AP®︎ Biology: Unit 7 Flashcards
Master key terms and definitions for Unit 7 of AP Biology – Natural Selection to help you prep for quizzes and the AP exam.
Evolution
Change in a population's genetic makeup across generations.
Change in a population's genetic makeup across generations.
Species change over time from common ancestors as favorable heritable traits spread.
Struggle among organisms for scarce food, space, mates, or other necessities.
An observable trait that increases survival or reproductive success in a given environment.
A heritable trait that increases fitness in a specific environment.
Living environmental influences such as predators, competitors, parasites, disease, and food sources.
Nonliving environmental influences such as temperature, rainfall, pH, light, and geography.
Changes in biotic or abiotic conditions that alter which traits are favored.
Selection can reduce, maintain, or increase variation depending on which traits are favored.
Galapagos birds whose beak differences reflect adaptation to different food sources.
Individuals with favorable phenotypes leave more surviving, reproducing offspring than others.
The number of viable offspring an organism produces relative to others.
Differences in observable traits among individuals in a population.
Biotic pressures come from living factors; abiotic pressures come from nonliving conditions.
Relative ability to survive and produce fertile offspring in a specific environment.
Differences in cellular molecules can change function and affect survival and reproduction.
The variety of alleles and genotypes present within a population.
Industrial soot favored dark moths over light moths by changing camouflage against predators.
Warmer conditions can favor plants that flower earlier if timing improves reproduction.
Rare resistant insects survive insecticide exposure and pass resistance alleles to offspring.
In malarial regions, heterozygotes have the highest fitness, maintaining both alleles in the population.
An organism's observable traits produced by gene expression and environmental influences.
The process in which individuals with heritable traits that improve survival or reproduction in a given environment leave more offspring, making those traits more common over generations.
Genetic differences in traits among individuals that can be passed from parents to offspring.
An environmental factor that causes some phenotypes to survive or reproduce more successfully than others.
The process in which individuals with heritable traits that improve survival or reproduction in a given environment leave more offspring, making those traits more common over generations.
Human preferences drive one; environmental pressures drive the other, though both change allele frequencies.
Breeding for a few traits often narrows the range of alleles within a population.
A loss of diversity caused when only a small subset of individuals contributes genes.
The long-term human shaping of species through repeated selection for useful or preferred traits.
Noticeable trait shifts can occur in few generations because humans control mating consistently.
Selected traits may increase usefulness while also causing health, fertility, or disease-susceptibility problems.
Some domesticated populations become unable to survive or reproduce effectively without human assistance.
Many dog breeds arose by repeatedly selecting wolf descendants for size, behavior, and body traits.
Teosinte to maize, wild mustard to brassicas, and wild watermelon to larger sweeter forms.
The proportion of a specific allele among all alleles for a gene in a population.
All alleles present in all individuals of a population.
A random change in DNA sequence that creates new alleles.
Point mutations alter one base pair; chromosomal mutations change larger chromosome segments or arrangement.
Differences in alleles among individuals in a population.
Random changes in allele frequencies caused by chance, especially in small populations.
Genetic drift when a few isolated individuals start a new population with limited alleles.
Smaller populations experience stronger random allele frequency changes than larger populations.
Chance transmission of alleles to offspring can shift frequencies between generations.
Studies how allele frequencies in populations change across generations, which defines evolution.
The movement of alleles between populations that increases variation within populations, reduces differences between them, and can prevent speciation.
A model in which allele and genotype frequencies stay constant in a non-evolving population.
The expectation that allele frequencies remain unchanged unless evolutionary forces act on the population.
p + q = 1 for allele frequencies; p^2 + 2pq + q^2 = 1 for genotype frequencies.
p is the frequency of one allele; q is the frequency of the other allele.
p^2 is homozygous dominant, 2pq is heterozygous, and q^2 is homozygous recessive.
Find q from q^2 if needed, calculate p as 1 minus q, then use p^2, 2pq, and q^2.
Large population, no migration, no mutation, random mating, and no natural selection prevent allele frequency change.
Scientific support from fossils, anatomy, molecules, geography, and quantitative analysis showing organisms changed over time.
The geographic distribution of species and populations across regions, islands, and barriers.
The ordered collection of fossils in rock layers documenting past life and evolutionary change.
Relative dating using rock layer positions to infer whether fossils are older or younger.
Absolute dating that uses radioactive isotope decay rates to estimate the age of rocks or fossils.
Radiometric dating of recent organic remains using carbon-14 decay, effective to about 50,000 years.
Reduced or nonfunctional remnants of features that were functional in ancestors.
Analysis of nucleotide similarity among organisms to infer relatedness and common ancestry.
Analysis of amino acid similarity in proteins to infer evolutionary relationships among organisms.
Nearly all organisms use the same codon-to-amino-acid system for protein synthesis.
The idea that different species descended from shared ancestral populations in the past.
A method for estimating divergence time from the accumulation of DNA or protein sequence differences over time.
Shared eukaryotic traits include membrane-bound organelles, linear chromosomes, and genes containing introns.
Internal cell compartments surrounded by membranes, such as the nucleus, mitochondria, and chloroplasts.
