Biology All Terms

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516 Terms

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Evolution
any change in the heritable traits within a population across generations, "descent with modification"
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Natural Selection
increases the frequency of favorable adaptations to an environment, the mechanism which drives evolution
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Taxonomy
The organization of species into a nested classification system
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artificial selection
a human-controlled process to produce individuals with certain traits
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Homology
Similarity in characteristics resulting from a shared ancestry.
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vestigial structures
remnant of a structure that may have had an important function in a species' ancestors.
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convergent evolution
Process by which unrelated organisms independently evolve similarities when adapting to similar environments
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analogous structures
Body parts that share a common function, but not structure
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Biogeography
Geographic distribution of species.
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Lamarck's (incorrect) Theory of Evolution
individuals can acquire traits during their lifetime and pass them onto their offspring
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3 Domains of Life
Bacteria, Archaea, Eukarya
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Eukarya
all organisms that have a nucleus
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Prokarya
organisms that do not have a nucleus
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Archaea
bacteria that live in extreme environments
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Eukarya Kingdoms
Protista, Plantae, Fungi, Animalia
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horizontal gene transfer
transfer of genes between cells of the same generation
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Phylogeny
Evolutionary history of a species / group of species
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Systematics
study of the evolutionary relationships between organisms
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Cladistics
classification based on common ancestry
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phylogenetic trees
Branching diagrams that depict hypotheses about evolutionary relationships.
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analogy
similarity of function and superficial resemblance of structures that have different origins
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Molecular Homologies
Similar DNA sequences in different taxa
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Molecular homoplasies
shared bases in nucleotide sequences that are otherwise very dissimilar
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Genus
A classification grouping that consists of a number of similar, closely related species
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Family
Group of genera that share many characteristics
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Order
Group of similar families
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Classes
In classification, the taxonomic category above order.
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Phyla
In classification, the taxonomic category above class.
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Kingdom
First and largest category used to classify organisms
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Domain
A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya.
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Taxon
any particular group within a taxonomic system
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monophyletic
ALL descendants came from one common ancestor
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paraphyletic
Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants.
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clades
A group of species that includes an ancestral species and all its descendants.
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binomial nomenclature
A system for giving each organism a two-word scientific name that consists of the genus name followed by the species name
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Microevolution
Change in allele frequencies in a population over generations.
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genetic variation
The variety of different types of genes in a species or population.
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population
a group of organisms of the same species populating a given area
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gene pool
All the genes that are present in a population at any one time
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Hardy-Weinberg equilibrium
condition that occurs when the frequency of alleles in a particular gene pool remain constant over time
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genetic drift
A change in the allele frequency of a population as a result of chance events rather than natural selection.
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founder effect
Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
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bottleneck effect
A change in allele frequency following a dramatic reduction in the size of a population
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allele
Different forms of a gene
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mutation
A change in a gene or chromosome.
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gene flow
movement of alleles from one population to another
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adaptive evolution
a process in which traits that enhance survival or reproduction tend to increase in frequency in a population over time
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relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
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directional selection
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
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disruptive selection
natural selection that favors individuals at both extremes of the phenotypic range
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stablizing selection
natural selection where individuals with the average form of a trait have the highest fitness
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balancing selection
natural selection that maintains two or more phenotypic forms in a population
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heterozygote advantage
occurs when heterozygotes have a higher fitness than do both homozygotes
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sexual selection
Natural selection for mating success.
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sexual dimorphism
distinct difference in size or appearance between the sexes of a species
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speciation
the formation of new and distinct species in the course of evolution.
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Macroevolution
large-scale evolutionary changes that take place over long periods of time
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biological species concept
Species is a group of populations whose members have the potential to produce fertile offspring.
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species
a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
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prezygotic barriers
prevent mating between species
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postzygotic barriers
Barriers that prevent the hybrid zygote from becoming a fertile adult.
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morphological species concept
characterizes a species by body shape and other structural features
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ecological species concept
A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.
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phylogenetic species concept
A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.
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allopatric speciation
The formation of new species in populations that are geographically isolated from one another.
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sympatric speciation
The formation of new species in populations that live in the same geographic area
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Polyploidy
condition in which an organism has extra sets of chromosomes
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Autopolyploid
an individual that has more than two chromosome sets that are all derived from a single species
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allopolyploid
a species with multiple sets of chromosomes derived from different species
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punctuated equilibria
The theory that species evolve during short periods of rapid change
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examples of prezygotic barriers
habitat isolation, temporal isolation, behavioral isolation
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examples of postzygotic barriers
hybrid sterility
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geologic record
a standard time scale that divides Earth's history into four eons and further subdivisions
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mass extinction
A large extinction of species in a relatively short period of time
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adaptive radiation
An evolutionary pattern in which many species evolve from a single ancestral species
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heterochrony
Change in the rate or timing of a developmental event
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Paedomorphosis
The retention in an adult organism of the juvenile features of its evolutionary ancestors.
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Conditions for Hardy-Weinberg Equilibrium
no mutations, random mating, no natural selection, extremely large population size, no gene flow
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2 examples of genetic drift
founder effect and bottleneck effect
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Linnaean Classification System
Kingdom, Phylum, Class, Order, Family, Genus, Species
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Gene Expression
conversion of the information encoded in a gene first into messenger RNA and then to a protein
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Transcription
synthesis of RNA from DNA
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Messenger RNA
copies the message from DNA in the nucleus and carries the message to the ribosome
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translation
Process by which mRNA is decoded and a protein is produced
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ribosomes
site of protein synthesis
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primary transcript
The initial mRNA transcript that is produced from DNA synthesis.
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triplet code
Three nucleotides that specifies a specific amino acid.
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Template Strand
The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.
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Codons
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
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nontemplate strand
the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA
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reading frame
Reading mRNA nucleotides in the correct groupings.
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RNA polymerase
Enzyme that transcribes DNA.
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Promoter
specific region of a gene where RNA polymerase can bind and begin transcription
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terminator
A special sequence of nucleotides that marks the end of a genes.
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transcription unit
A region of DNA that is transcribed into an RNA molecule.
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RNA splicing
Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.
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introns
sequence of DNA that is not involved in coding for a protein
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exons
expressed sequence of DNA; codes for a protein
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spliceosome
complex of enzymes that serves to splice out the introns of a pre-mRNA transcript
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ribozymes
RNA molecules that function as enzymes and can splice RNA