Biology, B2

Revison cards for gateway science B2 understanding our environments

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Natural Ecosystems= where humans don't control them e.g. lakes and woodlands

Artificial Ecosystems= where humans deliberately promote the growth of certain living organisms and get rid of others e.g. greenhouses and fish farms

Artificial ecosystems have less biodiversity than natural ones

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  • Divided into kingdoms
  • then divided into smaller groups e.g. Genus= closely related species

Living things are plants, animals or something else

  • Plant Kingdom- must have chloroplasts, be able to make their own food, fixed to the ground by roots, movement must be confined to spreading out
  • Animal Kingdom- move about, compact bodies, can't make own food
  • other things like bacteria and fungi are classified into other kingdoms
  • Some single cell organisms have features of both plants and animals
    • euglena can move by moving it flagellum and has chloroplasts so its put into a kingdom called Protoctista
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Animal Kingdom

Divided into invertebrates and vertebrates- vertebrates have a backbone and invertebrates don't

Vertebrates are divided into 5 groups called classes

  • Fish- live in water, scales and gills
  • Amphibians- exchange gas through skin, skin permeable and moist
  • Reptiles- adapted to land so dry scaly skin
  • Birds- Most fly, have feathers, have a beak
  • Mammals- have fur covering the body, give birth to young, produce milk
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Binomial system- 2 part name- 1st part=genus, 2nd part= species

Things of the same species can breed to produce fertile offspring

  • if you interbreed a male from one species with a female from a different species= hybrid- they are infertile so aren't a new species

unrelated species may have similar features

  • similar species often share a recent common ancestor, look alike but live in different habitats e.g. whales and dolphins
  • closely related species can look very different e.g. llamas and camels
  • similarities and differences between species can be explained in evolutionary terms and type of environment
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Estimating population size using a quadrat- count all the organisms in 1cm2 quadrat then multiply by the total area

Mark-release-capture method

  • capture a sample (nets, pitfall traps, pooters) and mark them
  • release them
  • recapture another sample of the population and count how many of these are marked
  • estimate population size using the equation:

Population size= no. animals in first sample time no. animals in second sample

       No. of marked animals in second sample

The sample size affects the accuracy of the estimate

The sample may not be representative of the whole population

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Produces glucose from sunlight, takes place in chloroplasts where the chlorophyll absorbs the light energy

Carbon dioxide + Water -------> Glucose + Oxygen

Glucose is converted into other substances as it is soluble so can be transported easily and its small so can easily diffuse

  • For respiration-releases energy so convert glucose into other substances
  • Making call walls- converted into cellulose
  • Stored in seeds- turned into lipids
  • Stored as starch- stored in roots, stems and leaves. starch is insoluble making it suitable for storing
  • Making Proteins- Combined with nitrates to make amino acids used in growth and repair
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Rate of Photosynthesis

  • Not enough light slows down the rate of photosynthesis
  • Too little carbon dioxide slows down photosynthesis
  • The temperature has to be just right

Photosynthesis and respiration are opposite processes

Photosynthesis= carbon dioxide + water---> Glucose + oxygen

Respiration= Glucose + oxygen ---> carbon dioxide + Water

plants respire all the time but during the day they make more oxygen by photosynthesis than they use in respiration

At night plants only respire as there is no light for photosynthesis

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Interactions between organisms

Population size is limited by available resources:

  • total amount of food
  • amount of water
  • amount of light
  • quality and amount of shelter

animals of the same and different species compete for these resources, similar organisms have a similar ecological niche

e.g. red and grey squirrels, like the same kind of habitat, food, shelter etc but grey squirrels are better adapted to deciduous woodland

populations of prey and predators go in cycles

  • population of any species is usually limited to food, when population of prey increase so does population of predators
  • however as population of predators increases prey will decrease
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Parasites and mutualistic relationships

Parasites live off the host and take what they need to survive without giving anything back, harming the host

  • e.g. tapeworms and fleas

Mutualism is a relationship where both organisms benefit

  • plants have nitrogen fixing bacteria in soil to get nitrates that they need, leguminous plants carry the bacteria in roots and the bacteria get a constant supply of sugar from the plant
  • 'cleaner species' e.g. oxpeckers live on the backs of buffalo they eat pests and alert when predators are coming
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Adaptation- polar bears

Polar bears are adapted to cold conditions;

  • large size,
  • compact shape,
  • layer of blubber for insulation,
  • small ears to reduce heat loss
  • thick hairy coat
  • white fur for camouflage
  • big feet to spread weight
  • strong swimmers and runners to help catch prey
  • fur on soles of paw to help grip the snow and ice
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Adaptations- Camel

Camels are adapted for dry desert conditions

  • store a lot of water
  • store fat in hump
  • can tolerate big changes in body temperature
  • thick coat reflects sunlight in day and keeps warm at night
  • bushy eyelashes and hair lined nostrils stop sand getting in
  • large feet to spread load
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Adaptations- Cactus

