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Creado por lauramarypowell
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| Pregunta | Respuesta |
| How have desert animals adapted to save water and keep cool? | 1) Large surface area compared to volume - this lets animals lose more body heat which helps to stop them overheating. 2) Efficient with water: a) Desert animals lose less water by producing small amounts of concentrated urine. b) They also make very little seat. Camels are able to do this by tolerating big changes in body temperature, while kangaroo rats live in burrows underground where it's cool. 3) Good in hot conditions - desert animals have very thin layers of body fat and a thin coat to help them loss body heat. E.g. camels keep nearly all their fat in their humps. 4) Camouflage - A sandy colour gives good camouflage to help them avoid predators or sneak up on prey. |
| How have arctic animals adapted to reduce heat loss? | 1) Small surface area compared to volume - animals living in cold conditions have a compact shape to keep their surface area to a minimum this reduces heat loss. 2) Well insulated: a) They also have a thick layer of blubber for insulation this also acts as an energy store when food is scares. b) Thick hairy coats keep body heat in, and greasy fur sheds water (this prevents cooling due to evaporation). 3) Camouflage - arctic animals have white fur to help them avoid predators, or sneak up on prey. |
| How have desert plants adapted to having little water? | 1) Small surface area compared to volume: a) Plants lose water vapour from the surface of their leaves. Cacti have spines instead of leaves - to reduce water loss. b) They also have a small surface area compared to their size (about 1000 times smaller surface area than normal plants), which also reduces water loss. 2) Water storage tissues - for example, a cactus stores water in its thick stem. 3) Maximising water absorption - some cacti have shallow but extensive roots to absorb water quickly over a large area. Others have deep roots to access underground water. |
| How are some plants and animals adapted to deter predators? | There are various special features used by animals and plants to help protect them against being eaten: 1) Some plants and animals have armour - like roses (thorns), cacti (sharp spines) and tortoises (shells). 2) Others produce poisons - like bees and poison ivy. 3) And some have amazing warning colours to scare off predators like wasps. |
| What adaptations do microorganisms have? | Microorganisms have a huge variety of adaptations so that they can live in a wide range of environments for example: 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. |
| Why do organisms compete for resources to survive? | Organisms need things from their environment and from other organisms in order to survive and reproduce: 1) Plants need light, space, water and minerals (nutrients) from the soil. 2) Animals need space (territory), food, water and mates. Organisms compete with other species (and members of their own species) for the same resources. E.g. red and grey squirrels live in the same habitat and eat the same food. Competition with the grey squirrels for these resources means there's not enough food for the red squirrels so the population of red squirrels is decreasing. |
| What are the factors that cause environmental changes? | The environment in which plants and animals live changes all the time. These changes are caused by living and non-living factors, such as: 1) Living factors are: - a) A change in the occurrence of infectious diseases. b) A change in the number of predators. c) A change in the number of prey or availability of food sources. d) A change in the number or types of competitors. 2) Non-living factors are: - a) A change in average temperature. b) A change in average rainfall. c) A change in the level of air or water pollution. |
| How do environmental changes cause population size to increase? | 1) Population size increases: - E.g. if the number of prey increases, then there's more food available for predators, so more predators survive and reproduce, and their numbers increase too. |
| How do environmental changes cause population size to decrease? | 1) Population size decreases: E.g. the number of bees in the US is falling rapidly. Experts aren't sure why but they think it be because: a) Some pesticides may be having a negative effect on bees. b) There's less food available - there aren't as many nectar-rich plants around anymore. c) There's more disease - bees are being killed by new pathogens or parasites. |
| How do environmental changes cause population distribution to change? | 1) Population distribution changes: - A change in distribution means a change in where an organism lives. For example, the distribution of bird species in Germany is changing because of a rise in average temperature. E.g. the European Bee-Eater bird is a Mediterranean species but it's now present in parts of Germany. |
| Why can environmental changes be measured using living indicators? | 1) Some organisms are very sensitive to changes in their environment and so can be studied to see the effect of human activities - these organisms are known as indicator species. |
