Outline the role of limiting factors in S and J population curves.

Fertility and crude birth rate can both be used as indicators of human population growth.

Explain the strengths and weaknesses of using each of these as indicators of growth in human populations.

Development policies may address a range of different aspects of development that influence human population growth either directly, or through education, healthcare and economic growth.

Evaluate the direct and indirect influences of such development policies on factors affecting human population curves.

the initial gradient of both S and J-curves is low due to limiting factors / low numbers reproducing / sub-optimum gender ratios / unmodified habitat;
initially (as these limiting factors are overcome, as biotic potential exceeds environmental resistance) exponential increase / positive feedback occurs in both S and J-curves;
in S-curves, (new) limiting factors eventually slow the population growth/maintain equilibrium/plateau (the population has reached its carrying capacity);
eg limited food / increased predation/disease / accumulation of wastes / competition;
limiting factors may be density dependent / provide negative feedback mechanism to maintain this equilibrium;
in J-curves, limiting factors eventually lead to rapid decline/population crash;
eg seasonal climate change / disease / overexploited food resources (typically r-selected species);
while both S and J curves may be influenced by density independent factors, it is the density-dependent factors that bring about an equilibrium in S-curves. 

Award [3 max] for responses that indicate no difference between S and J curves.

[4 max]

Definitions: [2 max]
Crude Birth Rate (CBR) is the number of births per thousand individuals in apopulation per year;
fertility is the number of births per thousand women of child–bearing age (fertility rate) / average number of children a woman has in her lifetime (total fertility);
CBR can still gain credit if no time element is added

Strengths
CBR/fertility both make it possible to compare relative numbers of births in populations of different size/times;
CBR is more directly related to/gives a better indication of overall growth rate/natural increase rate (NIR) / CBR when used in combination with CDR gives an indication of natural rate of increase;
fertility can be used to infer the role of women/cultural values/contraception may be influencing population growth;
TFR of 2.1 (2.0 to 2.5 depending on nation's death rate) is considered the replacement rate, so it is a straightforward indication / almost as precise as NIR itself of positive vs. negative growth (reduction of population);
FR is an efficient way to get an immediate indication of whether a population policy has effect/ suffers less from statistical ambiguity / only tool in cases where complete statistical data are not available, as in most LEDCs;

Weaknesses:
CBR/fertility do not give the actual numbers/increase in a population;
CBR/fertility do not take migration/immigration/emigration into account;
CBR/Fertility data collection reliability is not the same in all countries (unaccounted births/unrecorded communities especially in LEDCs and civil conflict areas);
CBR/fertility do not take death rates into account /infant mortality rates;
Fertility rate does not take into account the proportion of women of child bearing age/ gender ratios;
Fertility rate is ambiguous because the concept of "child-bearing/reproductive age" is uncertain (some suggest 15-44, others 15-49 / in some cultures women may commonly bear children outside this range). 

[4 max] for answers that only address weaknesses or strengths
Award [2 max] for definitions.

[6 max]

Please note: although "quality of expression" marking is no longer used in exams, this question from a past syllabus may still be useful for student practice. Part c questions in current programme are likely to address a far wider breadth of syllabus material.

Direct influences: [4 max]
pro-natalist policies may provide tax/welfare incentives for larger families/having children increasing fertility/CBR/NIR/population growth; (strength)
In principle these are particularly appropriate/employed by governments for a declining/aging population; (strength)
In practice, however, they have proved to be notoriously ineffective at controlling growth; (weakness)

anti-natalist policies (eg one-child policy/free contraception) may reduce fertility/CBR /NIR/population growth; (strength)
they can be effective for countries where population growth is too high / Anti-natalist policies can be effective if populations are compliant/because contraception is more readily available ( eg free contraception in China);(strength)
but they can give rise to female infanticide/selective abortion causing gender imbalances; (weakness) 

Indirect influences: [4 max]
healthcare policies/improvement may improve medical technology/services, decreasing CDR/IMR/increasing NIR;(strength)
these may benefit the community in terms of health/lifespan; (strength)
…but they may lead to rapid population growth and to the costs associated with a youthful population (due to reduced CDR/infant mortality); (weakness)
education may improve sex education/career employment/female emancipation, decreasing fertility/CBR/NIR/population growth; (strength)
but they can lead to declining/aging population growth; (weakness)
economic growth/capitalist ideals/agricultural improvements may reduce desire for large families decreasing fertility/CBR/NIR/population growth; (strength)
improved agricultural technology may reduce need for offspring to provide farm labour thus reducing CBR/fertility;(strength)
...but increased food production may provide better nutrition leading to reduced infant mortality/short term population increase; (strength/weakness) 

Award [5 max] for responses that address only weaknesses or only strengths.
Where responses misidentify direct v indirect influences, mark first point they make wrong, but award any succeeding points with ECF.

Award [7 max] for marking points above, and [1 max] for an explicit and valid conclusion that is justified by points raised.
Note to examiners: An isolated statement eg “Anti-natalist policies have the greatest effect on population growth” or an unjustified opinion eg “I think educational policies are best at regulating population” should not be considered as a valid conclusion. The conclusion must be supported/justified by points raised.

eg educational policies are the most effective because they not only control population growth but increase human equality in communities;
indirect policies are more effective as they address issues more holistically.

Alternative points of equivalent validity, significance and relevance to those given, should be credited.

[8 max]

Expression of ideas [2 max]

The candidates could generally describe S and J curves, however outlining how limiting factors influenced the shape was more difficult. A number of candidates incorrectly stated that J curves had no limiting factors at all influencing the population curve. Many students gained 2 or 3 marks for the S curve part of the answer. The stronger candidates did show an understanding of the J curve.

A wide range of definitions was accepted for fertility and crude birth rate. The students found it harder to mention the strengths of these indicators than the weaknesses. Many students only wrote 4 to 5 sentences and so there was limited scope for achieving the maximum marks. Weaker candidates generally described the population factors involved in growth.

Having the development policies for indirect influence mentioned in the question introduction helped guide the students to address these in their answers. This often led to the awarding of at least one mark to each policy. There was a tendency for the weaker candidates to give long detailed answers about one policy, usually the one child policy, this amount of detail for one policy was not required. Candidates should read the question carefully to ensure they remain focused on the question asked.