bio 102 test 2 Flashcards
A scientific discipline focused on classifying organisms and determining their evolutionary relationships.
What is systematics?
The movement of genes from one genome to another, complicating efforts to build a tree of life.
What is horizontal gene transfer?
Definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
What is the biological species concept?
A process in which individuals with certain inherited characteristics are more likely to obtain mates.
What is sexual selection?
A process in which traits that enhance survival or reproduction tend to increase in frequency over time.
What is adaptive evolution?
The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregations and recombination of alleles are at work.
What is the Hardy-Weinberg Theorem?
A change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus.
What are mutations?
Differences among individuals in the composition of their genes or other DNA sequences.
What is genetic variation?
The aggregate of all copies of every type of allele at all loci in every individual in a population.
What is a gene pool?
The group of organisms/taxa whose evolutionary relationships are the focus of a particular phylogenetic analysis.
What is an ingroup?
A species/group of species closely related to the ingroup that diverged before the ingroup.
What is an outgroup?
The simplest explanation for a phenomenon that is most likely to be correct.
What does parsimony refer to in evolutionary biology?
Characteristics present in an ancestral species shared exclusively by its descendants.
What are synapomorphies?
An evolutionary novelty unique to a particular clade.
What is a shared derived character?
A character that originated in an ancestor of the taxon.
What is a shared ancestral character?
Consists of an ancestral species and some, but not all, of the descendants.
What is a paraphyletic group?
A branch from which more than two groups emerge.
What is a polytomy?
Diverges early in the history of a group and originates near the common ancestor.
What is a basal taxon?
Groups that share an immediate common ancestor.
What is a sister taxon?
A hypothesis about evolutionary relationships, showing patterns of descent.
What does a phylogenetic tree represent?
Includes distantly related species but does not include their most recent common ancestor.
What is a polyphyletic group?
A valid clade that consists of an ancestor species and all its descendants.
What is a monophyletic group?
A group of species that includes an ancestral species and all its descendants.
What is a clade?
Groups organisms by common descent.
What is cladistics?
Uses molecular data (DNA/protein sequences) to infer evolutionary relationships.
What is molecular phylogenetics?
Inference of evolutionary trees using anatomical traits.
What is morphological phylogenetics?
Similarities due to convergent evolution.
What are analogies in evolutionary biology?
Phenotypic and genetic similarities due to shared ancestry.
What are homologies?
A system of naming organisms with a unique two-part scientific name, consisting of genus and species.
What is binomial nomenclature?
From broad to narrow: domain, kingdom, phylum, class, order, family, genus, species.
What is the taxonomic hierarchy?
The ordered division and naming of organisms.
What is taxonomy?
Master regulatory genes that determine where an organism’s features will develop.
What are homeotic genes?
An evolutionary change in the rate or timing of developmental events.
What is heterochrony?
Development of reproductive organs accelerates relative to other organs, leading to sexually mature individuals retaining juvenile features.
What is paedomorphosis?
Duplication produces new developmental genes and gives rise to new morphological forms.
What is the role of gene duplication in evolution?
Structures do not evolve in anticipation of future use; natural selection improves them in the context of current utility.
How do structures evolve according to natural selection?
Structures that evolve in one context but become co-opted for a different function.
What are exaptations?
Most novel biological structures evolve in many stages from simpler ancestral structures.
What is evolutionary novelty?
Opening of niches, evolution of novel characteristics, and colonization of new regions with few competitors.
What can trigger adaptive radiation?
A rapid period of evolutionary change where many new species arise and adapt to different ecological niches.
What is adaptive radiation?
The distribution of fossils and living groups.
What reflects the historic movement of continents?
Regions that were once connected become isolated, leading to divergence and allopatric speciation.
What occurs when supercontinents break apart?
Major changes in climate occur, requiring organisms to adapt, move, or face extinction.
What happens to organisms when a continent shifts toward or away from the equator?
The formation of the supercontinent Pangaea altered many habitats.
What significant event occurred about 250 million years ago?
The supercontinent formed about 250 million years ago that altered many habitats.
What is Pangaea?
Movements in the mantle cause the plates to gradually shift.
What is continental drift?
When a prokaryotic cell engulfs a small cell that evolves into a mitochondrion.
What is endosymbiosis?
An extreme episode of volcanism that caused a series of catastrophic events.
What triggered the Permian extinction?
Occur when large numbers of species rapidly become extinct worldwide.
What are mass extinction events?
Changes in the history of life on Earth based on the accumulation of fossils in sedimentary rock layers.
What does the fossil record reveal?
Layered rocks that form when prokaryotes bind thin films of sediment together.
What are stromatolites?
The time required for 50% of the parent isotope to decay.
What is half-life?
Used to determine the age of fossils based on the decay of radioactive isotopes.
What is radiometric dating?
Fossils of organisms that lived for a short period and were widespread.
What are index fossils?
Species diverge from one another more slowly and steadily over time.
What is the gradual model of speciation?
New species change most as they branch from a parent species and then change little for the rest of their existence.
What is punctuated equilibrium?
Continued formation of hybrid individuals that survive and reproduce better than members of either parent species.
What is stability in hybrid zones?
The weakening of reproductive barriers when two species meet in a hybrid zone.
What is fusion in hybrid zones?
Natural selection strengthens prezygotic barriers to reproduction to reduce the formation of unfit hybrids.
What is reinforcement in hybrid zones?
The formation of prezygotic barriers between populations that feed on different host plants.
What is habitat differentiation?
A species may originate from an accident during cell division that results in extra sets of chromosomes.
What is polyploidy?
Suggests that females choose mates based on traits that are honest indicators of the male’s ability to enhance offspring survival.
What is the good genes hypothesis?
A form of natural selection where individuals of one sex are choosy in selecting their mates from the other sex.
What is intersexual selection?
A form of natural selection where there is direct competition among individuals of one sex for mates.
What is intrasexual selection?
A recessively inherited human blood disease caused by a single nucleotide change in the alpha globin gene.
What is sickle-cell anemia?
Genetic variation that does not provide a selective advantage or disadvantage.
What is neutral variation?
Greater reproductive success of heterozygous individuals compared with homozygotes.
What is heterozygous advantage?
Selection in which the fitness of a phenotype depends on how common the phenotype is in a population.
What is frequency-dependent selection?
Natural selection that maintains two or more phenotypic forms in a population.
What is balancing selection?
An inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.
What is an adaptation?
Acts against both extreme phenotypes and favors intermediate variants.
What is stabilizing selection?
Occurs when conditions favor individuals at both extremes of a phenotypic range.
What is disruptive selection?
Occurs when conditions favor individuals exhibiting one extreme of a phenotypic range.
What is directional selection?
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.
What is fitness in evolutionary terms?
1) No mutations 2) Random mating 3) No natural selection.
What are the three conditions for Hardy-Weinberg equilibrium?
An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.
What is cladistics?
Characteristics that are similar because of convergent evolution, not homology.
What are analogies?
Similarities in characteristics resulting from a shared ancestry.
What are homologies?
The classification of all living organisms into eight categories: domain, kingdom, phylum, class, order, family, genus, species.
What is taxonomy?
Evolutionary change above the species level.
What is macroevolution?
The formation of new species in populations that live in the same geographic area.
What is sympatric speciation?
The formation of new species in populations that are geographically isolated from one another.
What is allopatric speciation?
Reproductive barriers that prevent hybrid zygotes produced by two different species from developing into viable, fertile adults.
What are postzygotic barriers?
Reproductive barriers that impede mating between species or hinder fertilization if interspecific mating is attempted.
What are prezygotic barriers?
