Evolution, Natural Selection, and Speciation – Lecture Review

These flashcards review key terms, experiments, theories, mechanisms, and examples related to evolution, natural selection, genetics, and speciation as presented in the lecture notes.

What did the early theory of spontaneous generation claim?

That living organisms could arise from non-living matter such as dust or dead flesh.

Which scientist disproved spontaneous generation and by what general approach?

Louis Pasteur, through controlled experimentation that prevented contamination by microorganisms.

What central question did the 1950s Miller-Urey experiment try to answer?

Whether organic molecules could form under the conditions of early Earth.

What key result came from the Miller-Urey experiment?

It produced organic molecules, showing a reducing primordial atmosphere could synthesize life’s building blocks.

What does the endosymbiotic theory propose about the origin of eukaryotic cells?

That eukaryotes arose from symbiotic communities of once-free-living prokaryotes.

Roughly how many years ago did prokaryotes begin evolving internal membranes leading toward eukaryotes?

About 2 billion years ago.

From which type of prokaryote did mitochondria originate, according to endosymbiotic theory?

Aerobic (oxygen-using) bacteria.

Which ancient prokaryotes gave rise to chloroplasts?

Photosynthetic bacteria.

In evolutionary biology, what is an adaptation?

An inherited trait that improves an organism’s chances of survival and reproduction in a specific environment.

Define evolution in one sentence.

The cumulative changes in characteristics of populations over successive generations.

What is a population in evolutionary terms?

A group of individuals of the same species occupying a given area at a certain time.

What type of evidence are fossils considered?

Direct evidence of evolution.

In which rock type are fossils most commonly found?

Sedimentary rock.

How is the relative age of fossils commonly determined?

By examining their positions within layers (strata) of rock.

What dating method provides an absolute age for fossils?

Radioactive (radiometric) dating.

List five kinds of indirect evidence for evolution.

DNA/molecular evidence, embryological evidence, vestigial structures, homologous structures, and analogous structures.

Name the three main components of Lamarck’s evolutionary theory.

Desire to change, use and disuse, and inheritance of acquired traits.

What fundamental flaw invalidates Lamarck’s theory?

Acquired traits are not passed on; only genetic information is inherited.

On which ship did Charles Darwin make the voyage that shaped his ideas?

H.M.S. Beagle.

What is the title of Darwin’s landmark 1859 book?

On the Origin of Species.

Which phrase did Darwin coin to describe competition for survival?

“Survival of the fittest.”

In Darwinian terms, what is fitness?

The ability of an individual to survive and reproduce in its environment.

State Darwin’s concept of natural selection in one sentence.

Individuals with heritable traits better suited to the environment tend to survive and leave more offspring.

What principle describes species descending with changes from ancestral forms over time?

Descent with modification.

Which three thinkers or groups strongly influenced Darwin’s theory?

Geologist Charles Lyell, economist Thomas Malthus, and farmers practicing artificial selection.

What does the acronym VISTA summarize in natural selection?

Variation, Inheritance, Selection (survival & reproduction), Time, Adaptation.

What is the ultimate source of heritable variation in populations?

Random mutations in DNA.

Differentiate genes and alleles.

A gene is a DNA segment controlling a trait; alleles are different versions of that gene.

What is a gene pool?

All genes and their alleles present in a population.

Define the relative frequency of an allele.

The percentage occurrence of a specific allele in a population’s gene pool.

Contrast microevolution and macroevolution.

Microevolution is small-scale allele-frequency change within a species; macroevolution involves large-scale changes that can create new species over long periods.

Name six agents that can change allele frequencies in a population.

Mutations, genetic drift, gene flow, non-random mating, natural selection, and artificial selection.

What is a mutation?

Any change in a DNA sequence.

When can a mutation be inherited by offspring?

Only if it occurs in gametes (egg or sperm cells).

What is a substitution mutation?

A single nucleotide is swapped for another, possibly altering one amino acid.

Why are insertion or deletion mutations often harmful?

They shift the reading frame, altering many amino acids and producing non-functional proteins.

Define genetic drift.

Random change in allele frequencies, especially in small populations.

Explain the bottleneck effect.

A dramatic population reduction lowers genetic diversity and alters allele frequencies.

Explain the founder effect.

A small group colonizes a new area, bringing allele frequencies that differ from the original population.

What is gene flow?

Movement of alleles into or out of a population via migration of individuals.

What is meant by non-random mating?

Individuals choose mates based on specific traits, altering allele frequencies.

Define artificial selection.

Human-directed breeding that favors desirable traits.

What is speciation?

The evolutionary process by which new species arise from existing ones.

State the biological species concept.

A species is a group that can interbreed and produce fertile offspring.

What is a niche?

The role an organism plays in its ecosystem, including habitat, interactions, and diet.

Differentiate allopatric and sympatric speciation.

Allopatric speciation occurs with geographic isolation; sympatric speciation occurs without geographic separation, often via reproductive barriers or new niches.

What is reproductive isolation?

When populations can no longer interbreed or produce fertile offspring.

List three main types of reproductive isolation.

Geographic, behavioral, and temporal isolation.

Define adaptive radiation.

Rapid evolution of a single species into multiple new species adapted to different niches.

What did the Grants observe about finches during food scarcity?

Finches with larger beaks had higher survival, demonstrating natural selection on beak size.

What is the first step of speciation illustrated by Galápagos finches?

Founding of a new population by a small group (founder effect).

What ultimately happens when two populations can no longer produce fertile offspring?

They become distinct species with separate gene pools.

Why are traits favored by natural selection environment-specific?

A trait beneficial in one environment may be neutral or harmful in another, so selection depends on local conditions.