TOPIC ONE: Classification, Variation and Inheritance

Transcription

1 GCSE BIOLOGY B1

2 TOPIC ONE: Classification, Variation and Inheritance 1.1. Demonstrate an understanding of how biologists classify organisms according to how closely they are related to one another including Species, Genus, Family, Order, Class, Phylum and the Five Kingdoms. All species are sorted like this: kingdom phylum class order family genus species For example, lions would be sorted: kingdom - animal phylum - vertebrate class - mammal order - carnivorous family - cat genus - big cat species - lion. Being able to classify species is important to scientists as it allows them to accurately identify individual species wherever they are. For example - a robin in America isn t the same as a robin in the UK as they have the same genus but different species.

3 1.2. Describe the main characteristics of the five kingdoms. Animalia Multicellular, no cell wall or chlorophyll, heterotrophic feeders. e.g. jellyfish, worms, arthropods, molluscs, echinoderms, fish, amphibia, reptiles, birds and mammals Plantae Multicellular, have cell walls and chlorophyll, autotrophic feeders. e.g. algae, ferns and mosses (plants that do not produce seeds), conifers and flowering plants (plants that do produce seeds) Fungi Multicellular, have cell walls, do not have chlorophyll, saprophytic feeders. e.g. moulds, mushrooms, yeast Protoctista Usually unicellular, with a nucleus eg amoeba. e.g. amoeba and paramecium Prokaryotes Unicellular, with no nucleus eg bacteria. e.g. bacteria and blue-green algae

4 1.3. Explain why scientists do not classify viruses in any of the five kingdoms and regard them as non-living Describe the main characteristics of the phylum Chordata as animals with a supporting rod running the length of the body, an example of this being the backbone in vertebrates. Viruses Scientists do not classify viruses as a living thing because they don t show the seven processes of life. Phylum Chordata Animals with a supporting rod running the length of the body. e.g. A backbone

5 1.5. Explain how scientists place vertebrates into groups based on oxygen absorption methods, reproduction and thermoregulation Demonstrate an understanding of the problems associated with assigning vertebrates to a specific group based on their anatomy and reproduction methods and why many vertebrates are difficult to classify. Vertebrates Vertebrates are split into fish, amphibians, reptiles, birds and mammals. This is done by looking at how the animal takes in oxygen (lungs, gills or though the skin), how they reproduce (internal or external fertilisation, laying eggs or give birth) and also how they maintain their temperature (maintain it themselves or change with environment). Difficulties Assigning vertebrates to different groups can be difficult as some fall into many categories: for example, sharks are fish but give birth to live young and use internal fertilisation.

6 1.9. Explain how accurate classification may be complicated by variation within a species, hybridisation in ducks and ring species. Variation within a species e.g. Different breeds of dog Hybridisation Closely related species breed to produce offspring which have characteristics of both. e.g. Ducks. Ring Species Neighbouring populations of species may have slightly different characteristics but can still interbreed as part of a chain but the two ends of the chain can t interbreed.

7 1.11. Explain how organisms are adapted to their environment and how some organisms have characteristics that enable them to survive in extreme environments, including deep-sea hydrothermal vents and polar regions. Organisms have features (characteristics) which help them live in their habitat. Polar Regions Polar bears have thick fur to keep them warm, which is white so they can camouflage into the snow and ice. Their coat gets greasy meaning water will fall off after swimming. This means the Polar Bear wont get frozen water all over them. Deep-Sea Hydrothermal Vents The Pompeii worm can live in the high temperatures of hydrothermal vents because they have a think layer of bacteria to protect it from the heat and it hides in a papery tube to protect itself from predators.

8 1.12. Demonstrate an understanding of Darwin s theory of evolution by natural selection including variation, over-production, survival, advantageous characteristics inherited and gradual change. Variation All populations contain organisms with slight differences from each other. Over-Production Organisms produce more offspring than will survive to adulthood. Survival Better adapted organisms are more likely to survive and so their characteristics will be passed to offspring. Advantageous characteristics inherited Better adapted organisms are more likely to produce meaning good characteristics are passed to offspring. Gradual Change Over time, useful characteristics are passed to offspring until nearly everybody has these characteristics.

9 1.13. Describe variation as continuous or discontinuous Interpret information on variation using normal distribution curves. Continuous Variation Human height is an example. Height ranges from the shortest person to the tallest person in the world and any height in-between is possible. You can use this data to create a distribution curve. Discontinuous Variation Human blood group is an example of discontinuous variation. There are only four types of blood group. There are no other possibilities and there are no values in between. So this is discontinuous variation.

