1-2 mark recall questions from exam papers:

Topic 1: Classification

Kingdoms

Russula silvicola is a multicellular organism that has a cell wall but does not have chlorophyll.Russula silvicola belongs to the kingdom … Fungi kingdom – have cells walls but no chlorophyll.

State two characteristics of the kingdom Plantae.

Have cell walls / have chlorophyll / are multicelled / feed autotrophically

Explain why the dodo was placed in the kingdom Animalia.

It feeds heterotrophically / it was multicelled / it has no cell wall or chlorophyll.

Euglena is placed in which kingdom? Protoctista

State the function of the nucleus in the Euglena.

Nucleus controls the cell / contains DNA (or genes , chromosomes)

Describe the function of chloroplasts in the Euglena.

Chloroplasts contain chlorophyll which absorbs light for photosynthesis

Explain why Euglena is a difficult organism to classify.

Euglena has features of different kingdoms. Euglena has a gullet to take in food like animalia, it has chloroplasts to photosynthesise like plantae.

Explain why viruses have not been classified in any of the five kingdoms.

Viruses are not alive – they have no cell structure and need host cells to reproduce in.

Organisms in the Kingdom Plantae are ......autotrophic ..... because they make their own glucose using sunlight. Fungi do not belong to the Kingdom Plantae because they are ..........saprophytic.........., which means they feed on dead and decaying organisms.

Which main organelle do bacteria not have inside their cells?

Nucleus - Bacteria are prokaryotes so do not have a nucleus.

Which plant cell structures use sunlight for photosynthesis? Chloroplasts.Which kingdom are unicellular and have a nucleus? Protoctista

Which kingdom are multicellular and autotrophic (or photosynthetic)? Plantae

Viruses are not classified into any of the five kingdoms. Suggest reasons for this.

The five kingdoms contain living organisms which are made up of cells. Viruses are not alive and have no cell structure.

Bacteria are classified as prokaryotes. State two characteristics of prokaryotes.

Single celled and no nucleus

Bacteria are classified into the kingdom ….Prokaryotae

Bacteria do not contain …a nucleus

Describe what a virus does after it has entered its host.

Inserts its DNA, enters the cell, replicates and then bursts out of the cell – this destroys the cell.

Name the process that plants use to make glucose. Photosynthesis

Vertebrates

All animals classified as chordate have …a spinal cord / supporting rod running the length of the body.

Describe how polar bears get oxygen into their bloodstream. Oxygen is absorbed into lungs, across a membrane into the blood.

State the structures that vertebrate organisms use to absorb oxygen from their surroundings. Lungs (mammals, birds, repiles and adult amphibians), gills (fish and young amphibians) and skin (amphibians). Suggest one advantage of being poikilothermic. It conserves energy.

An organism that relies on the environment to regulate its body temperature is known as …poikilothermermic.

Suggest why the internal body temperature of the snake has a wide range. It is poikilothermic so its body temperature will range with its surroundings.

Animals that keep their internal body temperature within a narrow range are …homeothermic.

Explain which features of gulls enable them to be classified in a vertebrate group.

Gulls are in the vertebrate group “birds” and so will have feathers covering its body, they will be homeothermic, oviparous (lay eggs) and have lungs to absorb oxygen). State the phylum that includes mammals such as tigers. (Chordata – the only name of a phylum you need to know).

State one feature that all members of the phylum Chordata have in common. (All have a spinal cord / supporting rod running the length of the body. )

Once fertilisation has occurred some vertebrates lay eggs. Vertebrates that lay eggs are known as .....oviparous....... Vertebrates that give birth to live young are known as ......viviparous....

Describe two other methods scientists can use to place vertebrates into groups.

Any two from – reproduction methods (external / internal fertilisation / oviparous / viviparous), temperature regulation (homeothermic or poikilothermic), body covering (fur, feathers, dry scales, moist slimy skin, wet scales) or oxygen absorption (lungs, gills or skin).

Which phylum do all vertebrates belong to? Chordata

Suggest why scientists find it difficult to classify the axolotl. It has features of more than one vertebrate group - eg it has gills all its life like fish, but has smooth moist skin like amphibians and can walk – it is classed as an amphibian.

Suggest why scientists find it difficult to classify the duck-billed platypus. It has features of more than one vertebrate group - it has a skeleton like a repile and lays leathery egg like repiles. It has a beak, webbed feed and lays eggs like birds, it is homeothermic and has fur and so is classed as a mammal.