| How can air pollution be measured by living indicators? | 1) For example, air pollution can be monitored by looking at particular types of lichen that are very sensitive to the concentration of sulfur dioxide in the atmosphere (and so can 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. the air is clean if there are lots of lichen). |
| How can water pollution be measured by living indicators? | If raw sewage is released into a river, the bacterial population in the water increases and uses up the oxygen. Some 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 you find mayfly larvae in a river, it indicates that the water is clean. |
| How can you tell if there's a problem with pollution using living indicators? | 1) Other invertebrate species have adapted to live in polluted conditions - so if you see a lot of them you know there's a problem. E.g. rat-tailed maggots and sludge worms indicate a very high level of water pollution. |
| How can environmental changes be measured using non-living indicators? | To find out about environmental change, scientists are busy collecting data about the environment. 1) They use satellites to measure the temperature of the sea surface and the amount of snow and ice cover. These are modern, accurate instruments and give us global coverage. 2) Automatic weather stations tell us the atmospheric temperature at various locations. They contain thermometers that are sensitive and accurate - they can measure to very small fractions of a degree. 3) They measure rainfall using rain gauges to find out how much the average rainfall changes year on year. 4) They use dissolved oxygen meters, which measure the concentration of dissolved oxygen in the water, to discover how the level of water pollution is changing. |
| What happens as you move up the food chain? But when is this not true and what is a better to look at the food chain? | There's less energy and less biomass every time you move up a stage (trophic level) in a food chain. There are usually fewer organisms every time you move up a level too: 100 dandelions feed 10 rabbits which feed 1 fox. This isn't always true though - for example, if 500 fleas are feeding on the fox, the number of organisms has increased as you move up that stage in the food chain. so a better way to look at the food chain is often to think about biomass instead of number of organisms. You can use information about biomass to construct a pyramid of biomass to represent the food chain. |
| How do you construct a pyramid of biomass and what does the pyramid represent? | 1) Each bar on a pyramid of biomass shows the mass of living material at that stage in the food chain - basically how much all the organisms at each level would "weigh" if you put them all together. 2) So the one fox would have a big biomass and the hundreds of fleas would have a very small biomass. Biomass pyramids are practically always pyramid-shaped: You need to be able to construct pyramids of biomass. Luckily it's pretty simple - they'll give you all the information you need to do it in the exam. 3) The big bar along the bottom of the pyramid always represents the producer (i.e. the plant). The next bar will be the primary consumer (the animal that eats the plant), then the secondary consumer (the animal that eats the primary consumer) and so on up the food chain. |
| How would you interpret pyramids of biomass? | You need to be able to look at pyramids of biomass and explain what they show about the food chain. Even if you know nothing about the natural world, you're probably aware that a tree is quite a bit bigger than an aphid. So what's going on here is that lots (probably thousands) of aphids are feeding on a few great big trees. Quite a lot of ladybirds are then eating the aphids, and a few partridges are eating the ladybirds. Biomass and energy are still decreasing as you go up the levels - it's just that one tree can have a very big biomass, and can fix a lot of the Sun's energy using all those levels. |
| How is energy used up by photosynthesis in a food chain? | 1) Energy from the sun is the source of energy for nearly all life on earth. 2) Green plants and algae use a small percentage of the light energy from the sun to make food during photosynthesis. This energy's stored in the substances which make up the cells of plants and algae, and then works its way through the food chain as animals eat them and each other. |
| How is energy used up by respiration in a food chain? | 1) Respiration supplies the energy for all life processes, including movement. Most of the energy is eventually lost to the surroundings as heat. This is especially true for mammals and birds, whose bodies must be kept at a constant temperature which is normally higher than their surroundings. |
| How does energy disappear in a food chain due to inedible materials? | 1) Some of the material which makes up plants and animals is inedible, so it doesn't pass to the next state of the food chain. Material and energy are also lost from the food chain in the organisms' waste materials. 2) This explains why you get biomass pyramids. Most of the biomass is lost and so does not become biomass in the next level up. |
| How does the loss of energy explain why there are so few trophic levels in a pyramid of biomass? | 1) It also explains why you hardly ever get food chains with more than about five trophic levels. So much energy is lost at each stage that there's not enough left to support more organisms after four or five stages. |
