Biology 1.

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  • Biology 1.
    • Variation.
      • Kingdom, phylum, class order, family, genus, species.
        • Kingdoms:     Plantae, Animalia, Fungi, Protoctists, Prokaryotes.
          • Plantae: Multicellular, have cell walls, have chlorophyll, feed auto-trophically.
          • Animalia: Multicellular, no cell wall, no chlorophyll, are heterotrophs.
          • Fungi: Multicellular, have cell walls, no chlorophyll, feed saprophyti-cally (digest food outside the body)
          • Protoctists: Unicellular, nucleus in cell, e.g. algea.
          • Prokaryote: Unicellular, no nucleus, e.g. bacteria.
      • Naming species.
        • Hybrids: Offspring of two different species, these are infertile.
        • Species: When two of the same organism reproduce to create fertile offspring.
        • Binomial naming system: A two part name; genus name + species name.
        • Ring species: Organisms that are slightly different due to habitat.
        • Adaptation: changes to the body to fit the environment the organism lives in.
      • Genetic disorders.
        • Cystic fybrosis: inherited as a recessive allele, sufferers produce thick mucus which blocks bronchioles, breathing problems, digesting problems, chest infection.
          • Arises as a mutation, mutations occur at random, mutations are changes in the DNA of genes,
        • Huntingtons disease: caused by one faulty dominant allele, can be developed in mid 30's, causes clumsiness, memory loss, tremors and mood changes.
        • Sickle cell Anaemia: characterised by odd shaped red blood cells, the blood cells get stuck in the capillaries, which deprives the body of oxygen. Its caused by inheriting two recessive alleles.
          • Symptoms include, tiredness, painful joints, muscles, fever and anaemia.
      • Inheritence.
        • Homozygous = both alleles are the same.
        • Heterozygous= Both alleles are different.
        • Genotype = Description of genes.
        • Phenotype = Description of physical characteri-stics.
        • Recessive = Must have two copies of a recessive allele to have that feature / disease.
        • Dominant = You only need one copy of a dominant allele to have that feature.
        • Genes = a section of DNA that codes for specific characteri-stics.
    • Responding to change.
      • Hormones: are chemical messengers which travel in the blood to activate target cells.
        • They are produced in various glands (endocrine glands). They are release directly into the blood.
          • They only affect particular cells (target cells), they have the right receptors to respond to that hormone, an organ that contains target cells is called a target organ.
        • Slower message than neurones, act for a long time, act in a more general way, chemical message.
      • Homeostasis: The bodies way of keeping its internal environment stable.
        • Thermo-regulation; The process of keeping the internal body temperature constant.
          • Vaso-constriction: When you get too cold the erector muscles contract, hairs stand on end to trap an insulating layer of air, blood vessels near the surface of the skin constrict, meaning less blood flow near the surface meaning less heat is lost.
          • Vasodilation: When you're too hot the erector muscles lie flat, blood vessels near the surface dilate, allowing more blood flow near the surface transferring more heat into the surroundings, sweat is produced and evaporates as a way of cooling the body down.
      • Neurones: transmit information as electrical impulses around the body.
        • They have branched endings called dendrons, so they can connect with lots of other neurones.
        • The electrical impulse is passed along the axon of the cell. Theres a myelin sheath along the axon that acts as an electrical insulator, which stops the impulse getting lost. It also speeds up the electrical impulse.
        • Neurones are long, which also speeds up the impulse (connecting with another neurone slows the impulse down.
          • So one long neurone is much quicker than lots of short ones joined together.
        • The connection between two neurones is called a synapse. It's basically just a very tiny gap; the nerve impulse is transmitted by chemicals called neuro-transmitters, which diffuse across the gap.
          • The neuro-transmitters then set off a new electrical impulse in the next neurone.
        • Very fast messages, act for a very short time, act on a very precise area, electrical message.
      • Reflex arc.
        • 1- Finger touches something hot.
        • 2- Stimulation of the pain receptor.
        • 3- Message travels along the sensory neurone.
        • 4- Message is passed along a relay neurone.
        • 5- Message travels along a motor neurone.
        • 6- When message reaches the muscle it contracts to move arm away from heat.
      • Insulin and diabetes.
        • Blood glucose level too high - insulin is added.
          • Blood with too much glucose, insulin is secreted by pancreas, glucose is removed by liver, insulin makes liver turn glucose into glycogen, blood glucose is reduced so insulin stops being secreted.
        • Blood glucose level too low - glucagon is added.
          • Blood with too little glucose, glucagon secreted by pancreas, glucose added by liver, glucagon makes liver turn glycogen into glucose, blood glucose increased so glucagon stops being secreted.
        • Type 1- the pancreas produces little or no insulin. the result is that a persons blood sugar can rise to a level that can kill them.
        • Type 2- the pancreas doesn't produce enough insulin or when a person becomes resistant to insulin.
      • Plant growth hormones.
        • Photo-trophism: The growth of a plant in response to light. Shoots are positively phototrophic - they grow towards light.
        • Gravi-trophism: The growth of a plant in response to gravity. Roots are positively gravitropic - they grow downwards.
        • Auxin: a plant hormone that controls growth at the tips of shoots and roots. Auxin is produced in the tips and diffuses backwards to stimulate the cells just behind the tips to elongate.