Species

The binomial name for polar bears is Ursus maritimus. Maritimus refers to which level of classification? Species

What is a hybrid? The offspring of two different species interbreeding.

Describe how hybrids are produced. Two different species have to interbreed. Eg a lion and tiger can breed to make a liger.

The discovery of organisms in hydrothermal vents occurred in 1977. Explain how the scientific community might have validated this new discovery. They might have peer reviewed the paper, attended a scientific conference, published the work in a journal or repeated the study themselves to see if they found the same thing.

American herring gulls can breed with (Alaskan) lesser black backed gulls. This type of interbreeding between different species is known as …hybridisationThe binomial term for the white herring gull is Larus argentatus. State the level of classification that Larus in the binomial name refers to. Genus

Pompeii worms were discovered by French marine biologists in the early 1980s. Explain how these biologists may have validated the evidence for the discovery of the Pompeii worms.They might have peer reviewed the paper, attended a scientific conference, published the work in a journal or repeated the study themselves to see if they found the same thing.

Variation

State the type of variation for blood groups of students. Discontinuous

Height can be illustrated by a normal distribution curve. Give the name of this type of variation. Continuous

State two causes of genetic variation. 1. Sexual reproduction of parents and passing on of genes 2. Mutation – a change in the DNA

Describe the causes of variation in a population. 1. Sexual reproduction of parents and passing on of genes 2. Mutation – a change in the DNA / the environment can cause variation in height and weight.

Discuss how interbreeding in gulls of different species may make accurate classification difficult. It goes against the definition of a species which states that different species do not interbreed. Accurate classification becomes difficult because hybrids will be produced with features of both species .

Explain why it is difficult to classify some living organisms. Some organisms look the same (eg some birds) but are different species as they will not interbreed with each other. Some organisms look very different but are the same species eg dogs. There are hybrids which have features of two different species making classification difficult.

State the type of variation that results in a normal distribution curve. Continuous variation.

Adaptations

Explain how one feature of the polar bear helps it to survive in the Arctic. Thick fur for insulation – keeps them warm. White fur for camouflage so they can sneak up on prey. Thick layer of blubber for extra energy reserves and insulation to keep warm. (There are others).

The conditions very close to hydrothermal vents are …high pressure, very hot, no light, acidic and toxic.

In extreme environments organisms have characteristics that enable them to survive. These characteristics are called …adaptations.

The temperature of these hydrothermal vents can be very high. Suggest a feature that helps to protect the Pompeii worm from the extreme heat. Pompeii worms have a layer of bacteria on their bodies. This protects them from the heat.

Evolution

Some rats have a mutation which enables them to eat the rat poison Warfarin and survive. Suggest how the use of Warfarin could lead to an increase in the number of rats with this mutation.

If warfarin is used then rats that are not resistant will eat it and die. Rats resistant to it will survive, breed and pass on their resistant gene to their offspring. The number os resistant rats will increase.

Variation in a population enables evolution to occur. Explain, using Darwin’s theory of evolution, how variation can lead to a species evolving.

Organisms sometimes over-produce. All offspring will vary. There will be competition for resources eg water and food. The best adapted organisms will survive (this is survival of the fittest or natural selection), breed and pass on their genes for the good characteristics. Over time only the best adapted organisms survive and their numbers increase. The change in a species over time is evolution.

Describe what is meant by the term speciation. A species over time evolving into two different species.

The formation of a new species due to geographical isolation is called …speciation.

Darwin’s finches are an example of speciation due to …natural selection and evolution.

Genes

In which part of the cell is a chromosome found? Nucleus

Genes exist in alternative forms called …alleles

What word is used to describe the genotype Cc. Heterozygous

What word is used to describe the genotype cc. Homozygous recessive

State where most genes are located in a human cell. Nucleus

An allele is …a different or alternative version of the same gene.

State the term used to describe an individual who is a carrier and has both a dominant and a recessive allele. Heterozygous

Genes are found on structures called .........chromosomes........ . These are found in the ......nucleus...... of a cell.

Chromosomes have sections which code for specific characteristics. Each characteristic is coded for by a ........gene..... . These exist in alternative forms called ........alleles........................ .