10 1.16. Demonstrate an understanding of the causes of variation, including genetic variation and environmental variation Demonstrate an understanding of how speciation occurs as a result of geographic isolation. Environmental and Geogrpahical Variation Animals evolve to adapt to their environment. This is why we get closely related species in the same genus, because they live in slightly different areas and have to adapt (either to the climate, food or habitat).

11 1.18. Explain how new evidence from DNA research and the emergence of resistant organisms supports Darwin s theory. Antibiotic Resistant Bacteria Microorganisms such as bacteria and viruses, reproduce rapidly and can evolve in a relatively short time. An example of this is the bacterium E.Coli. This has become resistant to certain antibiotics. This means that when the disease comes near the antibiotics, the resistant cells will survive whilst the normal cells would die. This proves Darwin s Theory of Evolution.

12 1.20. Describe the structure of the nucleus of the cell as containing chromosomes, on which genes are located. A cell s nucleus contains chromosomes made up of long DNA molecules (genes).

13 1.21. Demonstrate an understanding that genes exist in alternative forms called alleles which give rise to differences in inherited characteristics. Some characteristics, such as eye colour and the shape of the earlobe, are controlled by a single gene. These genes may have different forms. Different forms of the same gene are called alleles. The gene for eye colour has an allele for blue eye colour and an allele for brown eye colour. Alleles are dominant or recessive: the characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pair the characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair For example, the allele for brown eyes is dominant, while the allele for blue eyes is recessive. An individual who inherits one or two alleles for brown eyes will have brown eyes. An individual will only have blue eyes if they inherit two copies of the allele for blue eyes. Individuals A and B have brown eyes whereas Individual C has blue eyes.

14 1.23. Analyse and interpret patterns of monohybrid inheritance using a genetic diagram, Punnett squares and family pedigrees. Punnett Square Family Pedigree Genetic Diagram

15 1.24. Describe the symptoms of genetic disorders; sickle cell disease, cystic fibrosis. Sickle Cell Disease Sickle cell disease is a recessive condition which causes red blood cells to become misshapen and stick together which can block the blood vessels. People with the disease can become tired quickly and become out of breath. Caused by a recessive allele (small f). Cystic Fibrosis People which cystic fibrosis produce thick and sticky mucus in their lungs and airways. A result of this is that they are more likely to get respiratory infections. They need daily physiotherapy to help them relieve congestion. Caused by a recessive allele (small f).

16 TOPIC TWO: Responses to a changing environment 2.1. Define homeostasis as the maintenance of a stable internal environment Demonstrate an understanding of the homeostatic mechanisms of thermoregulation and the effect of temperature on enzymes, osmoregulation and blood glucose regulation. 2.3/4. Explain how thermoregulation takes place. It is important that the body s internal environment is controlled. For example, the amount of carbon dioxide in the bloodstream must be carefully controlled. Maintaining a constant internal environment is called homeostasis. The nervous system and hormones are responsible for this. Here are some of the other internal conditions that are controlled: Blood Sugar Level Controlled by the release and storage of glucose which is controlled by the hormone insulin.

17 Body Temperature Hairs on the skin trap warm air when standing up and don t when lying flat. Tiny muscles in the skin pull mussels up when it is cold. The body sweats, if it is too hot, to cool itself down. Blood vessels supply blood to the skin. When you are too hot, vasodilation occurs meaning more blood can go to the skins and be lost however if you are too cold, vasoconstriction occurs and blood vessels become narrower meaning less heat is lost. It is important to keep your body at a good temperature otherwise enzymes in your body will not work. Osmoregulation (control of body water content)

18 2.5. Recall that hormones are produced in endocrine glands and are transported by the blood to their target organs.

19 2.7. Explain how blood glucose levels are regulated by glucagon, causing the conversion of glycogen to glucose Explain how blood glucose levels are regulated by insulin and excess blood glucose is converted to glycogen in the liver. Glucose level Effect on pancreas Effect on liver Effect on glucose level too high insulin secreted into the blood liver converts glucose into glycogen goes down too low insulin not secreted into the blood liver does not convert glucose into glycogen goes up

20 2.8. Recall that Type 1 Diabetes is caused by a lack of Insulin Explain how Type 1 Diabetes can be controlled, including the roles of diet and injection of insulin usually into the subcutaneous fat Explain how, in Type 1 Diabetes, the level of physical activity and diet affect the amount of insulin required. Type 1 Diabetes Type 1 diabetes is caused by a lack of insulin. It can be controlled by: a monitored diet injecting more insulin People with type 1 diabetes have to monitor their blood sugar levels throughout the day as the level of physical activity and diet affect the amount of insulin required.