DNA molecules arranged as straight chromosomes rather than the circular form typical of prokaryotes.
Noncoding gene sequences transcribed into RNA and removed before the mature mRNA is translated.
Changes in a population's DNA over generations through mutation, recombination, and other evolutionary mechanisms.
Successive fossils show organisms changing over geologic time, with appearances, transitions, and extinctions.
Rapid genetic change in pathogens can produce new diseases or revive previously controlled ones.
Evolution is a change in allele frequencies in a population, not a change within one individual.
Natural selection spreads heritable traits that allow organisms to survive antibiotics, pesticides, herbicides, or other chemicals, shifting population traits over time.
A branching diagram showing relative relatedness based on shared derived characters, not time scale.
A branch point representing the most recent common ancestor and a speciation event.
The end of a branch representing an observed species or taxonomic group.
The lineage least closely related to the others, used to root the tree.
Shared characters occur in multiple groups; shared derived characters evolved later and indicate common ancestry.
Comparisons of physical traits in living or fossil organisms used to infer evolutionary relationships.
Molecular data are usually more accurate; morphology can be misleading from convergent evolution.
Using dated fossils to estimate when lineages diverged on a phylogenetic tree.
On phylogenetic trees, longer branches indicate more evolutionary change; cladograms are not scaled.
An ancestor and all of its descendants considered as one evolutionary group.
Paraphyletic groups exclude some descendants; polyphyletic groups combine members from different ancestors.
Establishing the ancestral base of a phylogeny, usually by comparing the ingroup with an outgroup.
Branches can rotate around a node without changing the evolutionary relationships shown.
Lineages sharing a more recent common ancestor are more closely related than those diverging earlier.
DNA or protein sequence comparisons infer relatedness, with greater similarity indicating closer ancestry.
Testable models of evolutionary relationships that are revised when new evidence appears.
Branching diagrams that show hypothesized evolutionary relationships based on shared ancestry; cladograms show relative relatedness based on shared derived characters without a time scale, while phylogenetic trees often indicate evolutionary change and sometimes time.
Structures with similar underlying anatomy due to common ancestry, even if their functions differ.
The formation of new species from existing populations through evolutionary divergence.
A condition in which populations can no longer interbreed and exchange genes.
A species is a group that can interbreed and produce viable, fertile offspring.
Random allele frequency changes can cause isolated populations, especially small ones, to diverge.
Related populations become increasingly different as they adapt to different environments.
Rapid diversification of one lineage into many species occupying different ecological niches.
New species form after populations become geographically separated and reproductively isolated.
New species form without geographic separation, often through niche differences or mate choice.
Populations live in different habitats and rarely encounter each other to mate.
Populations breed at different times, preventing mating and gene exchange.
Different courtship signals or mating behaviors prevent populations from interbreeding.
Differences in reproductive structures prevent successful mating between populations.
Egg and sperm cannot fuse successfully, so fertilization does not occur.
A hybrid embryo forms but fails to develop properly or survive.
A hybrid survives but cannot produce functional gametes or fertile offspring.
First-generation hybrids are viable, but later generations have reduced fitness or fertility.
Fruit flies on Hawaiian islands illustrate divergent evolution and allopatric speciation across islands.
A host shift from hawthorn to apple led to reduced gene flow without geographic separation.
Lizards with different displays, dewlap colors, and habitats show behavioral reproductive isolation.
Rapid evolutionary change after long stasis contrasts with slow, continuous change over time.
Before fertilization barriers prevent mating, while after fertilization barriers reduce hybrid viability or fertility.
The independent evolution of similar traits in unrelated lineages due to similar selective pressures.
A pattern of natural selection in which both extreme phenotypes are favored over intermediate forms within a population.
Genetic uniformity increases vulnerability to disease, environmental change, and population decline.
An allele can be advantageous in one environment but harmful in another.
Reduced survival or reproduction caused by mating among closely related individuals.
An endangered bird whose severe bottleneck left very low genetic variation.
An endangered mammal descended from few survivors, leaving limited genetic diversity.
A fragmented population that suffered inbreeding depression and reduced reproductive success.
A plant disease that devastated genetically uniform potato crops during the Irish famine.
A fungal disease whose impact is reduced by maintaining genetically diverse corn varieties.
Wildlife corridors, managed breeding, cryopreservation, and reintroduction help preserve variation.
Heritable variation increases the chance some individuals survive and reproduce after environmental change.
A drastic reduction in population size that leaves survivors with only a small sample of the original alleles, greatly reducing genetic diversity.
Ancient rocks and minerals reveal early Earth conditions such as atmosphere, temperature, and liquid water.
Young Earth was initially hot, volcanic, and heavily bombarded, then later cooled and stabilized.
An early period of intense meteorite impacts that made Earth's surface largely uninhabitable.
An RNA molecule that catalyzes chemical reactions without being a protein enzyme.
Earth formed 4.6 bya, became habitable by 3.9 bya, and fossils show life by 3.5 bya.
Early life may have relied on RNA because it stores information and catalyzes reactions.
RNA replication ensured continuity, base-pairing enabled copying, and proteins were not yet catalysts.
Layered rock structures formed by ancient microbial communities that provide early fossil evidence of life.