What is a mutation? A change in the DNA

The term used to describe an individual with two identical alleles is …homozygous

State the genetic term for a person’s physical characteristics. Phenotype

State what is meant by the term heterozygous. Have different alleles or is a carrier.

Genetic disorders

State two symptoms of cystic fibrosis. Any from Coughing / difficulty breathing / weight loss / lung infections.

State two symptoms of sickle cell disease. Pain in joints / tiredness / breathlessness

What is the genotype of people who have the genetic condition sickle cell disease? ss

Explain why this may cause sickle cell disease to be more prevalent in countries with a high incidence of malaria.

People who are SS don’t have sickle cell but could die from malaria. People with ss have sickle cell and die from sickle cell disease. People heterozygous for sickle cell are Ss so are only carriers and don’t have sickle cell disease, but also being a carrier seems to stop them getting malaria. Therefore they survive, breed (possibly with another carrier) which means they could pass the sickle cell gene on meaning it will become more common in the gene pool and more children born with sickle cell disease.

Sickle cell disease causes a change in the shape of the …red blood cell.

Explain why there would be no children with sickle cell disease if one of the parents had the genotype DD. The parent only has dominant alleles to pass down so all of their children will receive a dominant allele and so will be normal. You need to inherit two recessive alleles (one from each parent) to have sickle cell disease.

Explain why a person with cystic fibrosis (CF) may lose body mass. They lose weight (mass) because the thick sticky mucus blocks the pancreatic duct so enzymes made in the pancreas cannot get to the food to break it down in the intestines. Nutrients are not absorbed into blood.

Explain how a person inherited cystic fibrosis. The person would have inherited one recessive allele from mum and one recessive from dad because you need to have two recessive alleles to have cystic fibrosis.

Describe why cystic fibrosis may cause a person to have breathing problems. The thick sticky mucus blocks the airways leading to a difficulty breathing and coughing.

Topic 2: Homeostasis

The Nervous System

Impulses are carried along neurones as ......electrical ............ impulses.

There are gaps between neurones which are called ..........synapses.................. .

A sensory neurone sends electrical impulses to the …CNS.

Explain how the structure of a sensory neurone maximises the speed of the impulse passing along it. The axon is covered by a fatty layer called the myelin sheath which insulates the impulse making it travel faster.

Give the name for the gap between two neurones. Synapse

When the brain receives impulses from receptor cells it coordinates a response. Responses are carried out by …effectors (muscles or glands).

Describe how a reflex arc helps to protect the human body from danger. They are automatic (involuntary) so you don’t think about it – this also makes it a rapid response to protect you from danger.

Explain how information travels along the axon of a sensory neurone. As and electrical impulse from receptors to axon endings.

Describe the role of the myelin sheath. The myelin sheath insulates the axon making the electrical impulse travel faster, and prevents loss of signal.

Describe the pathway of a nerve impulse through a reflex arc. Receptor starts electrical impulse Impulse travels down a sensory neurone to the CNS. Impulse travels down a motor neurone to an effector which contracts and you respond.

The athlete starts to run when a gun is fired. State the athlete’s sense organ that detects this stimulus. Ear

Skin

Describe how sweating helps to control a person’s body temperature. The sweat gland produces sweat which contains water. This goes onto the skin surface and evaporates transferring heat from the skin to the surroundings keeping you cool.

Explain how the body uses hair to regulate temperature. When you get cold the erector muscle contracts, lifting the hairs. The hairs trap a layer of air for insulation to conserve heat. When you are hot the erector muscle is relaxed so hairs lay flat. No air is trapped so no insulation, air circulates cooling the skin.

What is the name given to the ability to maintain a constant internal environment? Homeostasis

Explain how vasodilation helps to maintain body temperature. Vasodilation is the widening of blood vessels when you are hot. More blood flows closer to the skin surface transferring heat from the blood to the surroundings.

Explain why reptiles lie in sunlight for long periods of time. They are poikilothermic and so body temperature varies with their surroundings. They lie in the sun to keep warm.

Temperature can be regulated by the human body. Describe how changes in external temperature are detected by the human body. Detected by receptors in the skin.

Explain why the muscle attached to the hair follicle is important when a person starts to feel cold. When you get cold the erector muscle contracts, lifting the hairs. The hairs trap a layer of air for insulation to conserve heat.

