This is the Continuity of life page.

Topics:

  • Reproduction in plants

  • Reproduction in animals

  • Cell division (mitosis and meiosis - basics)



REPRODUCTION IN PLANTS


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PARTS OF A FLOWER


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WIND-POLLINATED FLOWERS . Notice the hanging anthers and the hairy stigma exposed to the wind.

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FROM FLOWER TO FRUIT - APPLE




This is a good video showing the different ways seeds are dispersed.


http://www.youtube.com/watch?v=zbQ1jWl3AOM



REPRODUCTION IN HUMANS
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pregnancy
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sperms meet ovum
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fertilisation and implantation
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the placenta
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menstrual cycle 1


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menstrual cycle 2



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WHAT ARE THE AMNIOTIC SAC AND THE AMNIOTIC FLUID FOR?



The amniotic sac supports the fetus as it contains and secretes the amniotic fluid; it also prevents the entry of harmful pathogens from the vagina.

The amniotic fluid has many functions:
  • it supports fetus
  • cushions sudden movements or mother’s bumps, thus protecting the fetus against damage
  • provides constant temperature so it protects the developing baby against fluctuating temperature
  • allows fetus to move
  • is also needed for bone and muscle growth and development and helps lungs & gut to develop
  • collects fetal urine and other waste products and most importantly, it provides a sterile environment


AND WHAT ABOUT THE PLACENTA?

The placenta acts as a barrier between the mother’s and the fetus’s blood systems preventing maternal and fetal blood from mixing. This will protect the developing baby against the mother’s immune system and against possible pathogens present in mum’s blood, such as protozoa or bacteria.
But the placenta is very important because:
  • it supplies oxygen and nutrients such as glucose, vitamins, and amino acids to the fetus
  • it allows the loss of waste products such as carbon dioxide and urea from fetus
  • there is transfer of antibodies from mother to fetus, so that the baby is born with some protection against pathogens until his immune system matures
  • it supplies or removes water
  • it secretes hormones (oestrogen, progesterone and hCG), so it acts as an endocrine gland to keep the pregnancy going on.