Biology - Unit 1

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What is a balanced diet?
All of the nutrients in the correct amounts.
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How do you lose body mass?
Go on a slimming diet and exercise more
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Why do you lose body mass when dieting and exercising more?
More energy is being used up than taken in so the body is forced to use up stored fat for energy.
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What is the Metabolic Rate?
The rate at which chemical processes take place in the body
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What are the factors that affect metabolic rate?
Age, Genes, Amount of exercise, Gender, Pregnancy, Proportion of muscle to fat, Stress
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What are minerals and vitamins needed for?
To prevent deficiency diseases
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What is fibre needed for?
To prevent constipation
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What is water needed for?
To prevent dehydration
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What are carbohydrates needed for?
To provide energy
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What are fats needed for?
To provide insulation and energy storage
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How does anorexia affect the body?
No energy so weak immune system
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How does obesity affect the body?
Causes heart disease and diabetes
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How does salt affect the body?
Increases blood pressure which causes kidney damage
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How does a high level of cholesterol affect the body?
1. Plaque builds up in the wall of an artery 2. The plaque slows down the blood and a clot may form. 3. Clot blocks the artery so it cannot work, causing a heart attack
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What is low-density lipoprotein cholesterol?
'Bad' cholesterol which causes heart diseases
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What is high-density lipoprotein cholesterol?
'Good' cholesterol which protects against heart disease by helping to remove cholesterol from the walls of arteries
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What is a pathogen?
A micro-organism causing diseases.
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What is a bacteria?
A single-celled micro-organism which can reproduce very rapidly and produces toxins. Many are useful.
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What is a virus?
A micro-organism which reproduces rapidly inside a body cell and then destroys it when it bursts out. Invades other cells and is difficult to treat.
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What is an epidemic?
When a wide spread of people have a disease.
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What is a pandemic?
When the disease affects a whole country or goes worldwide.
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What is a white blood cell?
A blood cell which is involved with the immune system, engulfing bacteria, making antibodies and antitoxins
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How does a white blood cell defend the body? (1)
Ingestion - digests and destroys the pathogen by phagocytosis
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How does a white blood cell defend the body? (2)
Making antibodies - Lymphocytes produce chemicals called antibodies which attach to the pathogen's antigens and destroys the pathogen. A different antibody is required for each type of pathogen.
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How does a white blood cell defend the body? (3)
Making antitoxins - These counteract the toxins that pathogens produce and are also specific to the pathogen
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What are antibiotics?
Drugs that kill bacteria inside your body without killing your cells. E.g penicillin and streptomycin
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What are sources of contamination?
Soil, water, skin, or air
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What happens if a culture becomes contaminated?
Other bacteria could grow, including pathogens
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What does a culture medium contain?
-Carbohydrate as an energy source - Minerals - Sometimes other chemicals
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How do you keep the culture sterile?
Sterilise the petri dishes, agar, and other culture media by boiling, pass the inoculating loop through a flame to sterilise, tape pd halfway so oxygen doesn't contaminate the culture and the pathogens don't enter the air, max temp 25C
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Why is the maximum temperature 25C when culturing microorganisms in school?
At high temperatures bacteria grow and reproduce rapidly. Dangerous to incubate at 37C as harmful pathogens may grow.
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What happens when someone has a vaccine?
1. A dead/inactive cell of the disease is injected into the patient > Tricks immune system into responding > antibodies fight off harmful microbes > person is immune as wbc knows how to fight off the pathogen in the future.
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What happens during antibiotic resistance?
Due to natural selection, bacteria mutate randomly > When someone takes antibiotics, the normal bacteria are killed while the single bacterium is resistant > The bacterium has no competition and reproduces rapidly.
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Why do we need to reduce the use of antibiotics?
To reduce the chance of new strains forming
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Why is MRSA harmful?
It's resistant to most antibiotics
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What does MMR immunise against?
Measles, Mumps, and Rubella
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What are neurons?
Nerve cells which are found in nerves. They carry electrical impulses.
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What are the steps in the reflex action?
The receptor detects the stimulus > a sensory neuron transmits the impulse to the CNS > a relay neuron passes the impulse on > a motor neuron is stimulated > the impulse passes to an effector > response
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What is a synapse?
A gap between two neurons
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What happens at a synapse?
Chemical neurotransmitters diffuse across the gap and start an electrical impulse along the next neurone.
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How do muscles respond?
By contracting
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How do glands respond?
By secreting chemicals
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How do you lose water?
Through breathing, sweat, and urine
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How does sweating help you to lose heat?
The sweat gland secretes sweat > the sweat lies on the surface of the hot skin > the water in the sweat evaporates which takes heat from the skin
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How does the body lose heat?
By radiation from the skin and from the evaporation of sweat
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How do the kidneys help to keep the balance of water and ions?
By varying the amount of water and salt excreted from your body to urine
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How are ions lost?
Via sweat and water
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How is the temperature controlled in the body?