Explain the role of the sweat gland in regulating body temperature. The sweat gland produces sweat which contains water. This goes onto the skin surface and evaporates transferring heat from the skin to the surroundings keeping you cool.

Human body temperature is controlled by the …hypothalamus.

When the bobcat gets too hot, it can sweat through the skin on its paws. Explain how this helps the bobcat to regulate its internal body temperature. Sweat contains water. This goes onto the skin surface and evaporates transferring heat from the skin to the surroundings keeping you cool.

State the term used to describe the maintenance of a constant internal environment. Homeostasis.

State the part of the brain that controls body temperature. Hypothalamus.

The hypothalamus is involved in regulating body temperature. The hypothalamus is part of the …brain.

Explain how shivering can help a person regulate their body temperature. Shivering is the rapid contraction of muscles. When muscles contract they respire which releases heat energy to keep a person warm.

Describe one way in which the skin helps in the control of body temperature. Any from:

Blood vessels near the surface of the skin narrow (vasoconstriction), reducing blood near the surface, reducing the heat lost to the environment from the blood. Or they widen

Erector muscles in the skin at the bottom of each hair contract, raising hairs and trapping air, forming an insulating layer. Or they relax so hairs lay flat and do not trap the layer of air so no insulation.

The sweat gland in the dermis of the skin releases sweat containing water onto the skin surface, which evaporates transferring heat from the skin to the surroundings.

Explain why humans need to maintain their body temperature at 37 °C. Enzymes are responsible for many chemical reactions. Enzymes work best at 37°C. If the temperature gets too high they can get denatured and no longer work.

Explain why it is important that body temperature does not rise above 40°C. Enzymes work best at 37°C. If the temperature gets too high they can get denatured and no longer work.

Explain how hair on the skin helps to maintain body temperature in a cold environment. Erector muscles in the skin at the bottom of each hair contract, raising hairs and trapping air, forming an insulating layer.

Reptiles are poikilothermic and mammals are homeothermic. Explain how reptiles and mammals regulate their body temperature. Repile temperature will vary with surroundings so they will lie in the sun if they are too cold and go in the shade if too hot. Mammals can regulate their temperature by sweating, erector muscles raising hairs or laying them flat, shivering and by vasoconstriction and vasodilation.

The temperature that enzymes work most effectively in the human body is …37°C

Explain how exercise can cause body temperature to increase. Exercise will mean muscles are contracting a lot. Respiration rate will increase to release energy for this. Respiration releases heat.

Hormones: Glucose and water regulation

Excess glucose is converted into glycogen in the …liver.

Explain why, on a hot day, less water is lost from the body as urine. On a hot day you will sweat meaning your water levels decrease. The kidneys make little concentrated urine to conserve water in the blood.

The hormone that lowers the glucose content of the blood is …insulin.

Which organ releases insulin and glucagon? Pancreas.

Describe what happens in the liver to lower the blood glucose level. Insulin travels to the liver, the liver removes the excess glucose from the blood and stores it as glycogen.

Explain how the glucose content of the blood can be increased. Glucagon is produced by the pancreas. Glucagon travels in the blood to the liver. The liver converts the stored glycogen back to glucose and releases it into the blood.

Describe how the human body acts in response to low glucose levels in the blood. The pancreas releases glucagon. Glucagon travels in the blood to the liver. The liver converts the stored glycogen back to glucose and releases it into the blood.

Excess blood glucose is converted into …glycogen.

Diabetes

State which hormone a type 1 diabetic would use to control their blood glucose concentration. Insulin

Explain how type 2 diabetics control their blood glucose concentration. Take tablets (medication), exercise, eat less sugar and fat.

Explain how a Type 1 diabetic can control the glucose content of the blood. Inject insulin into the subcutaneous fat layer, exercise, eat less fat and sugar.

Calculate the BMI for a female who has a mass of 67.5 kg and a height of1.50 m. Answer: 30

BMI = mass in kg (height in metres)2

BMI is calculated using …Mass and height

Suggest why people with a high BMI may develop Type 2 diabetes. Becoming obese means their liver becomes resistant to the insulin. Suggest how a change in body mass may cause a person to develop type 2 diabetes. Becoming obese means their liver becomes resistant to the insulin.

A person with diabetes cannot control …blood glucose levels.

Plant hormones

What is the name given to a shoots response to light? Positive phototropism.

