Name the type of isolating mechanism that prevents interbreeding between these three snail populations.
State the term used to describe the random changes in allele frequency in a small population.
suggest how an ancestral species might have evolved into the two species, B. pratorum and B. terrestris.
1 idea of isolation / isolating mechanism / barrier ;
2 seasonal (difference) / temporal (difference) /
males and queens (in different populations) produced
in different months /
breeding (in different populations) in different months ;
3 behavioural (difference) / visit different (types of) flowers /
feed at different times / feed on different food types ;
4 different flower locations / different (micro)habitats ;
5 idea that gene flow restricted /
no gene flow (between populations) ;
6 different adaptations / specialisation / niche partitioning ;
Explain, using scientific terms, why a collection of small islands remote from the mainland provides optimal conditions for speciation.
1 geographical, isolation / separation / barrier ;
2 idea of reproductive isolation ;
3 different , selection pressures / adaptations
(on different islands) ;
4 small , populations / gene pools ;
5 idea of mp 4 resulting in founder effect ;
6 idea of mp 4 resulting in greater genetic drift ;
Suggest how different types of isolating mechanism allowed dogs to evolve separately to wolves.
1 geographic ;
2 wolves avoid human settlements / dogs confined by humans ;
3 behavioural ;
4 detail / description ;
5 mechanical ;
6 idea of different size of wolves and some small dogs ;
7 gamete incompatibility ;
8 possibility of different chromosome numbers ;
9 seasonal / temporal ;
10 different breeding, seasons / times ;
explain the problems of classifying wolves and different dog breeds according to:
• the biological species conceptand
• the phylogenetic species concept.
biological species concept
1 (members of same species) need can interbreed to produce
fertile offspring ;
2 not all dog breeds can do this therefore not same species ;
3 dog and wolf can so they should be same species ;
phylogenetic species concept
4 idea that dogs and wolves monophyletic group / tip of
5 genetic differences, between dogs and wolves small ;
6 gene flow between wolves big dogs little dogs
/ analagous to ring species ;
7 (PSC) one species (with a lot of phenotypic variation) ;
State the two essential steps that must have occurred for a breed to develop a distinctive metabolism, such as the ability to eat mainly seaweed.
mutation / described ;
selection / selection pressure / selective advantage ;
Suggest what particular problems make the North Ronaldsay breed one of the most endangered sheep breeds in the United Kingdom.
1 small , population / gene pool ;
2 ref. inbreeding / genetic drift ;
3 unusual diet / cannot eat grass / poisoned by grass /
must eat seaweed ;
4 may not be commercially viable / expensive to keep ;
State why the English Elm clone is genetically isolated from other varieties of elm.
rarely / do not , produce seed / cross-pollinate / interbreed ;
only reproduce asexually ;
Over time, the frequency of this new allele increased in the gene pool of the human populations whose diet included milk.Name the process by which this increase occurred.
natural / directional , selection
Suggest why information gained from studying such model organisms can be applied to humans.
similar / same, cells / metabolism ; similar / same / share, genes or have genes in common ; similar / same, (embryonic) development ; shared, ancestry / ancestor or all related by evolution ;
One allele of DRD4 has been found more frequently amongst individuals whose personality is described as ‘novelty-seeking’ and whose behaviour tends to be exploratory and impulsive.
Suggest how this particular allele of the DRD4 receptor could have become common in the human population.
natural selection ;
selective advantage ;
(allele / behaviour) increases, survival / breeding / AW ;
(because) helped, find food / find new resources /
make new tools / get mates ;
allele passed on (to next generation) ;
(allele / behaviour) increased in frequency over,
generations / time ;