Component 2 - Classification biodiversity and evolution Flashcards
What is continuous variation?
Controlled by a number of genes
Character shows a gradation from one extreme to another
What is continuous data like graphically?
Normally distributed
Bell shaped
What is discontinuous variation?
Controlled by a single gene
No intermediate forms
Characteristics are clear cut and easy to tell apart
What is discontinuous data like graphically?
Random
What does heritable variation result from?
Genetic changes due to sexual reproduction1
What does non-heritable variation result from?
Environmental influences that determine phenotypic variation
Name 3 ways in which heritable variation could come about
The mixing of 2 different parental genotypes in cross fertilisation
The random assortment of homologous chromosomes in metaphase I
Crossing over between homologous chromosomes during prophase I
What is inter-specific competetion?
Competition between individuals of different species
Illustrated by predator-prey relationships
What are the two ways in which non-heritable changes come about?
In humans examples include diet and exercise
In plants examples include temperature, light and availability of inorganic ions
What does heritable changes ultimately result in?
Establish new allele combinations
Only mutations novel long-lasting variations
What is intra-specific competition?
Competition between individuals of the same species
The basis of the origin of species by natural selection
What is a gene pool?
All the alleles of all the genes of all the individuals in a population at any one time
What is meant by allele frequency?
A measure of the relative frequency of an allele on a genetic locus in a population
How does variation influence a population?
Some will have characteristics that give them an advantage in the ‘struggle for survival’
What is selection?
The process by which organisms better adapted to their environment survive and breed, while those less well adapted fail
The better the adapted organisms are more likely to pass on their characteristics to succeeding generations
What does selection cause in an environment ulitmately?
Exerts a selection pressure which determines the frequency of the allele within the gene pool
What is Natural Selection?
Organisms which are better adapted to their environment are likely to survive and reproduce to produce offspring that are successful
In any population why is there variation?
Due to random mutations
Describe the 4/5 mark common structure question about natural selection (speciation)
Variation in … due to random mutations in the population
These individuals have a selective advantage (state why)
Survive to reproduce
Pass on their advantageous allele to the next generation
Over many generations the allele frequency increases in the population
What is a species?
A group of similar individuals that are able to interbreed and produce fertile offspring
Reproductively isolated from other such groups
What is genetic drift in isolated populations?
Variations in allele frequencies in populations that occur by chance
Particularly significant evolutionary mechanism in small or isolated pop.
What is the Founder effect?
When the population is isolated on an island or a new habitat, the founder members of that population are a small sample of the original population
By chance they may have very different allele frequency to the original population and if the pop. size remains small it may undergo genetic drift
What is the bottleneck effect?
Resulting from a disaster that drastically reduces population size
e.g. earthquakes, volcanic eruptions
These populations may survive after being squeezed through a bottleneck of low numbers
What is speciation?
Features of behaviour, morphology, or genetics which serve to prevent breeding between species
What is allopatric isolation?
The population becomes physically split in to separate demes
e..g. mountains, rivers, altitudes
These populations will evolve independently of each other to the environmental conditions where they live
The two populations may start to diverge and develop other mechanisms that will keep them reproductively isolated should they meet in the future
What is reproductive isolation?
When organisms inhabiting the same area become reproductively isolated into two groups when there are no physical barriers
What is adaptive radiation?
Where the present day species have all descended from a common ancestor and have over time successfully adapted to their environment
What is Temporal/Seasonal barriers?
When the breeding season or time of activity of two closely related populations don’t correspond
What is behavioural isolation?
Courtship behaviours:
Complex calls, dances, rituals, develops which are very specific
What is meant by morphological?
No longer able to physically mate as genitals are incompatible
What is Hybrid Sterility?
The sets of chromosomes from each parent are different, and therefore cannot pair up in Meiosis I and produces gametes
