Biology B1 (part 2)

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  • Created by: lucylulou
  • Created on: 12-05-16 18:12


  • Desert Animals: adapted to save water & keep cool
  • Large surface area to volume ratio > lose body heat
  • Efficient with water > produce small amounts of concentrated urine, produce little sweat
  • Good in hot conditions > thin layers of body fat & thin coat > lose body heat
  • Camouflage > avoid predators/ sneak up on prey (eg. sandy colour)
  • Arctic Animals: adapted to reduce heat loss
  • Small surface area to volume ratio > compact rounded shape > reduce heat loss
  • Well insulated > thick layer of blubber (also acts as energy store), thick hairy coats, greasy fur (sheds water, prevent evaporation)
  • Camouflage > avoid predators/ sneak up on prey (eg. white fur)
  • Desert Plants: adapted to having little water
  • Small surface area to volume ratio > because they lose water vapour from leaf surface, spines instead of leaves (reduce water loss)
  • Water storage tissues > eg. cacti stores water in thick stem
  • Maximise water absorption > shallow extensive roots (SA) or deep roots (underground water)
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Adaptations (2)

Plants & animals adapted to deter predators

  • Armour > thorns (roses), sharp spines (cacti), shells (tortoises)
  • Produce poisons > eg. bees and poison ivy
  • Warning colours > eg. wasps


  • Microorganisms (eg. bacteria) adapted to live in extreme conditions, like in hot volcano vents, salty lakes or at high pressure on the sea bed
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Competition & Env. Change

  • Organisms Compete for Resources to Survive: (with other species and their own)
    • Plants need light, space, water, minerals (from soil)
    • Animals need territory, mates, food, water
  • Environmental Change caused by...
    • Living factors > increase/decrease in infectious disease, change in number of predators, change in number of prey or availablilty of food sources, change in amount/type of competitors.
    • Non-living factors > change in average temperature, change in average rainfall, change in level of air or water pollution
  • Environmental Change Affects Populations
    • Population size increase > eg. more prey = more food for predators = survive & reproduce = population increase
    • Population size decrease > eg. bee population fall (pesticides, less food, more disease)
    • Population distribution change (where they live) > eg. distribution of bird species due to rise in temperature
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Measuring Env. Change

Using Living Indicators...

  • Indicator species: organisms that are very sensitive to changes in their environment
    • Air pollution > lichen are sensitive to the concentration of sulphur dioxide in atmosphere, number/ type of lichen in a certain area will indicate how clean the air is
    • Raw sewage released into river > bacterial population will increase & use up oxygen, some invertibrates are sensitive to concentration of dissolved oxygen in water
    • Other invertibrates have adapted to live in polluted conditions (high population indicates  bad pollution)

Using Non-living Indicators... (finding out about environmental change)

  • Satellites > measure temperature of sea surface, amount of snow & ice cover
  • Automatic weather stations > measure atmospheric temperature
  • Rain gauges > measure average annual rainfall 
  • Dissolved oxygen meters > measure concentration of dissolved oxygen in water to measure the level of water pollution
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Pyramids of Biomass

There's less energy and less biomass every time you move up a trophic level in a food chain, and usually fewer organisms too (but not if 500 fleas fed on one fox > therefore it's better to look at biomass)

  • Each bar on a pyramid of biomass shows mass of living material in that trophic level
  • Eg. 100 fleas would have less biomass than one fox and so it would be pyramid-shaped (unlike if it was a number pyramid)
  • The largest bar at the bottom represents the producer 
  • The next bar > primary consumer, then secondary consumer... etc.
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Energy Transfer & Decay

  • Energy from the sun > source of energy for most life on Earth
  • Green plants and algae use a small % of this light energy to make food in photosynthesis. This energy is stored in the plant and goes through the food chain, as animals eat them and each other.
  • Respiration supplies energy for all life processes (inc. movement). Most energy is lost to surroundings as heat.
  • Some material in plants and animals is inedible (eg. bone), so doesn't go to next stage of food chain. & Material and energy are lost from the food chain in organisms waste materials.
  • This explains biomass pyramids > most biomass is lost and doesn't make it to the next trophic level. Also explains why food chains arn't usually more than 5 trophic levels.
  • Living things > made of materials they take in
  • Plants take in CO2, O2, H2, N2 from soil or air > turn them into complex compounds (carbohydrates, fats, proteins) pass through the food chain
  • These are returned to the environment as waste products/when they die (decay, broken down by microorganisms & returned to soil > best in warm, moist conditions + O2)
  • Stable community > materials taken out balance those put back in (constant cycle)
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Carbon Cycle

How Carbon is Recycled...