| How are elements cycled back to the start of the food chain? | 1) Living things are made of materials they take from the world around them. 2) Plants take elements like carbon, oxygen, hydrogen and nitrogen from the soil or the air. They turn these elements into the complex compounds (carbs, proteins and fats) that make up living organisms, and these then pass through the food chain. 3) These elements are returned to the environment in waste products produced by the organisms, or when the organisms die. These materials decay because they're broken down (digested) by microorganisms - that's how the elements get put back into the soil. 4) Microorganisms work best in warm, moist conditions. Many microorganisms also break down material faster when there's plenty of oxygen available. Compost bins recreate these ideal conditions. 5) All the important elements are thus recycled - they return to the soil, ready to be used by new plants and put back into the food chain again. 6) 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. |
| What is compost? What is in a compost bin? | A compost bin - Kitchen waste (e.g. food peelings) can be made into compost. Compost id decayed remains of animal and plant matter that can be used as fertiliser. It recycles nutrients back in to the soil - giving you a lovely garden. Compost bins contain: - a) Mesh sides to let air in. b) Warmth generated by decomposition helps it all along. c) Extra decomposers add (compost maker). d) Finely shredded waste is best. |
| What is the carbon cycle (describe part 1 of it)? | 1) There's only one arrow going down from the atmosphere. The whole thing is "powered" by photosynthesis. Carbon dioxide is removed from the atmosphere by green plants and algae, and the carbon is used to make carbohydrates, fats and proteins in the plants and algae. 2) Some of the carbon is returned to the atmosphere as carbon dioxide when the plants and algae respire. Some of the carbon becomes part of the fats and proteins in animals when the plants and algae are eaten. The carbon then moves through the food chain. 3) Some of the carbon is returned to the atmosphere as carbon dioxide when the animals respire. 4) When plants, algae and animals die, other animals (called detritus feeders) and microorganisms feed on their remains. When these organisms respire, carbon dioxide is returned to the atmosphere. |
| What is the carbon cycle (describe part 2 of it)? | 5) Animals also produce waste, and this too is broken down by detritus feeders and microorganisms. Compounds in the waste are taken up from the soil by plants as nutrients - they're put back into the food chain again. 6) Some useful plant and animal products, e.g. wood and fossil fuels, are burnt (combustion). This also releases carbon dioxide back into the air. 7) So carbon is constantly being cycled - from the air, through food chains and eventually back out into the air again. |
| Why do organisms of the same species have differences and what two types of variations are there? | 1) Different species look different e.g. a dog always looks different from a daisy. 2) But even organisms of the same species will usually look at least slightly different - e.g. in a room full of people you'll see different colour hair, individually shaped noses, a variety of heights, etc. 3) These differences are called the variation within species - and there are two types of variation: genetic variation and environmental variation. |
| Why do different genes cause genetic variation? | 1)All plants and animals have characteristics that are in some ways similar to their parents'. 2)This is because organism's characteristics are determined by the genes inherited from their parents. (Genes are the codes inside your cells that control how you're made). 3)These genes are passed on in sex cells (gametes), which the offspring develops from. 4)Most animals (and quite a lot of plants) get some genes from the mother and some from the father. 5)This combining of genes from two parents causes genetic variation - no two of the species are genetically identical other than identical twins. 6) Some characteristics are determined only by genes (e.g. violet flower colour). In animals these include: eye colour, blood group and inherited disorders (e.g. haemophilia or cystic fibrosis). |
| What is environmental variation? | 1) The environment that organisms live and grow in also causes differences between members of the same species - this is called environmental variation. |
| How are characteristics also influenced by the environment? | 1) The environment that organisms live and grow in also causes differences between members of the same species - this is called environmental variation. 2) Environmental variation covers a wide range of differences - from losing your toes in a piranha attack, to getting a suntan, to having yellow leaves, and so on. 3) Basically, any difference that has been caused by the conditions something lives in, is an environmental variation. |
| How do the conditions a plant grows in cause environmental variations? | A plant grown on a nice sunny windowsill would grow luscious and green. The same plant grown in darkness would grow tall and spindly and its leaves would turn yellow - these are environmental variations. |
