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The sequence from receptor to effector is a reflex

  • A receptor detects a stimulus (i.e. pain, touch, sound, light, chem/temp changes)

  • Sensory neuron (in nerves) transmits electrical impulse to CNS (brain and spinal cord)

  • Relay neuron passes impulse across synapse (junction between two neurons). A chemical is released that causes an impulse to be sent along a relay neuron.

  • A motor neuron is stimulated and the impulse is passed to an effector – either a muscle or gland. Muscle responds by contracting and a gland responds by secreting

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What are the effects of taking cannabis (does it l

  • It’s  illegal + must be bought from dealers
  • This brings them into contact with harder drugs (heroin)
  • There is evidence that it can cause mental illness in some people
  • Teenager whom smoke it increase their risk of getting depression
  • Mot all cannabis users go on to smoke harder drugs
  • Nearly all heroin users previously smoked cannabis

 

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How can athletes use drugs to improve their perfor

  • Steroids (which are used to build up muscle mass) –other drugs may be used to increase stamina

  • Strong painkillers are banned as an athlete may ignore an injury + suffer further damage

  • Many performance-enhancing drugs are very expensive giving an unfair advantage to those who can afford them

  • Using performance enhancing drugs can damage the body permanently + even lead to death

  • Most think it’s unethical to take drugs to enhance performance

 

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There is energy wastage between each stage in the

  • Not all of the food eaten can be digested so, energy is stored in waste materials (urea in urine/faeces).

  • Some biomass is used for respiration (which releases energy for living processes) + much of the energy released in respiration is eventually transferred to the surroundings.

  • Some is used for movement.

  • Some biomass is used to keep a constant temperature

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Describe the decay process.

  • Detritus feeders (i.e. some types of worm) start the process by eating dead animals or plants and producing waste materials.

  • Decay organisms (microorganisms-bacteria + fungi) break down the waste or dead plants/animals. They are called decomposers

  • Decay is faster is it’s warm + wet. Many decomposers also need oxygen.

  • All of the materials + dead organisms are recycled, returning nutrients to the soil.

  • Humans can recycle waste in sewage treatment plants and compost heaps

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The recycling of carbon involves both photosynthes

 

  • Photosynthesis removes CO₂ from atmosphere

  • Carbon from CO2 used to make carbs, fats + proteins which make up the body of plants + algae. Green plants/animals respire, returning CO₂ to the atmosphere

  • When Green plants/algae are eaten by animals + these animals are eaten by other animals, some of the carbon becomes part of the fats + proteins that make up their bodies

  • When animals respire some of this carbon becomes CO2 + is released into the atmosphere

  • When plants, algae + animals die, some animals + micro-organisms feed on their bodies. Carbon is returned to the atmosphere as CO2 when these organisms respire.

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The recycling of carbon involves both photosynthes

  • Photosynthesis removes CO₂ from atmosphere

  • Carbon from CO2 used to make carbs, fats + proteins which make up the body of plants + algae. Green plants/animals respire, returning CO₂ to the atmosphere

  • When Green plants/algae are eaten by animals + these animals are eaten by other animals, some of the carbon becomes part of the fats + proteins that make up their bodies

  • When animals respire some of this carbon becomes CO2 + is released into the atmosphere

  • When plants, algae + animals die, some animals + micro-organisms feed on their bodies. Carbon is returned to the atmosphere as CO2 when these organisms respire.

  • By the time the micro-organisms + detritus feeders have broken down the waste products /dead bodies of organisms in ecosystems + cycled the materials as plant nutrients, all energy originally absorbed has been transferred

Combustion of wood + fossil fuels releases CO2 into the atmosphere

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Describe the process of adult cell cloning.

 

  • In adult cell cloning the nucleus of an adult cell (i.e.skin cell) replaces the nucleus of an egg cell.

  • The nucleus is removed from an unfertilised egg cell. The nucleus is removed from the skin cell + placed in the ‘empty’ egg cell.

  • The new cell is given an electric shock, causing it to start to divide (the ball of cells is called an embryo)

  • The embryo is genetically identical to the adult skin cell
    Once the embryo has developed into a ball of cells it is inserted into a host mother

  • Dolly the sheep was produced by adult cell cloning in 1997

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What are the advantages of using cloning and genet

  • Cloning cattle can produce herds of cattle with useful characteristics.

  • Adult cell cloning can be used to make copies of the best animals (i.e race horses).

  • If a person has a faulty gene, they may have a genetic disorder. If the correct gene can be transferred to the person, they could be cured.

  • Several medical drugs (insulin + antibodies) have been produced by genetic engineering

  • GM crops incl those resistant to herbicides/insect

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What are the advantages of using cloning and genet

 

  • GM crops have a bigger yield, but farmers have to buy new GM seed every year as the crops are infertile.

  • Concerns about accidentally introducing genes into wild flower populations

  • Insects which aren’t pests may be affected by GM crops.

  • Concerns about effects of eating GM crop on human health + long term effects are unknown.

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