Populations and Sustainability

Question 1

Outline the main ways in which increased human presence and activity have put endemic species on the Galapagos Islands, and in the sea around them, at risk of extinction.
In your answer you should link the ecological pressures imposed by human activity to examples of Galapagos Island species that have been affected.

Answer 1

1 habitat / ecosystem , disturbance / destruction ;
2 (land used for) (named) building / roads ;
3 (land used for) agriculture / farming ;
4 deforestation ;
5 effect of (tourist) , boats / divers, described ;
6 more / increased , pollution ;
7 sewage / eutrophication , in sea / water ;
8 oil / fuel , spill in sea ;
9 (humans) hunting / collecting / (over-) fishing ;
10 competition from introduced species ;
11 predation / overgrazing , by introduced species ;
12 (new / named) , diseases / pathogens, introduced ;

Question 2

In 2007, the United Nations (UN) put the Galapagos Islands on its Red List of endangered sites. The Galapagos government’s response to this action included making new laws and placing restrictions on human activity, issuing eviction orders and culling introduced species of animals.
Suggest one economic and one ethical problem that might have arisen from this 2007 UN decision.

Answer 2

economic
fewer jobs / smaller profits / business closure /
reduced tourism / less income / less revenue ;
ethical
question of , humane killing / animal suffering
or
people suffer through losing their ,
homes / friends / jobs ;

Question 3

in 1995, a population of grey wolves was introduced to Yellowstone Park and their numbers increased.
With reference to Fig. 2.1, discuss the factors that may have affected the size of the elk population:
• before 1995
• after 1995.

Answer 3

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 ;
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;

Population can decline at any time/ dips, due to
6 severe weather / natural disaster ;
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 ;

Question 4

Explain why the introduction of wolves to Yellowstone Park in 1995 is an example of conservation.

Answer 4

re-introduction of wolves is conservation because
1 restoring the ecosystem (to its original form) 
or 
maintains biodiversity ;
2 helps the (global) wolf population ; 
3 active / dynamic / sustainable, 
management / maintenance ; 
4 prevents over-population by the elk ; 
5 prevents over-grazing 
or 
damage to, habitat / ecosystem ;

Question 5

Suggest two reasons why the large scale removal of peat from bogs for use in gardens is discouraged by conservation groups.

Answer 5

bog / habitat / ecosystem, takes a long time to form / hard to
replace ;
loss of, biodiversity / rare species ;

Question 6

State and describe two types of ecological interaction that can occur between different species in a habitat.As part of each description, you should name the two species involved in your chosen example.

Answer 6

(interspecific) competition ;
species 1 and species 2 named ; 
description of interaction ; 
trophic / predator-prey / predation / parasitism / grazing / 
herbivory ; 
species 1 and species 2 named ; 
description of interaction ; 
mutualistic / mutualism ; 
species 1 and species 2 named ; 
description of interaction ;

Question 7

Suggest two factors that might have allowed a large population of hedgehogs to increase from just four individuals in area 2. Explain how each factor has led to an increase in the hedgehog population.

Answer 7

1 plenty of / enough , food / birds’ eggs / space ;
2 breed rapidly / breed successfully / young survive ;
3 no / few , predators ;
4 few die (young / before breeding) ;
5 idea that hedgehogs are introduced species ;
6 invasive / fill vacant niche /
not reached carrying capacity ;
7 these hedgehogs restricted to island ;
8 cannot , emigrate / leave island (so numbers build up) ;

Question 8

Explain, using your knowledge of factors affecting population growth, why the small squirrel population in this rainforest does not increase in size indefinitely.

Answer 8

limiting / density-dependent, factors ;
carrying capacity ; 
intraspecific competition ; 
for, food / nesting sites ; 
interspecific competition ; 
with, deer / tree shrew / giant squirrel ; 
larger squirrel populations 
attract more predators ; 
parasites / diseases, spread more easily ;

Question 9

Outline three reasons for conserving biological resources, such as the rainforest in Sarawak.

Answer 9

aesthetic / amenity / recreational, value ;
(eco)tourism ;
to, preserve biodiversity / preserve genetic diversity /
stop extinction ;
ref. interactions between species /
need to preserve whole habitat ;
(rainforest species / preserve gene pool as)
could be useful, in future / as potential,
for, medicine / genetic engineering / AW ;
to support indigenous peoples / AW ;
to stop effect of deforestation on,
atmosphere / climate / soil ;

Question 10

Describe and explain the benefits of two management practices used in sustainable timber production in a temperate country.

Answer 10

management practices
coppicing / pollarding / description ; 
selective felling / description ; 
rotational felling / description ; 
strip felling ; 
replant after felling ; 
explanation of benefits re. sustainability 
preserves / prevents disruption to, 
habitat / ecosystems / nesting sites ; 
maintains / increases, species diversity / biodiversity ; 
prevents, soil erosion / leaching ; 
less disturbance by machinery ;