Cactus are adapted for hot dry conditions

  • small surface area to reduce water loss
  • thick waxy cuticle and spines instead of leaves to reduce water loss
  • store water in thick stem
  • the green stem carries out photosynthesis
  • sharp spines stop it being eaten
  • shallow but extensive roots
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Wind or Insect pollination

Wind pollination

  • plants have long, feathery stigmas to provide a large surface area to trap pollen
  • pollen grains are light and dry

Insect pollination

  • brightly coloured scented petals and scented nectar
  • pollen grains are large and sticky
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Fossils are the remains of animals and plants

  • from gradual replacement by minerals
    • animal dies and does not decay
    • quickly covered in sediment
    • over many years bone is replaced by minerals (mineralisation)
  • from casts and impressions
    • found in soft material like clay
    • clay hardens around organism, this decays leaving a cast
  • preservation in places were no decay happens
    • In amber and tar pits there is no oxygen or moisture so decay microbes can't survive
    • in glaciers it's too cold for decay microbes to work
    • peat bogs are too acidic for decay microbes
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The Fossil Record

  • fossils provide evidence for the theory of evolution
  • fossils show how many species have changed and developed over millions of years
    • e.g. the horse- evolved from creature the size of a dog, middle toe got bigger to form a hoof
  • the fossil record is incomplete because very few dead plants or animals turn into fossils
  • some fossils may be undiscovered

There are different view about the fossil record

  • people who don't believe in evolution interpret it in different ways
  • creationists believe each species was created separately by god
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Charles Darwin- natural selection

natural selection= the organisms with variations to help them survive

  • species vary
  • more are born than 'needed'
  • competition occurs
  • the better adapted survive
  • survivors pass on genes
  • over time new species occur

Modern examples of natural selection:

  • Peppered moths adapted their colour to stay camouflaged
  • Bacteria adapt to beat antibiotics
  • Rats adapt to beat Poison (warfarin)

Lamarck believed that acquired charateristics could be passed on to the animals offspring

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Human impact on the environment

Human population is increasing exponentially, so environment is being putting under a lot of pressure as countries have become more developed there are more demands on resources

Increased pollution is leading to:

  • Global warming and acid rain
    • when fossil fuels are burnt they release carbon dioxide causing global warming and sulphur dioxide causing acid rain
  • Ozone depletion
    • CFCs break down the ozone in the upper atmosphere allowing harmful UV rays to reach the earth's surface
    • increases the risk of skin cancer
    • increase in UV rays might kill the plankton in the sea
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Indicator Species

-Show pollution levels

  • some species can only survive in unpolluted conditions
    • lichens are used to monitor air quality, they are damaged by pollution so the cleaner the air the greater the diversity of lichens survive
  • other species live in polluted conditions
    • blood worms, water lice, rat-tailed maggots and sludgeworms all indicate polluted water
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Endangered species

Endangered= have very low numbers left in the wild

Extinct= none left at all


  • fossil fuels leading to climate change mean animals and plants can't adapt fast enough
  • destroying habitats
  • many animals are being hunted
  • humans cause pollution which harms living things
  • increasing the competition between species
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Main ways to protect endangered species

  • Education programmes- RSPB and greenpeace teach people what to do and what not to do to protect species
  • Protected habitats- like the national trust obtain and preserve sites such as woodlands
  • Legal protection- legislation is sometimes used to stop people hunting or damaging certain species homes
  • Captive breeding- breeding from endangered species in captivity can increase their numbers before being introduced back into the wild
  • Creating Artificial ecosystems- sometimes can be created and controlled to favour endangered species
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Conservation programmes

benefit both humans and animals

  • Protecting human food supply- over fishing has reduced fish stocks, conservation programmes can ensure future generations have fish
  • Reducing the need for chemical pesticides- protecting predators of pests such as ladybirds
  • Providing future medicines- many of medicines we use today come from plants, undiscovered plants may contain new medicines
  • Cultural aspects- individual species may be important to a nation
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Sustainable development

we need more food, more energy, producing more waste, so need to find a way to exist without damaging the environment

SUSTAINABLE DEVELOPMENT= meets the needs of today's population without harming the ability of future generations to meet their own needs

  • e.g. fishing quotas have been introduced e.g cod
  • to make the production of wood and paper sustainable there are laws insisting that logging companies must plant new trees

education is important as people are more likely to help

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= endangered

  • have commercial value when alive or dead
  • they are a tourist attraction
  • whale meat and oil can be used and cosmetics can be made from their blubber
  • International whaling commission has struggled to get nations to agree, many countries have agreed to stop whaling except norway and japan, iceland and the faroe isles still catch whales for scientific purposes
  • some whales are kept in captivity
    • don't have much space
    • used for entertaining people
    • increases awareness of animals and their problems
    • captive breeding programmes
    • research on whales can help us understand their needs
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