1.	(a)	79% ± 2%	1
 
(b)	Gulf of Mexico / Atlantic	1
 
(c)	total number of Caribbean endemic species is greater
than in the Pacific / 425 and 450;
no Caribbean endemic species occur in great numbers / 
>32 compared to the Pacific / which has about 45;
the number of Caribbean endemic species occurring
in small numbers / 
1–2 is more than twice that in the Pacific / about 280 and 120;	2 max
 
(d)	the Caribbean region will have a greater extinction rate;
because of the great number of endemic species
occurring in small numbers;
small numbers of a species are more vulnerable
to extinction than high numbers;
for Caribbean ubiquitous species the percentage of
species occurring in high numbers / 
>32 is lower than in the Pacific;	2 max
 
(e)	the Arctic;	1
[7]

2.	(a)	30 (± 1) squirrels hectare^–1;	1
(b)	population decreases from 12 (± 1) squirrels hectare^–1 to 2 (± 1) in food
addition area; in food addition plus predator exclusion area decreases 
from 30 (± 1) to 2 (± 1);
reaches same level as control (in 2 years);
other numerical comparison;	2 max
(c)	addition of food and exclusion of predators results in more squirrels as 
conditions are ideal;
squirrels can feed well and are not predated / higher reproduction rate;
food addition alone also results in more squirrels;
because food affects population growth more than predator exclusion
(squirrels climb, hide);
no additional food but predator excluded does not confirm the hypothesis;	3 max
[6]

3.	(a)	proportion of rats in diet decrease with length / inversely proportional / 
negative correlation	1
 
(b)	(i)	no / little difference	1
Do not award marks to responses just stating values.
 
(ii)	proportion of rats in diet of females is lower than for males	1
 
(c)	larger snakes eat larger prey;
feeding frequency can be reduced if larger prey is eaten;
females shift earlier to larger prey to prepare for gestation;
larger snakes move to different habitats;
larger snakes may not be able to catch rats;	2 max
 
(d)	sample is biased / 22 females versus 13 males, so results not reliable;
small sample size;
no males collected above 400 cm;
time and date of capture not known;
seasonal change in feeding patterns;
smaller males more active in foraging therefore greater chance of capture;
not all snakes had full stomachs at the time of capture / prey 
availability not known;
some snakes may have been kept in captivity / artificial or forced diet;
larger prey takes longer to digest / rats are digested more quickly;
snakes collected or captured in different habitats;	2 max
[7]

4.	(a)	loggerheads / Caretta caretta	1
 
(b)	all three species nest over the same range of latitudes
on the same beaches / areas;
density of loggerheads is greatest and leatherbacks is lowest;
similar relative densities / numbers on the different beaches / latitudes;
all three had most nests on Jupiter;
more loggerheads at northern end of range / 	)	(Do not accept answers giving
around 28 (°N) / on Melbourne;	)	the range 26–28 or 26–30.)
			2 max
 
(c)	artificial lighting of beaches;
(Reject if human activity or other factors are also varied.)
lighting of an area / some areas / beaches
but not others (at the same time);
keep other variables constant / 
use similar areas / beaches;
measure nesting density / number of nests per kilometre;
(Reject count nests unqualified.)	 2 max
 
(d)	turtles (only) nest opposite / behind / 
in front of apartment blocks;
Do not accept answers only relating to tall buildings.

	turtles nest close to the buildings;
no / few nests opposite gaps between buildings; (Do not accept converse.)
light from inland penetrates between buildings;
greater density of nests opposite tall(er) buildings;
tall(er) buildings cast more shade / 
block more light; (Do not accept larger buildings.)
more nests by Whitehall South / 
Stratford Arms and fewer by Villa del Mar / Arvita;	4 max
 
(e)	more variation in direction with more light / 
direction more random with more light;
hatchlings change direction more with more light / 
go in circles with more light;
mean direction closer to direction of ocean	)	(Do not accept comments on whether
with less light / go straight to ocean with	)	the hatchlings reach the ocean or not)
less light;	)	2 max
 
(f)	light / moonlight / starlight from ocean / moon / 
stars reflected off ocean / darkness from inland	1
Only accept answers referring to light or dark.
 
(g)	(i)	light inhibits nesting / egg laying by females;
artificial light prevents the hatchlings from finding the ocean;
light increases risk of detection by predators;
turtles nest further up the beach so further
for hatchlings to reach ocean;	2 max
 
(ii)	any method outlined to prevent / 
reduce artificial light reaching the beach	1
[15]

5.	(a)	as the latitude increases so the length of day
needed to induce hibernation increases;
there is a direct correlation between
daylength and latitude;	1 max
 
(b)	the shortest daylength to induce hibernation is the same
at the lowest latitude in 1972 and 1996;
at higher latitudes, the daylength to induce hibernation is
less in 1996 than 1972;
for the same daylength, the latitude at which hibernation occurs
has moved further north in 1996 compared to 1972;
at lower latitudes the change in daylength is less
than at higher latitudes;	2 max

(c)	colder areas / higher latitudes become warmer / 
resemble lower latitudes (with shorter daylength);
warmer weather delays organisms from beginning
hibernation / mosquitos stay active longer into winter;
(the graphs show) that organisms at higher latitudes have
adapted to a shorter daylength (to begin hibernation);	2 max
[5]

6.	(a)	(i)	1990	1
(ii)	1970	1
 
(b)	(i)	the higher the temperature the earlier the date of leaf opening	1
(ii)	there is evidence of warming;
at the end of the twentieth century most years are warmer than the mean;
all but one of the last (12) years are warmer than the mean;
6 colder than mean years in the first 15 years and only 2 
in the second 15 years;	2 max
 
(c)	(i)	date of egg laying is (always) earlier than the date of maximum 
caterpillar biomass / date of maximum caterpillar biomass is (always) 
later than the date of egg laying	1
(ii)	many caterpillars available to feed the young when they have hatched	1
 
(d)	date of maximum caterpillar biomass has got earlier / reduced / decreased;	1
(e)	birds that lay eggs earlier find more caterpillars / their young are better fed;
offspring of early egg layers have a better chance of survival;
these birds inherit the early egg laying characteristic / others eliminated;	2 max
[10]