Topic 7 Key Words Flashcards
Diploid
Cells in which the nucleus contains two sets of chromosomes
Gene
A section of DNA on a chromosome coding for one or more polypeptide
Allele
An alternative form of a gene
Genotype
All of the alleles that an organism carries on its chromosomes
Pheonotype
Observable characteristics of an organism which are the result of the genotype and environmental factors
Dominant allele
An allele that is always expressed in the phenotype of an organism
Recessive allele
The characteristic is only expressed in the presence of another identical allele
Codominant allele
Both alleles for one gene in a heterozygous organism contribute to the phenotype
Homozygous
The allele of a gene are identical
Heterozygous
The alleles of a gene are different
Locus
The position of a gene on a chromosome
Monohybrid inhertiance
Inheritance of a characteristic controlled by a single gene
Dihybrid inheritance
Inheritance of two characteristics that are controlled by separate genes
Epistasis
An interaction between genes when the expression of one gene suppresses the expression of another gene
Autosome
All the non-sex chromosomes
Homologous pair
Diploid organisms have pairs of chromosomes
Sex-linkage
The expression of alleles located on sex chromosomes depends on the sex of the individual
Species
Organisms that can reproduce to produce fertile offspring
Population
All the organism of a species in one place at one time
Gene pool
All the alleles present in a population
Allele frequency
How common an allele is in the population
Evolution
A change in allele frequency over time
Differential reproductive success
Organisms with a phenotype better adapted to their environment have selective advantage and are not likely to survive and reproduce
Community
All the organisms of all the species in one place at one time
Speciation
The process of forming new species
The Hardy-Weinberg Principle
A model that predicts the frequency of alleles, genotype and phenotype in a population
Intraspecific variation
Individual of the same species have the same genes but different alleles - variation in their phenotype
Interspecific variation
Individuals of different species have different genes and live in different environments - variation in their phenotype
Continuous variation
Variation is smooth and continuous
Discontinuous variation
Individuals fall into discrete groups with no intermediates
Predation
When an organism (the predator) kills and eats another organism (the prey)
Genetic drift
A change in allele frequency between generations due to random chance
Directional selection
Individuals with an extreme type of characteristic are more likely to survive and reproduce
Stabilising selection
Individuals with extreme types of characteristics are less likely to survive and reproduce
Abundance
The number of individuals of a single in an ecosystem/ habitat and population size
Distribution
Where a species is found in an ecosystem/ habitat
Limiting factor
The thing that limits the maximum population size
Carrying capacity
The maximum stable population an ecosystem can support
Biotic factors
Ecological factors that make up part of the living environment
Abiotic
An ecological factor that makes up part of the non-biological environment of an organism
Niche
The role of species in an ecosystem
Succession
A series of changes in species composition in a given place over time
Climax community
Final stage of succession, few species dominant, stable equilibrium of species
Deflected succession
A community that remains stable only because human activity prevents natural succession from taking place
Environment
All the factors in a habitat that affect an organism
Biosphere
The region of the earth the encompasses all living organisms
Interspecific competion
Competition between organisms of a different species
Intraspecific competition
Competition between organisms of the same species
Habitat
The place where organisms live
Conservation
Managing succession and balancing the ethical and commercial interests
Biodiversity
The range and variety of genes, species and habitats within a particular region
Allopatric speciation
Process of forming new species due to geographical isolation
Sympatric speciation
The process of forming new species without geographical isolation
Disruptive selection
Both extremes of the phenotype are more likely to survive and reproduce than the mean phenotype
Ecosystem
A system in which all organisms interact with biotic and abiotic factors
