B1:topic 1 and 2

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  • B1: Topic 1 and 2
    • Classification
      • Classification means grouping things by their characteristics.
        • Kingdom- group of similar phyla e.g. Animalia. Phylum- group of similar classes e.g. Chordata. Class- group of similar orders e.g. Mammalia. Order- group of similar families e.g. Carnivora. Family- group of similar genera e.g. Canidae (dog family) Genus- group of similar species e.g. Canis. Species- organisms that have most characteristics in common e.g. Canis lupus (domesticated dog)
          • The Five Kingdoms: Animalia(animals)-multicellular (body made of many cells). have no cell walls. No chlorophyll in cells. Eat other organisms.
            • Plantae (plants)-multicellular. Have cell walls. Have chlorophyll. Make their own food
            • Fungi- multicellular. Have cell walls. No chlorophyll. Digest food outside the body.
            • Protoctista- mostly unicellular (body is a single cell). Nucleus in cell.
            • Prokaryotae (mostly bacteria). Unicellular. No nucleus in cell.
    • Vertebrates and Invertebrates
      • The phylum Chordata contains animals that have a supporting rod running the length of their bosy. Many animals in the Chordata are vertebrates (animals with backbones)
    • Species
      • A species is a group of organisms that can breed with each other and produce fertile offspring. A few species can interbreed to produce hybrids are sterile (cannot produce offspring).
    • Binomal Classification
      • Binomial names are useful because other people know exactly which species you mean. You can see the genus which species are very closely related. It helps us identify which environments contain the fewest species that are most at risk of extinction and need the most protection and conservation
        • The European herring gull and lesser black-backed gull rarely interbreed, even where they nest together. So we say they are different species. But they are the ends of a ring species of gulls that surrounds the North Pole. Neighbouring 'species' of gulls in the ring interbreed frequently, producing a continuous range of characteristics from one end of the ring to the other.
    • Reasons for variety
      • Different species are adapted to living in different environments. Organisms that live in extreme environments need special adaptations.
        • Acquired characteristic is one that is changed by the environment. Continuous variation is where a characteristic varies gradually and continuously between extremes, e.g. height or weight. Normal distribution curve has a bell shape, showing that the most common variation lies between two extremes, with fewer individuals having variations that are near to each extreme.
    • Evolution
      • Natural selection. Indviduals of a species show variation. this can mean that some indviduals will be better able to survive in their environment and produce more healthy offspring than others. this is natural selection, where the environment selects which inviduals pass on their genes to the next generation.
      • Being better adapted means being better able to survive, suchas surviving the climate, sompeting more successfully for a limited amount of food, or escaping from predation.
        • Charles Darwin (1809-1882) suggested that is the environment changes, natural selection will result in characteristics of a species changing gradually from generation to generation. This change is called evolution. New evidence supports his theory.
    • Genes
      • The chromosomes are placed within the nucleus of a cell. there are two copies of eachchrosome in body cells- each copy has the same genes in the same order along its length (except chromsomes that dertamine sex) A gene is a short piece of DNA at a particular point on a chromosome- a gene codes for characteristic, e.g. eye colour. A gene may come in different forms, called alleles, that produce different variations of charateristics, e.g. different eye colours.
        • Alleles- Different alleles of the same gene- the person is hetroxygous for this gene. Chrosomes of the same type are the same size and have the same genes in the same order. These genes have the same allele on both chromosomes -the person is homozygous for these genes.
        • Genetic definitions. Thegene for coat colour in rabbits has different alleles. The allele for brown colour (B) is dominant over the allele for the black colour (b). Genotype- BB will have the phenotype- brown coat. Genotype- Bb will have the phenotype- brown coat. Genotype bb- will have the phenotype- black coat.
          • Genotype shows the alleles in the individual. Remember that each body cell has two genes for each characteristic- either two alleles that are the same or two alleles that are the same or two that are different.
          • Phenotype means the characteristic that are produced, including what the individual looks like.
    • Explaining inhertiance
      • Monohybrid inheritance. Sometimes a characteristic is controlled by a single gene. This is called monohybrid inheritance. We can use a genetic diagram to help us understand how alleles are inherited.
    • Genetic disorders
      • Some genes faulty alleles that cause health problems. These are genetic disorders.
        • Sickle Cell Disease: caused by having two copies of recessive allele for the haemoglobin gene, which causes red blood cells to become sickle-shaped. People with the disease: become short of breath and tire easily. Have painful joints if red blood cells get stuck in capillaries. Have reduced blood flow if red blood cells block a blood vessel, which may cause damage to body tissues, heart attack, stroke or even death.
        • Cystic Fibrosis: caused by having two copies of a recessive allele for a cell membrane protein. This makes the mucus that lines tubes in the lungs and other parts of the human body much thicker and stickier than normal. This can: increase the risk of lung infections. Prevent enzymes getting into the digestive system to break down food, which can lead to weight loss.


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