January 2023

Contraception: Abstinence

By |2022-09-15T12:37:50+02:00January 24th, 2023|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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Causes of infertility

By |2022-09-15T12:37:49+02:00January 24th, 2023|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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Reproduction in Humans

By |2022-09-15T12:37:56+02:00January 24th, 2023|Notes, O Level Science Notes, Ordinary Level Notes|

A Zimbabwean family

A Zimbabwean family ZIMSEC O Level Combined Science Notes: Reproduction in Humans
  • Human being produce sexually
  • The process involves the fusion (joining) of the nuclei (sex cells) of the male gamete (sperm)
  • and the female gamete (ovum)
  • To form a zygote
  • The human and female sexual organs take […]

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Male Reproductive system

By |2022-09-15T12:37:55+02:00January 24th, 2023|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit raanetwork.org

Image credit raanetwork.org ZIMSEC O Level Combined Science Notes: Male Reproductive system
  • The diagram below shows the reproductive system of a man

Male reproductive system. Image credit goldiesroom.org

Male reproductive system. Image credit goldiesroom.org
  • Testes-this is where sperms are made.
      […]

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Population Dynamics

By |2022-09-15T12:37:48+02:00January 24th, 2023|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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Female Reproductive system

By |2022-09-15T12:37:55+02:00January 24th, 2023|Notes, O Level Science Notes, Ordinary Level Notes|

Image credit huffpost.com

Image credit huffpost.com ZIMSEC O Level Combined Science Notes: Female Reproductive system
  • The diagram below shows the reproductive system of a female

Female reproductive system

Female reproductive system
  • Ovaries-there are two ovaries
    • Their function is to produce and release ova […]

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Effects of population growth on natural resources

By |2022-09-15T12:37:48+02:00January 24th, 2023|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 |2022-09-15T12:37:54+02:00January 24th, 2023|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 |2022-09-15T12:37:54+02:00January 24th, 2023|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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