Trace how heritable variation exposed to a selection pressure changes survival and reproduction, producing evolutionary change in a population.
Insect pollinators are vital to maintaining the biodiversity of ecosystems, but they are threatened by some human actions. Some pollinators, such as honey bees (Apis mellifera), produce honey, which is rich in glucose.
Explain how a plant species may evolve by natural selection over a long period to produce insect-pollinated flowers.
a. variation exists within a species / OWTTE;
b. mutation generates variation/new alleles;
c. meiosis/sexual reproduction generates variation (new combinations of alleles);
d. example of flower's trait to be selected for in this context;
e. (natural selection is caused by) selection pressures / changes in the environment / due to competition for pollinators / pollination;
f. flowers that have an advantageous characteristic attract more insects;
g. (plants with attractive flowers are) more likely to be pollinated/reproduce;
h. pass on the new allele / combination of alleles/heritable trait;
i. allele frequency increases over many generations;
j. eventually different populations of this species can no longer produce fertile offspring/new species formed;
For d. Award anywhere in response and allow examples including bright petals / enclosed anthers / enclosed stigma / sticky pollen. Also accept suggestions such as odour / colour that is particularly attractive to bees.
For g. to j. Accept converse - i.e. individuals without the advantageous characteristic are less likely to reproduce and pass on their alleles, so alleles conferring a disadvantage are selected against.
For g. do not accept survival.
7 max