Shared Flashcard Set

Details

Biology 180, UW
Natural Selection
76
Biology
Undergraduate 1
10/28/2010

Additional Biology Flashcards

 


 

Cards

Term
Deleterious
Definition
Referring to any mutation, allele, or trait that reduces an individual's fitness.
Term
Dominant Allele
Definition
Allele that determines the phenotype of a heterozygous individual.
Term
Natural Selection
Definition
The process by which individuals with certain heritable trais tend to produce more surviving offspring than do individuals without those traits, often leading to a change in the genetic makeup of the population. A major mechanism of evolution.
Term
Evolution
Definition

(1) The theory that all organisms on Earth are related by common ancestry and that they have changed over time, predominantly via natural selection.

(2) Any change in the genetic characteristics of a population over time, especially, a change in allele frequencies.

Term
Population
Definition
Consists of individuals of the same species that are living in the same area at the same time.
Term
Descent with Modification
Definition
The phrase used by Darwin to describe his hypothesis of evolution by natural selection.
Term
Hardy-Weinberg Principle
Definition
Term
Mutation
Definition

Any change in the hereditary material of an organism (DNA in most organisms, RNA in some viruses). It's the ONLY source of new alleles.

Term
Migration
Definition
In population genetics, movement of individuals from one population to another.
Term
Genetic Drift
Definition
Any change in allele frequencies due to random events. Causes allele frequencies to drift up and down randomly over time, and eventually can lead to the fixation or loss of alleles.
Term
Gene Flow
Definition

The movement of alleles between populations; occurs when individuals leave one population, join another, and breed.

  • Effect on overall genetic diversity depends
  • Changes allele frequencies
  • The impact on fitness is random

Term
Inbreeding
Definition
Mating between closely related individuals. Increases homozygosity of a population and often leads to a decline in the average fitness (inbreeding depression).
Term
Trade-off
Definition

In evolutionary biology, an inescapable compromise between two traits that cannot be optimized simultaneously.

Term
Fixation
Definition

If directional selection continues over time, the favored alleles will eventually approach a frequency of 1.0 while disadvantageous alleles will approach a frequency of 00. Alleles that reach a frequency of 1.0 are said to be...

Term
Central Dogma
Definition
The long-accepted hypothesis that information in cells flows in one direction: DNA codes for RNA, which codes for proteins. 
Term
Directional Selection
Definition

A pattern of natural selection that favors one extreme phenotype with the result that the average phenotype of a population changes in one direction. Generally reduces overall genetic variation in a population.

Term
Gene Pool
Definition
All of the alleles of all of the genes in a certain population.
Term
Stabilizing Selection
Definition

A pattern of natural selection that favors phenotypes near the middle of the range of phenotypic variation. Reduces overall genetic variation in a population. 


decreases overall genetic diversity

changes allele frequencies

increases fitness

Term
Disruptive Selection
Definition
A pattern of natural selection that favors extreme phenotypes at both ends of the range of phenotypic variation. Maintains overall genetic variation in a population. 
Term
Heterozygote Advantage
Definition

A pattern of natural selection that favors heterozygous individuals compared with homozygotes. Tends to maintain genetic variation in a population. 

Term
Balancing Selection
Definition

A pattern of natural selection in which no single allele is favored in all populations of a species at all times. Instead, there is a balance among alleles in terms of fitness and frequency. 

Term
Founder Effect
Definition

A change in allele frequencies that often occurs when a new population is established from a small group of individuals (founder event) due to sampling error (i.e. the small group is not a representative sample of the source population).

Term
Genetic Bottleneck
Definition

A reduction in allelic diversity resulting from a sudden reduction in the size of a large population (population bottleneck) due to a random event.