| How do most characteristics depend on genes and characteristics use the height of a plant as an example? | 1) Most characteristic (e.g. body weight, height, skin colour, conditions of teeth, academic or athletic prowess, etc.) are determined by a mixture of genetic and environmental factors. 2) For example, the maximum height that an animal or plant could grow to is determined by genes. But whether it actually grows that tall depends on its environment (e.g. how much food it gets). |
| What do nuclei carry? | 1) Most cells in your body have a nucleus. The nucleus contains your genetic material in the form of chromosomes. 2) The human cell nucleus contains 23 pairs of chromosomes. There are two No.19 chromosomes, two No.12s, two No.3s, etc. |
| What do chromosomes carry? | Chromosomes carry genes. Different genes control different characteristics. |
| What are genes? | A gene is a short length of a chromosome which is quite a long length of DNA. Genes control the development of different characteristics, e.g. hair colour. |
| What happens to DNA to form chromosomes? | The DNA is coiled up to form the arms of the chromosomes. |
| What are different versions of the same gene called? | There can be different version of the same gene, which give different versions of a characteristic, like blue or brown eyes. The different versions of the same gene are called alleles instead of genes - it's more sensible than it sounds! |
| What is sexual reproduction? | Sexual reproduction involves the fusion of male and female gametes. Because there are two parent, the offspring contains a mixture of their parents' genes. |
| How does sexual reproduction produce genetically different cells? | 1)Sexual reproduction is where genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to either parent. 2)In sexual reproduction the mother and father produce gametes - e.g. eggs and sperm cells in animals. 3)In humans, each gamete contains 23 chromosomes - half the number of chromosomes in a normal cell (instead of having two of each chromosome, a gamete has just one of each chromosome). 4) The egg (from the mother) and the sperm cell (from the father) then fuse together (fertilisation) to form a cell with the full number of chromosomes (half from the father, half from the mother). 5) This is why the offspring inherits features from both parents - it's received a mixture of chromosomes from its mum and its dad (and it's the chromosomes that decide how you turn out). 6) This mixture of genetic material produces variation in the offspring. |
| What is asexual reproduction? | In asexual reproduction there's only one 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 - they're clones. |
| How does asexual reproduction produce genetically identical cells? | 1) An ordinary cell can make a new cell by simply dividing in two. The new cell has exactly the same genetic information (i.e. genes) as the parent cell - this is known as asexual reproduction. 2) X-shaped chromosomes have two identical halves so each chromosome splits down the middle to form two identical sets of 'half-chromosomes' (i.e. two sets of DNA strands). A membrane forms around each set and the DNA replicates itself to form two identical cells with complete sets of X-shaped chromosomes. 3) This is how all plants and animals grow and produce replacement cells. 4) Some organisms also produce offspring using asexual reproduction, e.g. bacteria and certain plants. |
| How can plants be cloned using cuttings? | 1) Gardeners can take cuttings from good parent plants, and then plant them to produce genetically identical copies (clones) of the parent plant. 2) These plants can be produced quickly and cheaply. |
| How can plants be cloned using tissue culture? | This is where a few plant cells are put in a growth medium with hormones, and they grow into new plants - clones of the parent plant. These plants can be made very quickly, in very little space, and be grown all year. |
| How can you make animal clones using embryo transplants? | Farmers can produced cloned offspring from their best bull and cow - using embryo transplants. 1) Sperm cells are taken from a prize bull and egg cells are taken from a prize cow. The sperm are then used to artificially fertilise an egg cell. The embryo that develops is then split many times (to form clones) before any cells become specialised. 2) These cloned embryos can then be implanted into lots of other cows where they grow into baby calves (which will all be genetically identical to each other). 3) Hundreds of "ideal" offspring can be produced every year from the best bull and cow. |
| How can adult cell cloning be used to make a clone? | 1) Adult cell cloning involves taking an unfertilised egg cell and removing its genetic material (the nucleus). A complete set of chromosomes from an adult body cell (e.g. skin cell) is inserted into the 'empty' egg cell. 2) The egg cell is then stimulated by an electric shock - this makes it divide, just like normal embryos. 3) When the embryo is a ball of cells, it's implanted into an adult female (the surrogate mother) to grow into a genetically identical copy (clone) of the original adult body cell. 4) This technique was used to create Dolly the famous cloned sheep. |
| What are the issues surrounding cloning to do with a new disease appearing? | 1) Cloning quickly gets you lots of "ideal" offspring. But you also get a "reduce gene pool" this means there are fewer different alleles in a population. If a population are all closely related and a new disease appears, they could all be wiped out - there may be no allele in the population giving resistance to the disease. |
