Core Science B1

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  • Biology 1
    • Homeostasis and Plant Hormones
      • Homeostasis is maintaining a constant internal environment of the body.
        • Keeps levels of temperature, water and carbon dioxide steady.
      • Temperature control.
        • vasoconstriction is the narrowing of blood vessels in the skin. It causes less flood flow and less heat transfer.
        • Vasodilation is the widening of small blood vessels in the skin. It causes more blood flow near the skin and results in in more heat transfer
      • Auxins are a group of plant hormones. they cause shoot curvature by cell elongation.
        • Auxins are involved in Phototropism and Geotropism.
        • Plant hormones are used as weed killers to increase crop yield and as rooting powder to increase root growth.
    • Drugs and Disease
      • People can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens.
        • 1. inject a harmless pathogen carrying antigens.
          • 2. the antigens trigger a response by white blood cells, producing the correct antibodies
            • 3. memory cells remain in the body, providing immunity to that disease.
      • Harmful drugs are classified as Class A,B and C.
        • Depressants block the transmission of nerve impulses across synapses
        • Stimulants speed up nerve impulses.
    • The Nervous System
      • Neurons are adapted by being long, having branched endings to pick up impulses and having an insulator sheath.
      • The gap between neurons is called a synapse.
      • Light rays are refracted as they pass through the cornea and lens.
        • The eye adapts by altering the shape of the lens.
          • Monocular vision has a wide field of view but is poorer at judging distance than binocular vision.
    • Diet and Exercise
      • Being fit is the ability to do exercise. Being healthy is being free from disease.
      • Blood pressure has two readings, Diastolic and Systolic.
        • It can be increase by alcohol smoking and being overweight.
        • It can be reduced by regular exercise and healthy eating.
        • High blood pressure can cause strokes
        • Low blood pressure and cause poor circulation and fainting.
      • You need to eat a balanced diet that has the right amounts of chemicals found in food. Three of these are, Carbohydrates, proteins and fats
        • Carbohydrates are stored in the liver as glycogen.
        • Fats are stored under the skin and around organs.
        • Proteins are made of amino acids.
          • Too little Protein causes kwashiorkor.
          • EAR=0.6x Body mass in kg
            • Daily protein intake
      • BMI= mass in kg / (Height in m)^2
        • 30+ is  overweight
        • 25-30 is obese
        • 20-25 is normal
        • less than 20 is underweight
    • Variation and Inheritance
      • Alleles are different versions of the same gene.
        • Dominant alleles are expressed if present, recessive alleles are expresses in the absence of dominant alleles.
        • Most faulty alleles are recessive.
          • Inherited disorders are caused by faulty alleles.
      • The human body has 23 pairs of chromosomes
        • Gender is determined by sex chromosomes XX in female XY in male.
      • Being Homozygous is having two identical alleles.
      • Genetic Variation is caused by mutations.


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