Blood sugar levels
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Why does the human body temperature need to be kept at 37C?
This is the temperature at which our enzymes work best
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What do hormones do?
Regulate the functions of the cells
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What is the process of hormones?
Secreted by glands and transported in the bloodstream
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What is the process of the menstrual cycle?
FSH secreted by the pituitary glands - eggs mature and stimulates ovaries to produce oestrogen > Oestrogen - lining of uterus grows thicker, stops production of FSH > LH stimulates the release of the eggs
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How are oral contraceptives used to inhibit FSH production?
Oestrogen to inhibit egg maturation, birth control pills, progesterone
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How does the rise of the concentration of oestrogen prevent pregnancy?
Causes the uterus lining to thicken so sperm can't enter
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What is IVF?
FSH + LH are given to the mother to stimulate eggs maturing > eggs are removed and fertilised with partner's sperm > balls of cells (embryo) is inserted into the mother's womb
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What is phototropism?
A growth response to light
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What is gravitropism?
A growth response to gravity
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What is auxin?
A plant hormone which makes cells in shoots get longer.
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Where is auxin made?
In the shoot tip
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What does auxin control?
Phototropism and gravitropism
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How does auxin make a shoot grow towards light?
When light shines onto a shoot, auxin diffuses down the shoot and is transported to the shady side, the cells grow longer where there is more auxin and the shoot bends towards the light
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How does auxin make a root grow towards gravity?
Auxin tends to accumulate on the lower side of a root where it reduces the rate of growth so the lower side of the shoot grows more slowly than the upper surface. This causes the root to bend downwards.
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When are plant growth hormones used?
In weed killers / rooting hormones
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What are plants sensitive to?
Light / Moisture / Gravity
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What do roots grow to?
Moisture
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Why do plants respond to light, gravity, and moisture?
Unequal distribution of hormones
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What are three things tested in drugs?
Toxicity / Efficacy / Dose
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Why are statins used?
Lowering the risk of heart and circulatory diseases
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How are drugs tested?
First tests are in scientific labs on cells, tissues, and organs > if those work they are tested on animals > tested on human volunteers > given to patients
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What is a placebo?
A substance that contains no drug and are used in medicine trials
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Why are patients given placebos?
To determine whether the drug really works
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What is a double-blind trial?
It means neither the doctor nor the patient know who has been given the drug or the placebo
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What is Thalidomide?
It was developed as a sleeping pill but could relieve morning sickness
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Why was Thalidomide banned?
Drugs hadn't been tested on pregnant women and caused limb deformities on the baby
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What is Thalidomide used to cure now?
Leprosy
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What are the effects of cannabis?
Mental illness, teenagers are at risk of depression, it can bring people into contact with harder drugs.
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Why do people become addicted to drugs?
They change the chemical processes in the body
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What are cigarettes made up of?
Tobacco (mixture of gases), tar droplets, and ash particles (4000 chemicals)
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What is the effect of carbon monoxide?
It attaches to red blood cells and stops them carrying oxygen
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What are the diseases linked to smoking?
Lung/throat/liver/mouth cancer, heart disease, and emphasima etc
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What are the problems with performance enhancing drugs?
They can damage the body permanently, they are unethical, they are legal drugs used illegally.
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Which performance enhancing drugs are banned?
Steroids - can stimulate the body to grow stronger muscles, Beta Blockers - can help someone stay calm and steady, Stimulants - Can increase the heart rate
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What is an adaptation?
A special feature that makes an organism particularly well suited to the environment where it lives
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What is a herbivore?
An animal that only feeds on plants
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What is a carnivore?
An animal that only eats other animals
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What do plants compete for?
Light / Space / Water / Nutrients / Spread their seeds over a wide area so they don't compete with themselves
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What do animals compete for?
Food / Mates / Territory/ Predators compete with prey / Prey compete with themselves to escape predators
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What do plants that live in dry conditions usually have?
Long, wide-spreading roots - the roots grow deep into the soil to reach water, Small/no leaves- the smaller the leaf SA, the less the amount of water evaporating, tissues that can store water
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What do animals that live in dry conditions usually have?
Large ears-large SA helps the body lose heat and stay cool / conserve water / hunt/feed at night to stay cool
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How do camels survive without much water?
Stomachs can hold over 20 litres of water, drink quickly, store water as fat in humps, produce very little urine
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How are animals that live in arctic conditions adapted?
Thick fur/layers of fat - insulation helps the animal reduce heat loss, white - camouflage against snow, changes to SA
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What other adaptations do plants and animals have?
Thorns, poisons, and warning colours to deter predators.
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What are the impacts of change in environment?
The distribution of living organisms/ Birds may fly North if climate is warmer/ decreased bee population due to viral diseases and changes in flower patterns
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What are extremophiles?
An organism which lives in environments that are very extreme e.g very high/low temperatures/pressures
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What can lichen be used as?
