.

What is disruptive (diversifying) selection?

Disruptive selection favors extreme phenotypes at both ends of the distribution, potentially increasing variance or promoting speciation.

What is stabilizing selection?

Stabilizing selection favors intermediate phenotypes and reduces variance around the mean.

What is sexual selection?

Sexual selection arises from variation in mating success, favoring traits that improve access to mates (e.g., ornamentation, combat).

What is mutation and how does it affect evolution?

Mutation is a change in DNA sequence that creates new alleles; it is the ultimate source of genetic variation.

What types of mutations were listed?

Point mutations, insertions/deletions (indels), gene duplications, chromosomal rearrangements, and whole-genome duplications (polyploidy).

What is recombination (starred as emphasized)?

Recombination is the shuffling of alleles during sexual reproduction (crossing-over and independent assortment) that produces new genotypic combinations.

Why can recombination be more important than mutation for adaptation?

Recombination reshuffles existing alleles into novel combinations, often producing phenotypic variation more rapidly than new mutations.

What is gene flow (migration)?

Gene flow is the movement of alleles between populations via immigration or emigration, which can homogenize populations.

What is the biological species concept?

The biological species concept defines species as groups of actually or potentially interbreeding natural populations that are reproductively cohesive and isolated from others.

What is reproductive isolation?

Reproductive isolation are mechanisms that prevent gene flow between populations, leading to speciation.

What are prezygotic barriers?

Prezygotic barriers prevent mating or fertilization (habitat, temporal, behavioral, mechanical, gametic isolation).

What is habitat isolation?

Habitat isolation occurs when populations live in different habitats and do not encounter each other to mate.

What is temporal isolation?

Temporal isolation occurs when populations breed at different times or seasons, preventing interbreeding.

What is behavioral isolation?

Behavioral isolation is when courtship behaviors or mating signals differ, preventing mating.

What is mechanical isolation?

Mechanical isolation results from incompatible reproductive structures preventing successful mating.

What is gametic isolation?

Gametic isolation occurs when gametes (sperm and egg) are incompatible and cannot fuse to form a zygote.

What are postzygotic barriers?

Postzygotic barriers reduce the viability or fertility of hybrids (reduced hybrid viability, reduced hybrid fertility, hybrid breakdown).

What is reduced hybrid viability?

Reduced hybrid viability occurs when hybrid offspring fail to develop or survive well.

What is reduced hybrid fertility?

Reduced hybrid fertility occurs when hybrids are sterile or have reduced fertility (e.g., mules).

What is hybrid breakdown?

Hybrid breakdown occurs when first-generation hybrids are fertile but subsequent generations are feeble or sterile.

What is allopatric speciation?

Allopatric speciation is speciation that occurs when populations become geographically isolated and diverge.

What is sympatric speciation?

Sympatric speciation occurs when populations diverge genetically while sharing the same geographic area, often due to ecological or genetic barriers.

How can polyploidy lead to sympatric speciation?

Polyploidy (whole-genome duplication), particularly in plants, can instantaneously create reproductive isolation from the parent population.

What is allopolyploidy?

Allopolyploidy is polyploidy resulting from hybridization between species followed by chromosome doubling, producing a fertile polyploid.

How was speciation demonstrated in laboratory Drosophila experiments?

Different media (starch vs. maltose) led to mating preference divergence after many generations, showing reproductive isolation can evolve.

What is the Law of Superposition?

The Law of Superposition states that in undisturbed sedimentary strata, older layers lie beneath younger layers, revealing relative ages of fossils.

What is radiometric dating?

Radiometric dating uses decay of parent isotopes to daughter isotopes with known half-lives to determine absolute ages of rocks and fossils.

What is a half-life?

A half-life is the time required for half of a parent radioactive isotope to decay to its daughter isotope.

What are mass extinction events and name two examples?

