what does cell metabolism lead to?
the build up of waste products in the blood, including carbon dioxide and urea
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what is carbon dioxide?
a waste product of respiration
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what is urea?
the product of excess amino acids in the liver
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how is urea removed?
by the kidneys
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what are the parts of the urinary system?
renal artery, renal vein, kidneys, ureters, bladder, urethra
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what do the renal arteries do?
carry blood from the body to the kidneys
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what do the renal veins do?
carry clean blood back to the body
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what do the kidneys do?
remove substances including urea from the blood and make urine
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what do the ureters do?
carry urine from the kidneys to the bladder
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what does the bladder do?
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what is the urethra?
urine flows through the urethra to the outside of the body
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what are sphincter muscles?
a muscle that keeps the exit from the bladder closed until we decide to urinate
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what is kidney failure?
when both kidneys stop working causing toxic urea to build up in the blood
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how can kidney failure be treated?
organ donation and kidney dialysis
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how does kidney dialysis work?
blood is passed through a dialysis machine to remove waste urea and excess substances before the blood is returned to the blood
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how does organ donation work?
a healthy kidney from another person is placed in the body and connected to the blood system, so that waste substances are removed from the blood
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what are nephrons?
millions of tiny tubules that lie in the kidney, they are responsible for making urine
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what are the structures inside of a nephron?
renal artery, glomerulus, bowman's capsule, convoluted tubules, loop of Henlé, collecting duct
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what are the processes that take place inside of the nephron?
filtration, selective reabsorption, osmoregulation
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how does filtration take place?
filtration in the nephron is of small molecules from blood into tubule,including water, glucose, salts and urea
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how does selective reabsorption take place?
selective reabsorption of glucose from the tubule back into blood by active transport
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how does osmoregulation take place?
reabsorption of water that the body NEEDS from the tubule goes back into the blood
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how are the structures of the glomerulus and the bowman's capsule related to their function?
high blood pressure. leaky walls (small molecules filter from the blood into the capsule), large surface area (filtration happens as quickly as possible
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how are the structures of the loop of henlé and the convoluted tubules related to their functions?
they lie close to the capillary (glucose and water can be reabsorbed into the blood from the tubule)
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what is the role of ADH?
regulates the water content of the blood
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where is ADH produced?
the pituitary gland
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how is ADH production controlled?
by a negative feedback mechanism
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what is the menstrual cycle controlled by?
the hormomes oestrogen and progesterone
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what are the main stages of the menstrual cycle?
menstruation, changes to uterus lining and ovulation
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what is menstruation?
the breakdown of the uterus lining. it begins on day 1 of the cycle and usually lasts between 4 and 7 days
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what happens to the uterus lining?
during the second week, the lining of the uterus is gradually built up
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what happens during ovulation?
an egg is released from an ovary. This usually takes place around day 14
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when is fertilisation most likely to occur?
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what happens in weeks 3 and 4?
the lining of the uterus continues to build up
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what happens if fertilisation does occur?
the uterus lining is maintained and menstruation does not happen
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why is the uterus lining maintained if fertilisation does occur?
the embryo that develops from a fertilised egg needs to embed in thick uterus lining, so that it can get nutrients from the mother
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what is the role of oestrogen in the menstrual cycle?
stimulates the release of LH and causes thickening of uterus wall, when levels fall, it triggers menstruation
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what is the role of F.S.H ?
follicle stimulating hormone - causes maturation and growth of follicles, this stimulates oestrogen production
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what is the role of LH?
triggers ovulation, which releases progesterone
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what is the role of progesterone?
it inhibits FSH and LH release, when it falls it triggers menstruation
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how is the control of the menstrual cycle a negative feedback mechanism?
changes caused by the release of one hormone inhibit the secretion of other hormones. for example, progesterone inhibits FSH and LH
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how is the structure of an egg adapted to its function?
cytoplasm (provides nutrients), haploid nucleus (one set of genetic material), cell membrane (blocks entry of other sperm after fertilisation)
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how is the structure of a sperm cell related to its function?
acrosome (contains enzymes), haploid nucleus (one set of genetic material), mitochondria (in middle section to release energy from respiration to power tail), tail (for motility)
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what is IVF?
in vitro fertilisation - egg cells taken from the woman's ovaries are mixed with sperm cells from the man in a dish. one or two healthy embryos are implanted to develop
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what is an advantage of IVF?
it is useful if a man produces only a few healthy sperm
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what is a disadvantage of IVF?
