Aqa Biology exam b

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  • Biology B
    • energy from respiration
      • Aerobic respiration
        • glucose + oxygen = carbon dioxide + water
        • Most of the reactions in aerobic respiration take place inside the mitochondria
        • The energy released during respiration is used to build large molecules from smaller ones and allows muscles to contract . In mammals and birds, it enables them to keep a constant temperature
      • The effect of exercise on your body
        • The energy released through respiration enables muscles to contract
        • When you use your muscles you need more glucose and oxygen and let out more carbon dioxide
        • Body responses to exercise include: an increase in heart rate. Glycegen stores are coverted to glucose for cellular respiration
        • These act to increase the supply of glucose for cellular respiration
      • Anaerobic respiration
        • If muscles work for a long time they don't contract efficiently . They will therefore respire anaerobically.
        • Anaerobic respiration is without oxygen. Glucose is incompletely broken down to form lactic acid
        • The anaerobic breakdown of glucose releases less energy.
        • Oxygen is needed to break down the lactic acid. The amount of oxygen needed is know as the oxygen debt
    • Simple inheritance in animals and plants
      • Cell division and growth
        • In body cells chromosomes are found in pairs.
        • They divide by mitosis to produce identical cells for growth, repair and replacement
        • Most types of animal cells differentiate early. Many plant cells differentiate through their life.
      • Cell division in sexual repoduction
        • Cells in the reproductive system divide by meiosis to produce gametes
        • Body cells have two chromosomes, gametes have only one
        • In meiosis the gm is copied and divides twice to form four gametes, each with one set of chromosome
        • Sexual reproduction gives rise to variety as gi is combined from two parents
      • Stem cells
        • Embryonic stem cells and adult stem cells can be made to differentiate into many different types of cell
        • Stem cells have the potential to treat previously incurable conditions. we may be able to grow nerve cells or new organs.
      • From Mendel to DNA
        • Gregor Mendel was the first to suggest seperately inherited factors, which we call genes
        • Chromosomes are made up of large molecules of DNA
        • A gene is a small section of DNA that codes for a particular combination of amino acids, which make a specific protein
        • Everyone has unique DNA to identify them.
      • Inheritance in action
        • In human cells the chromosomes determine whether you ate female (xx) or male (xy)
        • Some features are controlled by a single gene
        • Genes can have different forms called alleles
        • Some alleles are dominant and some are recessive
        • We can construct genetic diagrams to predict characteristic
      • Inherited conditions in humans
        • Some disorders are inherited
        • Polydactyly is caused by a dominant allele of a gene and can be caused by one parent
        • Cystic fibrosis is caused by a rsecessive allele of a gene and so must be caused by both parents
        • You can use genetic diagrams to predict how genetic disorders might be inherited or the inheritance of genetic diseases
      • Stem cells and embryos
        • It is important people make informed judgements about the use of embryonic stem cells in medical research and treatment
        • There are a number of economic, social and ethical issues surrounding the screening of embryos
    • Old and new species
      • The origins of life on earth
        • Fossils are the remains of organisms from many years ago that are found in rocks
        • Fossils may be formed in different ways
        • Fossils give us information about organisms that lived ages ago.
        • It is difficult for scientists to know how life on earth began as there is little valid evidence
      • Exploring the fossil evidence
        • We can learn from fossils how much or little organisms have changed
        • Extinction may be caused by new predators, new diseases or new more successful competitors
      • More about extinction
        • Extinction can be caused by an environment change over geological time
        • Mass extinctions may be caused by single catastrophic incidents like volcanoes or asteroid strikes
      • Isolation and the evolution of new species
        • New species arise when two populations become isolated
        • In an isolated population alleles are selected that cause successful breeding
        • Speciation takes place when an isolated population becomes so different from the original that successful interbreeding can no longer take place.

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