Mass extinctions are periods of unusually high extinction rates; examples include the Permian and the Cretaceous/Paleogene (K/Pg) events.

What evidence links the K/Pg extinction to an impact event?

The Chicxulub crater, global iridium layer, and sudden fossil turnover support an impact at the K/Pg boundary.

What is heterochrony?

Heterochrony is evolutionary change in the timing or rate of developmental events, altering adult morphology.

What is allometry?

Allometry studies changes in proportion of body parts relative to overall size during growth or evolution.

What is homeosis?

Homeosis is the transformation of one body part into another due to developmental gene changes (homeotic mutations).

What are Hox (homeobox) genes?

Hox genes are a family of transcription factors that control major developmental programs and body plan segment identity.

How can evolutionary novelty arise from gene regulation?

Changes in when, where, or how much genes are expressed (regulatory mutations) can produce morphological novelties without coding changes.

What did the stickleback Pitx1 example show?

The stickleback example showed morphological change due to altered regulation of Pitx1 (expression differences), not coding sequence changes.

What is the difference between changes in genes vs. changes in gene regulation?

Changes in coding sequence alter protein structure; regulatory changes alter spatiotemporal expression, often producing phenotypic differences.

What is phylogeny?

Phylogeny is the study of evolutionary relationships and the pattern of descent among organisms.

What is monophyly?

Monophyly is a group consisting of a common ancestor and all of its descendants (a clade).

What is non-monophyly?

Non-monophyly is a group that fails to include all descendants of a common ancestor (paraphyletic or polyphyletic).

What are sister taxa?

Sister taxa are two lineages that are each other’s closest relatives, sharing an immediate common ancestor.

What is an ingroup and an outgroup?

Ingroup is the set of taxa under study; outgroup is a reference taxon used to infer ancestral character states.

What is an apomorphy (derived trait)?

An apomorphy is a derived character that evolved in the lineage leading to a group and can diagnose monophyly.

What is a plesiomorphy (ancestral trait)?

A plesiomorphy is an ancestral character state present before the divergence of the group and not useful for diagnosing monophyly.

How do scientists build phylogenetic trees?

Scientists use morphological and molecular character data, outgroups, and methods (parsimony, likelihood, Bayesian inference) to infer trees.

What is binomial nomenclature?

Binomial nomenclature assigns each species a two-part Latin name: genus and species (e.g., Panthera pardus).

What is the Linnaean hierarchy?

The Linnaean hierarchy is the ranked classification system (Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species).

Why is taxon sampling important in phylogenetic inference?

Dense taxon sampling can change tree topology and improve accuracy by reducing long-branch attraction and revealing character distributions.

What is the role of molecular data in phylogeny?

Molecular sequences provide abundant heritable characters for reconstructing evolutionary relationships and timing divergence.

How can fossils inform phylogeny?

Fossils provide direct evidence of extinct lineages, morphological intermediates, and calibration points for divergence time estimates.

What is a node on a phylogenetic tree?

A node represents a common ancestor from which descendant lineages diverge.

What is homoplasy?

Homoplasy is similarity due to convergent evolution or reversal, not common ancestry, and can mislead phylogenetic analysis.

What is convergent evolution?

Convergent evolution is the independent evolution of similar traits in distantly related lineages due to similar selection pressures.

What is the practical significance of recognizing derived vs. ancestral traits?

Distinguishing derived vs ancestral traits helps identify clades and avoid grouping taxa by shared ancestral features.

How do experimental studies (e.g., guppy predation) demonstrate natural selection?

They show trait frequency changes (coloration, behavior) in response to predator regimes consistent with differential survival and reproduction.

What evidence suggests sex differences in selection (sexual dimorphism)?

Differences in mating success and secondary sexual traits (ornaments, weaponry) arise from sexual selection pressures.

What is the relationship between genotype and phenotype in evolution?

Genotypes code for phenotypes via development; selection acts on phenotypes, causing changes in genotype frequencies.