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Flashcards by Isabel Knight, updated more than 1 year ago
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Created by Isabel Knight
over 7 years ago
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| Question | Answer |
| Name all the food groups you should eat to have a balanced diet. | CARBOHYDRATES- to release energy FATS- to keep warm and release energy PROTEINS- for growth, cell repair and cell replacement FIBRE- to keep everything moving smoothly through your digestive system VITAMIN and MINERAL ions-to keep skin, bones, blood...etc generally healthy |
| What is meant by the terms Metabolism and Metabolic rate? | METABOLISM: the chemical processes that occur within a living organism in order to maintain life. METABOLIC RATE: the speed at which such chemical reactions take place in the body. |
| What factors determine your metabolic rate? | 1)age 2)gender 3) the proportion of muscle to fat in the body 4)the amount of exercise and other physical activity 5)genetic traits |
| What can eating too much lead to? | 1)Obesity (20% over maximum recommended body mass) 2)An increased blood cholesterol level (too much saturated fat) 3)High blood pressure and heart problems (too much salt) |
| What health problems can arise as a result of obesity? | 1)Arthritis (inflammation of the joints) 2)Type 2 diabetes (inability to control blood sugar level) 3)High blood pressure 4)heart disease 5)Risk of some cancers |
| What can eating too little lead to? | 1) Slow growth (in children) 2) Fatigue 3) Poor resistance to infection 4) Irregular periods in women 5)Deficiency diseases (caused by lack of vitamins or minerals) -e.g. lack of vitamin C causes scurvy (causes problems with the skin, joints and gums) |
| What is Cholesterol? | Cholesterol is a substance found in the blood. It is made in the liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease, and of diseased arteries. |
| Give examples of how Inherited factors can affect your health. | -Some inherited factors cause an underactive thyroid gland which can lower the metabolic rate and cause obesity. -Some may affect their blood cholesterol level |
| Describe the 2 main types of Pathogen. | BACTERIA: very small living cells about 1/100th the size of your body cells. They can reproduce rapidly inside your body. They make you feel ill by -damaging your cells -producing toxins (poisons) VIRUSES: not cells- are 1/100th the size of bacterium. They replicate themselves by invading your cells and using the cells machinery to produce copies of themselves- cells burst releasing new viruses. Cell damage is what makes you feel ill. |
| What are vaccinations? | Vaccinations involve injecting small amounts of dead or inactive microorganisms (carrying antigens that cause the body to produce antibodies) which protect the body from future infections. E.g. MMR vaccine contains weakened versions of the viruses that cause measles, mumps and rubella. |
| What can be taken if a vaccination wears off? | Booster injections, to increase levels of antibodies again. |
| Give the PROS and CONS of vaccinations. | PROS: -Vaccines have helped control lots of infectious diseases that were once common (Smallpox and Polio infections) -Epidemics (big outbreaks of disease) can be prevented if a large percentage of the population is vaccinated. CONS: -Vaccines don't always work (sometimes don't give you immunity) -you can have bad reactions (rare) |
| What new dangers can we face with Bacteria? | -Bacteria can mutate to produce NEW STRAINS -A new strain could be antibiotic resistant meaning current treatments would no longer clear the infection -A new strain-never encountered before-no-one would be immune -New strain could spread rapidly-cause an epidemic |
| What new dangers can we face with Viruses? | -They MUTATE often-hard to develop vaccines against them as the changes in their DNA lead them to having different antigens. -A virus could evolve so that it was both deadly and very infectious (flu virus-a flu pandemic could kill billions of people all over the world) |
| Describe 3 ways the Immune system defends the body against invading microbes. | 1)WBC's engulf foreign cells and digest them 2)Producing Antibodies: WBC's produce proteins (antibodies) to kill invading cells -specific to types of antigen contained in every invading cell Antibodies produce rapidly-kill similar pathogens around the body- body becomes naturally immune to that pathogen 3)Producing Antitoxins: counteract toxins produced by the invading bacteria |
| What do painkillers do? | Painkillers (e.g. aspirin) are drugs that relieve pain but don't actually cure the disease-only reduce the symptoms. |
| What do antibiotics do? | Antibiotics (e.g. penicillin) kill/prevent the growth of the bacteria causing disease without killing your own body cells. Different antibiotics kill different types of bacteria but antibiotics don't destroy viruses (e.g. flu/cold) as they reproduce using your own body cells-very difficult to develop drugs that destroy just the virus without the body's cells. |
