February 2025

Population Dynamics

By |2025-02-12T08:59:06+02:00February 12th, 2025|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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Effects of population growth on natural resources

By |2025-02-12T09:00:15+02:00February 12th, 2025|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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The menstrual cycle

By |2025-02-12T09:34:10+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit lifestylechallenge.deborahgabriel.com Image credit lifestylechallenge.deborahgabriel.com ZIMSEC O Level Combined Science Notes: The menstrual cycle

  • The reproductive cycle in females is called the menstrual/estrus cycle
  • It has an average of 28 days
  • It varies from individual to individual but it follows a set pattern
  • The cycle is regulated by hormones produced […]
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Pregnancy

By |2025-02-12T09:35:40+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

ZIMSEC O Level Combined Science Notes: Pregnancy

  • The vagina receives an erect penis during sexual intercourse
  • During sexual intercourse, sperms are ejaculated into the vagina
  • There they begin to swim up to the oviducts
  • If an ovum is released at this time it may be fertilised in the oviduct
  • Although many sperms reach the ovum only one will […]
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Contraception:Ways to prevent pregnancy

By |2025-02-12T09:37:24+02:00February 12th, 2025|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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Rhythm/Natural Family Planning

By |2025-02-12T09:38:33+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit atlantablackstar.com Image credit atlantablackstar.com ZIMSEC O Level Combined Science Notes:Contraception:Rhythm/Natural Family Planning

How it works

  • Various techniques are used:
  • Learn to recognise the fertile periods in the menstrual cycle and avoid sex during that period
  • Several techniques are used to identify this fertile period:
    1. The temperature method is when […]
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Contraception: The pill

By |2025-02-12T09:39:17+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit citifmonline.com Image credit citifmonline.com ZIMSEC O Level Combined Science Notes:Contraception: The pill

  • Are also known as birth control pills (BCPs) or
  • Oral Contraceptive Pills (OCPs)

How it works

  • They contain the two female hormones: oestrogen and progesterone
  • They prevent the release of ova/female sex cells
  • They cause growth of an […]
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Injection (Depo Provera)

By |2025-02-12T09:40:01+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit star.ng Image credit star.ng ZIMSEC O Level Combined Science Notes:Contraception:Injection (Depo Provera)

  • Also simply known as Depo
  • It is an injection containing medroxyprogesterone, a contraceptive injection for women that contains the hormone progestin

How it works Depo provera Depo provera injection

  • Prevents the […]
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