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5. Cause and effect

We have now established that changes do not occur at random – one change brings about another. You probably know the concept of cause and effect. At this stage it should be great fun to think and chat about cause and effect. Argumentation is nothing new to you; after all, you are in Grade 7!

Activity 5:

To choose the best options with regard to population changes

[lo 3.2]

CHOOSE THE BEST OPTION

Underline the correct answer from the words in brackets:

1. As the fertility in any community increases, the births in that community will (decrease/increase).

2. Good medical care for the entire community normally leads to a drop in the (death rate/life expectancy).

3. If the mortality rate in a [primitive] society is very high, the birth rate will definitely be (high/low).

4. When any society is used to receiving state benefits for the aged, families will tend to get (smaller/bigger).

5. A population with a high fertility rate and a low mortality rate, will (shrink/grow).

6. The population of any country that is severely affected by the Aids-pandemic, will experience a drop in (fertility/life expectancy).

At the moment the developing countries are experiencing a rapid growth in their population, so that the population pyramid in each case shows a typically young population. Developed countries , such as almost all of the European states, the USA and Canada, once experienced times when the population could be described as young. These states have since undergone demographic change.

6. Demographic change, and how it can be represented by means of population pyramids

Here we have a description (a history in a certain sense) of the population structure of England and Wales. This is a good example of the different stages through which a population progresses.

Population pyramids

Over the centuries the population has remained relatively constant. The birth as well as the mortality rate was high, and the life expectancy short. The pyramid of this group probably resembled the one in Figure 1(a) at the beginning of this learning unit.

  1. After the changes effected by the agricultural and industrial revolutions when farms started to produce more food due to mechanisation, and people turned to factory jobs for an income, the population showed a marked growth. The birth rate gradually started to overtake the mortality rate because of better nutrition, improved medical care, and better sanitation. As before, families were still quite large, but as fewer babies and youths died, the total population took on a “young” character.
  2. Fifty years later the population pyramid showed a marked difference from the previous pyramid. A lower fertility rate then caused the younger part of the population to shrink proportionally. The lower fertility rate was due to the fact that women were prepared and chose to have fewer children, as they preferred to join the workforce to help earn an extra income for their families. Moreover, the state took on the responsibility of caring for the aged, which meant that they were no longer dependent on their children. (In earlier times children were regarded as an “insurance policy for old age”.)

Questions & Answers

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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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AMJAD
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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AMJAD
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Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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Source:  OpenStax, Geography grade 7. OpenStax CNX. Sep 09, 2009 Download for free at http://cnx.org/content/col11021/1.1
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