7 Genetics & Ecosystems- Evolution Flashcards
What is phenotypic variation and what is it caused by?
-visible differences in characteristics between individuals
-caused by a combination of genetic variation & the environment
What is genetic variation and how does it happen?
-Variation caused by the genetic code
-Happens when individuals of the same species have different alleles
What is environmental variation and what is it caused by?
-Environmental factors contribute to phenotypic variation
-Genotype of an individual interacting with the environment
What are the causes of genetic variation + explain?
-Mutation; changes in base sequence, may cause structure of proteins encoded by DNA to alter. Can be harmful/beneficial/no effect on survival
-Recombination; In meiosis, genes on homologous chromosomes are reshuffled in recombination/crossing over, makes new combinations of genes
-Independent segregation; Homologous chromosomes are randomly separated into haploid cells in meiosis
-Random fertilisation; gametes of 2 unrelated individuals are fused in sexual reproduction to produce a diploid individual.
What are the factors influencing whether an individual is capable of surviving?
-Predation; high= more likely to be eaten by predator. An individual better at avoiding predators= more likely to survive & reproduce, genes allowing individual to avoid predation more likely to be passed onto offspring
-Disease; individual better at combatting disease/avoiding infection= more likely to survive & reproduce. Genes allowing individual to avoid disease= more likely to be passed onto offspring
-Competition; exist between species (interspecific)/within species (intraspecific) If individual is better at outcompeting other individuals= more likely to survive & reproduce. Genes allowing individual to outcompete= more likely to be passed onto offspring
What is natural selection and what does it give rise to?
-The process where frequency of alleles in population changes over time
-Gives rise to evolution
-If a harmful allele develops in an individual, this individual= less likely to survive & harmful allele will decrease in frequency
What is a selective advantage and what does it cause?
-Some individuals are more likely to survive than others due to genetic variation
-These individuals have a selective advantage and are more likely to reproduce and pass this on to offspring
-Allelic frequency providing a selective advantage increase
What is evolution defined by?
A change in allele frequencies over time
What is a selection pressure and why is it imposed?
-An external factor influencing reproductive success of an individual
-Natural selection acts on an individual by imposing a selection pressure
What is stabilising selection and where does it take place?
-Natural selection favours an average phenotype
-Selection pressure select against the extreme phenotypes
-Take place in environments that do NOT change
What is directional selection and where does it take place?
-Natural selection favours one extreme phenotype
-Selection pressures in directional selection select against all other phenotypes.
-Takes place after an environment has experienced a change
What is disruptive selection and what can it lead to?
-Natural selection favours two extremes of a phenotype
-Selection pressures select against average phenotype
-Takes place in an environment that favours more than one phenotype
-Can eventually lead to production of 2 new species
What is speciation?
Where 2 new species arise from a single species
What is the process of speciation occurring?
-Reproductive isolation; two populations are prevented from interbreeding & differences accumulate in the two gene pools. The gene flow (movement of alleles between population) of the populations is restricted
-As genetic differences accumulate, the two populations can no longer interbreed to produce fertile offspring; are separate species
What is allopatric speciation?
Where two or more populations are geographically (physically) isolated from each other; via environmental change like the emergence of a river or random events like a storm carrying birds to another island
What is the process of allopatric speciation occurring?
-Populations of a species can split into two or more through geographical isolation (enviro/random)
-Populations in diff environments will be exposed to diff environmental conditions (climate, food)
-This will place diff selection pressures on the populations; they’ll drive natural selection in diff directions
-diff selection pressures on populations—> allele frequencies in the populations change
-If populations continue to be geographically isolated for long time, eventually allele frequencies will change so much that if they’re brought back together they can no longer interbreed= now considered two diff species
What is sympatric speciation?
Where two or more populations aren’t geographically isolated from each other; may arise when mutation emerges preventing members from interbreeding w/ others
What is the process of sympatric speciation occurring?
-A population of species is reproductively isolated w/ out geographical (eg via mutation)
-The mutations influence many diff factors; eg polyploidy (extra set of chromosomes causing them to be reproductively isolated from diploid organisms), flowering/mating times of individuals, altering reproductive organs & mating behaviours
-The emergence of a mutation prevents two (or more) populations from interbreeding, eventually will no longer be able to create fertile offspring and will be 2 diff species
What is genetic drift and what can it drive?
-The random change in allele frequencies in a population
-Can drive speciation
What is genetic drift and how does it contribute to speciation?
-By chance, some alleles—> passed onto offspring, some aren’t
-Causes random changes in allele frequencies in population.
-Contributes to speciation by causing random changes in allele frequencies of two populations
-As the two populations can no longer interbreed, gene pools will become increasingly different; causes speciation
-Tends to have larger influence on evolutionary change in smaller populations as gene pool= smaller, so any change in allele frequencies has larger impact on overall gene pool
How are speciation and evolution important for diversity of life?
-Speciation= process that led to huge diversity of species that exist in life today; every species originally stemmed from a single population
-New species can emerge via speciation due to -evolution; as two populations—> reproductively isolated, natural selection causes separate populations to evolve in diff directions
-continuous cycle of evolution & speciation is what has led to the diversity we see today