Explain how shoots respond to the light. The light stimulates auxin to be made in the shoot. The auxin travels to the shaded side and makes cells elongate. this bends the the shoot towards the light.

The growth of the grass shoots towards the direction of the light is called phototropism. Give the name of the hormone that causes this reaction in grass shoot tips. Auxin

Give two ways that plant hormones are used by commercial plant growers. Sprayed on plant flowers which causes grapes to grow seedless which are required more by consumers.

Auxins cause the shoot of a plant to grow towards light in a process called …positive phototropism.

Explain how auxins cause the shoot of a plant to grow towards light. Light stimulates the production of auxin in the shoot tip which travels to the shaded side of the shoot. Auxin causes cells there to elongate bending the shoot towards the light.

Explain how auxins cause the roots of a plant to bend and grow towards gravity. Auxin is produced in the root tip and travels to the underside of the root where it stops cells elongating. The root then bends and grows downwards.

State the force that acts on plant roots causing them to grow downwards into the soil. Gravity

Why is it beneficial for roots to grow downwards into the soil? To collect more water and minerals.

Why is it beneficial for shoots to bend towards the light. So leaves can absorb more light for photosynthesis.

The response of roots to gravity is called …positive gravitropism (or positive geotropism).

Topic 3: Drugs and interdependence: Types and effects of drugs

What type of drug is morphine? Painkiller

What type of drug is LSD? Hallucinogen

Explain how drinking coffee containing caffeine may help when driving long distances.Caffeine is a stimulant and so will make you feel more alert.

State the effect of caffeine on reaction time. Caffeine is a stimulant and so decreases the time it takes you to react.

Explain the effect of caffeine on reaction time. Caffeine is a stimulant which speeds up neurotransmission across synapses by making more neurotransmitter be released.

Alcohol is an example of a …depressant.

State the group of drugs which increase the speed of reactions. Stimulants.

Which drug is a stimulant? Caffeine

Explain how stimulants affect reaction times. Stimulants speeds up neurotransmission across synapses by making more neurotransmitter be released. Therefore reactions will be quicker and reaction times will decrease.

Describe the effects of caffeine on the nervous system. Caffeine speeds up the activity of the nervous system / brain and also Stimulants speeds up neurotransmission across synapses by making more neurotransmitter be released.

Define the term drug. A drug is a chemical substance which alters the way the body works and your behaviour.

Explain why alcohol is classed as a depressant. Alcohol is a depressant because it slows down activity of the brain and makes reactions slower. Neurotransmission is slowed because alcohol binds with receptors on the next neurone – stopping neurotransmitter from binding there.

A chemical in tobacco acts as a stimulant. Explain how stimulants affect neurotransmission. Stimulants speed up neurotransmission across synapses by making more neurotransmitter be released.

Alcohol

Which body organ is affected by cirrhosis? Liver

Explain one effect of drinking alcohol that could cause a person driving a car to have an accident. Alcohol is a depressant and slows reactions so it will take longer to brake if something runs in front of you.

Describe the short term and the long term effects of alcohol abuse. Short term: hangover, being sick, slurring, lowers inhibitions (more likely to take risks). Long term: Addiction or alcoholism, liver cirrhosis, kidney damage and brain damage.

State the two organs in the body most affected by long term alcohol abuse. Liver and brain.

Explain the effect that alcohol has on the speed of reactions. Alcohol is a depressant because it slows down activity of the brain and makes reactions slower. Neurotransmission is slowed because alcohol binds with receptors on the next neurone – stopping neurotransmitter from binding there.

A drug has been developed which blocks the ‘feel good’ effects of drinking alcohol. Suggest why this may be beneficial to people with alcoholism. People drink alcohol because it makes them feel good. If they do not get those feelings they may be more likely to give up drinking. This could stop them getting liver cirrhosis.

Suggest one reason why some people disagree with alcoholics being given organ transplants. They have damaged their own organ / someone else may deserve it more if they haven’t damaged their own organ / they may continue to drink after the transplant and destroy the new liver.

State the effect alcohol has on the time taken to respond to a stimulus. Alcohol slows reactions so will increase reaction time.

Drinking excess alcohol over a long period of time can result in alcoholism. Suggest two other long-term effects of alcoholism in the human body. Liver cirrhosis and brain damage.

Discuss the ethics of allowing alcoholics to have an organ transplant. Arguments against: They have damaged their own organ / someone else may deserve it more if they haven’t damaged their own organ / they may continue to drink after the transplant and destroy the new liver.

