species and taxonomy Flashcards
what is a species
a group of organisms with similar morphological, physiological and behavioural features which can interbreed to produce fertile offspring and are reproductively isolated form one and other eg donkey + horse = mule
mule = infertile
why is it difficult to test whether an organism is able to produce fertile offspring
-2 specimens under review are often fossil specimens
-two test may be of the same sex
-may be sexually immature or not in season
-may not breed successfully incaptivity
-may not co-operate
so often rely on morpho and physio aspects
what is speciation
process in which a new species evolve form existing ones
what do all organisms in species share
a common gene pool- so can interbreed successfully
also have to be isolated reproductively eg geographical
what is adaptive radiation
when organisms in different environments experience different selective pressures
-so mutation takes place and natural selection takes place to ensure that the adaptations are best suited to the environment
-pop become adapted to own eniviro so become so different that they can no longer interbreed to produce fertile offspring
eg darwin and finches
separated by islands nut all have similar internal anatomy but have different feeding habits and beak size
-adapted to enviro
what is genetic drift
seen in small pop
-limited no. of alleles so limited genetic diversity
-one allele more favourable so passed on and the other alleles are lost
-or new favorable mutations arise and quickly affect whole pop so disadvantageous alleles are lost
-effects of mutations are diluted by greater genetic diversity in pop
give the two types of speciation
allopatric
sympatric
what is allopatric speciation
reproductive isolation that relies on geographical isolation
what is sympatric speciation
does not involve geographical isolation but some other cause of reproductive isolation eg genetic
how does allopatric work
-two pop become geographically isolated as a result of land movements, rivers or mountains etc
-two pop now occupy diff habitats so will have diff selective pressures
-in each pop variation du to mutation will cause best adapted organisms to have selective advantage
-these survive, reproduce and pass on their alleles
-achieve differential reproductive success
-overtime pops become so different they can no longer interbreed to produce fertile offspring
what 2 types of sympatric speciation are there
pre-zygotic - mechanisms stop the gametes actually meeting and forming a zygote
post-zygotic- a zygote is formed but either does not develop or the offspring firmed is sterile and is unable to reproduce
what are the 5 types of pre-zygotic sympatric speciation is there
-temporal isolation
-ecological ‘’
-behavioural ‘’
-mechanical ‘’
-gamete incompatibility
what is temporal isolation
when two pop breed at different times of the year so they cannot interbreed
eg wild grass Agrostis tenius
-grass sensitive to high levels of copper + mine waste
-mutation cause resistant allele to develop
-so some wild grass can grow in high cooper levels and less growth in pasteurised land
-allele causes growth effects and resistant grass grows and flowers quicker than non-resistant
-so cannot interbreed as non-resistant is not able to be pollinated
-so just pollinate themselves
what is ecological isolation
organisms live in the same habitat but use the space differently and thus never come into contact