| How can bacteria become resistant to some antibiotics? | Bacteria can mutate-sometimes cause them to to be resistant to an antibiotic. The individual resistant bacteria will survive and reproduce and the population of the resistant strain will increase (example of natural selection). This resistant strain could cause a serious infection that can be treated by antibiotics (e.g. MRSA- methicillin-resistant Strahylococcus aureus- causes serious wound infections-resistant to the antibiotic methicillin) |
| How do you slow down the development of resistant strains? | Doctors should avoid over-prescribing antibiotics and don't use them for a sore throat-only for something more serious. |
| How can you investigate or test the action of antibiotics? | Growing cultures of microorganisms in a 'culture medium'-usually agar jelly containing the carbohydrates, minerals, proteins and vitamins they need to grow. |
| How did Ignaz Semmelweis reduce death rates from puerperal fever? | While working in Vienna General Hospital in the 1840's, Semmelweis saw that women were dying in huge numbers after childbirth from puerperal fever. He believed hat doctors were spreading the disease on their unwashed hands. By telling doctors entering his ward to wash their hands in an antiseptic solution, he cut the death rate from 12% to 2%. |
| What is the Central Nervous System? | (CNS) is where all the information from the sense organs is sent and where reflexes and actions are coordinated. It consists of the brain and spinal cord only. Neurones transmit the electrical impulses very quickly to and from CNS. 'instructions' fro the CNS are sent to the effectors which respond accordingly. |
| What are Neurones and give 3 examples? | Nerve cells: -Sensory neurones (carry signals as electrical impulses from the receptors in the sense organs to the CNS) -Relay neurones (carry signals from sensory to motor neurones) -Motor neurones (carry signals from the CNS to the effectors) |
| What are Effectors? | They are Muscles and Glands. They respond in different ways. Muscles contract in response to a nervous impulse whereas glands secrete hormones. |
| List 5 sense organs and the receptors that they contain. | 1) EYES- light receptors 2) EARS- Sound receptors 3) NOSE- Smell receptors 4) TONGUE- Taste receptors 5) SKIN- sensitive to touch, pressure, pain and temperature change |
| Give the sequence of the Reflex Arc. | 1) STIMULUS (e.g. a painful bee sting) 2) RECEPTOR 3) Impulses are sent along a sensory neurone to the CNS. 4) When the impulses reach a synapse between the sensory and relay neurone, they trigger chemicals to be released-cause impulses to be sent along the RELAY NEURONE 5) synapse between the relay and motor neurone-chemicals released-impulses along the motor neurone. 6)impulses travel along the motor neurone to the effector. 7)(e.g. muscle contracts)-reflex |
| What are Synapses? | The connection between two neurones. The nerve signal is transferred by chemicals which diffuse across the gap. These chemicals then set off a new electrical signal in the next neurone. |
| Give the 4 stages of the Menstrual Cycle | STAGE 1) Day 1 is when the bleeding starts- the uterus lining breaks down for about 4 days. STAGE 2) The lining of the uterus builds up again from day 4-14 into a thick spongy layer full of blood vessels ready to receive a fertilised egg. STAGE 3) An egg is released from the ovary at day 14 STAGE 4) The wall is maintained for about 14 days until day 28-stages repeated if no fertilised egg has landed on the uterus. |
| What is FSH? | Follicle-Stimulating Hormone: -produced by the pituitary gland -causes an egg to mature in one of the ovaries -stimulates the ovaries to produce oestrogen |
| What is Oestrogen? | -Hormone produced in the ovaries -causes pituitary to produce LH -inhabits the further release of FSH |
| What is LH? | Luteinising Hormone: -produced by the Pituitary gland -stimulates the release of an egg at around the middle of the menstrual cycle. |
| List 4 hormones involved in the Menstrual Cycle | 1)FSH 2)Oestrogen 3)LH 4)Progesterone |
| What are hormones? | Hormones are chemical messengers which travel in the blood to activate target cells. |
| What are the difference between Nerves and Hormones? | NERVES: -very fast action -Act for a very short time -Act on a very precise area HORMONES: -slower action -act for a long time -act in a more general way |
| How is the 'pill' used to reduce fertility? | It is an oral contraceptive(made in the 1950's) containing high levels of oestrogen and progesterone. Oestrogen an be used to prevent the release of an egg when taken everyday as the permanent high levels of the hormone inhabit the production of FSH. Progesterone reduces fertility by stimulating the production of thick cervical mucus which prevents sperm from reaching an egg. |