Arguments for: They will die without it and everyone has a right to survive / if they give up drinking for a period of time they should be allowed one.

Tobacco

The addictive substance in cigarette smoke is …nicotine.

Some of the chemicals in cigarette smoke are carcinogens. Define the word carcinogen. A cancer causing substance.

Carbon monoxide from cigarette smoke can enter the bloodstream of a pregnant woman who smokes. Explain how carbon monoxide could reduce the birth mass of her baby. Carbon monoxide binds to haemoglobin instead of oxygen. Less oxygen passes the placenta to the foetus and so less respiration. Less respiration means less energy for growth.

The active compound in cigarette smoke that causes lung cancer is …tar.

Explain how smoking tobacco can cause cancer. Tobacco contains tar. Tar contains cacirnogens which are cancer causing substances.

Describe the effect caffeine can have on the human body. Caffeine makes you more awake and alert. It also makes you reactions faster as it is a stimulant and so speeds up neurotransmission across synapses by making more neurotransmitter be released.

One part of cigarette smoke acts on receptor sites in the brain. Explain why it can be very difficult to give up smoking. Nicotine acts of receptor sites in the brain which get used to the drug. You need to some more to feel normal – you start to crave it and become addicted.

Explain the effect of breathing in carbon monoxide on the function of the blood. Carbon monoxide binds with haemoglobin in red blood cells so they carry less oxygen to respiring cells.

Smoking tobacco reduces the oxygen carrying ability of the blood because it contains … carbon monoxide which binds with haemoglobin in red blood cells so they carry less oxygen to respiring cells.

Marijuana is often smoked with tobacco. Suggest why combining tobacco with marijuana makes it more difficult to give up smoking marijuana. Tobacco contains nicotine which is addictive. You need more to feel normal – you start to crave it and become addicted.

Pathogens: Disease and transmission

What is a pathogen? A microbe that causes disease.

Salmonella bacteria can cause disease, these bacteria get into the body by …eating contaminated food.

Influenza is caused by …viruses… in the air.

The disease dysentery is caused by a …bacterium.

Describe how a housefly can cause a person to become infected with dysentery. Dysentry bacteria are on faeces (pooh). Housefly lands on faeces and bacterium sticks to housefly, which flies onto food – leaving the bacteria on the food. Food is eaten. Explain how the Anopheles mosquito can spread the disease malaria. Anopholes mosquito carries the protozoa that causes malaria. The mosquito bites the skin to suck blood and transfers the protozoa into the persons blood.

What are vectors? Vectors are animals that spread disease.

Athletes foot is caused by a ….fungus.

Cholera is caused by a …bacterium.

The cholera pathogen is spread by …drinking contaminated water.

The female mosquito can carry the Plasmodium protoctist. This protoctist causes malaria in humans. When the female mosquito breaks the skin of a person the Plasmodium is transferred into the blood of that person. State the name of this type of disease transmission. Vector transmission.

What is the name given to any disease causing organism? Pathogen

Describe how the housefly spreads disease. Dysentry bacteria are on faeces (pooh). Housefly lands on faeces and bacterium sticks to housefly, which flies onto food – leaving the bacteria on the food. Food is eaten.

Athlete’s foot fungus is a pathogen. Describe how athlete’s foot fungus is spread. By direct contact such as walking on moist floors.

Preventing disease

State two chemical barriers the body has to protect itself from pathogens.

Hydrochloric acid in the stomach kills microbes in food. Lysozymes in tears kill microbes going into the eye.

The human body has many physical barriers to protect itself from the influenza virus. These barriers include ...........mucus.. which is sticky and can trap the influenza virus if it enters the human body. The body has ......cilia......... which can move any trapped influenza viruses out of the body.

Explain how a chemical defence mechanism of the human body can reduce the chance of dysentery. You get dysentery by eating contaminated food. Hydrochloric acid in the stomach kills microbes in food.

Suggest why a doctor would not give antibiotics to a person suffering from the influenza virus. Antibiotics work on bacteria but do not work on viruses.

Describe how pathogens are prevented from entering the human body. Chemical and physical barriers or defences prevent the entry of pathogens. Chemical barriers such as hydrochloric acid in the stomach kills microbes in food. Lysozymes in tears kill microbes going into the eye.

