Bio 115 Lecture 4: Darwin, Wallace, and Natural Selection Lecture Review

Flashcards testing core concepts, historical figures, mathematical calculations, evidence, selection types, and sexual selection mechanisms from the lecture notes.

At what level of biological organization does biological evolution occur?

Evolution acts on populations or species over generations; individuals do not evolve.

What pre-Darwinian concept suggested that traits acquired during an organism's lifetime could be passed on to offspring?

The inheritance of acquired traits.

What were the main points of Jean-Baptiste Lamarck's mechanism for evolution?

Nature produced all forms of life, environmentally induced behavioral changes lead the way in species change, and he erected a testable mechanism.

How is natural selection defined in the lecture notes?

Natural selection is differential survival and reproduction within a population/species, resulting in evolutionary change.

In what year was Charles Darwin and Alfred Russel Wallace's joint paper presented?

1858

What core facts about populations and resources did Darwin highlight to infer a struggle for survival?

Every species is fertile enough to grow exponentially if all offspring survived, populations remain roughly stable in size, and resources such as food are limited and relatively stable over time.

What concept does Charles Darwin illustrate in his famous Notebook B sketch shown here under the phrase 'I think'?

Branching evolution and common descent represented as a phylogenetic tree.

What social causes did Alfred Russel Wallace actively advocate for?

Wallace supported women's suffrage and opposed eugenics.

Whose 1798 work, Essay on the Principle of Population, inspired Darwin's theory of natural selection in October 1838?

Thomas Malthus

How did Greek historian Herodotus attempt to calculate the age of the Earth?

He dated the age of the Earth using the rate of sediment growth he observed in the Nile Delta, concluding the Earth was several thousand years old.

How did John Joly calculate in 1899 that the Earth was approximately $100\text{ million years}$ old?

He measured the total NaCl in the oceans ($16 \times 10^{12}\text{ tons}$) and divided it by the annual rate of NaCl delivery from rivers ($160\text{ million tons}$).

What estimate did John Joly and Sir Ernest Rutherford publish in 1913 regarding the Devonian Period?

Using radioactive decay in minerals, they estimated that the beginning of the Devonian Period could not be less than $400\text{ million years}$ ago.

What age range did Lord Kelvin calculate for the Earth using geothermal gradient and cooling models?

He initially estimated the Earth to be $20\text{--}400\text{ million years}$ old, which he later revised to $24\text{--}30\text{ Ma}$.

How is fecundity defined?

The ability to reproduce, specifically a measure of how easily and often an organism produces offspring.

How is evolutionary fitness defined?

A genotype's success at reproducing relative to other genotypes, measured by how many offspring it leaves in the next generation.

What is the difference between genotype and phenotype?

Genotype is the complete set of genetic material carried by an organism, whereas phenotype is the set of all observable traits resulting from gene expression and environmental interaction.

What is the difference between abiotic and biotic factors in natural selection?

Abiotic factors are non-living physical world conditions (e.g., climate, soil pH, light, rainfall), while biotic factors stem from living organisms (e.g., competition, predators, parasites, mates).

Why is natural selection described as a probabilistic process rather than an 'all or nothing' event?

Possessing favorable traits makes successful reproduction more likely but does not guarantee it; even a $1\%$ difference in reproductive success is sufficient to gradually increase a trait's frequency over generations.

What type of selection is demonstrated by the shift in Geospiza fortis beak depth following the 1977 drought shown in this graph?

Directional selection, which shifts the population mean toward one extreme phenotype (deeper beaks).

How does stabilizing selection affect phenotype variance in a population?

It favours intermediate/average phenotypes and selects against extreme phenotypes, decreasing phenotypic variance.

Why is clutch size in robins an example of stabilizing selection?

Robins typically lay four eggs because larger clutches risk malnourished chicks and smaller clutches risk leaving no viable offspring.

How does disruptive (or diversifying) selection affect phenotypic variation in a population?

It favours both extreme phenotypes over intermediate traits, increasing phenotypic variance.

What is a 'sneaker male' strategy in animal reproduction?

A phenomenon where smaller or non-fighting males avoid direct physical confrontation for mates and instead sneak fertilizations to pass on their genes.

What is frequency-dependent selection?

A form of natural selection where a phenotype's fitness depends on its frequency in the population, serving to maintain genetic variation.

Under what condition is Batesian mimicry effective as an adaptation?

Batesian mimicry only works when the non-toxic/harmless mimic species is less common than the toxic/dangerous model species.

In this side-blotched lizard system, what form of selection maintains all three throat-color morphs in a rock-paper-scissors dynamic?

Frequency-dependent selection.

What is the difference between intersexual and intrasexual selection?

Intersexual selection occurs when individuals of one sex (typically females) choose mates based on phenotypic traits, while intrasexual selection involves direct competition within one sex (typically males) for mates or territory.

What is a lek in animal behavior?

An aggregation of male animals gathered to perform competitive courtship displays and rituals to entice visiting females.

What distribution of mating success is typically observed among males in a lek arena?

About $70\text{--}80\%$ of matings are performed by only $10\text{--}20\%$ of the males present, which tend to be older and more experienced.