| What are the PROSand CONS of using the 'pill'? | PROS: -over 99% effective at preventing pregnancy -reduces the risk of getting some types of cancer CONS: -isn't 100% effective-still chance of pregnancy -can causes side effects (e.g.headaches, nausea, irregular periods, fluid retention) -doesn't protect against STD's |
| Give the PROS and CONS of increasing fertility by injecting women with FSH and LH hormones to stimulate egg release in their ovaries. | PROS: Helps women get pregnant CONS: -it doesn't always work- may have to be repeated which is expensive -too many eggs could be stimulated, resulting in unexpected multiple pregnancies |
| What is IVF? | "In Vitro Fertilistion" involves collecting eggs for the woman's ovaries and fertilising them in a lab using the man's sperm. These are grown into embryos. Once these are tiny balls of cells, 1 or 2 of them are transferred to the woman's uterus to improve the chance of pregnancy. |
| What are the PROS and CONS of using IVF? | PRO: can give an infertile couple a child CONS: -some women have a strong reaction to the hormones (e.g. Abdominal pain, vomiting , dehydration) -may increase the risk of cancer due to the hormonal treatment. -Multiple births may occur if more than 1 embryo grows into a baby-higher risk of miscarriage |
| What is Auxin? | A plant hormone that controls growth near the tips of roots and shoots in response to light (phototropism), Gravity (gravitropism/geotropism) and moisture. |
| How does auxin cause plant shoots to grow towards light? | When a shoot tip is exposed to light, more auxin accumulates on the side that's in the shade than the side in the light. This makes the cells grow(elongate) faster on the shaded side so the shoot bends towards the light. |
| How does auxin cause plant shoots to grow away from gravity? | When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the lower side to grow faster, bending the shoot upwards. |
| How does auxin cause plant roots to grow towards gravity? | A root growing sideways will also have more auxin on its lower side. But in a root the extra auxin inhabits growth. This means the cells on top elongate faster, and the root bends downwards. |
| How does auxin cause plant roots to grow towards moisture? | An uneven amount of moisture either side of a root produces more auxin on the side with more moisture. This inhabits growth on that side, causing the root to bend in that direction, towards the moisture. |
| Give 2 ways plants hormones are used in agriculture? | 1)Selective WEEDKILLERS- made up of plant growth hormones-only affect broad-leaved plants. They disrupt their normal growth patterns, which soon kills them but leave the crops untouched. 2)ROOTING POWDER (contain auxin)-produce roots rapidly-start growing like new plants-produce lots of clones very quickly. |
| How is ion content controlled in the body? | Ion content is regulated by the KIDNEYS. Ions (e.g. sodium) are taken into the body in food, then absorbed into the blood. Some ions are lost in sweat. Kidneys remove the excess from the blood-removed via urine. |
| Give 3 ways water is lost from the body. | 1)through the SKIN as SWEAT 2)via the LUNGS in BREATH 3)via the KIDNEYS as URINE |
| Give the difference in the balance of sweat and urine in the body on a COLD day when you're NOT EXERCISING and on a HOT day when you're EXERCISING. | COLD day (no exercise): -don't sweat much -produce more urine (pale- waste is more diluted) HOT day (exercise): -sweat a lot -produce less urine (more concentrated) -lose more water through your breath |
| How is temperature kept constant in the body? | Body temperature is controlled by the BRAIN. All enzymes work best at a certain temperature-human body (37%) Part of the brain is sensitive to the blood temperature and receives messages from the ski to provide info about skin temp. |
| How is Blood Sugar Level controlled in the body? | It is maintained with the hormone INSULIN so your cells get a constant supply of energy. The normal metabolism of cells removes glucose from the blood but with more vigorous exercise more glucose is lost so insulin is used to help. |
| What is Homeostasis? | Homeostasis is the maintenance of a constant internal environment. The nervous system and hormones are responsible for this. |
| Give 2 examples of Performance-enhancing drugs and a possible negative health effect. | 1) Anabolic steroids (increase muscle size)-can cause HIGH BLOOD PRESSURE 2)Stimulants (increase heart rate) |
| Give arguments for and against using performance-enhancing drugs in sport. | AGAINST: -unfair if people gain an advantage through drugs instead of training -Athletes may not be fully informed of the serious health risks. FOR: -Athletes have the right to make their own decision -Drug-free sport isn't fair anyway-different athletes-different coaches, training facilities, equipment |