          • It promotes growth in the shoot but high concen-trations inhibit growth in the root.
    • Inter -relationships.
      • Drugs.
        • A substance that when taken affects the body and mind.
        • Depressants: e.g. alcohol, these decrease the activity of the brain. They slow down responses of the CNS, causing slow reactions.
        • Stimulants: e.g. caffeine, increase activity of the brain, by increasing the amount of neurotransmitters at some neurone synapses. Increases speed of reactions. Decreasing reaction times.
        • Painkillers: e.g. narcotics like morphine, these decrease the feeling of pain.
        • Hallucino-gens: e.g. LSD, they distort whats seen and heard by altering the pathways nerve impulses normally travel along.
        • Smoking.
          • Tobacco smoke contains carbon monoxide - this combines with haemoglobin in the red blood cells, meaning the blood can carry less oxygen.
          • It also contains carcinogens (chemicals that can lead to cancer)  like tar.
          • Addictive due to nicotine.
        • Alcohol.
          • Short term: slows reactions, blurred vision, lower inhibitions.
          • Long term: poisonous, death of liver cells, forming scar tissue that starts to block blood flow through the liver - this is called cirrhosis.
            • Dangerous substances can build up and damage the body. too much drinking can lead to brain damage.
        • More drugs.
          • Antiseptics: Are used outside the body to stop disease spreading. They are chemicals that destroy bacteria or stop them growing.
          • Anti-bacterials: antibiotics are used to treat bacterial infections. They work by killing bacteria or stopping them from growing.
          • Anti- fungals: are used to treat fungal infections, they work by killing the fungi or stopping them growing.
      • Infectious diseases.
        • Pathogens: are micro-organisms that cause disease. They include bacteria, protozoa, fungi. They can spread in different ways.
          • Water: e.g. Cholera is a bacterial infection that causes diarrhoea and dehydration. It's spread when drinking water is contaminated with the diarrhoea of other sufferers.
          • Food: e.g. Salmonella bacteria cause food poisoning and are found in food that has been kept too long or not cooked properly.
          • Air: carried in the air in droplets produced when you cough or sneeze so other people can breath them in. E.g. the influenza virus.
          • Contact: touching contaminated surfaces. E.g. athletes foot.
          • Body fluids: such as blood, breast milk, and semen. E.g. the HIV virus that causes AIDS.
          • Animal vectors: Anopheles mosquito carries the protozoan that causes malaria, it spreads it by biting other organisms.
            • House fly - carries the bacterium that causes dysentery, it spreads the disease by carrying the bacteria onto food.
        • Physical and chemical barriers that stop pathogens entering the body.
          • The skin: undamaged skin is a very effective barrier against micro-organisms. And if it does get damaged, blood clots quickly to seal cuts and keep micro-organisms out.
          • The respiratory system: the respiratory tract is lined with mucus and cilia. The mucus catches dust and bacteria before they reach the lungs and the cilia push the gunk-filled mucus away from the lungs.
          • The eyes: eyes produce (in tears) a chemical called lysozyme which kills bacteria on the surface of the eye.
          • The stomach: the hydrochloric acid in the stomach will kill most pathogens that are digested.
      • Parasitism:
        • Parasites live in or on a host. They take what they need to survive, without giving anything back, this often harms the host.
          • Fleas: They live in the fur and bedding of animals, they feed by sucking the blood of their hosts and can reproduce quickly.
          • Head lice: insects that live n human scalps, sucking blood for food and making the person itch.
          • Tapeworms: attatch to the intestinal wall of their hosts, they absorb lots of nutrients from the host, causing them to suffer from malnutrition.
          • Mistletoe: is a parasitic plant that grows on trees and shrubs, it absorbs water and nutrients from its host, which can reduce the hosts growth.
      • Mutualism:
        • A relationship where both organisms benefit.
          • Oxpeckers: Live on the backs of buffalo. They eat pests like ticks, flies and maggots. They also alert the animal to any predators that are near by hissing.
          • Cleaner fish: they eat dead skin and parasites off larger fish. In return they get a source of food, and avoid being eaten by fish.
          • Nitrogen fixing bacteria in Legumes: Leguminous plants carry nitrogen-fixing bacteria in nodules in their roots. The bacteria get a constant supply of sugar from the plant, and the plant gets essential nitrates from the bacteria.
          • Chemo-synthetic bacteria in deep sea vents: some chemo-synthetic bacteria live inside giant tube worms or in the gills of molluscs in deep-sea vents.
            • The tube worms supply the bacteria with chemicals from the sea water, which the bacteria turns into food for themselves and the host worms.
      • Eutro-phication.
        • 1-Excess nitrates wash into river causing rapid growth of algae.
        • 2-Some plants start dying due to competition for light.
        • 3-Microbe numbers increase as they feed on the dead material.
        • 4-Microbes use up all the oxygen. Fish and other aquatic animals suffocate.
    • Theories.
      • Darwins theory of evolution.
        • Natural selection - survival of the fittest; A giraffe with a longer neck than the others can reach the food high up, he is more likely to survive, will pass on long neck to offspring.
      • Lamaracks theory, a characteristic which is used more and more by an organism becomes bigger and stronger.
        • A giraffe will stretch its neck trying to reach the higher fruit, the neck gets longer as its used, the offspring inherit the long neck.

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