IVF babies may be born early, which can cause problems at birth or later in life
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what is egg donation?
eggs from another woman are fertilised by the man's sperm using IVF. one or two are implanted in the uterus of the woman in the couple to develop
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what is an advantage of egg donation?
it can be used when the woman of the couple has no eggs in her ovaries
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what is a disadvantage of egg donation?
hormones used to collect eggs may cause a bad reaction. the egg donor may want access to the child
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what is a surrogate mother?
eggs and sperm from the couple are mixed in a petri dish. A healthy embryo is placed in the uterus of another woman - the surrogate - to develop
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what is an advantage of a surrogate mother?
it can be used when the woman of a couple cannot grow an embryo in her uterus
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what is a disadvantage of a surrogate mother?
some surrogate mothers find it hard to hand over the baby to the couple
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what are hormones (as an infertility treatment)?
the woman is given extra hormones to help her ovaries release eggs
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what is an advantage of hormones?
they can be used when the woman's hormones are not enough to cause ovulation
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what is a disadvantage of hormones?
there is a greater risk of having several babies at the same time. these babies tend to be born earlier than normal, which can cause problems at birth or later in life
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what is the sex of a person controlled by?
one pair of chromosomes, x,x, in a female, x,y, in a male
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when is the sex of offspring determined?
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how can you show how it is determined?
genetic diagram or punnett square
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how can you show how sex -linked genetic disorders are inherited?
genetic diagrams, punnett squares
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what are two examples of sex-linked genetic disorders?
haemophillia and colour blindness
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what scientist contributed to the development of vaccines?
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what was the first step of the process?
he gave a boy a pathogen that causes cowpox, the boy developed the cowpox and recovered
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what is the second step of the process?
he gave the same boy the pathogen with smallpox, the boy did not develop smallpox
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what had he discovered?
the cowpox vaccine made him immune to smallpox
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what can immunisation do?
can protect you from infection
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what are antigens?
surface proteins that identify a cell
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what are antibodys?
chemicals made by lymphocytes
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what is step 1 in the process of immunisation?
a vaccine containing a dead or weakened pathogen is injected
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what is step 2 in the process of immunisation?
a type of white blood cell (lymphocyte), with an antibody that perfectly fits the antigen is activated
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what is step 3 of immunisation?
this lymphocyte divides over and over again to produce clones of identical lymphocytes
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what is step 4 of immunisation?
some of the lymphocytes secrete large amounts of antibodies, this stick to the antigens and destroy the pathogen. other lymphocytes remain in the blood as memory lymphocytes, ready to respond immediately if the same antigen ever turns up again
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what are some risks of immunisation?
some people get a mild reaction or mild form of the disease,very rarely but sometimes, a person has a major harmful reaction
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what are some advantages of immunisation?
immunity is produced without being ill, it lasts a long time, often for life, if most people are immune, then the few who aren't are also less likely to catch the disease.
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what is the role of a memory lymphocyte?
a secondary response to an antigen
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what are monoclonal antibodies?
antibodies that carry useful chemicals markers or treatments. a set of monoclonal antibodies are identical because they are produced in large quantities from the same hybridoma cells
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how can B lymphocytes by produced?
by mice, it makes particular antibodies continuously but they do not divide
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what are the beneficial properties of a cancer cell?
it divides continuously, but does not make antibodies
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how can hybridoma cells be produced?
by fusing a B lymphocyte cell and a cancer cell, the hybridoma cell divides and produces antibodies all at the same time
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what are the uses of monoclonal antibodies?
in pregnancy tests, in blood clots, in radiotherapy treatments
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how are monoclonal antibodies used in pregnancy tests?
to identify if the pregnancy hormone is present in urine
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how are monoclonal antibodies used in blood clots?
they stick to blood clots or cancer cells so they can be detected and treated
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how are monoclonal antibodies used in radiotherapy?
used to deliver drugs to the target cells, only the target cells are affected and smaller amounts of drugs are used
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what can growth of a population of bacteria lead to?
exponential growth of a population of bacteria can lead to rapid development of an infection
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what did Louis Pasteur do?
he carried out experiments showing that once micro-organisms are destroyed- they don't suddenly appear again
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how can micro-organisms be transferred?
micro-organisms can only be transferred from something that already contains them, e.g. the air
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what was his experiment?
he used two different sized beakers to show that if micro organisms are not present in a solution, it can stay fresh for much longer
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why did he boil his experiments?