| What is the drug Statins? | Statins are prescribed drugs used to lower the risk of heart and circulatory disease. There's evidence it lowers blood cholesterol and significantly lowers risk of heart disease for diabetics. Research was done by the government, comparing 2 groups of students(had taken/hadn't taken) |
| What are some claims about Cannabis? | Cannabis is an illegal drug. Scientists have investigated whether the chemicals in cannabis smoke cause mental health problems-the results vary. |
| Describe the 3 main stages of drug testing. | 1)Drugs are tested on human cells and tissues in the lab 2)Test drug on live animals-see if the drug works, it's toxicity and the most effective dosage 3)tested on human volunteers in a clinical trial (blind/double blind-2 groups (placebo))-first healthy volunteers (see if there are harmful side effects-second, people suffering from the illness. |
| Explain the unfortunate consequence using the drug Thalidomide in the 1950's caused. | Thalidomide was intended as a sleeping pill-later found to be effective for relieving morning sickness in pregnant women. However, it hadn't been tested for morning sickness so it wasn't know it could pass through the placenta and affect the fetus, causing abnormal limb development. Approx. 10,000 babies were affected and only half of them survived. The drug was banned. |
| Briefly describe how a double-blind drug trial works. | Neither the patient nor the doctor knows until all the results have been gathered so the patients don't know whether they have the placebo or the drug and the doctors monitoring the patients and analysing the results aren't subconsciously influenced by their knowledge. |
| Describe 3 opinions about the link between cannabis and hard drug use. | 1)Cannabis is a 'STEPPING STONE'-effects of it creates a desire to try harder drugs. 2)Cannabis is a 'GATEWAY DRUG'- brings people into contact with drug dealers 3)It's down to genetics- certain people are more likely to take drugs generally, cannabis users will try other drugs |
| Which has the bigger impact on society in the UK, legal or illegal drugs and why? | LEGAL: Tobacco and alcohol are taken by many people meaning the NHS spend loads of money on people with lung diseases caused by smoking and the injuries commonly cause by drinking alcohol (crime and the economy effects) |
| What are the medical affects of Smoking and Alcohol? | SMOKING: -smoking causes disease of the heart, blood vessels and lungs -Tobacco causes cancer -Nicotine is addictive ALCOHOL: -affects the nervous system-slows body's reactions -too much can lead to impaired judgement, poor coordination and unconsciousness -can cause liver disease and brain damage -addictive |
| Give 4 ways desert animals have adapted. | 1) Large surface area compared to volume- lose more body heat 2) Efficient with water- lose less water (small amounts of concentrated urine)- very little sweat 3)Good in hot conditions- thin layers of body fat + a thin coat-lose body heat 4)Camouflage- sandy colours- avoid predators/sneak up on prey |
| In what 3 ways have Arctic animals adapted to reduce heat loss? | 1) Small surface area compared to volume 2) Well insulated- thick layer of blubber- acts as an energy story when food is scarce- thick hairy coats-keep body hair in. 3) Camouflage- white fur-avoid predators/sneak up on prey |
| How have desert plants adapted to having little water? | 1) Small surface area compared to volume- (x1000 smaller)- plants lose water vapour on surface of leaves-cacti have spines instead of leaves 2) Water storage tissues-e.g. store water in thick stem (cactus) 3) Maximising water absorption-e.g. cacti have shallow but extensive roots-absorb water quickly over a large area. or some plants have deep roots-underground water |
| Give examples of how plants and animals have adapted to deter predators. | 1) Armour- e.g. roses (thorns), cacti (sharp spines), tortoises (shells) 2) Poisons- e.g. bees + poison ivy 3) Warning colours to scare off predators- e.g. wasps |
| Why do some microorganisms have a huge variety of adaptations? | Some microorganisms (e.g. bacteria) are known as extremophiles- they're adapted to live in seriously extreme conditions like super hot volcanic vents, in very salty lakes or at high pressure on the sea bed. |
| What environmental properties do plants and animals need in order to survive and reproduce? | PLANTS: light, space, water, minerals (nutrients) from the soil. ANIMALS: space (territory), food, water, mates |
| List 4 living factors that cause environmental changes. | 1) A change in the occurrence of infectious diseases 2) A change in the number of predators 3) A change in the number of prey or the availability of food resources 4) A change in the number or types of competitors |
