Biology 1

• Allele


  One of two or more versions of a gene that arise by mutation and are found at the same place on the chromosome
• Mutation


  A permanent alteration to the genetic material of an organism (the genome)
• Genotype


  The genetic constitution of an individual
• Polygenic traits


  Traits that are controlled by multiple genes instead of just one
• Phenotype


  The observable physical properties of an organism resulting from its genotype
• Genotype by environment interaction (GxE)


  When two different genotypes respond to environment variation in different ways
• Phenotypic plasticity


  Some of the changes in an organism's behaviour, morphology, and physiology in response to a unique environment
• Evolution


  The change in the heritable characteristics of biological populations over successive generations
• Genetic drift


  The change in the frequency of an existing allele in a population due to random chance
• Genetic bottleneck


  A loss of genetic variation that occurs after outside forces destroy most of the population. The surviving individuals have a limited gene pool to pass onto their offspring. This can reduce the adaptability and survival of the species
• Gene flow


  The movement of genetic material from one population to another. Can occur in many ways, such as through interbreeding, migration, or vertical transfer. Gene flow changes the gene pool and the allele frequency of the receiving population and increases its genetic variability
• Natural selection


  The process through which living organisms adapt and change. It is what drives evolution. Individuals with adaptive traits (those with a survival advantage) are more likely to survive and reproduce. These adaptive traits are then passed on to the offspring. Over time, these favourable traits become more common in the population
• Adaptation


  The process of change by which an organism or species becomes better suited to its environment
• Fitness


  The capacity of an individual to pass on its DNA to its offspring. Generally it is restricted to an asexual population without genetic recombination in order to avoid the complications of sex and recombination. The lifetime number of offspring an individual can produce
• Reproductive value


  A measure of the relative reproductive potential of an individual at any age. Reproductive value is influenced by the probability of survival as well as the probability of successful reproduction
• Optimality


  Evaluating the costs and benefits of different organismal features, traits, and characteristics
• Pleiotropy


  When one gene influences two or more seemingly unrelated phenotypic traits. A gene that is an example of this is called a pleiotropic gene
• Trade-offs


  The process through which a trait increases in fitness at the expense of decreased fitness in another trait
• Historical (phylogenetic) constraints


  The limitations on future evolutionary pathways imposed by previous adaptations
• Limit of selection


  The maximum possible value of a trait that can be achieved through selection
• Artificial selection


  The identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations. Works the same as natural selection, except instead of the driving force being nature, it is humans
• Human-induced selection


  Evolutionary changes as a result of direct or indirect pressures imposed by human activities
• Directional selection


  A mode of negative natural selection in which an extreme phenotype is favoured over other phenotypes in an extreme changing environment
• Stabilising selection


  The population mean stabilises on a particular non-extreme trait value. It favours the average individuals in a population and reduces extremes
• Disruptive selection


  Favours the extreme traits over the intermediate traits and puts the population into two distinct groups
• Frequency-dependent selection


  An evolutionary process where the fitness of a phenotype is dependent on its frequency relative to the other phenotypes present in the population
• Negative frequency-dependent selection


  Serves to increase the population's genetic variance by selecting for rare phenotypes
• Positive frequency-dependent selection


  Serves to decrease the population's genetic variance by selecting for common phenotypes
• Sexual selection


  A mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection) and compete with members of the same sex for access to members of the opposite sex (intrasexual selection)
• Coevolution


  A process of reciprocal evolutionary changes that occur between two or more species that interact with each other. The interaction applies selection pressure on both species, which affects their evolution. They reciprocally affect each other's evolution
• Heritability


  The ratio of variation due to genetic differences between genotypes to the total phenotypic variation for a character or trait in a population
• Additive genetic variation


  Involves the inheritance of a particular allele from your parent and this allele's independent effect on the specific phenotype, which will cause the phenotype deviation from the mean phenotype
• Heterosis


  The improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced by as a result of mixing the genetic contributions of its parents
• Heterozygous advantage


  This occurs when the heterozygous genotype has a higher relative fitness than the homozygous dominant or recessive genotype
• Balancing selection


  A number of selective processes by which multiple alleles are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone
• Antagonistic pleiotropy


  A situation in which a single gene or allele affects multiple traits, where some are advantageous and some are disadvantageous to the organism's fitness. Antagonistic pleiotropy has been proposed as a possible explanation as to why organisms age, as genes that confer advantages earlier in life may also cause senescence later in life
• Individual selection


  Natural selection operates at the level of the individual. Adaptive features are acquired by and passed onto individual organisms, not groups or species, and they benefit individual organisms directly and groups or species only incidentally
• Group selection


  A proposed mechanism of evolution in which evolution acts on the level of the group or species as a whole rather than on the individual or gene
• Gene's eye view (selfish gene)

  According to this viewpoint, adaptive evolution occurs through the differential survival of competing genes. The central idea is that genes are the ultimate beneficiaries of selection. Genes compete for survival, and those alleles that promote their own propagation become more prevalent in the population
• Unit of selection


  Refers to a biological entity within the hierarchy of biological organisation that is subject to natural selection. These entities can be at various levels, including genes, cells, individuals, groups, and species