| What are the positives surrounding cloning? | 1) The study of animal clones could lead to greater understanding of the development of the embryo, and of ageing and age-related disorders. 2) Cloning could also be used to help preserve endangered species. |
| What are the issues surrounding health and the future? | 1) However, it's possible that cloned animals might not be as healthy as normal ones, e.g. Dolly the sheep had arthritis, which tends to occur in older sheep (but the jury's still out on if this was due to cloning). 2) Some people worry that humans might be cloned in the future. If it was allowed, any successful cloning may follow many unsuccessful attempts, e.g. children born severely disabled. |
| How does genetic engineering use enzymes? | The basic idea is to copy a useful gene from one organism's chromosome into the cells of another: - 1) A useful gene is "cut" from one organism's chromosome and then to insert the useful gene. 2) Enzymes are then used to cut another organism's chromosome and then to insert the useful gene. 3) Scientists use this method to do all sorts of things - for example, the human insulin gene can be inserted into bacteria to produce human insulin. |
| How is genetic engineering used to make human insulin? | 1) Scientists use genetic engineering to do all sorts of things - for example, the human insulin gene can be inserted into bacteria to produce human insulin: a) The insulin gene is cut out of human DNA. b) Enzymes cut the DNA of bacteria. c) The scientists then insert the human DNA of the insulin gene into the bacteria DNA. d) The bacteria are then grown like mad. e) The insulin produced is purified and used by people with diabetes. |
| How have plants been made resistant? | The same method of genetic engineering can be used to transfer useful genes into animals and plants at the very early stages of their development (i.e. shortly after fertilisation). This means they'll develop useful characteristics, e.g: 1) Genetically modified (GM) crops have had their genes modified, e.g. to make them resistant to viruses, insects or herbicides (chemicals used to kill weeds). |
| How have genes be used to produce drugs from sheep? | The same method of genetic engineering can be used to transfer useful genes into animals and plants at the very early stages of their development (i.e. shortly after fertilisation). This means they'll develop useful characteristics, e.g: 1) Sheep have been genetically engineered to produce substances, like drugs, in their milk that can be used to treat human diseases. |
| How has genetic engineering been used in gene therapy? | The same method of genetic engineering can be used to transfer useful genes into animals and plants at the very early stages of their development (i.e. shortly after fertilisation). This means they'll develop useful characteristics, e.g: 1) Genetic disorder like cystic fibrosis are caused by faulty genes. Scientists are trying to treat these disorders by inserting working genes into sufferers. This is called gene therapy. |
| Why is genetic engineering a controversial topic? | 1) Genetic engineering is an exciting new area in science which had the potential for solving many of our problems (e.g. treating diseases, more efficient food production etc.) but not everyone thinks it's a great idea. 2) There are worries about the long-term effects of genetic engineering - that changing a person's genes might accidentally create unplanned problems, which could then get passed on to future generations. |
| What are the pros/ defences for genetically modified crops? | 1) GM crops can increase the yield of a crop making more food. 2) People living in developing nations often lack nutrients in their diets. GM crops could be engineered to contain the nutrient that's missing. For example, they're testing 'golden rice' that contain beta-carotene - lack of the is substance causes blindness. 3) GM crops are already being grown elsewhere in the world (not the UK) often without any problems. |
| What are the cons/defences against GM crops? | 1) Some people say that growing GM crops will affect the number of weeds and flowers (and so the population of insects) that live in and around the crops - reducing farmland biodiversity. 2) Not everyone is convinced that GM crops are safe. People are worried they may develop allergies to the food - although there's probably no more risk for this than eating usual foods. 3) A big concern is that transplanted genes may get out into the natural environment. For example, the herbicide resistance gene may be picked up by weeds, creating a 'super weed' variety. |
| What is the theory of evolution? | Theory of evolution: More than 3 billion years ago, life on Earth began as simple organisms from which all the more complex organisms evolved (rather than just popping into existence). |
| How does looking at the similarities and differences between organisms allow us the put them into groups? | Looking at the similarities and differences between organisms allows us to classify them into groups. E.g: 1) Plants make their own food (by photosynthesis) and are fixed in the ground. 2) Animals move about the place and can't make their own food. 3) Microorganisms are different to plants and animals, e.g. bacteria are single-celled. |