| List 3 Non-living factors that cause environmental changes. | 1) A change in average temperature 2) A change in average rainfall 3) A change in the level of air or water pollution |
| Give 3 ways environmental changes can affect animals and plants. | 1) Population SIZE INCREASES- prey increases, more food for predators-survive and reproduce-increased numbers 2) Population SIZE DECEASES- number of bees in the US is falling because of pesticides, less food and more disease 3) Population DISTRIBUTION CHANGES- distribution of birds species in Germany is changing because of a rise in temp. |
| Explain how lichen can be used as an indicator of air pollution. | Particular types of lichen are very sensitive to the concentration of sulphur dioxide in the atmosphere and so give a good idea about the level of pollution from car exhausts, power stations. etc... The number and type of lichen at a particular location will indicate how clean the air is (e.g. air is clean if there are lots of lichen) |
| Name an organism that can be used as an indicator of water pollution. | Invertebrate animals, like MAYFLY LARVAE, are good indicators for water pollution because they're very sensitive to the concentration of dissolved oxygen in the water. If raw sewage is released into a river, the bacterial population in the water increases and uses up oxygen. Finding mayfly larvae indicates the water is clean. |
| Give 4 examples of non-living indicators to find out about environmental change. | 1) SATELLITES- measure the temp. of the sea surface and the amount of snow and ice cover. 2) AUTOMATIC WEATHER STATIONS- shows atmospheric temp. at various locations. They contain thermometers that are sensitive and accurate 3) RAIN GAUGES measure annual average rainfall 4) DISSOLVED OXYGEN METERS- measure the concentration of dissolved oxygen in water- discover how the level of water pollution is changing. |
| What does each bar on a pyramid of biomass represent? | Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain (how much all the organisms would 'weigh' all together at each level) |
| Give 2 ways that energy is lost from a food chain. | 1)Most of the energy is lost to the surroundings as heat 2) Energy is also lost in the organisms' waste materials |
| Give 4 features of a compost bin that aid the process of decomposition? | 1) Extra decomposes added (compost maker) 2) Finely shredded waste is best 3) Warmth generated by decomposition helps it all along 4) Mesh sides to let air in |
| What is meant by the term stable community? | In a stable community the materials taken out of the soil and used are balanced by those that are put back in. There's a constant cycle happening. |
| Name 4 elements plant take in from the air and how they are returned to the environment? | 1) carbon 2) oxygen 3) hydrogen 4) nitrogen These elements are returned to the environment in waste products produced by the organisms (in the food chain) or when the organisms die. These materials decay because they're broken down by microorganisms. |
| Give 5 ways that carbon compounds in a food chain become carbon dioxide in the air again. | 1) When PLANTS + ALGAE RESPIRE 2) Some of the carbon becomes parts of fats + proteins in animals when plants (+algae) are eaten- carbon moves down the food chain- ANIMALS RESPIRE 3) decay- microorganisms and detritus feeders feed on remains- ORGANISMS RESPIRE 4) useful plant + animal products e.g. WOOD- burnt (combustion) 5) useful plant + animal products e.g. FOSSIL FUELS- burnt (combustion) |
| Describe the 2 types of variation. | 1) GENETIC VARIATION- an organism's characteristics are determined by the genes inherited from their parents which are passed on in gametes (sex cells). The combination of the mother and the father's genes causes genetic variation. 2) ENVIRONMENTAL VARIATION-the environment that organisms live and grow in causes differences between members of the same species. |
| Name 3 animal characteristics that are determined only by genes. | 1) Eye colour 2) Blood group 3) Inherited disorders (e.g. haemophilia or cystic fibrosis) |
| What animal characteristics are determined by a mixture of genes and the environment? | -body weight -height -skin colour -condition of teeth -academic or athletic prowess |
| Give the difference the environment would have on a plant grown on a sunny windowsill compared to a plant grown in the dark. | SUN: plant would grow luscious and green DARK: plant would grow tall and spindly- leaves would turn yellow |
| What was Lamarck's hypothesis about evolution and why was it rejected? | Lamarck (1744-1829) argued that if a characteristic was used a lot y an organism then it would become more developed during it's lifetime. The acquired characteristics would be passed on to the next generation. It was rejected because experiments didn't support his hypothesis (e.g. dying a hamsters fur pink would not mean that the offspring's fur would be pink-it would be normal colour) |
