D1. (a) (i) Pine Warblers/Dendroica pinus (of Delmarva) [1]
(ii) 2.6mm (accept answers in the range of 2.5 mm to 2.7 mm) [1]
(iii) Yellow-throated Warblers have a bigger range / greater variation (of beak
length) in Delmarva than in Midwest (accept numerical values) [1] Accept
converse.
(b) allows them to eat other foods / changes feeding behaviour;
reduces competition with Pine Warblers; [1 max]
(c)
1.
2.
3.
4.
allopatric speciation occurs between populations that live in different areas;
(when populations are geographically isolated) there is no interbreeding;
natural selection works on each population independently;
competition with the Pine Warbler only occurs in Delmarva / the Pine Warbler
acts as selective pressure on the Yellow-throated Warbler in Delmarva;
5. eventually Yellow-throated Warblers in the two areas could become two species
instead of one / OWTTE; [3 max]
D.2
1.
both explain similar structures in different organisms;
Convergent evolution
Divergent evolution
different ancestor
common ancestor;
converge to produce similar
solutions/analogous structures
diverge to suit different functions/homologous
structures;
e.g.wings in insects and birds
e.g.vertebrate limb structure;
species appearance becomes more similar over
time
species appearance becomes more different
over time;
unrelated species look similar but are
genetically different
species look different but are closely related
genetically;
3 max
2.
(a)
1. varied members of a single species occupy a variety of niches / migration
of a species to an
area with a variety of niches;
2. natural selection/selection pressure will be different in various niches
causing adaptation of
groups to the varied niches;
3. results in many species from one ancestral species;
4. reproductive isolation enhances adaptive radiation;
adaptive radiation results in speciation;3 max
(b)
1. in gradualism evolution occurs at a constant pace;
2. fossil records of gradual change with intermediate forms support
this theory;
3. evolution of modern horse/another suitable example seems to
support this view;
4. in punctuated equilibrium evolution proceeds rapidly for short
periods of time
5. intermittent with long periods of little change/stability;
6. gaps in the fossil record/lack of intermediate forms support the idea of
punctuated
equilibrium;
7. strata in the fossil record with appearance of many new species following
a mass
extinction supports the idea of punctuated equilibrium;
4 max
3.
(a)
1. both involve reproductive isolation / separation of gene pools;
2. sympatric is speciation due to isolation of populations living in the same
geographic area
whereas allopatric is speciation due to geographic isolation;
2
(b)
analogous structure similar in appearance/function but with different
evolutionary
history e.g. wing of bat and wing of bird;
1
4.
(b)
1. a population colonizes a new habitat that involves unique selection pressures / becomes
geographically isolated;
2. eg Darwin’s finches;
3. polyploidy;
4. eg some variants of wheat;
4