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Define the term transpiration
the loss of water through evaporation
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Describe the effect of humidity on the rate of transpiration by a plant
the more humid it is, the less the rate of transpiration
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List 2 factors which should have to be kept constant during the experiment
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What is the function of the reservoir in a potometer
to reset the bubble
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What effect does larger leaf surface area have on the amount of water loss?
the larger the leaf, the more water requirement
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Define the term osmosis
the movement of water from a dilute solution to a stronger solution through a selectively permeable membrane
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In an experiment, the centre of a potato was carved out and filled with a strong sugar solution. The potato was then suspended in a beaker of water. After one hour, the level of the sugar solution has risen. Explain this result.
the water molecules move form a region of high concentration to a region of low concentration down a concentration gradient, across a selectively permeable membrane until equilibrium is reached
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Where does evaporation usually take place in leaves
the spongy mesophyll cells
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What can a potometer be used to measure effects of
- wind speed
- temperature
- humidity
- leaf surface area
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What is a visking tube?
A visking tube is a artificial selectively permeable membrane which allows smaller molecules like water and glucose to pass through and stops larger molecules like starch from passing through
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What did Chargaff discover and with what approach
- Base pairing
- Chemical analysis
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Frank and Wilkins
- Overall shape
- Xray diffraction
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What are the 3 sub-units used in DNA structure
deoxyribose sugar, phosphate and bases.
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what are the 4 types of base
- adenine
- guanine
- cytosine
- thymine
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What is each repeating unit of DNA consisting of a phosphate, sugar and base called
a nucleotide
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what is the arrangement known as base pairing
adenine only combines with thymine and guanine only combines with cytosine.
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How does DNA work?
By providing a code to allow the cell to make the proteins it needs.
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What is mitosis used for?
it is used for growth and repair. It produces clones.
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what is the process of mitosis
- 1.chromosone becomes visible
- 2. replication
- 3. equator
- 4.poles
- 5. constriction
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what is meiosis used for?
Meiosis is used for cell reduction. It is used in the ovaries and testies. Results in production of sperm and eggs
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3 points on Mitosis
- takes place throughout the body
- important growth and replacing damaged cells
- all new cells have exactly the same chromosome arrangement as each other and parent cell.
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3 points on meiosis
- occurs in sex organs (testies and ovaries) only
- produces gametes
- produces gametes with half the number of chromosomes (haploid number) as other cells (diploid number)- ensures when gametes fuse the normal diploid number is restored
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Explain the base triplet hypothesis
a group of 3 bases which codes for a particular amino acid.
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A length of DNA consists of 180 bases. How many amino acids does this section code for?
30 because only 90 of the 180 are in the coding strand
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What is tissue cloning
cloning that involves treating small sections of plants with hormones to produce new plants
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what is cancer
uncontrolled cell division
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give 3 causes of cancer
- UV Radiation
- Chemicals in cigarette smoke
- Viruses
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what are the two types of tumour
- Benign- does not spread through body
- Malignant- spreads through body
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3 treatments for cancer
- surgery
- radiotherapy
- chemotherapy
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what are screening programmes for
designed to detect cancer at the earliest possible stage- before the cancer spreads
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what are genetics
the passing on of characteristics from parents to offspring
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what is a gene
short section of chromosome that codes for a characteristic
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what is an allele
a particular form of gene
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what does homozygous mean
both alleles of a gene are the same
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what does heterozygous mean
alleles of a gene are different
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what is a genotype
paired symbols showing the allele arrangement in an individual
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what is a phenotype
outward appearance of an individual
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Explain sexual reproduction
- Fertilisation occurs- restoring the diploid number, occurs in the oviduct to produce a gamete
- The gamete divides by mitosis to form an embryo
- The embryo implants in the uterus wall
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what does the placenta do
provides oxygen and nutrients to the foetus and removes carbon dioxide and urea
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what does the umbilical cord do
carries the umbilical artery and vein and links foetus to placenta
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what does the amnion do
contains the amniotic fluid which cushions the foetus
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state the 3 types of contraception and how they work
- mechanical (condom)-prevents sperm from entering
- chemical (contraceptive pill)-releases hormones preventing egg production
- surgical (vasectomy/sterilisation)-cutting of sperm tubes/oviducts
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give an adaptation of the placenta
large surface area for the diffusion of materials to and from the foetus
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name the 2 sex hormones and describe
- testosterone, produced by testes in males: sexual organs enlarge, voice deepens, body hair grows
- oestrogen, produced by ovaries in females: sexual organs and creates enlarge, pubic hair grows
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what is menstruation
blood rich uterine lining breaks down if pregnancy does not occur during previous menstrual cycle
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what is ovulation
14 days into the cycle an egg is released- by this time the uterine lining has built up in preparation for pregnancy
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give 3 treatments for fertility problems
- fertility drugs
- IVF
- replacing embryos
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what is a mutation
changes in the chromosome number or structure.
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what is skin cancer caused by
random changes to gene structure.
