September 2016

Effects of population growth on natural resources

By |2022-09-15T12:37:48+02:00September 7th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Environmental degradation in Epworth. Image credit newsday.co.zw

Environmental degradation in Epworth. Image credit newsday.co.zw ZIMSEC O Level Combined Science Notes: Population and natural resources

Environmental Effects

  • Soil erosion
  • Deforestation
  • Desertification
  • Reduced soil fertility

Social Effects

  • Overcrowding
  • Criminal activities
  • Immorality
  • Poor health services
  • Poor education facilities
  • General increase in poverty

To […]


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Population Dynamics

By |2022-09-15T12:37:48+02:00September 7th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit idealscounseling.org

Image credit idealscounseling.orgZIMSEC O Level Combined Science Notes: Population Dynamics

  • Population-all the inhabitants of a particular place/area at one given time
  • The study of changes in population is known as demograph

Factors affecting population change

  • The birth rate-the number of live births per 1000 people per year.
  • Death/Mortality rate-is the number of […]

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Causes of infertility

By |2022-09-15T12:37:49+02:00September 7th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Sterility can cause strain in a relationship. Image credit    colossiansfamilynetwork.org

Sterility can cause strain in a relationship. Image credit colossiansfamilynetwork.org ZIMSEC O Level Combined Science Notes: Causes of infertility
  • Sterility is the inability to reproduce
  • There are a number of causes for sterility
  • Low sperm count (makes it […]

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Contraception:Ways to prevent pregnancy

By |2022-09-15T12:37:50+02:00September 6th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

There are several major methods of contraception. Image credit relationshipplaybook.com

There are several major methods of contraception. Image credit relationshipplaybook.com ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy
  • Contraception-the deliberate use of artificial methods or other techniques to prevent pregnancy as a consequence of sexual intercourse
  • Common methods of contraception […]

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Contraception: Abstinence

By |2022-09-15T12:37:50+02:00September 6th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Couple holding hands. Image credit neguswhoread.com

Couple holding hands. Image credit neguswhoread.com ZIMSEC O Level Combined Science Notes:Contraception: Abstinence
  • It involves total avoidance of sexual intercourse

Adavantages

  • Many couples agree to wait until marriage
  • There is no risk of contracting  Sexually Transmitted Infections
  • It is 100% effective
  • It is supported by most religious […]

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Contraception: Sterilisation

By |2022-09-15T12:37:51+02:00September 6th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Black couple. Image credit blackcouplegetaways.com

Black couple. Image credit blackcouplegetaways.com ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy

How it works

  • Can be done in both men and women
  • In men it is known as a vasectomy
    • Sperm duct is cut and tied
    • During sexual intercourse ejaculated fluid contains no sperm
  • […]


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Contraception: Loop/IUD (intrauterine device)

By |2022-09-15T12:37:51+02:00September 6th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Black couple. Image credit classic105.com

Black couple. Image credit classic105.com ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy

How it works IUD

IUD
  • Is a small copper/plastic device placed inside the uterus
  • It prevents the embryo from implanting in the uterus
  • by […]

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Contraception: The use of spermicides

By |2022-09-15T12:37:51+02:00September 6th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

Couple having dinner. Image credit singleblackmale.org

Couple having dinner. Image credit singleblackmale.org ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy
  • Spermicides are sperm killing chemicals

How it works

  • Are usually in the form of jelly cream placed into the vagina before sexual intercourse
  • The chemical kills spermatozoa

Effectiveness

  • 60-95%

Advantages

  • Does not require […]

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Contraception: Diaphragm/Dutch cup

By |2022-09-15T12:37:52+02:00September 2nd, 2016|Notes, O Level Science Notes, Ordinary Level Notes|

A married couple. Image credit rawstory.com

A married couple. Image credit rawstory.com ZIMSEC O Level Combined Science Notes:Contraception:Diaphragm/Dutch cup
  • Is also known as a cervical cap

How it works A diaphragm/cervical cap. Image credit path.org

A diaphragm/cervical cap. Image credit path.org
  • Rubber cap/dome placed […]

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