speciation Flashcards
speciation extended response, 4 steps
variation: - mutation - random assortment - crossing over - migration isolation: allopatric or sympatric, split into 2 habitats with new environments, geographic or reproductive natural selection: - favors the best suited phenotype, speciation: - the 2 populations are no longer able to breed
antibiotic resistance
antibiotics: drugs that kill bacteria by interfering with the metabolic processes
- affected people are treated with antibiotics
- antibiotics kill bacteria / cure most individuals
- stop the spread of the disease
- bacterium squired resistance through mutation
- those bacteria were unaffected by the antibiotic
- antibiotic bacteria continued to reproduce
- resistant bacteria becomes more common
- natural selection favored the antibiotic resistance strains
- antibiotic represents a changed environment
insecticide resistance
- are pesticides used to control pest insects
- form of natural selection in which the most resistance organisms survive to pass on their genes to their offspring
types of speciation
allopatric: geographical isolation, evolution of two or more species in the presence of a physical barrier
sympatric: reproductive isolation,
speciation
ancestral species diverge into 2 or more species unable to interbreed due to biological or behavioral barriers
reproductive barriers / sympatric
prezygotic: pre fertilization, different habitats, incompatible behavior
post zygotic: post fertilisation, egg and sperm fail to meet
ecological / microhabitats
species occupy different microhabitats within the same area
eg forms in forrests, frogs in streams
temporal isolation
species have different activity patterns
- nocturnal, diurnal
- different breeding seasons
behavioral isolation
specific calls, rituals to recognize potential mates
intersexual isolation
between 2 sexes preference by one sex for the features of the other sex
intrasexual selection
within one sex, competition between members of one sex usually males
conservation strategies
populations with reduced genetic diversity face increased risk of extinction
conservation planning to maintain viable gene pools includes considerations of biogeography, reproductive and population dynamics
- Tasmanian devils are dying from facial tumor disease
- spread by biting when feeding and mating
- tumors make it difficult to eat therefore death by starvation
- now endangered
biogeography: - aim to ensure wide geographical spread to several sites to reduce effects of disease and catastrophe
- in many institution, free ranges enclosures, zoos
reproductive behavior: - mate selection: multiple making increase biodiversity
- females must replace itself and its partner, therefore min 2 kids
- parental care: suckled in pouch and protected until 2yr
population dynamics: - aim to maintain a healthy biodiversity
- select healthy young disease free
- quarantine to ensure disease free then relocate
- ensure high population, enough to cope with genetic drift
- maximise and maintain genetic diversity
- ensure all founding animals contribute to gene pool
- protect food: supply and habitat
- reduce predators
- monitor breeding and remove devils who’s genes are well represented
- fence protect and monitor
biogeography conservation
- nature reserves need to be large enough and have suitable conditions
- small populations lose genetic diversity
- need connections between reserves so populations can exchange genes
- exchange will boost diversity
- populations of a species in different locations will be genetically different because they evolved in different species
reproductive behavior, conservation
- behavior associated with mating
- behavior may change in captivity
- this could mean only a small population of individuals reproduce and produce surviving offspring
- gene pool would only reflect the genes of those individuals
- high levels of inbreeding
population dynamics
- how and why population sizes change
- population sizes fluctuate
- population will loose genetic diversity when small
- happens through genetic drift
- conservation planning should be based around small populations
- can identify and possible correct the factors that cause numbers to drop
allopatric speciation
- population is divided by a physical barrier such as a mountain or river
- preventing them from moving
- no gene flow between populations
- evolve differently
- different environments therefore face different selection pressures
- natural selection will favor different traits
- result in different allele frequencies
- populations will adapt to different environemtns
- genetic differences increase over time
- eventually unable to interbreed because individuals no longer compatible
- once they are unable to interbreed they are considered different species
- they evolve differently in their locations
how genetic drift changes allele frequency
- random changes in allele frequency that occur as a result of chance events and not natural selection
- can result in a loss of alleles
- occurs in small populations
- non - directional
how does gene flow change allele frequency
- changes in allele frequency due to migration
- occurs when alleles are added to a gene pool due to the movement of individuals from one population to another
consequence of a deletion
- proteins are essential to cell structure and function
- proteins catalyse cheimcal reactions, provide structural support and are cell communications
- absence of essential protein could disrupt cell structure and cause the cell to die
how can environmental factors cause mutations
a mutation is a (permanent) change in the structure of DNA
environmental factors can cause changes in the structure of DNA
physical mutagens e.g. radiation/ultra violet light
produce energy (that damages/changes the structure of DNA/gene)
chemical mutagens - e.g. alcohol, smoke, mustard gas
may substitute a base or add/remove bases or change the chemical properties of a base (depends on chemical)
biological mutagen example of a type of virus/bacteria/microorganisms that infect cells (and damage/change DNA of the cell)
specific example of the action of a mutagen (e.g. ultra violet light cause adjacent bases in DNA to bind together
how can errors in meiosis cause mutations
(normal meiosis) members of homologous pair go to opposite poles/different gametes
(errors in meiosis) can result in both members of a homologous pair going to same pole/non-disjunction
will be an extra chromosome at this pole/chromosome missing from other pole
(results in gametes/cells) with extra or missing chromosomes
(if gamete is fertilised can get an) individual with an extra or a missing chromosome
why are populations with reduced genetic diversity at high risk of extinction
(population) cannot evolve/adapt/change/respond
to changing environment or diverse/heterogeneous environment
because all/most individuals are the same or there are no/few genetic differences among individuals/small gene pool
natural selection requires/operates on differences among individuals
disease can spread (quickly) through population
no/few resistant individuals or all/most individuals are susceptible
how can biotechnology reduce risk of extinction
monitor the gene pool of the population/DNA profiling of individuals in populations
identify at risk populations
can then protect or intervene
assess the gene pool for breeding programs
identify/select genetically suitable/more distantly related breeding
individuals (from within the population)
introduce (genetically different) individuals from other populations
to increase genetic diversity in the population
genetically modify individuals/gene therapy/recombinant DNA technology
can introduce genes from other populations/species or directly edit genes
create genetically superior types
(modified) individuals can better cope with a particular
threat/disease/adverse condition
artificially propagate individuals (especially plants)
specific example -collect eggs and sperm from endangered animal and implant embryo in common
species
to increase the number of individuals
bottleneck
when a catastrophic event occurs or when a period of adverse conditions leads to a decrease in population size and loss of alleles from a gene pool
founder effect
a few individuals carry alleles to a new isolated area and a new population is formed with different allele frequencies to the original population
- decrease in variation