| How by studying similarities and differences between organisms can we understand how all living things are related (evolutionary relationships)? | 1) Species with similar characteristics often have similar genes because they share a recent common ancestor, so they're closely related. They often look very alike and tend to live in similar types of habitat, e.g. whales and dolphins. 2) Occasionally, genetically different species might look alike too. E.g. dolphins and sharks look pretty similar because they've both adapted to living in the same habitat. But they're not closely related - they've evolved from different ancestors. 3) Evolutionary trees show common ancestors and relationships between organisms. The more recent the common ancestor, the more closely related the two species. |
| How by studying the similarities and differences between organisms can help us to understand how they interact with each other (ecological relationships)? | 1) If we see organisms in the same environment with similar characteristics (e.g. dolphins and sharks) it suggests they might be in competition (e.g. for the same food source). 2) Differences between organisms in the same environment (e.g. dolphins swim in small groups, but herring swim in giant shoals) can show predate-prey relationships (e.g. dolphins hunt herring). |
| How does natural selection work? Use rabbits with big ears and small ears as an example. | Charles Darwin came up with the idea of natural selection. It works like this: 1) Individuals within a species show variation because of the differences in their genes, e.g. some rabbits have big ears and some have small ones. 2) Individuals with characteristics that make them better adapted to the environment have a better chance of survival and do are more likely to breed successfully. E.g. big-eared rabbits are more likely to hear a fox sneaking up on them, and so are more likely to live and have millions of babies. Small-eared rabbits are more likely to end up as fox food. 3) So, the genes that are responsible for the useful characteristics are more likely to be passed on to the next generation. E.g. all the baby rabbits are born with big ears. |
| What is a mutation? | A mutation is a change in an organism's DNA. |
| Why does evolution occur sometimes due to mutations? | 1) Most of the time mutations have no effect, but occasionally they can be beneficial by producing a useful characteristic. This characteristic may give the organism a better chance of surviving and reproducing. 2) If so, the beneficial mutation is more likely to be passed on to future generations by natural selection. 3) Over time, the beneficial mutation will accumulate in a population, e.g. some species of bacteria have become resistant to antibiotics due to mutation. |
| Why didn't everyone agree with Darwin? | Darwin's idea was very controversial at the time - for various reasons: 1) It went against common religious beliefs about how life on Earth developed - it was the first plausible explanation for our own existence without the need for a "Creator" (God). 2) Darwin couldn't give a good explanation for why these new, useful characteristics appeared or exactly how individual organisms passed on their beneficial characteristics to their offspring. But then he didn't know anything about genes or mutations - they weren't discovered 'til 50 years after his theory was published. 3) There wasn't enough evidence to convince many scientists, because not many other studies had been done into how organisms change over time. |
| What was Lamarck's theory? Use the legs of a rabbit to explain it. | There were different scientific hypotheses about evolution around at the same time, such as Lamarck's: 1) Lamarck (1744-1829) argued that if a characteristic was used a lot by an organism then it would become more developed during its lifetime. E.g. if a rabbit used its legs to run a lot (to escape predators), then its legs would get longer. 2) Lamarck believed that these acquired characteristics would be passed on to the next generation, e.g. the rabbit's offspring would have longer legs. |
| Why do scientists develop different hypotheses from similar observations? | 1) Often scientists come up with different hypotheses to explain similar observations. 2) Scientists might develop different hypotheses because they have different beliefs (e.g. religious) or they have been influenced by different people (e.g. other scientists and their way of thinking)… or they just think differently. 3) The only way to find out whose hypothesis is right is to find evidence to support or disprove each one. |
| Lamarck and Darwin both had different hypotheses to explain how evolution happens so what happened in the end with each hypothesis? | 1) For example, Lamarck and Darwin both had different hypotheses to explain how evolution happens. In the end: a) Lamarck's hypothesis was eventually rejected because experiments didn't support his hypothesis. You can see it for yourself, e.g. if you dye a hamster's fur bright pink, its offspring will still be born with the normal fur colour because the new characteristic won't have been passed on. b) The discovery of genetics supported Darwin's idea because it provided an explanation of how organisms born with beneficial characteristics can pass them on (i.e. via their genes). |
| Why is Darwin's hypothesis now known as a theory? | There's so much evidence for Darwin's idea that it's now an accepted hypothesis (a theory). |
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