Physical barriers such as skin which acts as a barrier to pathogens over the whole body. Also we have mucus.. which is sticky and can trap microbes if they enter the body.Cilia in the windpipe move any trapped microbes in the mucus upwards and out of the body.

Chemicals, other than antibiotics, can be used to prevent bacterial growth. Give the name of one of these chemicals. Antiseptic /disinfectant.

Bees can sting people. State the physical barrier of the human body that would have to be broken by the bee sting. Skin

Honey produced by bees is a natural antiseptic. Describe how antiseptics can be used, during food preparation, to prevent the spread of infections. Antiseptics can be sprayed on kitchen surfaces to kill microbes so they don’t get in the food.

Describe how antiseptics can be used to prevent the spread of infection in a kitchen. . Antiseptics can be sprayed on kitchen surfaces to kill microbes so they don’t get in the food.

State two physical barriers the body has to protect itself from pathogens. Skin / Cilia / Mucus / Nose hairs

One chemical that prevents the entry of pathogens is …hydrochloric acid / lysozymes in tears. .

State the type of medication that can be used to treat athletes foot. Antifungal

Interdependence: Food chains, parasites and mutualists.

Tubeworms rely on bacteria to gain the correct amount of nutrition. The bacteria also rely on the tubeworms to survive. What is the name given to this type of relationship? Mutualism

A food chain has four trophic levels. What limits the length of a food chain? Energy is lost at each trophic level. Eventually there will not be enough energy to pass on to a further trophic level.

What is the name of the type of bacteria that live in the root nodules in a clover plant? Nitrogen fixing bacteria

The bacterial colonies and the clover plant work together for survival. Describe how this relationship is an example of mutualism. Clover plants have root nodules in which nitrogen fixing bacteria live. These bacteria convert nitrogen gas from the air straight into nitrogen compounds for the plants to use. In return the bacteria have protection in the nodules and receive sugars from the plant.

State two ways in which energy can be lost between the trophic levels of a rabbit and fox in a food chain. Any 2 from: Movement / keeping warm / excretion / respirationSuggest how a farmer rearing chickens could limit energy loss from the chickens. Keep lots of them in a small pen to limit movement. Because there are lots of them they will keep each other warm. This will use less energy for movement and keeping warm – so more energy for growth.

Fleas are parasites that feed on foxes. Another example of parasites are …mistletoe / tapeworm / ticks

The survival of the Plasmodium is dependent on living in the blood of another species. This relationship is an example of …parasitism.

State the type of organism that is found at the start of most food chains. Producer (green plant)

The mistletoe plant also gains energy from sunlight to produce glucose. State the name of this process. Photosynthesis

The Mistle Thrush is a bird that spreads mistletoe seeds to other trees. Suggest how the Mistle Thrush spreads the mistletoe seeds to other trees. Mistlethrush eats the seeds, flies to another tree, excretes the seeds onto the new tree through waste (pooh).

The tapeworm absorbs food in the human intestine. A tapeworm is an example of a…parasite.

State two adaptations of a tapeworm that aid their survival in the host’s intestines. Has hooks and suckers to attach itself to the intestine wall. / Has both male and female reproductive organs so it can reproduce without the need of another tapeworm. / Has a long flat body giving it a large surface area for the absorption of nutrients. / Has a special coating that protects it from being broken down by digestive enzymes.

Suggest how humans could avoid becoming infected with tapeworms. Cook food thoroughly to kill tapeworm eggs / don’t eat meat.

Indicator species, pollution and recycling

Explain how continued deforestation is likely to affect the levels of carbon dioxide in the atmosphere. Cutting down trees means they wont take in CO2 for photosynthesis so therefore CO2 levels increase.Explain how high levels of sulfur dioxide in the atmosphere can impact on the environment. Sulfur dioxide can react with rainwater and oxygen to make sulphuric acid (acid rain) which can chemically weather certain rocks in buidings, kill aquatic life in lakes and kill plants or stop them growing.

Indicator species for air pollution in the environment are …..blackspot fungus and lichens.

Explain how scientists can use blackspot fungus to estimate the level of air pollution in an area. Blackspot fungus grow when there is unpolluted air (no sulphur dixide). Blackspot fungus are killed so don’t grow in polluted air (where there is sulphur dioxide).