because boiling (for one hour) kills any microorganisms already in a broth
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why did he use broth?
because broth is a liquid containing nutrients
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what did Pasteur's work lead to?
the development of aseptic techniques that are used to destroy microorganisms
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how are these 'aseptic techniques' used?
to prevent spoilage of food and in surgery (operations) to prevent infections of wounds
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what are plant defences?
plans protect themselves from attack by producing chemicals
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what do they make?
poisons that deter pests and chemicals that kill pathogens which infect them and cause disease
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what do we use plant chemicals for?
we use some of the defence chemicals found in plants as medicines
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what are some examples of plant chemicals?
quinine (from cinchona tree) to treat human disease (e.g. malaria), digoxin (from foxglove) to treat human disorders ( e.g. heart), aspirin (willow tree and other plants), to relieve symptoms (e.g. pain and fever)
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what is the impact of pests on food supply?
pathogens and pests that attack crop plants cause damage, this reduces the yield of the crop.
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why does this impact our food supply?
because most of the food we eat comes from plants
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what is photoperiodicity?
the response of a plant that changes as day length changes
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where is it most noticeable?
in places where day length varies significantly throughout the year
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what are some examples of photoperiodism?
germination, growth and reproduction (flowering)
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how does germination show photoperiodicity?
seeds are not affected by light as they grow underground but they germinate in spring hen conditions for growth are getting better (e.g. lettuce)
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how does growth show photoperiodicity?
plants stop growing over winter, some trees lose their leaves
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how does reproduction show photoperiodicity?
plants in seasonal areas produce flowers at a particular time of year. some produce flowers in response to days getting longer (spring/summer) other plants flower when day length gets shorter (autumn)
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what is a circadian rhythm?
a pattern of behaviour that changes over a 24 hour period, controlled by an internal biological clock and external factors such as day or night help to match this clock to changes in the environment
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what does sexual reproduction require?
finding and selecting a suitable mate, this can involve courtship behaviour
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how do some animals have different mating strategies?
some animals mater for life and only choose another if their mate dies, some have several mates over their lifetime, some have one mate for a breeding season, some have several mates for a breeding season
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what is an example of courtship behaviour?
roaring of an animal - demonstrates its strength, males that roar the longest will mate with more females
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what is the role of a female in courtship?
selecting between males, so that their offspring inherit the best genes possible
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what are parenting behaviours?
some animals, particularly birds and mammals, have special behaviours for rearing young, these are parenting behaviours
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what are some examples of parenting behaviours?
protecting the youth from danger, helping the young to find food, sheltering the young from cold and wet, teaching the young new skills, such as hunting
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why can parental care be a successful evolutionary strategy?
because there is an increased chance of survival and the offspring also inherits the genes for good parenting and are more likely themselves to have young that survive
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how may parental care involve risks to the parents?
parents may try so hard to deter predators away from their offspring that they are killed themselves and their offspring are now in more danger than before
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what is innate behaviour?
a behaviour that an animal does not have to learn
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what is imprinting?
a simple learned behaviour, e.g. a gosling learning to recognise its mother after hatching. imrpinting only happens at a particular time but may last throughout life without change
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what is habituation?
a simple form of learned behaviour. it happens when an animal "switches off" its response to a repeated harmless stimulus. this helps the animal to concentrate on changes in the environment that are important
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what is classical conditioning?
it occurs when an innate behaviour is changed through associating a new stimulus with the old response
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what is operant conditioning?
a chance behaviour is strengthened by receiving a reward. At first, the behaviour is chance, but the animal learns to associate the reward with the behaviour and so carry out the behaviour more often
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how are sniffer dogs trained with use of behaviours?
in operant conditioning - they are trained with a toy that they enjoy playing with. the first time in training that they find drugs they are given the toy to play with - this happens again and again until the dog will look for the drugs.
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how are dolphins trained with use of behaviours?
in operant conditioning - they are trained with a reward , e.g. food, that they enjoy. the first time they do a trick they are given the food - this happens again and again until the dolphin will do the trick alone.
