6.6: Population, sustainabilty

Question 1

Fig. 2.1 shows the number of worker bees of B. pratorum and B. terrestris observed at one
location over a year. Graph: B. pr from Mar to Sep, peaks at Jun/ B. tr from May to Nov, peaks at Jul.
Table 2.1 shows some differences in the food collecting behaviour of worker bees of these species.
Species of bumble bee/// B. pratorum/// B. terrestris;
Mean depth of flower visited (mm)/// 7.4/// 6.3;
Visits to flowers when nectar only collected (%)/// 23/// 80;
Visits to flowers when pollen only collected (%)/// 10/// 11;
Visits to flowers when both nectar and
pollen collected (%)/// 67/// 9
Evaluate the extent to which the two species may compete. (4mks) [f215 jun 14 q2bi)]

Answer 1

1 not much / little / some, competition / niche overlap;
reasons for LITTLE competition
2 use / feed on, different sized flowers / different depth of flowers; [e.g. B. pratorum feed on, bigger / longer / deeper, flowers or B. pratorum 7.4(mm) AND B. terrestris 6.3(mm)]
3 vary in proportions of pollen and nectar they collect; [e.g. B. pratorum mostly pollen and nectar and B. terrestris mostly nectar only]
4 fly / live / active / feed / visit flowers, at different times; [e.g. B. pratorum peak in June and B. terrestris
in July]
reason for competition
5 idea that fly / live / active / feed / visit flowers, overlaps there must be competition; [e.g. both compete for food between May and Sept/ both collect pollen only from same % flowers]
6 e.g. use / feed on, different species of flowers]

Question 2

Use Fig. 2.1 and Table 2.1, and the information given on page 7, to suggest how an ancestral species might have evolved into the two species,
B. pratorum and B. terrestris. (3mks) [f215 jun 14 q2bii)]
.

Answer 2

1 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; [example of seasonal/ temporal
(e.g. B. pratorum has its peak number of workers in Jun and B. terrestris in Jul]
3 behavioural (difference)/ visit different (types of) flowers/ feed at different times/ feed on different food types; [different mating rituals]
4 different flower locations/ different (micro)habitats;
5 gene flow restricted/ no gene flow (between populations); [must ref to gene/ allele]
6 different adaptations/ specialisation/ niche partitioning;

Question 3

Observation: The time taken for a worker bee to
collect food from a flower decreases
with practice.
Type of behavior? f215 jun 14 q2ci

Answer 3

learned (behaviour)/ learning/ operant conditioning/

trial and error

Question 4

Observation: All bumble bees start at the bottom of
a vertical spike of flowers and work
upwards.
Type of behavior? f215 jun 14 q2ci

Answer 4

innate/ instinctive

Question 5

On returning to the colony, worker bees perform ‘dances’ to tell other bees the direction and distance of a food source. How might this social behaviour benefit the colony? f215 jun 14 q2cii

Answer 5

better/ more efficient, at, finding/ getting, food; [more food can be collected less, time/ energy, spent looking for food easier to find food; e.g. ref to reduces competition from other colonies]

Question 6

A batch fermenter is used during the production of beer. Fig. 5.1(a) and Fig. 5.1(b) show some changes that take place in the fermenter over the first 6 days.
(a) (i) Describe the pattern of growth of the yeast population in this fermenter. (4mks)
[f215 june 14 q5ai]

Answer 6

1 lag phase / slow increase (in , population / number / percentage) , at start / initially / day 0 - 1 / during day 1 ;
2 log phase / exponential increase / rapid increase , day 1 - 3 ;
3 rate of increase , slows / less steep , days 3 - 4 / during day 3 ;
4 stationary phase / population levels off / population stays at 100% , at end / finally / remaining days / days 4 - 6 ;
5 comparative figures quoted with 2 x-y readings

Question 7

(3mks) f215 june15 q2ai

Answer 7

1 peak in , 1988 / 1994 ; [increases until / highest number in, 1988/1994]
2 trend decrease after 1994 ;
3 ref. decrease and then increase , 1988 to 1994 ;
4 fluctuations (within pattern) ; [‘goes up and down’ / oscillates]
5 overall increase from 1965 to 2002 ;

Question 8

(2mks) f215 june15 q2aii

Answer 8

accurate because idea that actual number of elk shot is recorded; [elks shot are counted / reported]
method not valid because idea that number of elk shot / hunting success, varies independently of population size; [suitable reason// e.g. numbers of licences issued / number of hunters // set quotas to hunt // illegal hunting // if weather suitable for hunting //
only younger / older / diseased / larger, elk killed]

Question 9

(6mks) f215 june15 q2bi

Answer 9

1 idea that population size is determined by limiting factor(s) ;
Before 1995, population increases due to
2 example of factor that is not limiting population ; [e.g. plenty of, enough, food; Less / no predation; Less / no overcrowding/ enough space; less hunting]
Before 1995, population levels off because
3 reaches carrying capacity ;
Before 1995, population becomes limited by
4 intraspecific competition for named resource;
5 interspecific competition for named resource; [any suitable limiting factor eg. competition for, food / space / mates/ overcrowding]
Population can decline at any time/ dips, due to
6 severe weather / natural disaster ; [ref to parasites/disease/ drought/floods/fires]
7 decrease before 1995 not due to wolves
(as none present) ;
8 decrease after 1995 (probably) due to wolves;
9 idea that effect of wolves on population may be debatable ; [e.g. lack of data in 1996 and 1997 makes it difficult to form conclusions]

Question 10

(2mks) f215 june15 q2bii

Answer 10

re-introduction of wolves is conservation because
1 restoring the ecosystem (to its original form)
or maintains biodiversity ; [controls/ increases, biodiversity]
2 helps the (global) wolf population ; [wolves do not become extinct / increase in number]
3 active / dynamic / sustainable, management / maintenance ; [Actively maintains biodiversity’ = 1 + 3]
4 prevents over-population by the elk ; [wolves, limit / control, elk population or lack of wolves causes elk population to grow]
5 prevents over-grazing or damage to, habitat / ecosystem ; [if wolves absent, elk would damage habitat / other species may become extinct]