21 2.11. Recall that Type 2 diabetes is caused by a person becoming resistant to insulin Explain how Type 2 diabetes can be controlled by diet and physical activity Evaluate the correlation between obesity and Type 2 Diabetes. Type 2 Diabetes Type 2 diabetes is when a person is resistant to insulin. It can be controlled by a monitored diet exercise There s a link between Type 2 Diabetes and obesity. Obesity is when you have a BMI (body mass index) over 30. It is calculated by:

22 2.14. Explain how plant growth substances (hormones) bring about positive phototropisms in shoots and positive gravitropism in roots Explain how auxins bring about shoot curvature using cell elongation Analyse, interpret and evaluate data from plant hormone experiments, including the action of auxins and gibberellins. Auxin is a plant hormone responsible for controlling the direction of growth of root tips and stem tips in response to different stimuli including light and gravity. Auxin is made at the tips of stems and roots. It's moved in solution to older parts of the stem and root where it changes the elasticity of the cells. More elastic cells absorb more water and grow longer, causing bending in the stem or root. It's thought that light and gravity can interfere with the transport of auxin causing it to be unevenly distributed. You may have noticed that a houseplant grows towards the window and turns its leaves towards the light. It does this because light coming from the window side of the plant destroys the auxin in that side of the stem. So growth on that side slows down. On the shaded side of the plant there is more auxin. So growth on this side speeds up. The result is that the shoots and leaves are turned towards the light for photosynthesis.

23 2.18. Demonstrate an understanding of the uses of plant hormones including selective weed killers, rooting powder, seedless fruit and fruit ripening. Selective weedkillers Selective weedkillers kill some plants but not others. This can be useful for getting rid of dandelions in a lawn without killing the grass, or getting rid of thistles in a field without killing the wheat plants. The selective weedkiller contains growth hormone that causes the weeds to grow too quickly. The weedkiller is absorbed in larger quantities by the weeds than the beneficial plants. Rooting powder Rooting powder makes stem cuttings quickly develop roots. Rooting powder contains growth hormones. Controlling fruit ripening Some hormones slow the ripening of fruits and others speed it up. These hormones and their inhibitors are useful for delaying ripening during transport or when fruit is displayed in shops. Dormancy Dormancy stops seeds germinating until conditions are ideal for growth. Hormones can be used to remove the dormancy of a seed so it can germinate at all times of year. Buds and flowers can also be naturally dormant. Hormones can also be used to make plants grow bushier, make them flower or control the growth of hedge plants.

24 2.19. Recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves Describe how stimulation of receptors in the sense organs sends electrical impulses along neurones. Receptors Receptors are groups of cells which can detect changes in the environment (stimuli), and turn them into electrical impulses. Receptors are often in sense organs such as the eye, ear, skin. sense organs Skin Tongue Nose Eyes Ears receptors sensitive to touch, pressure, pain and temperature chemicals in food chemicals in the air light sound and position of the head

25 2.20. Explain the structure and function of dendrons and axons in the nervous system Describe the structure and function of sensory, relay and motor neurones including the myelin sheath, the neurotransmitters and the reflex arc. Motor Neurone The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster. Basically it insulates the axon. sensory neurones carry signals from receptors to the spinal cord and brain. relay neurones carry messages from one part of the CNS to another. motor neurones carry signals from the CNS to effectors.

26 Myelin Sheath

27 TOPIC THREE: Problems of and solutions to a changing environment 3.1. Define a drug as a chemical substance, such as a narcotic or hallucinogen, that affects the central nervous system, causing changes in psychological behavior and possible addiction. Drugs Drugs are chemicals that cause changes in the body. Some are legal (e.g. Caffeine, Tobacco) and some are illegal (e.g. Heroine, Cocaine). Some drugs are addictive which means more and more drugs have to be taken to achieve the same affect.

28 3.2. Describe the general affects of painkillers, hallucinogens, stimulants and depressants. Painkillers Painkillers block nerve impulses from a painful part of the body. This makes you not feel the pain as much. Examples are Paracetamol and Morphine. Hallucinogens Hallucinogens change how our brain works and distorts your senses. An example is LSD. Stimulants Stimulants increase the speed of your reactions and neurotansmission as the synapse. Examples include Caffine and Cannabis. Depressants Depressants slow down the activity of the brain. An example is alchohol.

