sexual reproduction

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 […]
  

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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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 […]
  

Image credit singleblackmale.org ZIMSEC O Level Combined Science Notes: Sexually Transmitted Infections (STIs)

To access more topics go to the Combined Science Notes page

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 […]