The burning of fossil fuels can pollute the environment by releasing more…sulphur dioxide… which can cause acid rain.

A factory produces nitrate fertilisers. Some nitrate fertilisers can leak into the stream and cause …eutrophication.

The gas produced when coal burns that can lead to acid rain formation is …sulphur dioxide.

Describe how acid rain is formed. Sulfur dioxide can react with rainwater and oxygen to make sulphuric acid (acid rain). Nitrogen oxides can react with rainwater and oxygen to make nitric acid (acid rain).

Suggest one effect acid rain has on the environment. Any one from : chemically weather certain rocks in buildings / kill aquatic life in lakes / kill plants or stop them growing.

Explain how the quality of a river can be monitored by studying the organisms present in the water. You can look to see if bloodworms or sludgeworms live there. If they do the water is polluted with low levels of oxygen (might indicate eutrophication). If freshwater shrimp or stonefly larvae live there then the water is not polluted with high levels of oxygen.

The human population is increasing. Explain how this could change the concentration of carbon dioxide in the atmosphere. More people means more people respiring and releasing carbon dioxide. / More people means more electricity needed. More coal burned in powerstations which releases carbon dioxide.

Air quality can be monitored using indicator species. Name an indicator species used to monitor air quality. Lichen

Suggest one reason why a large mass of paper is recycled. Paper is readily used everyday in large quantities , and easy to recycle.

Explain how one human activity (apart from composting) contributes to an increase in carbondioxide concentration in the air. More people means more people respiring and releasing carbon dioxide. / More people means more electricity needed. More coal burned in powerstations which releases carbon dioxide.

The build-up of nutrients in an aquatic environment is known as …eutrophication.

Suggest how farming can lead to a build-up of nutrients in the lake. Farmers spray fertiliser on crops which washes into a lake. Algae grow rapidly covering the surface of the lake. This blocks light and so plants in the water cannot photosynthesise. Plants die and get broken down by decomposing bacteria which respire and remove oxygen from the water. Oxygen levels decrease killing animals in the water.

Certain indicator species can indicate clean water. Clean water can be indicated by the presence of which organisms? Freshwater shrimp / Stonefly larvae

Certain indicator species can indicate polluted water which may be low in oxygen. Polluted water can be indicated by the presence of which organisms? Blood worms / sludgeworms

As the human population …increases…., more food needs to be grown. This can lead to more …fertiliser.. being used which can pollute the environment.

Lichens are examples of …indicator species.Carbon and nitrogen cycle

Name the processes that put carbon back into the atmosphere. Respiration / Combustion / Decomposition

Name the processes that take carbon from the atmosphere. Photosynthesis / dissolving into oceans

Explain how carbon is cycled in nature. Carbon dioxide in the air is taken into plants for photosynthesis. Animals eat the plants transferring the carbon into the animal. Animals produce waste / or die. Plants die. Dead matter and waste is decomposed by bacteria. Plants, animals and bacteria all respire putting carbon dioxide back into the air. Dead fossilised plants can be burned through combustion again releasing carbon dioxide into the air.

The nitrate content of soil can be increased without using bacteria. State one way in which this can be done. Lightning.

Explain why nitrates are important for plants. Plants use nitrates to build proteins such as DNA and chlorophyll (which absorbs sunlight for photosynthesis).

Plants use nitrates to make … proteins such as DNA and chlorophyll (which absorbs sunlight for photosynthesis).

Name the process by which bacteria release carbon dioxide into the atmosphere. Respiration

Explain how composting increases carbon dioxide concentration in the air. Decomposing bacteria decompose or rot down the potato peelings or paper. When they do this they respire putting carbon dioxide into the air.

State the effects of nitrates on plant growth. Nitrates help the plant to grow taller.

Name one type of bacteria that reduce the nitrate content of soil. Denitrifying bacteria.

State the name of the process in which plants remove carbon dioxide from the atmosphere. Photosynthesis.

Name each type of bacteria in the nitrogen cycle and explain what each does to cycle nitrogen. Decomposers: Rot down dead matter or waste into ammonia.Nitrifying bacteria: Convert ammonia into nitrates that the plant takes in through roots. Denitrifying bacteria: Converts nitrates into nitrogen gas and puts it back in the air. Nitrogen fixing bacteria: Lives in root nodules of legumes (peas/ clover). They convert nitrogen gas into nitrogen compounds for the plant to use.