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what is down syndrome caused by
an error during meiosis. sometimes the 2 chromosomes in a pair fail to segregate properly, leaving one gamete with 24 chromosomes
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what is genetic screening used for
to identify the presence of genetic conditions in an individual
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give 3 possible issues for genetic screening
- whether it should be used for all genetic diseases
- whether we should be allowed to screen for the sex of the child
- whether results should be made available to insurance companies
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why is amniocentesis testing not compulsory for all mothers
there is a chance of miscarriage involved
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what is genetic engineering
adding a human gene to the DNA of another organism- which makes the product that the human DNA codes for
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what are enzymes needed for in genetic engineering
to cut out both the human insulin gene and a gap in the plasmid to allow the gene to fit into it
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How is human DNA cut
restriction enzymes cut the human gene in such a way as to leave overlapping strands of DNA. The same enzymes cut the plasmid the same way to leave complementary sticky ends. The human and bacterial DNA can then join through base pairing
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What is variation
Living organisms that belong to the same species resemble each other but usually differ in a number of ways. These differences are known as variation
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give and example of continuous variation and discontinuous
- continuous- height/weight
- discontinuous- tongue rolling
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Who was the first person to understand the significance of natural selection
Charles Darwin
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summarise natural selection
- variation exists between individuals in a population
- competition for resources means struggle for existence
- the best adapted survive and then breed to pass their genes to their offspring
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Explain antibiotic resistance
- When treated with an antibiotic some bacteria may already be resistant (due to mutation)
- These bacteria survive as the rest are killed
- The resistant bacteria survive to breed and soon become dominant in the population
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Explain the link between natural selection and evolution
Natural selection can explain how species have changed gradually over a long period of time in a process called evolution.
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What are the two main functions of the circulatory system
- transport-blood cells, food. carbon dioxide, urea
- protection- against disease
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how have red blood cells adapted to transport oxygen
- biconcave shape gives a large surface area
- absence of a nucleus to carry more haemoglobin
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what do white blood cells do and how
- defend against disease
- lymphocytes produce antibodies then phagocytes engulf and digest micro-organisms
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name the 3 types of blood vessels and their blood flow
- artery- away from heart
- vein- back to heart
- capillary- joins arteries and veins
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what connects the brain to the heart
jugular vein
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what connects the brain to all organs
carotid artery
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what connects the lungs to the heart
pulmonary vein
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what connects the liver to he heart
hepatic vein
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what connects the kidney to the heart
renal vein
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what connects the liver, small intest. and kidney to the heart
vena cava
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what is double circulation
the blood travels through the heart twice for each complete circuit of the body
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why are the valves important
to prevent back flow
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what is the difference between the left and right ventricles and why
left has thicker muscular wall to pump blood all round the body.
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why are the coronary arteries affected most in heart disease
- there are the arteries that supply the heart with blood
- they are very thing so get blocked easily
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what is a stroke caused by
circulatory blockages in the brain
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how is heart disease caused
build up of cholesterol or fats causing coronary arteries to narrow
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explain the relationship between plasma, tissue fluid and lymph
- blood pressure forces plasma through the capillaries and into the tissue fluid surrounding body cells
- the oxygen and glucose (from plasma) diffuse into body cells and replaced by carbon dioxide.
- the lymph vessels mop up the left over liquid, which then drains into the circulatory system
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explain the theory of spontaneous generation
Most people assumed that micro-organisms spontaneously appeared from non living material.
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what is pasteurisation
a technique used to reduce contamination of milk and other products by heating to a high temperature below boiling point then rapidly chilled to kill most bacteria present
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list 3 controlled variables in Pasteur's investigation
- the type of broth used must be constant throughout
- the flasks must be kept ar the same temperature
- must be left for the same amount of time
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what type of microbes are HIV, rubella, measles, mumps and polio
Viruses
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what type of microbes are salmonella, gonorrhoea, tuberculosis and chlamydia
Bacteriums
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why do antibodies have different shapes and sizes?
because each antibody has a unique shape complimentary to a type of microorganism it responds to.
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name the 2 natural immunities and explain
- innate- from birth (antibodies pass from mother to baby)
- acquired-develops during life
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name the 2 artificial immunities
- active- having a vaccination which causes the body to produce antibodies
- passive- antibodies from another source injected into body
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Who did the first vaccination? explain briefly
Jenner injected a boy with cowpox then sometime later with smallpox and he didn't catch the smallpox. The 2 diseases are very alike and so immunity built up to both diseases.
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what are antibiotics
chemicals that kill bacteria or reduce their growth
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what can the overuse of antibiotics result in?
the bacteria becoming resistant.
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what is a resistant bacteria known as
a superbug
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what effects does antibiotics have on bacterial and viral infections?
- only work against bacterial
- no effect on viral
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explain 3 ways that fermenters can maximise penicillin production
- optimum temperature for enzyme activity
- optimum oxygen levels for respiration
- nutrients added to prevent food source becoming limiting
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what effects does tar, nicotine and carbon monoxide have in the body
- tar- causes bronchioles to narrow (reducing area for gas exchange)
- nicotine- addictive and affects heart rate
- carbon monoxide- combines with red blood cells and reduces oxygen carrying capacity of the blood
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name 4 aseptic techniques
- not eating or drinking in lab
- culturing microbes in sealed containers
- flaming the necks of culture bottles to prevent contamination
- washing hands thoroughly at the end of work
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name and explain 3 initial defences against disease
- skin- acts as a barrier
- mucous membranes-trap and expel micro-organisms
- clotting- closes wounds quickly to prevent microorganisms entering.
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