Scientific Theory and Evolution Flashcards

Flashcards covering key concepts in scientific theory and evolution.

What is a scientific theory?

A well-substantiated explanation of some aspect of the natural world, based on a body of evidence repeatedly confirmed through observation and experimentation.

What is evolution?

The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.

How does descent with modification explain similarities and differences among species?

It suggests species change over time, give rise to new species, and share a common ancestor, explaining similarities (common ancestry) and differences (modifications over time) among species.

Why is natural selection not simply a matter of chance?

Because it acts on existing variation within a population, favoring traits that enhance survival and reproduction.

What is an adaptation?

A trait evolved through natural selection, enhancing an organism's ability to survive and reproduce in a particular environment.

Why is natural selection the only mechanism of evolution leading to adaptations?

Natural selection is the only mechanism that consistently increases the frequency of traits that are beneficial for survival and reproduction.

How does adaptation to an environment differ from acclimation?

Adaptation is a genetic change that occurs over generations, while acclimation is a short-term physiological adjustment to environmental changes.

How did Darwin and Wallace’s ideas on evolution by natural selection fit with previous thinking?

Darwin and Wallace proposed that natural selection was the mechanism driving evolution, contrasting with earlier ideas that species were immutable and created independently.

What are the four principal requirements of evolution by natural selection?

Variation in traits, differential survival and reproduction, inheritance of traits, and time.

Understand what evidence from direct observations of populations supports the four criteria.

Examples include changes in beak morphology in Galapagos finches and the evolution of antibiotic resistance in bacteria.

What is a homology?

Traits inherited by two different organisms from a common ancestor.

What testable predictions can be derived from the theory of evolution regarding homologies?

Similarities in bone structures, embryonic development patterns, cellular structures, and DNA sequences.

What is convergent evolution?

• Convergent evolution is the process where unrelated organisms independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

What are analogous structures?

Traits that are similar due to convergent evolution, not common ancestry.

What is microevolution?

Changes in allele frequencies within a population over time.

Explain the three main mechanisms of microevolution.

Natural selection, genetic drift, and gene flow.

Why is genetic variation within a population a pre-requisite for evolution?

Genetic variation provides the raw material for natural selection to act upon.

How is genetic variation created?

Through mutations and sexual reproduction.

What are the major kinds of mutations, and how do they alter DNA sequences?

Point mutations, insertions, deletions, and chromosomal rearrangements, which can change the DNA sequence and potentially affect gene function.

Do mutations arise by chance or nonrandomly?

Mutations arise by chance.

Are most mutations harmful or beneficial?

Most mutations are neutral or harmful; beneficial mutations are rare.

How does sexual reproduction contribute to genetic variation?

Through recombination and independent assortment during meiosis.

State the Hardy-Weinberg equation and its conditions.

The Hardy-Weinberg equation is p2+2pq+q2=1. Conditions include no mutation, random mating, no gene flow, infinite population size, and no selection.

What does it mean if a population is in Hardy-Weinberg equilibrium, and what if it is not?

If a population is in equilibrium, allele frequencies remain constant. If not, evolutionary forces are acting on the population.

How would you determine relative allele frequencies given genotype frequencies?

Use the frequencies of homozygous and heterozygous genotypes to calculate allele frequencies.

How would you determine expected genotype frequencies at Hardy-Weinberg equilibrium, given allele frequencies?

Apply the Hardy-Weinberg equation to calculate expected genotype frequencies.

What is genetic drift?

Genetic drift is the random fluctuation of allele frequencies in a population.

What consequences does genetic drift have for genetic variation?

It can lead to a loss of genetic variation, especially in small populations.

What effect does population size have on genetic drift?

Smaller populations experience stronger genetic drift.

What are the founder effect and bottleneck effect, and how do they relate to genetic drift?

The founder effect occurs when a new population is established by a small number of individuals. The bottleneck effect occurs when a population's size is significantly reduced. Both lead to reduced genetic variation.

What is gene flow?

Gene flow is the transfer of alleles between populations.

What effect does gene flow have on within and between population genetic variation?

It increases genetic variation within populations and reduces differences between populations.

How can gene flow hinder or help adaptation?

Gene flow can introduce beneficial alleles or dilute local adaptations.

Why is natural selection the only mechanism of evolution that consistently leads to adaptive evolution?

Because it favors traits that enhance survival and reproduction.

What are the various modes of selection and how do they alter the frequency distribution of a trait?

Directional, stabilizing, and disruptive selection. They shift, narrow, or widen the trait distribution, respectively.

What is sexual selection?

Sexual selection is a form of natural selection where traits that increase mating success are favored.

What are the two mechanisms by which adaptations that promote mating success can evolve?

Intrasexual selection (competition among males) and intersexual selection (female choice).

Why might females prefer males with exaggerated secondary sexual traits?

These traits may indicate genetic quality or health.

What limits evolution by natural selection?

Constraints such as genetic variation, trade-offs, and environmental changes.

What is speciation?

Speciation is the process by which new species arise.

What is the biological species concept?

A species is a group of interbreeding populations that are reproductively isolated from other such groups.

What are the limitations associated with the biological species definition?

It doesn't apply to asexual organisms or fossils and can be difficult to test.

What is a reproductive isolating mechanism?

Mechanisms that prevent gene flow between species.

What are the various ways reproductive isolating mechanisms can prevent gene flow?

Prezygotic barriers (e.g., temporal, behavioral isolation) and postzygotic barriers (e.g., hybrid sterility).

What are the two major mechanisms of speciation and how do they operate?

Allopatric speciation (geographic isolation) and sympatric speciation (reproductive isolation within the same area).

What are the various avenues of sympatric speciation?

Polyploidy, habitat differentiation, and sexual selection.

What process of sympatric speciation is especially applicable to plants?

Polyploidy.

What are hybrid zones?

Regions where different species meet and mate, producing hybrids.

What are the three possible outcomes when two incipient species come into secondary contact?

Reinforcement, fusion, or stability.

What is reinforcement, and how does it promote reproductive isolation?

Reinforcement strengthens prezygotic barriers to prevent hybrid formation.

How does gradual evolution differ from punctuated equilibria?

Gradual evolution involves slow, continuous change, while punctuated equilibria involve rapid bursts of change followed by periods of stasis.

What are the main steps believed to have led to the origin of life on Earth?

Formation of organic molecules, polymerization, formation of protocells, and development of self-replicating molecules.

Why is it likely that the first genetic material was RNA?

RNA is capable of both storing genetic information and catalyzing chemical reactions, which suggests it could have supported early life forms before the evolution of DNA and proteins.

How would you calculate the age of a fossil using radiometric dating?

By measuring the ratio of parent to daughter isotopes in a sample and knowing the half-life of the parent isotope. you can calculate the age of the fossil.

Be familiar with some of the key events in the history of life, including the origin of unicellular and multicellular organisms, and the colonization of land.

Key events include the formation of the first cells, the rise of photosynthesis, the emergence of eukaryotic cells, the development of multicellular organisms, and the colonization of land by plants and animals.

What are the five major extinctions that have dramatically influenced the diversity of life on Earth?

The five major extinctions are the Ordovician-Silurian, Late Devonian, Permian-Triassic, Triassic-Jurassic, and Cretaceous-Paleogene extinctions.

What is adaptive radiation and how does it lead to an increase in species diversity?

Adaptive radiation is the rapid evolution of diversely adapted species from a common ancestor when new environmental opportunities arise. It leads to an increase in species diversity as organisms adapt to different niches.

What factors can promote adaptive radiations?

Factors include the availability of new habitats, the evolution of novel traits, and the extinction of competitors.