At MyTutor, we’ve got lots of dedicated Biology tutors across the UK who love helping teens achieve their best when exams come around. Since we started in 2013, we’ve given more than 250,000 one-to-one lessons, and over 1 million school pupils have used our online resource centre. Over time we’ve been able to get a strong understanding of exactly the topics in each subject that kids tend to need that extra help with.
Here are the top five Biology GCSE topics our students struggle most with, and some example answers which can double as handy study notes for your child to get them revision-ready.
Active immunity involves your body’s direct response to an unknown pathogen. This response is the production of antibodies specific to the antigen of a particular pathogen.
This type of immunity is not immediate as it takes time to create enough of the correct antibodies to fight the pathogen. However, the response lasts for a long period of time and in some cases, where antibodies remain in the body as memory cells, immunity to the specific pathogen may be life long.
Conversely, passive immunity is an immune response which involves antibodies obtained from outside the body. An example of this is the antibodies a mother passes to her infant through her breast milk. Immunity to the pathogens which these antibodies are specific to is therefore immediate, as no time is needed to create them. However, this immunity is not long term and may only last a few days.
Passive and active immunity both have natural and artificial forms. So, for example, the natural form of passive immunity is antibodies transferred in breast milk as mentioned, however an artificial form of passive immunity is the use of antidotes such as that for rabies where specific antibodies are injected into an infected individual.
Additionally, the natural form of active immunity is the normal process of an individual contracting an infection and their immune system responding, conversely the artificial form of active immunity is immunization, where an individual is deliberately exposed to a weakened form of a particular pathogen in order to elicit an immune response.
Arteries and veins both carry blood around the body, and they each have three main layers of tissue (a ring of endothelial tissue at the centre of the blood vessel surrounded by a layer of muscle and elastic fibres, which is surrounded by a layer of connective tissue).
However, there are several differences between them:
Arteries carry blood from the heart to the rest of the body, whereas veins carry blood from the rest of the body back to the heart.
Almost all arteries carry oxygenated blood and almost all veins carry deoxygenated blood. The only exceptions are the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the pulmonary vein, which carries oxygenated blood from the lungs to the heart.
Arteries have a thick elastic muscle layer, whereas the muscle layer for veins is much thinner. This is because the heart pumps blood into the arteries at high pressures, so the walls of the arteries must be able to cope with the changes in pressure during a heartbeat. Veins carry blood at much lower pressures so do not need such a thick wall.
Arteries have a much narrower lumen (the hole at the centre that the blood flows through) than veins. This helps keep higher blood pressures in the arteries, which is needed to keep blood flowing quickly to body tissues.
Veins have valves and arteries do not. In arteries, blood flows in the right direction because of the heart pumping it forwards at high pressures. The lower blood pressure in veins means that valves are needed to stop blood flowing backwards (for example, in veins in the legs, blood needs to flow upwards against the pull of gravity).
Breathing is the physical process where you inhale and exhale air in and out of your lungs.
Inhaling brings in air containing Oxygen, which is absorbed and exchanged for Carbon Dioxide. The Carbon Dioxide, now in the air inside your lungs, is expelled when you exhale.
The Oxygen is carried in your blood to the cells around your body where respiration takes place.
Respiration is a chemical reaction where Oxygen is used to breakdown Glucose in order to generate energy which is then used by the cell to function.
Enzymes are biological catalysts. They speed up reactions – but are not changed in the reaction. Enzymes are proteins, and therefore are folded chains of amino acids with a specific shape. This shape is determined by the sequence of amino acids held together by bonds, for example Hydrogen bonds. Enzymes speed up reactions by bringing reactants together and reducing the activation energy required to start the reaction (enzymatic reaction).
Enzymes are specific: they have a specific shape, therefore only a certain substrate will fit its active site. There are two theories of enzyme action: Lock and Key and Induced Fit. The lock and key theory states that only a certain substrate will fit a certain active site, just like a key fits a lock. Induced Fit, likewise, states that enzymes wrap around substrates, attracted to each other by opposite charges, forming an enzyme substrate complex.
Darwin and Lamarck were both scientists who tried to understand evolution.
Lamarck’s theory of evolution was based around how organisms (e.g. animals, plants) change during their lifetime, and then pass these changes onto their offspring. For example, Lamarck believes that the giraffe had a long neck because its neck grew longer during its lifetime, as it stretched to reach leaves in high-up trees, meaning that each generation of giraffe had a longer neck than previous generations.
Darwin’s theory, known as natural selection, believed that organisms possessed variation (each individual was slightly different from one another), and these variations led to some being more likely to survive and reproduce than others. Features that made an organism more likely to survive or reproduce are therefore more likely to appear to each generation. In terms of the giraffe, Darwin’s theory would state that longer necked giraffes were more likely to survive, because they could eat leaves from taller trees, and therefore more long-necked giraffes will be born, which eventually caused giraffes to have longer necks. Longer necked giraffes survived because they were a better fit for their environment. It is from this idea that we get the phrase ‘survival of the fittest’.
Darwin’s theory became accepted because it had more evidence that supported it. Lamarck’s theory suggest that all organisms become more complicated over time, and therefore doesn’t account for simple organisms, such as single-cell organisms. We also know through observation that characteristics inherited during an individual’s lifetime do not get passed onto their offspring; for example, if someone pierces their ear, it doesn’t mean that their children will be born with pierced ears.
Darwin’s theory became even stronger when, many years after his death, the study of genetics emerged. Genetics ultimately showed that all inherited traits were passed on through genes, which are unaffected by outside world, as Lamarck would predict, and are instead naturally varied, as Darwin predicted. Though Darwin didn’t know what genes were, he could see their effect on natural selection.
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