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how are police horses trained with use of behaviours?
police horses are exposed to crowds during their training so that they learn to become used to the noise - this is habituation
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what is an example of classical conditioning?
salivating when food is present, bell rung when food is presented, bell associated with food being presented, salivating when a bell is rung, even with no food
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what are choice chambers?
a choice chamber can be used to investigate innate behaviour in small animals
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what is ethology?
the study of animal behaviour. Niko Tinbergen was an ethologist who studied the innate behaviour of gull chicks
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what was his experiment with gull chicks?
he noticed that gull chicks peck at their parent's beak to ask for food, he tested different models of adult gull beaks to see which model the chicks would innately respond to and peck at the most frequently
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what did Konrad Lorenz show?
that newly hatched goslings could imprint on an object rather than their mother goose if they saw the object first
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why is this an example of learning and not innate behaviour?
if recognising the mother was innate, then the goslings would not become attatched to the object. Imprinting is a learned behaviour because the goslings learn to recognise what they see first as their parent, and this can be different
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what does some animal behaviour require?
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what are the different types of signals in animal communication?
sound, chemical and visual
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what are some examples of sound communication?
birds sing to establish and maintain territory, cats hiss to frighten other cats, deer stags roar to challenge other stags and attract females
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what are some examples of chemical communication?
animals release hormone like chemicals called pheremones into the air, e.g. female moths release them to attract male moths
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what are some examples of visual communication?
gestures - such as head nodding or hand waving, body language - the position of the body can express feelings and emotion, facial expressions - such as showing teeth
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what is social behaviour?
social behaviour occurs between individuals in a group. it includes the use of different types of signal. social behaviour can increase the change of survival of individuals and all of the group
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what are examples of social behaviour?
defending a larger territory, some individuals watching for danger while others feed, fighting off predators as a group, working as a group to hunt for food
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Who was Dian Fossey?
an ethologist who studied the social behaviour of gorillas by watching them in the wild. Fossey learned the meaning of many gorilla calls and found that gorillas had complex social relationships. She also showed that gorillas were not violent
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how has the work of Jane Goodall contributed to our understanding of chimpanzee behaviour?
she watched chimpanzee groups for many years and recorded what she saw. her work shows that chimpanzees live in complex family groups that communicate using many different calls, she was first to record chimpanzees using tools and hunting as a group
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how do plants communicate?
using chemicals with animals and with other plants
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how do plants communicate with animals?
flowering plants produce scents to attract particular animals, such as some insects. as the animal feeds on nectar, the pollen attatches to the animal and is transported to the next. mutualistic relationship
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how do plants communicate with other plants?
they produce chemicals from their roots tat damage the roots of other plants, reduces competition for resources (water and mineral ions), release chemicals into the air when they are attacked by herbivores, surrounding plants produce poisons
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what is co-evolution?
is evolution that is caused in one species by a change in another species.
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how have plants and animals co-evolved?
plants have co-evolved the shape of their flowers with animal pollinators so that only one or a few species of animal can feed at the flower
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how does this benefit both the plant and animal?
pollen from the plant's flowers is more likely to be taken to a flower of the same species, the animal is less likely to have to compete to get the nectar in the flower
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what will happen if the relationship becomes too specialised?
the populations can become too dependent on each other. if one population crashes, the other can be affected
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why do plants growing in areas of herbivores produce more poison than areas with fewer herbivores?
this is an example of co-evolution because where there are many herbivores, the plants that survive and reproduce have large amounts of poison. so the neext generation inherit the genes for producing lots of poison
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where does the evidence we have for evolution come from?
fossils, of bones and teeth
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when did 'ardi' exist?
ardipithecus ramidus existed 4.4 million years ago
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when did 'lucy' exist?
australopithecus afarensis existed 3.2 million years ago
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when did "handy man" exist?
homo habilis existed 2.4 -1.4 million years ago
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when did "upright man" exist?
homo erectus existed 1.8- 0.5 million years ago
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when did 'modern man' exist?
since c.200 000 years ago
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what species are known as part of the 'Leakey family'?
homo habilis and homo erectus
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how has height changed over time?
went down from ramidus to afarensis but has increased since then
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how has brain size changed over time?
it has increased
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what are some major changes over time?
use of tools, walking upright, build
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how do stone tools also give us evidence for evolution?
the earliest stone tools are around 2.4 million years old. Over time more complex tools were made, and a greater range of tool types
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what are some examples of how tools have changed?
2 million years ago - a large stone that has had some chips flaked off it (simple hand axe), 40 000 years ago fine flake split from larger stones (arrow head, spear head, scraper, knife)
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how can stone tools be dated from their environment?
the amount of radiation in samples of sediment just above and below the layer in which the tools are found can be used to date the sediment and so give a range of dates when the tools were left there
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why can the stone not be used to date when the tool was made?
because the stone used to make the tools is much older than the tools, so cannot be used to date when the tool was made
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what is the African Eve theory?
all people today can trace their inheritance back to one female who lived in Africa between 130,000 and 200,000 years ago
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how does mitochondrial DNA provide evidence for the African Eve theory?