29 3.4. Explain the effects of some chemicals in cigarette smoke, including nicotine, tar and carbon monoxide Evaluate data relating to the correlation between smoking and its negative effects on health. HARMFUL CHEMICALS IN CIGARETTES: Nicotine is the addictive substance in cigarettes. It reaches the brain and creates a dependency so that smokers become addicted. Tar is the substance that causes cancer (called a carcinogen). Smoking increases the risk of you getting cancer. Carbon Monoxide gets into red blood cells and reduces their ability to carry oxygen. This puts more strain on the circulatory system which can in turn mean a higher chance of getting heart disease or a stroke. Effects on health This graph shows that there is a clear link between smoking cigarettes and getting lung cancer.

30 3.6. Evaluate evidence of some harmful effects of alcohol abuse including short and long term effects Discuss the ethics of organ transplants. Short Term Effects Alcohol has short-term effects such as sleepiness and impaired judgment, balance and muscle control. This can mean blurry vision and slurred speech. Vasodilatation occurs (blood vessels widen) leading to heat loss. Long Term Effects Long-term effects include damage to the liver and brain. Damage to the liver is done when the liver tries to remove alcohol from the bloodstream (due to it being a toxic chemical). Over time the liver gets damaged doing this. Organ Transplants Donors are people who want their organs to be given to people when they die. For instance their kidney might be taken and given to someone who needs a new kidney. However organ transplanting is a large ethical issue due to the supply of organs being limited. Sometimes organ donors do not want their organs to go to someone who will abuse them e.g. Liver transplants for alcoholics or Heart transplants for obese people.

31 3.8. Recall that infectious diseases are caused by pathogens Describe how pathogens are spread. Pathogens Pathogens are microorganisms that cause infectious diseases. They can be bacteria, viruses, fungi and protoctists. How they can be spread Water e.g. Cholera Food e.g. Salmonella Airborne e.g. Flu Contact such as touching or kissing. e.g. Chickenpox Body Fluids such as blood. e.g. HIV Animal Vectors such as mosquitoes. E.g. Malaria

32 3.10. Explain how the human body can be effective against attack from pathogens including physical barriers and chemical defence. Physicals Barriers Physical Barriers are the body s first line of defence. This includes your skin, nasal hairs, mucus and tears. The skin covers the whole body against physical damage, microbe infection and dehydration. It is difficult to penetrate and glands produce oils which kill microbes. Nasel hair keep out dust and larger microorganisms whilst mucus traps dust and microbes which are carried away by cilia (tiny hairs on the cells that line the gaseous exchange tract). Chemical Defence Chemical defences of the body include hydrochloric acid in the stomach which destroys microorganisms.

33 3.11. Demonstrate an understanding that plants produce chemicals that have antibacterial effects in order to defend themselves, some of which are used by humans. Plants produce antibacterial chemicals to help them defend themselves against microorganisms. Some of these chemicals are used by humans. Mint Mint has antibacterial properties which is why it is used in toothpaste. Witch Hazel Witch Hazel can be used to prevent infections getting through the skin.

34 3.12. Describe how antiseptics can be used to prevent the spread of infection Explain the use of anitbiotics to control infection, including antibacterials to treat bacterial infections and antifungus to treat fungal infections. Antibiotics are substances that kill bacteria or stop their growth. They do not work on viruses. Antifungal kills fungi. e.g. Nyastatin kills the fungus; candida albicans. Antiseptics kill bacteria which are Antibiotic How it works inside the body. They are used to penicillin breaks down cell walls cleans wounds as erythromycin stops protein synthesis well as surfaces neomycin stops protein synthesis on objects such as toilets or baths. vancomycin stops protein synthesis ciprofloxacin stops DNA replication

35 3.14. Evaluate evidence that resistant strains of bacteria, including MRSA, can arise from the misuse of antibiotics. Over time, bacteria can become resistant to antibiotics. This is an example of natural selecetion as, in a large group of bacteria, there may be some that are not affected by the antibiotic and go on to breed. MRSA MRSA stands for methicillin-resistant-staphylococcus-aureus. It is a bacteria and is resistant to most antibiotics. To slow down or stop the development of resistant bacteria we should: avoid use of unnecessary antibiotics always complete the full course. Development of Resistance 1. Random changes or mutations occur in the genes of individual bacterial cells. 2. Some mutations protect the bacterial cell from the effects of the antibiotic. 3. Bacteria without the mutation die or cannot reproduce with the antibiotic present. 4. The resistant bacteria are able to reproduce with less competition from normal bacterial strains.

36 3.16. Recall that interdependence is the dynamic relationship between all living things Demonstrate an understanding of how some energy is transferred to less useful forms at each trophic level and this limits the length of a food chain. Interdependence is the relationship between all living things. This is a food chain. Energy is transferred from the first thing in the chain to the last thing.

