Edexcel GCSE Biology 3 - Topic 1 Notes

Here are my notes for the first topic in B3, sorry if there are any mistakes, hope this helps :)

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  • Created on: 05-05-13 15:51
Preview of Edexcel GCSE Biology 3 - Topic 1 Notes

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Topic 1 ­ Control Systems
Circadium rhythm ­ a 24 hour rhythm found in plants and animals.
Photoperiodicity ­ the way in which living things respond to changes in day
length.
Photoperiodicity has three main uses in plants:
1. Germination ­ when plants die in the winter, their seeds survive. In
spring, as the days get longer the seeds germinate.
2. Growth ­ As the days get longer the plants respond by growing faster
and when the days get shorter they stop growing and prepare
themselves for winter.
3. Reproduction ­ It allows the plants to flower at the correct time,
increasing the possibility of pollination.
The Urinary System
The purpose of the urinary system is to produce, store and remove urine from
the body.
The kidney removes excess water and urea from the blood stream.
Urea is amino acids that have been broken down in the liver.
Be careful not to get ureter
and urethra mixed up!
Kidney Failure:
-when your kidney do not function correctly.
This could be because of restriction to blood flow, a high dosage of toxins or
medical conditions such as diabetes and high blood pressure.
There are two solutions:

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The four hormones that control the menstrual cycle are Oestrogen,
Progesterone, LH and FSH.
Oestrogen ­ produced in the ovaries, causes uterus lining to thicken.
Progesterone ­ Produced by the empty follicle, maintains the uterus wall. If a
women gets pregnant, progesterone causes the placenta to form.
FSH ­ stimulates the maturity of eggs, made in the pituitary gland.
LH ­ triggers ovulation, made in the pituitary gland.…read more

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Surrogate Mothers ­ IVF is performed but the fertilised egg is placed into
another mother's womb.
Using FSH ­ this stimulates the maturation of follicles so more eggs are
released to use in IVF. Could cause complications.
Inheritance of gender
The 23rd pair of human chromosomes is called the sex chromosome and
determines the gender of the baby.
All eggs have the X chromosome
Half of sperm have the X chromosome, half of them have the Y chromosome.…read more

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Passive immunisation ­ provide from antibodies outside the body (e.g.
vaccination or breast milk)
Active immunisation ­ normal infection by a pathogen (natural immunity) or
after vaccination (artificial immunity)
Jenner's contribution
Edward Jenner discovered immunisation. He observed that milkmaids never
got small pox but instead they got cowpox (which was less harmful).
He suspected that the pus from the blisters on the milkmaids' hands caused by
cowpox protected them from smallpox.
Jenner inoculated (infected on purpose) a boy with pus from the cowpox virus.…read more

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Louis Pasteur first proved that microorganisms were responsible for souring
milk, wine and beer and that microorganisms were no longer able to grow in
liquids if the liquid has been boiled.
He proved that microorganisms were present in the environment and could not
spontaneously generate. He did this by comparing sterile broths that were
open to the air with ones that were kept sealed. He discovered that
microorganisms only grew in the broths that were open to the air.…read more

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