Mitochondrial DNA is passed from mother to child, differences in mitochondrial DNA are caused by mutations. Analysis of these mutations suggest that all people are related to one female who is referred to as 'African Eve' because she lived in africa
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why is mitochondrial DNA more useful than nuclear DNA?
it is easier to extract as it is more abundant, it is only passed from mother to child, it is less likely to degrade in fossils, it has a higher mutation rate, so there are more differences between people
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what impact did climate change have on human behaviour?
the ice age - more water was frozen, sea levels were lower, humans could walk between places separated by water today (e.g. Africa to Asia ), low sea levels (25,000 years ago) humans could walk from Siberia across into north America
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what happened at the end of the ice age?
humans migrated north as the land became habitable
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what is biotechnology?
the alteration of natural biomolecules using science and engineering to provide goods and services
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what is a fermenter?
a vessel used to cultivate micro-organisms for the production of biomolecules on a large scale
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what are the suitable conditions needed inside of a fermenter?
aseptic precautions( stops competing microorganisms getting in), nutrients (for growth), optimum temperature, optimum pH (for growth), oxygenation (for aerobic respiration) and agitation (stirrer to keep everything mixed)
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what is biotechnology used to provide?
useful substances (e.g. foods such as cheese and bread, and chemicals such as insulin), services (e.g. tests for chemical pollutants)
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what are the examples of food from microorganims?
bread (yeast), yogurt (Lactobacillus bacteria), mycoprotein (Fusarium fungus) and beer/wine (yeast)
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what are the factors of using micro-organisms for food production?
rapid population growth, ease of manipulation, production independent of climate, use of waste products from other industrial processes
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what is the advantage of rapid population growth?
microorganisms grow and reproduce much more quickly than animals or plants
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what is the advantage of ease of manipulation?
microorganisms are easier to handle than whole plants and animals
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what is the advantage of production independent of climate?
fermenters need a relatively small area and can be built almost anywhere, while plants and animals need large areas of particular environmental conditions
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what is the advantage of the use of waste products?
waste products from other processes, such as from making flour, can be used as nutrients for growing microorganisms - this is cheaper and reduces the amount of waste disposal needed
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how is mycoprotein manufactured?
using the fungus Fusarium sp. The fungus is grown in large fermenters.
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what is the role of Fusarium sp?
the fungus makes long thread-like hyphae, which gives mycoprotein a fibrous texture.The broth in the fermenter isn't stirred as this would damage the hyphae
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how is mycoprotein fermented?
ammonia and air pumped in, excess gases removed, glucose syrup and minerals are added to supply energy and nutrients for growth, heat kills cells and removes bitter taste, drying and pressing removes water, mycoprotein is ready for packaging
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why is mycoprotein a healthier protein than red meat?
no saturated fat, which is a risk factor for heart disease, high fibre content, many healthy effects, can reduce rate of glucose absorption and so reduce gluose and insulin surges, also moves food through the intestines faster (carcinogens removed)
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what is the process of making yoghurt from milk?
fresh milk is warmed to about 40°C a culture of bacteria (Lactobacillus bulgaricus) is added to the milk, the bacteria convert lactose in the milk to lactic acid, the lactic acid makes the mixture taste more sour and causes it to thicken
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what are the different factors in yoghurt making?
type of bacteria used, type of milk used, temerature of the mixture, pH of the mixture all can change the speed at which and type of yoghurt produced
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what are the uses of enzyme technology?
vegetarian cheese, sweets and washing powder
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What is Chymosin?
an enzyme that affects proteins in milk, making it separate into solid curds and whey. The curds are then used to make cheese. Natural chymosin is extracted from calves' stomachs, but it can also be made using GM bacteria and used to make vegetarian
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what is Invertase?
a.k.a sucrase is the enzyme that converts the sugar sucrose into glucose and fructose. Sucrase is commercially produced by Saccharomyces cerevisiae (yeast). It is used to make sweets taste sweeter and for making soft centres of some sweets
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What are the two types of enzymes used in biological washing powders?
protease enzymes digest proteins and lipases digest fats and oils. Proteins, fats and oils are often found as food stains on clothes. Washing powders with these enzymes work more quickly at lower temperatures than washing powders without enzymes
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how can you investigate enzymes?
lactase is an enzyme that breaks down lactose sugar, it can be immobilised in alginate beads before it is used to produce lactose-free milk.Immobilising enzymes mean that the enzymes can be easily separated from the product so they can be reused.