37 3.18. Demonstrate an understanding that the shape of a pyramid of biomass is determined by energy transferred at each trophic level. Pyramid of Biomass A pyramid of biomass is a chart, drawn to scale, showing the biomass at each stage in a food chain. The bars become narrower as you reach the top. Note that you do not need to draw the organisms. But you must draw your pyramid of biomass to scale. Each bar should be labelled with the name of the organism. Biomass is the mass of an organism when it has been dried out.

38 3.19. Explain how the survival of some organisms may depend on the presence of another species including parasitism and mutualism. Parasitism Parasites are animals or organisms that live off another animal or organism (called the host). The parasite benefits from this but the host does not. Fleas are parasites and live on dogs. A tapeworm is a parasite, as it lives in the belly of another animal. Mutualism Mutualism is basically the same as parasitism except that both creatures benefit. For example cleaner fish feed off the dead skin and parasites on larger fish. The provides the cleaner fish with food and the bigger fish can keep clean.

39 3.20. Analyse, interpret and evaluate data on global population change Explain how the increase in human population contributes to an increase in the production of pollutants, including phosphates, nitrates and sulphur dioxide. The population is growing. The more humans there are, the more factories we need to make all the stuff we need. We use a lot of non-renewable resources and that means a lot of pollution is caused e.g. Sulphur Dioxide. Indicators of Air Pollution Lichens are plants that grow in exposed places such as rocks or tree bark. They need to be very good at absorbing water and nutrients to grow there. Air pollutants can damage lichens and prevent them from growing. This means that crusty lichens are an indicator of air pollution.

40 3.22. Explain how eutrophication occurs and the problems associated with eutrophication in a aquatic environment. Fertilisers are washed off the land by rainwater and into rivers and lakes. This increase of nitrates and phosphates in the water causes algae to grow which blocks the sun getting to other plants in the river

41 3.24. Demonstrate an understanding of how scientists can use the presence or absence of indicator species as evidence to assess the level of pollution. Indicator Species If there is evidence of an indicator species, this tells us whether or not there is pollution. pollution level of water species present polluted polluted clean water clean water bloodworm sludgeworm stonefly fresh water shrimp

42 3.25. Demonstrate an understanding of how recycling can reduce the demand for resources and the problem of waste disposal, including paper, plastics and metals. Resources on the Earth are limited, It's important that the way we behave now does not make life difficult or impossible for future generations. Recycling is an important way to help us achieve sustainable development. Glass is easily recycled. It can be melted and remoulded to make new objects, such as bottles. The energy needed to do this is less than the energy needed to make new glass from its raw materials. However, we need to sort different coloured glass ready for recycling, and transport it to the recycling plant. Metal - Just like glass, it takes less energy to melt and remould metals than it does to extract new metals from their ores. Aluminium is a valuable metal that melts at a relatively low temperature, and is particularly attractive for recycling. However, a lot of metals that we use are mixtures called alloys, and it can be difficult to sort different metals ready for recycling. Paper - Paper is not melted when it is recycled. Instead, it is broken up into small pieces and reformed to make new sheets of paper. This takes less energy than making paper from trees. However, paper can only be recycled a few times before its fibres become too short to be useful, and the recycled paper is often only good enough for toilet paper or cardboard. But it can be used as a fuel or compost instead. Plastic - Plastic can be recycled as fleece clothing so that we use less crude oil, the raw material required for plastic and a scarce resource that is running out. Different types of plastics have to be sorted out and this can be difficult. Recycling plastic also stops much of it ending up in landfill sites.

43 3.26. Demonstrate an understanding of how carbon is recycled. Removing carbon dioxide from the atmosphere Green plants remove carbon dioxide from the atmosphere by photosynthesis. The carbon becomes part of complex molecules such as proteins, fats and carbohydrates in the plants. Returning carbon dioxide to the atmosphere Organisms return carbon dioxide to the atmosphere by respiration. It is not just animals that respire. Plants and microorganisms do, too. Passing carbon on When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these microorganisms and detritus feeders.

44 3.27. Demonstrate an understanding of how nitrogen is recycled. nitrogen gas in the air cannot be used directly by plants and animals nitrogen-fixing bacteria living in root nodules or the soil can fix nitrogen gas the action of lightning can convert nitrogen gas into nitrates decomposers break down dead animals and plants soil bacteria convert proteins and urea into ammonia nitrifying bacteria convert this ammonia to nitrates plants absorb nitrates from the soil nitrates are needed by plants to make proteins for growth nitrogen compounds pass along a food chain or web denitrifying bacteria convert nitrates to nitrogen gas