  • All cells contain proteins, carbohydrates & fats (which all contain carbon)
  • CO2 present in the atmosphere > taken in by plants in photosynthesis
  • Plants digested by animals (carbon becomes part of their proteins, carbohydrates & fats) > animals eaten by other animals
  • Waste materials from animals
  • Microorganisms & ditritus feeders break down waste materials and dead animals
  • Carbon comounds in soil > nutrients taken up by plants
  • Organisms respire > CO2 into the atmosphere
  • Wood & fossil fuels burned (combustion) > CO2 produced
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2 Types of Variation Within a Species: genetic variation & environmental variation

  • An organism's characteristics are determined by the genes inherited from their parents
  • These genes are passed on in gametes, which the offspring develop from
  • Some genes from father, some from mother > combination of genes = genetic variation
  • Some characteristics are only determined by genes (in animals: eye colour, blood group & inherited disorders)
  • The environment that organisms live & grow in causes differences in members of the same species - environmental variation.
  • Characteristics could be affected by climate, diet, accidents, culture and lifestyle
  • Eg. a plant grown in darkness may grow tall and spindly with yellow leaves
  • However, most characteristics are due to both GENES and ENVIRONMENT
  • Eg. body weight, height, skin colour, academic, condition of teeth > all determined by a mixture of genetic and environmental factors
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Genes, Chroms. & DNA

Most cells in the human body have a nucleus > the nucleus conatins genetic material

In the nucleus there are 23 pairs of chromosomes

Chromosomes carry genes and are made up of DNA

A gene is a section of DNA


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Sexual Reproduction (produces genetically dif. cells) > where genetic info from 2 organisms (a mother and a father) is combined to produce offspring which are genetically dif.

  • The mother and father produce gametes (egg & sperm) > in humans each gamete contains 23 chromosomes (only one of each)
  • The egg and the sperm fuse together (fertilisation) to form a cell with the full number of chromosomes (half from mum, half from dad) > therefore the offspring contain a mixture of their parents' genes (variation)

Asexual Reproduction (produces genetically identical cells)

  • An ordinary cell can make a new cell by dividing in 2 > the new cell has exactly the same genes as the parent cell
  • Only one parent > no genetic variation > offspring are clones
  • What happens:  X-shaped chromosomes have 2 identical halves > each chromosome splits in half > a membrane forms around each set > the DNA replicates itself to form 2 identical cells with complete sets of X-shaped chromosomes.
  • This is how plants & animals grow and produce replacement cells. Some organisms produce offspring using asexual reproduction (eg. bacteria)
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Cloning Plants > Cuttings: Take cuttings from good parent plants, plant them to produce genetically identical copies of parent plant. Produced quickly and cheaply 

Cloning Plants > Tissue Culture: A few plant cells are put in growth medium + hormones, they grow into new plants (clones of parent plant). Produced quickly, in little space, all year

Animal Cloning > Embryo TransplantsCloned offspring in farming (best cow & bull). Sperm cells taken from prize bull and egg cells from prize cow > artificial fertilisation > embryo develops > split many times (before cells specialise) to form clones. Cloned embryos implanted into other cows > genetically identical calves are born. Lots of 'ideal' offspring can be produced                  

Animal Cloning > Adult Cell Cloning: Unfertilised egg cell taken > genetic material removed (nucleus) > complete set of chromosomes from adult body cell inserted into 'empty' egg cell > egg cell stimulated by electric shock > makes it divide > becomes ball of cells > implanted into adult female (surrogate mother) > clone of original adult body cell.                                          Issues with Cloning - 'Reduced gene pool' most alleles same in population, disease could wipe out whole. - Studying clones, better understanding. - Help preserve endangered species. - Clones may not be as healthy. - Some worry of future human cloning.

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Genetic Engineering

Useful gene 'cut' from organism's chromosome using enzymes > enzymes used to cut another organism's chromosome > useful gene inserted - Eg. used to produce insulin (in bacteria)

Transferring Genes into Animals & Plants (useful characteristics): > GM crops have their genes modified, eg. induce resistance to viruses/insects/herbicides. > Sheep have been modified to produce eg. drugs in their milk to treat human diseases. > Gene therapy, replace faulty genes with working ones (genetic disorders like cystic fibrosis)

Controversial Topic: Has potential for treating diseases, increasing food production efficiency. But possibilty of unplanned gene problems being passed onto future generations. 

  • GM Crops: Pros + Cons
    • Affect no. of flowers, weeds and insects > reduce farmland biodiversity
    • Not everyone convinced GM crops are safe (allergies)
    • Concern, transplanted genes may get out into natural environment (eg. resistance)
    • GM crops increase yield > make more food
    • GM crops to contain specific nutrients > developing countries
    • They're already being grown in other countries without problems
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Organisms can be classified as PLANTS (make their own food, fixed in ground), ANIMALS (move around but can't make own food) or MICROORGANISMS (dif. to animals & plants)

Similarites & