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Flashcards in Biology 1 Deck (180):
1

What is classification?

-The process of sorting organisms into groups, depending on their characteristics.

2

How are organisms classified?

-Kingdom; Phylum; Class; Order; Family; Genus; Species.
-Organisms that have many characteristics in common are grouped together as a species. Species that share many characteristics are grouped together as a genus (plural genera). Genera that share many characteristics are grouped as a family and so on up to the level of Kingdom.

3

How is the African Lion classified?
How is are humans classified?

-Animalia Chordata Mammalia Carnivora Felidae Panthera Leo.
-Animalia Chordata Mammalia Primate Homindae Homo Sapiens

4

What are the five kingdoms of organisms?

-Animalia; all multicellular animals
-Plantae; all green plants
-Fungi; moulds, mushrooms, yeast
-Protoctista; Amoeba, Paramecium
-Prokaryotae; bacteria, blue-green algae

5

How are organisms classified into Kingdoms?

-Organisms may be classified into one of five kingdoms according to some very basic characteristics.
-Organisms are classified into Kingdoms, depending on;
-Whether they are multicellular or unicellular
-Whether they contain a nucleus
-The way the organism gets its food
-Etc.

6

What are the main characteristics of Animalia?

-Multicellular
-Heterotrophic feeders; no chlorophyll
-No cell walls
-Complex cell structure with nucleus

7

What are the main characteristics of Plantae?

-Multicellular
-Autotrophic feeders using chlorophyll
-Cell walls made of cellulose
-Complex cell structure with nucleus

8

What are the main characteristics of Fungi?

-Multicellular
-Saprophytic feeders so no chlorophyll
-Cell walls not made of cellulose
-Complex cell structure with nucleus

9

What are the main characteristics of Protoctista?

-Mostly unicellular (a few are multicellular)
-Complex cell structure with nucleus

10

What are the main characteristics of Prokaryotae?

-Unicellular
-Simple cell structure with no nucleus

11

Why is there no kingdom for viruses?

-There is no kingdom for viruses because most scientists do not think of them as being alive, as they do not show all seven processes for life. When a virus particle enters a living cell, it changes the way the cell works and causes it to make copies of the virus. However, the actual virus particle does not show other life processes, such a growth or feeding, like other organisms.

12

Why is it important to classify organisms?

-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, so by using the binomial name Turdusmigratorius (American Robin) or Erithacusrubecula (UK Robin) then there is no confusion.

13

What are vertebrates and invertebrates?

-A vertebrate is an animal that does has a backbone. They all belong to the phylum Chordata, because they have a supporting rod that runs the length of their body.
-An invertebrate is an animal that does not have a backbone.

14

What are the five groups of vertebrates?

-Fish; They exchange oxygen and carbon dioxide across gills, and lay eggs (oviparous) that are fertilised externally.
-Amphibians; They exchange gases though their moist, permeable skin and lay externally fertilised eggs.
-Reptiles and Birds; They exchange gases via their lungs, and lay internally fertilised eggs.
-Mammals; They give birth to live young, which grow inside the body of the mother. Eggs are fertilised internally.

15

What ways can vertebrates be divided into different groups?

-The way they absorb oxygen for respiration
-The way they reproduce
-Whether they are Homeotherms or Poikilotherms.

16

How does they way vertebrates absorb oxygen for respiration help us classify them?

-Some vertebrates absorb oxygen with their lungs (mammals, reptiles and birds), gills (fish have these to take oxygen from water) and amphibians have both gills (young) and lungs (adult) but they can also absorb oxygen through their moist skin.

17

How does the way vertebrates reproduce help us classify them?

-It is easy to divide vertebrates into group by using reproduction characteristics.
-External fertilisation; this is where the adult female releases her eggs into the water where they are fertilised by sperm released by an adult male.
-Internal fertilisation; this is where vertebrates reproduce by placing the sperm inside the female so fertilisation takes place inside her body.
-Many vertebrates in this group then lay eggs, meaning they are oviparous.
-Mammals give birth to live young, meaning they are viviparous.

18

How does the vertebrates being homeotherms or poikilotherms help us classify them?

-Homeotherms; this means that they keep their body temperature constant, and often warmer, than their surroundings by releasing heat from reactions in their body.
-Poikilotherms; this means that their body temperature varies with the temperature of their surroundings.

19

How can complications between species in a group occur?

-Within a group, some species have different characteristics to the rest of the group. This means we have to look at many characteristics to help decide which group to place an organisation.
-E.g. a few amphibians have gills, even as adults.
-E.g. Sharks are fish but use internal fertilisation and some give birth to live young.

20

What happens as you get further down the classification chart?

-The organisms next to each other get more and more closely related and they have much more in common with each other.

21

What is a species?

-A species is defined as a group of organisms that can interbreed (reproduce with one another) to produce offspring that are fertile (able to produce).

22

Why is the definition of species not always true?

-It is possible for two closely related species to breed and produce hybrids. Hybrids are neither one species nor the other, and show characteristics of both parents.
-Hybrids are usually infertile but not always. Being infertile means that they are unlikely to have offspring of their own and pass on their mix of characteristics.
-Also some organisms don not always need to interbreed to produce offspring. If we never see interbreeding in an organism, we cannot test whether or not two individuals are the same species.
-For example, many plants and fungi can produce new individuals from parts of adult organisms. Also bacteria and many proctoctists may reproduce by splitting in half. This means each new individual has just one parent.

23

What is an example of a fertile hybrid?

-Mallard ducks can hybridise with other closely related species to produce fertile hybrid offspring. These offspring then breed with other hybrids, mallard ducks or closely related ducks. This produces ducks with a continuous range of characteristics, rather than separate species.

24

What is a ring species?

-A ring species is when a species are connected by a series of adjoining places, each interbreeding with their closely sited inhabitants. Neighbouring populations of the same species may have slightly different characteristics but can still breed. However, there are at least two 'end' populations in the series which are too distantly related to interbreed.

25

What is an example of a ring species?

-An example of a ring species is Larus Gulls, which live in a ring around the North Pole. The Herring Gull which lives in Great Britain and Ireland, can breed with the American Herring Gull, which can also breed with the Vega/East Siberian Herring Gull and so on. Even though tey are next to each other, the Herring Gull and the Lesser Black-backed Gull can't breed because they are sufficiently different, they are the two 'end' populations in the ring.

26

What is the binomial system?

-An organism's specific name has two Latin words (Genus and Species).

27

Why is the binomial system useful?

-Organisms that share the first word in their name (e.g. Equus, Larus) are closely related. This means that using the binomial system, scientists can easily tell from their name whether two organisms are closely related.
-The binomial system is also useful because organisms with the same common names my actually b different species. For example, a robin in America is not the same bird as a robin in the UK. The system is agreed by scientists all over the world to allow them to communicate clearly whatever their language.

28

What is variation?

-Differences in characteristics are called variation. There is variation within a species but much more variation between different species.

29

Why does variation make classification difficult?

-The variation within a species can make classification difficult. Scientists must make sure that any 'new' organism is not just a hybrid or due to variation in a known species. They do this by finding more than one of the organisms.
-From the Bosavi woolly rats that have been found, scientists can tell that they are closely related to the other 'hairy rats' because they share many characteristics. However, Bosavi woolly rats have sufficient variation in new species.

30

What are keys?

-Keys are used to identify different species, using statements and pathways, to eventually led you to the name of the organism, which is found out by knowing its characteristics.

31

Why is accurate classification so important?

-Accurate classification using the binomial system allows biologists to:
-Easily identify existing species and new species.
-See how organisms are related.
-Identify areas of greater and lesser biodiversity.

32

What is biodiversity?

-Biodiversity is a measure of the total number of different species in an area. To count the species you need to be able to identify them, which can be tricky if species are very similar to one another. The more accurate your classification system, the easier identification becomes.

33

Why is biodiversity important?

-Biodiversity is important because we obtain many products from living things (e.g. foods, medicines). The more species there are, the more choices we will have, both now and in the future. Biodiverse areas are also much better at recovering from natural disasters (e.g. floods) than less diverse areas.

34

Where are some biodiversity hotspots?

-Caribbean, New Zealand, Philippines, Madagascar, Tropical Andes.
-Many islands and the outskirts of areas, near the sea.

35

What do biologists think of biodiversity hotspots?

-Many biologists think that areas of greater diversity ('biodiversity hotspots') are the ones that need the most time and money spent on trying to conserve them because this will result in a greater number of species being conserved.

36

What is continuous variation and discontinuous variation?

-Continuous variation is when the variation values can be any number within a certain range. Human height, caused by both inherited and environmental variation, is an example of this.
-Discontinuous variation is a characteristic with a fixed set of values. Shoe size is an example of this.

37

Why does variation occur?

-All organisms are adapted to their surroundings, so they have variations in their characteristics that allow them to survive in their habitats.
-Organisms from polar regions, like Greenland sharks and polar bears, are adapted to the cold. Organisms living near deep-sea hydrothermal vents cope with the opposite problem. Hot fluids more than 350degrees come out of these vents and cool quickly The organisms living here must cope with big temperature changes, complete darkness and huge pressures.

38

How have polar bears adapted to the cold?

-Thick fur for insulation
-Large feet to spread out its weight and stop it sinking in the snow, also good for swimming
-Rough sole to grip the ice
-Thick layers of blubber under the skin for insulation
-White fur for camouflage
-Small ears to stop it losing too much heat.

39

How have deep-sea Pompeii worms (Alvinella pompejana) adapted to living near hydrothermal vents, at depths of over 2km?

-Its body is adapted to pressures over 200 times those at sea level
-Th worm spends a lot of its time inside a papery tube to protect it form predators
-The body of the worm is covered in a thick layer of bacteria that helps protect it from the heat. It copes with temperature changes of 40-90degrees
-It has no eyes but has very sensitive tentacles.

40

What are the different types of variation?

-Most characteristics show variation between individuals of the same species. Some characteristics show discontinuous variation, usually caused by the instructions within your cells. This is called genetic variation, and human blood groups is an example of this.
-Characteristics that show continuous variation are often controlled by both genes and the environment. You may inherit a tendency for being tall from your parents, however if you don't eat healthily in childhood, or have an accident that damages your bones, you may never grow tall. Your shortness will have been an acquired characteristic. Acquired characteristics are caused by the environment and so cause environmental variation between organisms.

41

How do we measure continuous variation?

-If a characteristic shows continuous variation, and we measure a large enough number of individuals, when we plot the results we often get a graph with a particular shape. The shape is called a normal distribution curve. It shows that most individuals measure within the middle part of the range in variation, and there are fewer individuals with measurements at the extremes of the range.

42

What is natural selection?

-Organisms generally produce far more offspring than the environment can support. Most will die before they reach adulthood because there are not enough resources (e.g. food and space) for them all.
-The offspring will show variation in their characteristics. Some variations will be better adapted to the environment than others. The limited resources will cause competition between the individuals. Individuals that happen to have variations that are better adapted will be more likely to survive and others will die. We call this 'survival of the fittest' or natural selection. Individuals that survive may breed and so many pass their variations on to their offspring.

43

What is Charles Darwin's theory?

-Evolution by natural selection.
-Evolution means a 'gradual change over time'. In the early 1800's some scientists realised that species can change over time, but theories of why this happened didn't explain all the facts. Charles Darwin (1809-1882) drew together several ideas to produce a new theory that was better at explaining the facts.
-Darwin knew that there was competition between individuals. He also knew that pigeon breeders selected birds with certain characteristics to breed, which meant that those characteristics were inherited by the offspring. Darwin realised that if the environment changes, then different variations may be better suited to the new conditions. Individuals with those variations will be more likely to survive and pass their characteristics onto their offspring. So the range of variation in characteristics of the population will gradually change over generations, which is evolution. If the environment changes too rapidly, and no individuals have adaptations that help them survive, they will all die out and the species may become extinct.

44

Why didn't some scientists like Darwin's theory of Evolution?

-Darwin published his theory in his book, 'On the Origin of Species by Means of Natural Selection' in 1859. Some scientists didn't like the theory because it didn't support what they believed. The theory was discussed and challenged at scientific conferences by scientists studying similar areas of science.
-One of the biggest problems with Darwin's theory when he published it was that there was little evidence for it. Evolution takes time to observe.

45

What new evidence is there now to support Darwin's theory of Evolution?

-Warfarin is a chemical that was used to poison rats in the 1940s and 1950s. When it was first used most rats that ate it died within a few days. But within 10 years, most rats were resistant to warfarin and not affected by it. As a result of variation, there had always been a few rats that were resistant, but at the start nobody realised this. As the poison killed the non-resistant rats, the only ones left to breed were resistant.
-Scientists are also finding new evidence for Darwin's theory from the genetic information in different species. Darwin could infer relationships between species from the observable characteristics but now we are able to confirm them using genetic evidence.

46

What is Speciation?

-Darwin started thinking about evolution after noticing differences between mockingbirds from different Galapagos Islands. He realised they were all very closely related, but each island had its own species. His theory helped him explain this observation. Darwin guessed that originally individuals from one species of mockingbird had reached the islands from South America. The environmental conditions varied between islands, so on each island different adaptation would have been more successful. So each island population evolved in a different way. Over time, the individuals on each island became so different that they couldn't interbreed with birds from another island. They had become a new species, a process called speciation.

47

Where is genetic information held?

-Inside the nucleus of a cell, there are long strands of a substance called DNA. Each strand forms a structure called a chromosome, there are usually two copies of each type of chromosome.
-Chromosomes are divided up into genes. Each chromosome carries a large number of genes and each gene does a particular job. For example, many genes control variations in our characteristics - what we look like (e.g. eye colour, face shape). Variation caused by genes is inherited variation because we inherit our genes from our parents.

48

What are alleles?

-Some genes for the same characteristic (e.g. eye colour) may contain slightly different instructions to create variations (e.g. brown, blue). Different forms of the same gene are called alleles.
-Since there are two copies of every chromosome in a body cell nucleus, there are two copies of every gene. Each copy of a gene may be a different allele.

49

Why do different sets of alleles give us different characteristics form each other?

-Different organisms have different numbers of chromosomes. Human body cell nuclei contain 23 pairs of chromosomes, which contain about 23,000 different genes in total. There are many alleles for each gene, so it is easy to see why each of us can inherit a different set of alleles from our parents. Each different set of alleles gives us slightly different characteristics.

50

What are gametes?

-Plants and animals produce gametes (sex cells). The male gametes are sperm cells in animals and pollen grains in plants. The female gametes are egg cells in plants and animals. Gametes are different to most body cells because they only have one cope of each chromosome.

51

What happens to gametes during sexual reproduction?

-Gametes only have one allele for each gene. In sexual reproduction gametes fuse together. The new organism that is formed contains two alleles for each gene (a full set), one from the the male parent and one from the female.

52

How is the characteristic determined from the alleles?

-If the offspring receives two alleles for a characteristic from its parents, only one of the alleles will have an effect, this is called the dominant gene. The other allele will have no effect, if the dominant allele is there. We call this the recessive allele and the recessive characteristic is only seen if both alleles are recessive.

53

What is a genetic cross diagram used to show?

-A genetic cross diagram is used to show the possible combinations of alleles when two organisms breed.
-A dominant gene is shown by a capital letter and the recessive gene has a lower case version of the same letter.
-The alleles in an organism are its genotype. What the animal looks like is its phenotype.

54

What do we call the different combinations of alleles?

-If both alleles for a gene in an organism are the same, the organism is homozygous.
-If they are different, it is heterozygous.

55

What is a Punnett Square used for?

-The possible genotypes produced when two organisms breed can also be shown in a Punnet Square.
-It is easy to work out the probability of each phenotype occurring if the organisms breed.

56

What is a genetic disorder?

-A genetic disorder is a disease caused by an abnormality in an individual's DNA. This can range from a small mutation in a single gene to the addition or subtraction of an entire set of chromosomes. Some diseases, including many types of cancer are caused by a mutation in a gene or group of genes. These mutations can occur randomly or because of environmental exposure, such as smoking.

57

What does autosomal dominant and autosomal recessive mean?

-An autosomal dominant means only one copy of an abnormal gene from one parent is needed in order for the disease or trait to develop.
-An autosomal recessive means two copies of an abnormal gene must be present in order for the disease or trait to develop.

58

What is sickle cell disorder?

-Sickle cell disorder is a genetic disorder. People with the disease easily become very tired and short of breath. Sufferers can also have times when their joints are incredibly painful because their red blood cells stick together and block blood vessels. The blocking of blood vessels can sometimes be fatal.
-The sickle cell allele is recessive, so people who have two copies of the allele suffer from the disorder.

59

What is cystic fibrosis?

-Cystic fibrosis is a genetic disorder where the lungs get clogged with thick mucus making breathing difficult and leading to infections. Mucus also blocks some of the tubes that carry enzymes to the small intestine to digest food. Lack of enzymes can result in weight loss.
-The cystic fibrosis allele is recessive, so people who have two copies of the allele suffer from the disorder.

60

What is albinism?

-Albinism is a genetic disorder determined by the complete or partial absence of pigment in the skin, hair and eyes. This is due to the absence or defect of an enzyme involved in the production of melanin.
-The albino allele is recessive, so people who have two copies of the allele suffer from the disorder.

61

What is Alzheimer's disease?

-Alzheimer's disease is a genetic disorder that causes dementia or loss of brain function. It affects parts of the brain that deal with memory, thought and language.
-The Alzheimer's disease allele is dominant, so people only need one copy of the allele to suffer from the disorder.

62

What is a family pedigree chart used for?

-Doctors can use pedigree charts, and an understanding of how a genetic disorder is inherited, to work out the probability that a person may have inherited the disorder from their parents. This is called pedigree analysis.
-If the risk is high, the doctor may get tests done to see if they have the faulty allele. The doctor will also advise the person on how to stay as healthy as possible.
-Doctors also do genetic screening for couples who know that there is a genetic disorder in he family and are worried about passing it on to their children. The doctor will give advice on how to interpret the results and help the couple decide whether to try for a baby or not.

63

What is homeostasis?

-Keeping the body's internal environment stable.

64

Why must the body's internal environment be kept stable?

-The conditions inside the body (the internal environment) must remain stable . For example, it needs enough water for substances to dissolve and for chemical reactions to take place inside the cells. Too much water, however, can cause swelling and high blood pressure.
-Temperature is also kept constant so that the enzymes that help reactions to occur can work quickly.
-Things the body needs to keep stable in order to survive; body temperature, water levels, blood sugar, amount of oxygen.

65

What is thermoregulation?

-The control of body temperature is called thermoregulation. The body maintains a temperature of 37degrees, this is needed because many chemical reactions in your body work best at 37degrees.

66

How is our body temperature measured?

-The hypothalamus is a small part of the brain that constantly monitors temperature. It receives information from nerve endings in the dermis of the skin about the temperature outside the body. It also receives information about the temperature inside the body from the blood.

67

How does out body regulate our temperature if it drops below 37degrees?

If the body temperature goes below 27degrees, the hypothalamus causes the muscles to shiver. This releases heat which warms you up.
-The hypothalamus also cause erector muscles in the dermis to contract. This causes the body hairs to stand upright. In humans this has little effect, but in other mammals it can trap more air next to the skin as insulation. Oils released from the sebaceous glands at the base of the hairs keep the skin lubricated and in good condition.
-The hypothalamus also reduces blood flow near the skin, keeping the warm blood deeper in so that heat loss to the air is reduced.

68

How does our body regulate our temperature if it rises above 37degrees?

-If body temperature goes above 37degrees, the hypothalamus detects this and causes sweating. As sweat evaporates it transfers heat energy from the skin to the surroundings, so the skin cools down.
-The hypothalamus also increases blood flow nearer to the surface of the skin, making us look pinker. This makes it easier for the blood to lose heat to the air so we cool down.

69

What is vasoconstriction and vasodilation?

-When it is old, the hypothalamus reduces blood flow to the skin by narrowing the blood vessels closest to the surface. This is called vasoconstriction.
-The opposite of this is vasodilation, which happens when the body is hot and needs to lose heat. It widens the blood vessels nearest to the skin, s blood can lose heat to the air easier.

70

How is the control of body temperature an example of negative feedback?

-The control of body temperature is an example of negative feedback. This means as a change to the body happens in one direction (e.g. increase in heat), mechanisms in the body work to make the change in the opposite direction. This helps keep conditions in the body under control at around the right level.

71

What is osmoregulation?

-Osmoregulation is the control of water in the body.
-The body loses water in breath and sweat. Sweat is produced by sweat glands in the skin (a gland is a part of the body that makes substances and then releases them). It also loses water in urine, and if the body contains too much water, the kidneys produce more urine.
-If the body does not have enough water, the kidneys produce little urine and the brain also responds by making you feel thirsty.

72

What is blood glucose regulation?

-The body also controls the concentration of some materials in the body, such as glucose in the blood. Blood glucose regulation is important because if glucose concentration gets too high or falls too low, you can become very ill.

73

What are sense organs?

-Sense organs detect changes, both in and outside your body. Scientists used to think that humans had five senses - touch, sight, hearing, taste and smell. Now we know that we have many more, including heat, cold, pain, balance and changes in position.
-Anything your body is sensitive to, including changes that you detect in your surroundings, is called a stimulus.
-Sense organs contain receptor cells, which detect a stimulus. For example, your skin contains certain receptor cells to detect the stimulus of temperature change.

74

What do receptor cells do?

-Receptor cells create electrical signals, called impulses, which usually travel to the brain. The brain then processes this information and can send impulses to other organs to alter the way the body works.

75

Where do electrical impulses travel along?

-Electrical impulses travel along cells called neurones (or nerve cells). This travelling, or transmission, of impulses is called neurotransmission.
-Neurones have a cell body and long extensions that carry the nerve impulse. The dendron has many branches at the end called dendrites that receive impulses from receptor cells or other neurones. The impulse moves along the dendron, past the cell body to the axon. The impulse then passes along the axon to the endings where it passes across the other neurones.

76

What is the central nervous system (CNS)?

-The brain and the spinal cord together form the central nervous system (CNS). The CNS controls your body.
-Bundles of neurones and blood vessels are packed together into nerves. An organ called the spinal cord (about 43-45cm long in an adult), which connects to the brain, contains many nerves packed together.

77

What is the relationship between the diameter of the neurone and the impulse speed?

-The thinker the diameter of the neurone, the quicker the speed of the neurone.
-The sciatic nerve is the thickest in the body - about 1.5cm in diameter.

78

What happens when the brain receives an impulse?

-When the brain receives impulses from receptor cells it coordinates a response. In the response, impulses are sent to effectors and these carry out an action. Effectors include muscles and glands (e.g. sweat glands).

79

What are the three types of neurones?

-Sensory neurones; these are the neurones that receive impulses form receptor cells. They have a long dendron as well as an axon.
-Motor neurones; these are the neurones that take impulses to effectors. They have no dendron, the dendrites are on the cell body.
-Relay neurones; these are the short neurones that are found in the spinal cord where they link motor an sensory neurones. They also make up the brain.

80

What is the myelin sheath?

-Many neurones have a fatty layer surrounding the axon. This is called the myelin sheath. The sheath helps to insulate the neurone from surrounding tissue, especially other neurones and also allows impulses to be carried faster.

81

What are synapses?

-Where one neurone connects with another, there is a small gap called a synapse. Impulses are transmitted across the gaps in synapses by chemical substances called neurotransmitters. All impulses are slowed down slightly by synapses. However, having synapses is useful because the chemicals are only released from axon endings. This makes sure the impulses can only flow in one direction.

82

What are reflexes?

-If you pick up a very hot object you must drop it as soon as possible to stop it burning you, and you don't want to have to think about it first. For these situations reflexes are used.
-Reflex actions are responses that are automatic, extremely quick and protect the body.
-They use neurone pathways called reflex arch in which a sensory neurone directly controls a motor neurone. Reflex arcs bypass the part of the brain involved in concious thought and so are quicker than coordinated responses. For example, when the area just below the kneecap is tapped, the knee jerk reflex only takes about 0.05 seconds to occur. This reflex arc contains just two neurones, although some reflex arcs have an 'interneurone' to connect the sensory neurone to the motor neurone.
-Other human reflexes include the pupil in your eyes getting smaller in strong light and blinking if something flies towards your face.

83

What is the difference between reflexes and coordinated responses?

-Reflexes don't involve much thought because there is only one option (e.g. dropping a hot object). This means they use reflex arcs which directly controls a motor neurone involved in the only action.
-A coordinated response is a response that involves conscious thought, meaning the sensory nerve has to go all the way to the brain in order to make a decision. For example, when you are driving and have the option to break, swerve, slow down or speed up when faced with an obstacle. Because your brain needs to make a decision, the reaction time will be loner than a reflex reaction.

84

What are hormones?

-Hormones are produced and released by glands called endocrine glands. Hormones travel in the blood and act as 'chemical messengers', causing certain parts of the body to respond to their presence. For example, when there is a rise in human growth hormone during puberty, muscles and bones start to grow at a faster rate.
-An organ that responds to a certain hormone is a target organ.

85

What are some examples of hormones produced in human?

-The pituitary gland releases anti-diuretic hormone, which causes the kidneys to produce more concentrated urine.
-Adrenaline is produced by the adrenal glands. It speeds up the heartbeat.
-Insulin is made by the pancreas and lowers bloods glucose levels.
-Glucagon raises blood glucose levels and is produced by the pancreas.
-Oestrogen is made by the ovaries and causes the development of female reproductive organs during puberty.
-The testes releases testosterone, which causes the development of the male reproductive organs during puberty.

86

How are blood glucose levels controlled?

-Carbohydrates in your food are mainly digested into a sugar called glucose. After a meal the concentration of glucose in your blood goes up. When it gets above a certain concentration, your pancreas releases a hormone called insulin. The insulin is carried around your body in your blood.
-Insulin affects certain cells, including those in your liver, which then take glucose out of the blood and convert it into glycogen. Glycogen acts as a store of glucose. This process means that the levels of glucose in the blood decreases.
-When your blood sugar falls below a certain level, your pancreas releases another hormone, called glucagon. This is also carried in the blood and causes the cells in the liver to turn glycogen back into glucose, which is then released into the blood. The levels of glucose in the blood increase.

87

What is diabetes?

-People who have a disease called diabetes cannot control their blood glucose levels very well. Low blood glucose concentrations may cause unconsciousness. High blood glucose concentrations cause tiredness and can damage organs, such as the yes. If blood glucose concentrations become too high, the kidney can get rid of it by putting it into the urine.

88

What is Type 1 diabetes?

-Between 5 and 10% of diabetics have Type 1 diabetes, in which the pancreas does not produce insulin. This means that when blood glucose concentrations rise, the body cannot bring them back down to the correct levels. SO, people with Type 1 diabetes usually inject insulin every day.
-Insulin needs to be injected into the fat layer beneath the skin (the subcutaneous fat layer) because fat easily absorbs insulin. The insulin then spreads into blood vessels and is carried around the body in the blood.
-To successfully control their disease, diabetics need to balance the factors that lower blood glucose levels (insulin and exercise) with those that increase the level (fast food and chocolate). The more exercise diabetics take, the less insulin they need.

89

What is Type 2 diabetes?

-Type 2 diabetes usually occurs when the cells in a person's body respond less well to insulin - the cells start to become 'resistant' to insulin, even though the hormone is being produced.
-Scientists have discovered a number of risk factors that may help to cause Type 2 diabetes, including high-fat diets, lack of exercise, getting older and being obese.
-Type 2 diabetes can often be controlled by changing a person's diet and by increasing the amount of exercise they take.
-(Over the past 10 years there has been an increase in obesity in adults who are obese and also an increase in adults with Type 2 diabetes).

90

How can doctors measure whether someone is overweight or not?

-Doctors class people as obese if they have a body mass index (BMI) of over 30. A BMI gives an estimate of how healthy a person's mass is for their height. An obese person is likely to suffer health problems because of their mass.

91

How do you measure a person's BMI?

-BMI = weight in kilograms / (height in metres)2

92

What are tropic responses?

-A response to a stimulus.
-Like humans, plants respond to stimuli. Roots respond to the direction of gravity by growing towards it. Also, stems and shoots grow towards the light.
-Charles Darwin was not only interested in evolution. In 1880, he published a book called 'The Power of Movement in Plants'. In it, he described many observations including, how barley seedlings responded to light coming in from one direction. He discovered that the barley seedlings bent as they grew towards the light.

93

What are different types of tropisms?

-Tropism; any response to a stimulus.
-Positive tropism; a response towards a stimulus.
-Negative tropism; a response away from a stimulus.
-Phototropism; a response to light.
-Hydrotropism; a response to water.
-Geotropism; a response to gravity.

94

How do plants respond to stimuli?

-Plant roots are negatively phototropic, so they grow away from light.
-Plant shoots are positively phototropic, so they grow towards the sun, in order to get enough light for photosynthesis, so they can make their own food.

95

What are plant growth substances?

-Like humans, plants produce hormones (also called plant growth substances) to respond to stimuli. Positive phototropism is caused by plant hormones called auxins.

96

What are auxins?

-Auxins are plant hormones and are produced in the tips of a shoot, where they cause elongation of the cells. If a shoot is grown with light coming from only on direction, auxins move to the shaded side of the shoot. This makes the cells on the shaded side of the shoot elongate more, which in turn causes the shoot to grow towards the light.

97

How do auxins react to geotropism?

-Auxins are also found in root tips, where they have the opposite effect to that in shoots. In roots, auxins cause cells to stop elongating and this causes positive gravitropism or geotropism - growth towards the direction of gravity. It helps plant roots to anchor the plant in place and to rech moisture underground.

98

What are gibberellins?

-Auxins are not the only plant hormone. When a seed germinates, roots and a shoot (a new stem) start to grow. Some seeds need periods of darkness or cold before they will germinate. Once this period is completed, the seed releases plant hormones called gibberellins. They cause the starch stored in a seed to be turned into sugars that the seed uses for energy to grow. Gibberellins also stimulate flower and fruit production is some plant species.

99

What are the results of different experiments with tropisms?

-Tip removed; does not grow
-Tip covered with opaque cap; grows upwards
-Tip covered with transparent cap; grows towards the light
-Base covered with opaque collar; grows towards the light
-Tip separated by jelly block; grows towards the light
-Tip separated by plastic; grows upwards
-Jelly block with auxin on half the cut tip; grows towards the light.

100

What is artificial auxin used for?

-Artificial auxin is still used as a selective weedkiller because it only makes plants with broad leaves (like daisies and dandelions) grow out of control and die. Plants with narrow leaves (like wheat and grass) are unaffected. Farmers can kill all the weeds in a field of a cereal crop (like wheat) without affecting their crop.
-Synthetic auxins are also used in rooting powders. Plant cuttings (parts of plants) are dipped in rooting powder, which makes then develop roots quickly. Large numbers of the same plant can be produced quickly using cutting, compared to growing plants from seed.

101

How are seedless fruits produced?

-Some seedless fruits are produced using plant hormones. The flowers are sprayed with plant hormones that cause fruits to develop by not their seeds.
-Other plants, like some varieties of grape, have naturally seedless but small fruits. The fruits are sprayed with gibberellins to increase their size.

102

What are plant hormones used for?

-Plant hormones naturally control the ripening of fruits. Farmers can make use of this and control when and how ripening occurs. For example, plant hormones are sprayed onto:
-Fruit trees to stop the fruit falling and becoming damaged and also allow the fruit to grow bigger.
-Fruit trees to speed up ripening. All the fruit ripens together and can be picked in one go.
-Unripe fruit to make them ripe. The fruit reaches shops in a 'just ripened' condition.

103

What is a drug?

-Our bodies make many chemical substances. Some of these (e.g. hormones, neurotransmitters) coordinate how we behave and respond to stimuli. Adding other chemical substances to our bodies can interfere with the chemicals that our bodies make and change the way we work. Any chemical substance that changes the way in which the body works, including our behaviour, is called a drug. Some drugs particularly affect the central nervous system and change our psychological behaviour in the way we feel, think and act.

104

What are the different types of drugs?

-Narcotic
-Painkillers
-Hallucinogens
-Stimulants
-Depressants

105

What is a narcotic drug?

-A narcotic is a drug that makes us feel sleepy.

106

What is a painkiller drug?

-We feel pain when electrical impulses from a swollen or damaged area of the body are sent via neurones to the brain. Painkillers, such as morphine, block some of these nerve impulses, so we feel less pain.

107

What is a hallucinogen drug?

-Hallucinogens change the way the brain works, particularly how we respond to what we see, hear and feel. Drugs like LSD can distort our senses of colour, time and space.

108

What is a stimulant drug?

-Stimulants like caffeine increase the speed of neurotransmission (of nerve impulses) across synapses. This speeds up reaction times (the time it takes for the body to respond to an outside stimulus, such as a sound).

109

What is a depressant drug?

-Depressants, such as alcohol, slow down the activity of neurones in the brain and can help us relax.

110

What are drugs used for?

-Any drug that is used to make people feel a certain way is a recreational drug, such as alcohol.
-Some drugs are medicines - they help to limit damage caused by disease or injuries.

111

What types of drugs are legal?

-Some drugs are legal (e.g. caffeine in cola drinks) but some are only legal to buy at certain ages (e.g. alcohol at 18).

112

Why are some drugs illegal?

-Other drugs are illegal to buy because that can have dangerous effects.
-Some illegal drugs (e.g. heroin) are used in carefully controlled conditions in hospitals.

113

What is drug addiction?

-Most drugs can be addictive which means that people become dependent on the drug and feel that they cannot function properly without it.

114

What do cigarettes contain?

-4000 different chemicals at least 80 of these can cause cancer, these include, tar, arsenic, benzene, cadmium, formaldehyde, nicotine and hundreds of other poisons such as cyanide, carbon monoxide and ammonia.

115

What damage is caused from tar in cigarettes?

-Tobacco smoke contains many chemical substances that damage living tissue. The sticky tar in smoke contains chemical substances called carcinogens. These can cause cancers, which develop most often in the lungs and mouth. An estimated 42,000 people in the UK die each year from cancers related to smoking.

116

What is carbon monoxide?

-Carbon monoxide is a gas that is poisonous because it reduces the amount of oxygen that red blood cells can carry, It is found in tobacco smoke. Cells all around the body need oxygen to work properly. A lack of oxygen to active muscles can cause pain, such as in the legs when walking.

117

What damage is caused from carbon monoxide in tobacco smoke?

Carbon monoxide makes blood vessels narrower. Therefore, body cells supplied by those blood vessels get even less oxygen and may die. Dead tissues easily get infected and must then be removed. If the heart muscles get too little oxygen, this causes a heart attack which may kill. Each year in the UK, smoking causes about 30,000 deaths from circulatory diseases (diseases of the heart and blood vessels).
-Carbon monoxide and other gases in tobacco smoke can also damage lung tissue. This causes respiratory diseases such as emphysema and chronic bronchitis. Each year in the UK, smoking causes another 30,000 deaths from lung diseases.

118

What is the problem with nicotine?

-A drug in tobacco smoke is nicotine. It is the addictive part of tobacco smoke and makes it difficult to give up smoking. Addiction may start after smoking just four cigarettes but may last for years, even after giving up.

119

What heart problems can smoking cause?

-Smoking can contribute to coronary artery disease (atherosclerosis), where the heart's blood supply become narrow or blocked. This is starving the heart of vital nutrients and oxygen, resulting in a heart attack.

120

Why is it hard to prove that smoking is the cause of death?

-It can take many years for smoking to create sufficient damage in the body to cause death. During that time a person will be exposed to many other substances. This makes proving that smoking was the cause of death (and not exposure to other substances) more difficult.

121

How is research about smoking made reliable?

-There have been many studies on the links between smoking and disease. We have to evaluate these studies to see if their conclusions are reliable. Long-term studies that look at individual people for many years and studies that include large numbers of people are more likely to give is reliable evidence because they help to average out the effects of normal variation in results.

122

What does research on the links between smoking and disease tell us?

-That men aged 35 and over die from cancer, repository diseases and circulatory diseases linked to smoking, more than women.
-The more cigarettes smoked by men, the more likely they are to develop lung cancer.

123

What are the short term effects of alcohol?

-Alcohol is quickly absorbed by cells and so effects all the organs of the body.
-It first slows down activity in the brain and nervous system. This affects reaction times so the person takes longer to respond.
-People drink alcohol because it reduces negative feelings and makes them feel happier.
-It can also lower inhibitions, so users are more likely to do things that they wouldn't normally do, including taking greater risks.
-The more alcohol there is in the body the slower the nervous system becomes. This causes blurred vision and affects coordination, making it more difficult to do simple physical and mental tasks.
-Very large amounts can cause unconsciousness and possible death by choking on vomit. It can also slow the nervous system down so much that breathing stops.

124

What are the long term effects of alcohol?

-Drinking alcohol frequently can damage all the organs of the body.
-Alcohol in the blood is taken to the liver to be broken down. Long-term heavy drinking can cause cirrhosis of the liver, where normal tissue is destroyed so the liver cannot function properly and this can lead to death.
-Heavy drinking over a long period of time will also damage the brain, affecting learning and memory or causing a blood clot in the brain.
-Alcohol can also be addictive; people who become dependent on its effects are called alcoholics.

125

What is the cost of alcohol to society?

-As alcohol affects the way we behave, it not only affects us but also the people around us. Violence towards others is more common when people are drunk. Accidents, such as falling, are more likely when someone is drunk, as is suicide.
-Each year in the UK, there are over 9,000 deaths that can be directly related to alcohol. However, it have been estimated that up to 40,000 deaths a year may be the result of alcohol and that up to 5% of the money spent on health in the UK each year is used to treat people who have been drinking excessively.

126

What is a transplant?

-In a transplant, a healthy organ such as a heart or liver is taken from one body (the donor) and put into a patient to replace an organ that no longer functions properly.

127

Why do people die while waiting for an organ donor?

-Each year more than 1,000 people in the UK die waiting for transplants because there are not enough donor organs. Doctors must decide which patients to operate on.

128

What scientific criteria do doctors use to decide who gets a donated organ?

-Doctors use scientific criteria to make decisions based on the likelihood of success. These include whether the patient and donor:
-Have similar tissues; the surfaces of cells come in different 'types' and the closer the match the more likely the transplant will be successful.
-Are similar ages; a child'd organ is less likely to be successful in an adult and vice versa.
-Are geographically close; the quicker the organ is transplanted the more likely the operation will be successful.
-How ill the patient is; a very ill patient is less likely to survive and operation than a more healthy one.

129

What is ethical criteria for organ donations?

-Other criteria, other than scientific, are based on what people think is right or wrong. These are ethical criteria and they are often based on patients' lifestyles.
-People who abuse alcohol may get a disease called cirrhosis, which destroys their liver. Some hospitals will not give liver transplants to patients who abuse alcohol unless they can stay off alcohol for more than six months outside hospital.
-Being clinically obese can damage the heart. So some hospitals will not perform heart transplants on obese people unless they can stick to a weight loss diet.

130

What is an ethical decision?

-An ethical decision uses ethical criteria to reach an answer that most people think is right or fair. Ethical decisions are hard because different people have different standards by which they judge what is right and what is wrong. For example, some people think that certain lifestyles that cause diseases (e.g. alcohol addiction) are not the person's fault, so they should have the same chances for treatment as everyone else. Other people think that lifestyle is a choice - you can choose whether or not t drink or smoke heavily and risk disease, so you shouldn't be allowed the same chance for treatment.
-Some donors would like to choose who should or should not get their organs. Some people think that it should be possible to sell organs from relatives who have recently died or from themselves (e.g. you have two kidneys but can live with only one).

131

What are pathogens?

-Microorganisms are organisms that are too small to see without magnification. There are millions of species of microorganisms, some of which live on or in our bodies.
-A few are pathogens because they cause infectious diseases when they are passed from an infected person to someone who is not infected.

132

What are the different types of pathogens?

-Many pathogens are bacteria, such as those that cause cholera, food poisoning, dysentery and tuberculosis (TB).
-Other diseases are caused by viruses (e.g. influenza mumps, measles and AIDS).
-A few pathogens are fungi, such as the athlete's foot fungus.
-Some are protoctists, such as the protozoan that causes malaria.

133

How do pathogens pass between people?

-For pathogens that cause human diseases to spread they need to pass from an infected person to someone who is not infected. They do this in many different ways, sometimes through direct contact between people and sometimes carried by vectors (animals that pass pathogens from one person to another).

134

What way do pathogens spread between people?

-Water; Water may contain bacteria such as those that cause cholera.
-Food; Food may contain food-poisoning bacteria such as salmonella.
-Contact; Athlete's food fungus is usually transferred to skin from moist surfaces such as in the shower or swimming pool.
-Airborne; Influenza and cold viruses and TB bacteria are spread in air, e.g. from coughs and sneezes.
-Body fluid; Pathogens like HIV can be transferred in body fluids such as blood on a shared syringe or during sexual intercourse.
-Vectors, Mosquitoes; biting insects, such as the Anopheles mosquito, can pass pathogens into human blood.
-Vectors, Houseflies; Houseflies can carry dysentery bacteria from human faeces to food.

135

How do animals protect themselves from invasion by pathogens?

-Animals, including humans, have many different ways to protect themselves against invasion by pathogens. They are separated into two catorgories, physical barriers and chemical barriers.

136

What are physical barriers?

-Physical barriers stop pathogens getting into the body.

137

What are chemical barriers?

-Chemical barriers help to kill pathogens before they can harm us.

138

What physical barriers does the human body have to protect it from pathogens?

-Tear glands make a liquid containing enzymes called lysozymes that kill microorganisms.
-Hairs in the nose filter out dust that might carry pathogens. Mucus in the nose, throat and breathing passages traps microorganisms.
-If the skin is broken, the blood clots to block entry by pathogens.
-The stomach makes hydrochloric acid to kill harmful microorganisms in food.
-The tube in the lungs also produces mucus. Tiny hairs called cilia sweep out the mucus and microorganisms trapped in it.
-The skin forms a protective barrier. Swear glands in skin make chemical substances that kill harmful microorganisms.

139

What are antiseptics?

-We can reduce infection by preventing the pathogen that causes it from getting into the body. Chemical substances that kill microorganisms outside the body are called antiseptics.
-Antiseptics can help prevent pathogens getting into an open wound. They are also important where there are a lot of pathogens, such as around the toilet or where fresh meat, which may contain food-poisoning bacteria, is being prepared.

140

How do pants defend themselves against attack?

-Plants also defend themselves against attack. They use chemical substances that are antibacterials to prevent pathogens from causing damage.

141

How do we use antibacterials produced by plants?

-We use antibacterials for their antiseptic properties. For example, witch hazel from Hamamelis is used in some aftershaves to help prevent infection through cuts in the skin and mint in toothpaste may do more than give a fresh taste.

142

What are antibiotics?

-If pathogens get into the body then we need a way of killing them without killing the patient. Antibiotics are chemical substances that kill or prevent the growth of bacteria and some fungi but not human cells. Antibiotics that only affect fungi, such as nystatin, are called antifungals. Those that only affect bacteria, such as penicillin, are called antibacterials. Unfortunately, antibiotics do not kill viruses.

143

Why are some bacteria more resistant than others?

-Individual bacteria in a population show variation, so some will naturally be more resistant to an antibiotic and take much longer to be killed than others.

144

What is the problem with using antibiotics?

-When the antibiotic is first used, the less resistant bacteria are killed first and the patient starts to feel better. However, the more resistant bacteria are still there and can cause infection again if the patient stops taking the antibiotics. And if these more resistant bacteria reproduce and spread to other people, they can cause an infection that cannot be treated with that antibiotic. So, using antibiotics encourages bacterial resistance to become more common. MRSA is a bacterium that is resistant to many antibiotics.
-Overusing antibiotics also allows resitance to develop because each antibiotic kills many types of bacteria, not just those it is being used against. This means that resistant bacteria of all those different types will be left behind when the antibiotic treatment stops.

145

What organisms are part of food webs?

-All organisms need food. Some organisms are producers and make their own food, such as green plants which use photosynthesis. The rest get their food from other organisms either as primary consumers (by eating plants) or secondary consumers (by eating primary consumers).

146

What are food chains?

-Food chains show what eats what. Organisms that feed at the same level in a food chain are in the same trophic level.

147

What are food webs?

-Food chains from a habitat can be joined together in a food web, which shows the feeding relationships between the different organisms. You can see that organisms in an area depend on each other for food - they are interdependent. As the numbers of one organism change, other organisms are affected, so the relationships among the organisms are always changing. We call this a dynamic relationship. Dynamic means changing.

148

How is energy transferred in food chains?

-Inside an organism, energy stored in food is released during respiration. Some of this energy is transferred into biomass (substances that form tissues) as the organism grows. The energy stored in biomass will be transferred to the next organism in the food chain when it is eaten.
-However, some of the energy that is released in respiration is transferred into forms of energy that are not useful. This energy is transferred to the environment and is therefore wasted and is not available to organisms in the next trophic level.

149

What is a pyramid of biomass?

-If we measured the biomass of all the lettuces in a field and all the caterpillars that were eating the lettuces and all the thrushes that were eating the caterpillars, we could draw a pyramid of biomass.

150

Why is there a limit to the length of a food chain?

-At the top of the trophic level of a food chain there is not enough energy in the biomass to provide enough energy for another level. This means there is a limit to the length of a food chain.

151

What are parasitism?

-In most feeding relationships a predator kills and eats its prey and moves on to find more prey. Parasitism is a feeding relationship in which two organisms live together with one feeding off the other. The organism doing the feeding is a parasite and the organism it feeds on is the host.

152

Where do parasites live?

-Some parasites, like headlice and fleas, live on the outside of their host. Others live inside. For example, tapeworms live in vertebrate intestines.

153

What are tapeworms?

-Tapeworms live in vertebrate intestines. Their eggs leave the host in its faeces. Eggs swallowed by other animals hatch and grow inside their bodies.
-Tapeworms absorb nutrients from the host's gut, which can cause the host to lose a lot of weight. The worm can also grow large enough to block the host's intestines.

154

How have tapeworms adapted to living inside their hosts?

-Hooks and suckers are used to attach it to the intestine well. It has no use for eyes, so it doesn't have any.
-The flat body gives it a large surface area for food absorption. It has no need for a circulatory system, intestines or much of a nervous system.
-The outside of the worm contains substances that stop digestive enzymes working so that the worm is not digested.
-Each section contains male and female reproductive organs so the worm can self fertilise its eggs if other tapeworms are not nearby.

155

Do parasites harm their hosts?

-Parasites usually harm their hosts. Tapeworms absorb nutrients from the host's gut, which can cause the host to lose a lot of weight. The worm can also grow large enough to block the host's intestines.
-European mistletoe is also a parasite. It has leaves that can photosynthesise but its roots grow into the veins of the host tree and absorb water and mineral salts.

156

What are mutualists?

-Some organisms live in close relationships where both organisms benefit. This is called mutualism.

157

What is an example of a mutualistic relationship?

-Oxpeckers have a mutualistic relationship with large herbivores in Africa. Both the oxpecker and the herbivore benefit from the relationship. The oxpecker eats parasitic insects that live on the skin of the herbivore.
-A similar relationship is found in oceans, where small cleaner fish eat dead skin and parasites from the skin or larger fish, such as sharks.

158

What mutualistic relationship involves nitrogen-fixing bacteria?

-Some organisms live in mutualistic relationships inside other organisms. Bacteria that can turn nitrogen in the air into nitrogen compounds are called nitrogen-fixing bacteria. Some live inside the roots of legumes (plants, like peas, that produce pods). The bacteria are protected from the environment and obtain chemical substances from the plant that they use as food. The plant gets nitrogen compounds, which it needs to grow well, from the bacteria.

159

What mutualistic relationship involves chemosynthetic bacteria?

-Chemosynthetic bacteria are producers that get their energy from chemical substances rather than from light. Some live inside giant tubeworms - the tubeworms gather the chemical substances that the bacteria need for chemosynthesis and the tubeworms feed on substances made by the bacteria.

160

What was the world human population growth like in the nineteenth and twentieth century?

-During the nineteenth and twentieth centuries there was rapid human population growth. Increases in food production, medicines and better living conditions for many meant that more babies were born and survived to have their own children.

161

What is the world human population growth like now?

-The rate of population growth is slowing don but estimates that make different assumptions about how many people will die each year and how many babies will be born predict different population sizes in the future.

162

What do we need to do as the human population increases?

-People need food and fresh water to survive. As the human population increases, we need to find more water and produce more food. Crops often grow better with fertiliser (containing nitrates and phosphates) added to the soil. These compounds are nutrients needed by plants to grow well.
-Everything we use every day requires resources, including fossil fuel to generate electricity to make them.

163

How are we causing pollution because of the growing population?

-If we are not careful about the way we make and use resources, we risk releasing pollutants into the environment and damaging the organisms. Sulfur dioxide gas is released from burning fossil fuels and pollutes the air if the concentration is high.

164

What are the different pollutants and where do they come from?

-Sulfur dioxide gas
-Comes from; burning fossil fuels and motor vehicle emissions.
-Nitrates and phosphates
-Comes from; fertilisers and washing powder (bio).

165

What is eutrophication?