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what is Recombinant DNA technology?
the use of technology to make genetically modified organisms
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what is step 1 in making human insulin?
DNA from the human cell is cut into piece using enzymes called restriction enzymes. These make staggered cuts across the double- stranded DNA, leaving a few unpaired bases at each end, called sticky ends
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what is step 2 in making human insulin?
bacteria cells contain small circles of DNA called plasmids. the same restriction enzymes are used to cut plasmids open, leaving sticky ends with matching sets of unpaired bases
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what is step 3 in making human insulin?
the pieces of DNA containing the insulin gee are mixed with the plasmids. The bases at the sticky ends 'pair up'. an enzyme called DNA ligase is added, linking the DNA back into a continuous circle
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what is step 4 in making human insulin?
the recombiant plasmids are inserted into bacteria, the bacteria can now be grown in huge fermenters where they make human insulin.
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what is the role of enzymes in the formation of genetically modified bacteria?
restriction enzymes cut the required gene out of the human DNA. They leave 'sticky ends' on the gene. The same restriction enzymes cut open the plasmid, creating matching sticky ends. The DNA ligase enzyme joins the matching sticky ends.
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what is global food security?
the ability to provide enough food for all the people on Earth. As the human population grows, we need to grow more food so there is enough for everyone
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how has food production increased?
conventional plant-breeding programmes can develop new varieties of plants that have higher yields
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how do these programmes work?
plants with good features are crossed, plants grown from seeds of these crosses are selected for their good features and crosses with eachother, selection and crossing is repeated many times until a high-yielding variety is produced
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how have pest management strategies increased food production?
by killing the pests that damage crop plants
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what do these strategies include?
pheremone traps to attract/kill pests, crop varieties that are less attractive, attracting natural predators, using pesticides, rotating crops between different fields
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what is a biofuel?
a fuel that is produced from living organisms, such as oil palm trees
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what are the advantages of biofuels?
they are renewable, fossil fuels are not. crop growth also takes carbon dioxide from the air
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what are the disadvantages of biofuels?
biofuel crops need land to grow on, and this may take land needed for growing food crops
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what is a 'vector'?
something that carries a gene into another cell and inserts it into the DNA of that cell
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how can plants be genetically modified?
using a bacterium called Agrobacterium tumefaciens as the vector
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what is an example of this?
the gene for making flavonoid can be inserted into tomato cells to make purple tomatoes
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what are the benefits of flavonoid?
tests have shown that mice with cancer live longer if they eat flavonoids
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what is a transgenic plant?
a plant that has genes from another species
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how can genetic modification be used to increase food production?
a gene that helps a plant grow faster or cope better with difficult conditions and produce more seeds could be inserted into a crop plant such as wheat. Growing these GM plants would increase the yield of the crop in an area
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what are the benefits of GM of crop plants?
eating purple tomatoes that contain flavonoids might help anyone with cancer live longer, but they cost more to buy
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what are the costs of GM crop plants?
GM crop seeds may be too expensive for poor farmers to buy
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what is Bacillus thuringiensis?
a bacterium that naturally produces a chemical that is poisonus to insect pests such as caterpillars. This chemical is caalled Bt toxin
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what can you do with Bt toxin?
the gene can be cut out of the bacterial DNA and inserted into the DNA of a plant cell using Agrobacterium tumefaciens. Plants grown from these cells produce the Bt toxin. when an insect tries to eat them, the poison kills the insect pest
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what are the advantages of using Bt plants?
crop damage is reduced so crop yield should increase, less chemical insecticide is needed so other, harmless and useful insects are less likely to be harmed
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what are the disadvantages of using Bt plants?
seed is more expensive, insect pests may become resistant to Bt toxin, Bt gene may transfer to closely related wild plants by pollination, which would make those plants resistant to pests too
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how can GM with the Bt toxin gene increase food production?
damage to a plant's leaves by an insect pest will reduce food production by photosynthesis. This will reduce the rate of plant growth, including growth of the parts of the plant that we eat. Bt toxin kills insect pests that eat the leaves
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Other cards in this set
what is carbon dioxide?
a waste product of respiration
what is urea?
how is urea removed?
what are the parts of the urinary system?