1 Flashcards
Define abiotic factor
> Non-living, physical conditions in an ecosystem
>Example: temperature, light, soil conditions and pH
Define adaptation
> An individual increases their chances of survival + reproduction
By altering / adjusting structure / habits, often occuring through natural selection
Define allele
A different version of a gene
Define allele frequency
How often an allele occurs in a population
Define autosomal-linkage
Two or more genes with loci on the same autosome (i.e. not a sex chromosome)
Define biotic factors
> Effect of activities of living organisms on other organisms
>Example: food availability, predation and competition
Define carrying capacity
Maximum number in a population that can be sustainably supported in an ecosystem
Define climax community
Fairly stable, final community at the end of succession
Define codominant
Alleles that are both expressed in the phenotype i.e. neither is recessive
Define ecological niche
> The role of a species within its habitat
>Governed by adaptation to both abiotic and biotic conditions
Define epistasis
The allele of one gene masks the expression of another gene in the phenotype
Define evolution
Change in allele frequencies (in a population) over time
Define gene
> Sequence of bases on DNA molecule located on chromosomes
>Instruct protein synthesis
Define genotype
The genetic constitution of an organism i.e. the alleles an organism has
Define homologous chromosome
> Capable of doing meiosis
>Similar/same sequence of genes/loci
Define interspecific competition
Competition between organisms of different species
Define intraspecific competition
Competition between organisms of the same species
Define locus
Fixed position of a gene on a chromosome
Define multiple alleles
When a gene has more than two alleles
Define phenotype
The expression of the genetic constitution and its interaction with the environment i.e. an organism’s characteristics
Define population
All the organisms of one species in a particular habitat (at the same time)
Define sex-linked
Gene with loci a sex chromosome (X or Y)
Define succession
Process by which an ecosystem changes over time
Describe and explain the process of primary succession
> Pioneer species
Adapted to hostile abiotic conditions colonise environment
Make conditions less hostile
New species outcompetes pioneer species -> may change environment to be less suitable for previous species
Becomes dominant species, until outcompeted
Biodiversity, and therefore complexity + stability, of ecosystem increases
Until climx community, the final stage, is reached
Describe directional selection
> Selection in favour of individuals with a single, extreme phenotype
Occurs in response to an environmental change
Describe disruptive selection
> Selection in favour of individuals with extreme phenotypes, opposing stabilising selection
Occurs whes when environment favours more than one phenotype
Describe how abiotic factors can affect population size
> Ideal conditions allow for fast growth and successful reproduction
Otherwise, energy expended on body processes compensating for non-ideal conditions
Example: environment above / below mammal’s body temperature => more energy expended on maintaining core temperature
Describe how natural selection arises
> Variation in individuals of the same species
Selection pressures -> predation, disease, competition
Result in differential survival and reproductive success
Describe how quadrats placed along a belt transect can be used for estimating the size of population
> Lay measuring tape along length of area being measured
Place quadrats all along the tape (belt transect)
Or at regular intervals (interrupted belt transect)
Record percentage cover or abundance of species within each quadrat
Describe how randomly placed quadrats can be used for estimating the size of population
> Frame quadrats placed on the ground at different, randomly generated co-ordinates
Percentage cover of each species present calculated
A square is counted if species covers > 50% of square