-If farmers use too much fertiliser, or rain washes it away, it can get into water and raise the natural concentration of nitrates and phosphates. This is called eutrophication.
-As nutrient concentration increases, organisms in the water are affected, which can lead to a decrease in oxygen concentration in the water and the death of many animals.

166

What happens in the process of eutrophication?

-Fertiliser, containing nitrates and phosphates, is spread on fields to help crop plants grow better.
-If it rains heavily, the nitrates and phosphates will be washed off the field into surrounding streams, rivers or lakes.
-Nitrates and phosphates left on the field dissolve in water in the soil.
-Any nitrates and phosphates not taken up by crop plants soak away in soil water into the surrounding streams, rivers or lakes.
-The presence of extra nitrates and phosphates in streams, rivers and other water is called eutrophication.
-Eutrophication encourages water plants, including algae to grow more rapidly than usual.
-Algae form dense mats on the surface of the water, blocking light to plants below.
-Plants that don't get enough light will die, and stop producing oxygen through photosynthesis.
-Animals living the the water cannot get the oxygen they need for respiration so they will die.
-The amount of oxygen dissolved in the water decreases.
-Decay organisms use oxygen from the water to help break down dead plant tissues.

167

How can sulfur dioxide cause pollution damage?

-The gas cloud from the volcano causes damage because it contains a lot of sulfur dioxide, which dissolves in the water vapour in air to make a very strong acid.
-Sulfur dioxide is also produced by power stations. When it dissolves in the water vapour in clouds it forms sulphuric acid and can fall as acid rain. Acid rain is responsible for destroying the trees in many forests around the world. It can also make lakes too acidic for fish and other water organisms to live in.

168

What are indicator species?

-The more pollution we cause, the more harm there is to habitats. Some organisms are so sensitive to polluting chemicals that we can use them to help us show the presence of pollution. We call them indicator species.

169

What are blackspot fungus an indicator species for?

-Air pollution
-Blackspot fungus is an infection of roses that is killed by sulfur dioxide pollution in the air.

170

What are lichens an indicator species for?

-Air pollution
-Lichens are mutualistic relationships between a fungus and an alga that lives inside the fungus. Different species of lichen can tolerate different amounts of sulfur dioxide and other polluting gases such as nitrogen oxides and indicate the presence and absence of these gases in the air. Lichen surveys in the UK have shown that laws to reduce the amount of sulfur dioxide released into the air are working well.

171

What are the different types of indicator species for water pollution?

-Different animals that live in water need varying amounts of oxygen. For example, stonefly larvae and freshwater shrimps need lots of oxygen, but bloodworms and sludgeworms are adapted to live where there is little oxygen in the water. We can use the presence or absence of these organisms as simple indicators of the level of pollution in water.

172

What is recycling?

-Recycling is the process of taking materials out of waste before disposal and converting them into new products that we can use. Recycling can help supply more of the materials we need that are difficult to get hold of or are running out.

173

What types of things can be recycled?

-Metals in drinks cans can be melted down and recycled as new drinks cans or parts of cars.
-Paper can be recycled as more paper of cardboard.
-Plastic bottles can be recycled as fleece clothing.

174

Why is recycling important?

-In the UK we produce over 100 million tonnes of waste each year from homes, businesses and industry. This waste includes paper, plastics and many metals, and much of it ends up buried in the ground in landfill sites. This not only uses a lot of land, there is also a risk of pollution and it means that the materials cannot be used again. We are in danger of needing more of some materials than we can supply and even running out of some raw materials completely.
-Gallium (flat screen TVs) - 15 years before we could run out.
-Platinum (catalytic converters) - 15 years before we could run out.
-Zinc (cars, roofs, computers) - 30 years before we could run out.

175

How is carbon dioxide removed from the air?

-Imagine a carbon atom that is a part of a carbon dioxide molecule in the atmosphere. That carbon dioxide molecule could diffuse into a leaf. There, during photosynthesis, the carbon atom from the carbon dioxide molecule will become part of another carbon compound called glucose.
-If glucose is used by the plant for respiration, the carbon atom will become part of carbon dioxide again and will be released back into the atmosphere. However, the glucose might instead be changed into other carbon compounds and used to make more plant biomass.

176

How does carbon dioxide become a part of food chains?

-Carbohydrates, fats and proteins in plants are all compounds that contain carbon atoms. When an animal eats a plant, some of these compounds are broken down during digestion and taken into its body. The rest will leave the animal's body as faeces.
-Some of the carbon compounds taken into the body will be used for respiration and some may form waste products that are excreted in urine. The rest are used to build more complex compounds inside the animal and make more animal biomass.
-If the animal is eaten by a predator, the same processes will happen again.
-If plants and animals are not eaten and just die, detritus feeders, such as worms and fly larvae (maggots) and decomposer organisms, such as fungi and bacteria, start the process of decay. They also feed on animal waste (e.g. faeces, urine). They break down the carbon-containing compounds and use some of them for respiration and the rest to build more complex compounds in their bodies. When they die, their bodies will be broken down by other detritus feeders and decomposers and so on.

177

What happens to carbon dioxide after it has been through the food chain?

-If many large dead plants are buried so quickly that decomposer organisms can't feed on them, then over millions of years they may be changed by heat and pressure into peat and coal. In the same way, oil and natural gas are formed from tiny dead sea plants and animals which have not been decomposed.
-Coal, peat, oil and natural gas are fossil fuels; they contain carbon compounds formed from dead organisms. When we burn fossil fuels, in the process called combustion, the carbon in these compounds is converted to carbon in carbon dioxide and is released into the atmosphere.
-The movement of carbon through dead and living organisms and the atmosphere is shown in the carbon cycle and is an example of natural recycling.

178

Why is nitrogen important for organisms and where do they get it from?

-Nitrogen is important for organisms because it is used to make proteins and other substances in new tissues as they grow. However, plants and animals cannot use nitrogen gas from the air; they need to get nitrogen from nitrogen-containing substances. Plant roots absorb nitrogen compounds, such as nitrates, from the soil and use them to make proteins and other nitrogen compounds in their biomass. Animals get nitrogen compounds in their food. They use most of these to make nitrogen compounds in new biomass, but some are lost to the environment in faeces and urine.

179

What part does bacteria play in the nitrogen cycle?

-If there were no way to convert nitrogen compounds from biomass and waste back to nitrates in the soil, plants would quickly die out. Fortunately, when decomposers feed on dead plants and animals and animal wastes they break down some proteins and urea (a nitrogen-rich substance in urine) to ammonia and release it into the soil.
-Other bacteria also plays a part in keeping the soil healthy for plant growth. The soil contains nitrogen-fixing bacteria that can fix nitrogen gas into ammonia.
-Mutualistic nitrogen-fixing bacteria are also found in legume roots. These bacteria live inside root nodules and provide these plants directly with ammonia.
-Although plants can use ammonia, they grow better with nitrates. Some nitrifying bacteria in the soil convert ammonia into nitrates.
-If soils are lacking in oxygen, such as when they are waterlogged, then some denitrifying bacteria will convert the nitrates back to nitrites and other convert nitrites back to nitrogen gas.

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What part does lightning play in the nitrogen cycle?

-Occasionally, lightning can provide the energy to combine oxygen and nitrogen gases in the air, forming oxides that quickly form nitrates.