Indicators of the concentration of sulphur dioxide in the air
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How are lichen used as indicators of sulphur dioxide?
The higher the number of different lichen species that grow in the area, the lower the levels of sulfur dioxide in the air
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What can invertebrate animals be used as?
Indicators for the concentration of pollution / oxygen in water
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What equipment is used to monitor non living changes?
Rain gauges, thermometers, pH and oxygen sensors, data loggers
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What are living factors?
Plants / predators / disease
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What are non-living factors?
Temperature / light / oxygen / rainfall
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What is the source of energy for most organisms?
The sun
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What is biomass?
The mass of living material in plants and animals
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What does a pyramid of biomass represent?
The mass of the organisms at each stage in a food chain
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Why do green plants only capture a small amount of energy?
Some light- Misses the leaves altogether/Hits the leaf and reflects back from the leaf surface/ hits the leaf without hitting any chlorophyll/ Hits the chlorophyll but is not absorbed as it's the wrong wavelength
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What are detritus feeders?
A microorganism that breaks down waste products and dead bodies
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What conditions cause decay to be quicker?
Warm / Moist / Aerobic conditions
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What does the decay process do?
Release substances plants need
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What is the carbon cycle?
Photosynthesis removes Co2 from the atmosphere > plants and animals respire returning Co2 to the atmosphere > cutting down and burning trees, releases Co2 > MOs release Co2 through respiration when decomposing dead bodies
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Where are chromosomes found in a cell?
In the nucleus
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What do genes control?
Characteristics
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What makes species different?
Genetic and environmental causes
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What do chromosomes carry?
Genes
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What is sexual reproduction?
Reproduction which involves the fusion of male and female gametes producing genetic variety in the offspring
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What is asexual reproduction?
Reproduction that involves only one individual with no fusing gametes to produce the offspring. The offspring are identical to the parent.
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What is a clone?
Offspring produced by asexual reproduction which is identical to it's parent organism
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What are three modern cloning techniques?
Tissue culture / Embryo transplants / Adult cell cloning
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Why do people clone plants?
It is cheap and effective.
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How can new plants be produced quickly?
By taking cuttings of stems from the parent plant and dipping the ends in hormone rooting powder. They are then placed in soil and grow into new plants which are genetically identical.
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What is the process of tissue culture?
A small piece of tissue is taken from a root, stem or leaf to the parent plant > the tissue is then grown on a jelly containing nutrients > tiny groups of cells grow into a complete adult plant
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What is the process of embyro transplants?
Egg cells are taken from a female animal and fertilised with the sperm from a male, one embryo is split and becomes specialised before transplanted into the host mother
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What is the process of adult cell cloning?
Nucleus is removed from an unfertilised egg cell > N is taken from another cell in an adult's body > N is put into egg cell > EC is given an electric shock to form an embryo > once the embryo has developed it is inserted into host mother
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What are the advantages of adult cell cloning?
Development of cloned animals which have been GE to produce valuable characteristics/ Cloning can save animals from extinction
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What are the disadvantages of adult cell cloning?
Concerns about ethics / cloning limits the variation in population, problem for natural selection / concerns about using the technique to clone humans in the future
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What is genetic engineering?
A technique for changing the genetic information of a cell
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What is the process of genetic engineering?
Genes can be transferred to the cells of animals/plants/MOs at early stage of development > gene is cut out of the organism using enzyme > the gene is placed in the chromosome of another organism > genes may be placed in same species for desired char
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How have bacteria been genetically engineered to make human insulin?
insulin gene is cut out using enzymes/ chromosome is taken out of bacterium and split open > insulin gene is inserted into bacterium's chromosome > chromosome is put back into a bacterium > bacterium divides to make more bacteria, containing the gene
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What are GM crops resistant to?
Insects / herbicides
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Why are GM crops used?
To increase yield / Keep prices down / Reduces amount of pesticide sprayed
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What is evolution?
The process of slow change in living organisms over long periods of time as those best adapted to survive breed successfully
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What was Jean-Baptiste Lamarck's theory?
Inheritance of acquired characteristics - characteristics that are developed during an organism's lifetime can be passed on to the next generation
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What is Charles Darwin's theory?
Natural Selection - small changes in organisms took place over a very long time. All organisms in a species vary and therefore some are more likely to survive. Those that are best adapted breed and pass on their genes
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Why was Charles Darwin's theory only gradually accepted?
The theory challenged the idea that God made everything / Many scientists weren't convinced as there wasn't sufficient evidence / mechanism of inheritance and variation wasn't known
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How does natural selection work?
Living organisms produce many offspring > the offspring may vary from one another due to differences in their genes > some have a better chance of survival and are most likely to reproduce > genes will be passed on to offspring
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How do mutations affect an organism?
Unpredictable changes to chromosomes and genes happen > new form of gene increases an organism's chance of surviving and reproducing > likely to be passed on to next generation > over time the new feature becomes more common in the species
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