| What are chromosomes and how many are contained in: 1) the human cell nucleus? 2) gametes? | A chromosome is a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. 1) 23 pairs (1 from each parent) 2) 23 (half the number in a normal cell) |
| What is Sexual Reproduction? | Sexual Reproduction involves the fusion of male and female gametes. Because there are 2 parents, the offspring contain a mixture of their parents' genes. |
| What is Asexual Reproduction? | In Asexual Reproduction there is only 1 parent. There's no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offspring are genetically identical to the parent (clones) |
| Describe 2 ways plants can be cloned. | 1) CUTTINGS- gardeners takes cuttings from good parent plants and then plant them to produce genetically identical copies (quickly and cheaply) 2) TISSUE CULTURE- a few plant cells are put in a growth medium with hormones and they grow into new plants (clones) (quickly, in very little space and can be grown all year) |
| How can you make animal clones using embryo transplants? | Sperm cells and egg cells are taken from the best animals. The sperm are used to artificially fertilise the egg cell. The embryo that develops then splits many times to form clones. The cloned embryos are implanted into many other animals (genetically identical offspring). e.g. a farmer may clone their best bull and cow |
| How can you make a clone using Adult Cell Cloning? | it involves taking an unfertilised egg cell and removing it's genetic material (nucleus). A complete set of chromosomes from an adult body cell is inserted into the empty egg cell which is then stimulated by an electric shock to make it divide. When the embryo is a ball of cells, it's implanted into an adult female to grow into a clone. e.g. Dolly the sheep (clone) |
| Give the advantages and disadvantages of cloning. | PROS: -may lead to greater understanding of the development of the embryo, and of ageing and age-related disorders -could preserve endangered species CONS: -could get 'reduced gene pool'- fewer different alleles in a population- easily wiped out with no allele giving resistance to a disease -clones may not be as healthy (e.g. Dolly the sheep had arthritis) -success on humans may follow many unsuccessful attempts |
| What is genetic engineering and how does it work? | The deliberate modification of the characteristics of an organism by manipulating its genetic material. A useful gene is 'cut' from one organism's chromosomes using enzymes which are then used to cut another organism's chromosomes and insert the useful gene. |
| Give 3 examples of useful applications of genetic engineering. | 1) Genetically modified (GM) crops (e.g. make them resistant to viruses, insects or herbicides) 2) Sheep have been genetically engineered to produce substances, like drugs, in their milk- can treat human diseases 3) Genetic disorders (e.g. cystic fibrosis) are caused by faulty genes- gene therapy is used (insert working genes) |
| Why are people concerned about genetic modified crops? | -growing GM crops will affect the number of weeds + flowers- population of insects- reducing farmland biodiversity -may develop allergies from GM crops-(unproven) -transplanted genes may get out into the natural environment- the herbicide resistance gene may be picked up by weeds- create new 'super-weed' |
| Give the advantages of GM crops. | -can increase the yield of a crop, making more food -lack of nutrients can be engineered to contain the nutrients that are missing (e.g. 'golden rice' contains beta-carotene -lack of this substance causes blindness -GM crops are being used elsewhere in the world without any problems |
| What is the theory of evolution? | More than 3 billion years ago, life on Earth began as simple organisms from which all the more complex organisms evolved. |
| Explain Darwin's theory of natural selection. | -Individuals within a species show variation because of the differences in their genes -Individuals with characteristics that make them better adapted to the environment have a better chance of survival- more likely to breed successfully- passed on to the next generation |
| How can evolution occur from mutations? | A mutation is a change in an organism's DNA which can occasionally be beneficial by producing a useful characteristic giving them a better chance of surviving and reproducing (natural selection) |
| Give 3 reasons why Charles Darwin's theory of evolution by natural selection was controversial. | 1) It went against common religious beliefs about how life on Earth developed (God) 2) Darwin couldn't give a good explanation for why these new useful characteristics appeared or how they were passed on through generations (didn't know about genes or mutations) 3) There wasn' enough evidence to convince many scientists |
| What are alleles? | Different versions of the same gene. |
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