Term
RNA Polymerase
Definition
One of a class of enzymes that catalyze synthesis of RNA from ribonucleotides using a DNA template.
Term
Messenger RNA (mRNA)
Definition
An RNA molecule that carries encoded information, transcribed from DNA, that specifies the amino acid sequence of a polypeptide.
Term
Genetic Code
Definition
The set of all 64 codons and the particular amino acids that each specifies.
Term
Codon
Definition
A sequence of three nucleotides in DNA or RNA that codes for a certain amino acid or that initiates or terminates protein synthesis.
Term
Reading Frame
Definition
The division of a sequence of DNA or RNA into a particular series of three-nucleotide codons. There are three possible reading frames for any sequence.
Term
Start Codon
Definition
The AUG triplet in mRNA at which protein synthesis begins; codes for the amino acid methionine. 
Term
Stop Codon
Definition
One of three mRNA triplets (UAG, UGA, or UAA) that cause termination of protein synthesis.
Term
Point Mutation
Definition
A mutation that results in a change in a single nucleotide pair in a DNA molecule.
Term
Polyploidy
Definition
The state of having more than two full sets of chromosomes.
Term
Aneuploidy
Definition
The state of having an abnormal number of copies of a certain chromosome. 
Term
Chromosome Inversion
Definition
A mutation in which a segment of a chromosome breaks from the rest of the chromosome, flips, and rejoins with opposite orientation as before. 
Term
Replacement Mutation
Definition
A point mutation that causes a change in the amino acid sequence of a protein.
Term
Silent Mutation
Definition
A mutation that does not detectably affect the phenotype of the organism.
Term
Autosome
Definition
Any chromosome that does not carry genes involved in determining the sex of an individual. 
Term
Autosomal Inheritance
Definition
The inheritance patterns that occur when genes are located on autosomes rather than on sex chromosomes.
Term
Sex-linkage
Definition
Genes located on sex chromosomes. Patterns of inheritance in males and females differ.
Term
Linkage
Definition
Two genes found on the same chromosome. Linked genes violate the Principle of Independent Assortment. 
Term
Incomplete Dominance
Definition
Heterozygotes have intermediate phenotype. Polymorphis - heterozygotes have unique phenotype.
Term
Codominance
Definition
Heterozygotes have phenotype of both alleles.
Term
Multiple Allelism
Definition
In a population, more than two alleles present at a locus.
Term
Polymorphism
Definition
In a population, more than two alleles present at a locus.
Term
Polymorphism
Definition
In a population, more than two phenotypes associated with a single gene are present. 
Term
Pleiotropy
Definition
A single allele affects many traits.
Term
Gene-by Gene Interaction
Definition
In discrete traits, the phenotype associated with an allele depends on which alleles are present at another gene.
Term
Gene-by-environment Interaction
Definition
Phenotype influenced by environment experienced by individual.
Term
Pedigree
Definition
A family tree of parents and offspring, showing inheritance of particular traits of interest.
Term
Autosomal Recessive
Definition
In general, a recessive phenotype should show up in offspring ONLY when both parents have that recessive allele and pass it on to their offspring.
Term
X-linked Recessive 
Definition
Allele that appears in every male that carries it. The appearance of the trait skips a generation in a pedigree. 
Term
The Principle of Independent Assortment
Definition
The concept that each pair of hereditary elements (alleles of the same gene) behaves independently of other genes during meiosis. Variation AMONG chromosomes.
Term
Genetic Recombination
Definition
A change in the combination of genes or alleles on a given chromosome or in a given individual. Variation WITHIN chromosomes.
Term
Purifying Selection
Definition
Selection that lowers the frequency or even eliminates deleterious alleles.
Term
Fixed Allele
Definition
If directional selection continues over time, the favored alleles will eventually approach a frequency of 1.0 while disadvantageous alleles will approach a frequency of 0.0. The alleles that reach a frequency of 0.0 are said to be...
Term
High Genetic Variation
Definition
Variation that is only good when the environment is changing.
Term
Temporal Reproductive Isolation
Definition
Populations are isolated because they breed at different times.
Term
Habitat Reproductive Isolation
Definition
Populations are isolated because they breed in different habitats.
Term
Behavioral Reproductive Isolation
Definition
Populations do not interbreed because their courtship displays differ.
Term
Gametic barrier Reproductive Isolation
Definition
Matings fail because eggs and sperm are incompatible.
Term
Mechanical Reproductive Isolation
Definition
Matings fail because male and female reproductive structures are incompatible.
Term
Hybrid viability
Definition
Hybrid offspring do not develop normally and die as embryos. 
Term
Hybrid sterility
Definition
Hybrid offspring mature but are sterile as adults.
Term
Phylogenetic species concept
Definition
The definition of a species as the smallest monophyletic group in a phylogenetic tree.
Term
Monophyletic group
Definition
An evolutionary unit that includes an ancestral population and all of its descendants and no others.
Term
Synapomorphy
Definition
A shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors. Useful for inferring evolutionary relationships. 
Term
Biological Species Concepts
Definition

Reproductive isolation between populations (they don't breed and don't produce viable offspring).


Advantages: Reproductive isolation = evolutionary independence. 


Disadvantages: Not applicable to asexual or fossil species; difficult to assess if populations do not overlap geographically.

Term
Morphospecies Concept
Definition

Morphologically distinct populations.

 

Advantages: Widely applicable 

 

Disadvantages: Subjective; misses cryptic species

Term
Phylogenetic Concept
Definition

Smallest monophyletic group on phylogenetic tree. 


Advantages: widely applicable; based on testable criteria


Disadvantages: Relatively few well-estimated phylogenies are currently available.

Term
Vicariance
Definition
The physical splitting of a population into smaller, isolated populations by a geographic barrier.
Term
t-test
Definition
Categorical versus categorical. 
Term
Chi-square
Definition
Lots of categories
Term
Linear regression
Definition
Continuous versus continuous.
Term
Non-random mating
Definition

Increases homozygosity and does not cause evolution, because allele frequencies do not change in the population as a whole.

  • As no effect on overal genetic diversity
  • No impact on fitness
  • Changes genotype frequencies - not allele frequencies

 

Term
Inbreeding depression
Definition
In inbred offspring, fitness declines due to deleterious recessive alleles that are homozygous.
Term
Convergent Evolution
Definition
The independent evolution of analogous traits in distantly related organisms due to adaptation to similar environments and similar way of life. 
Supporting users have an ad free experience!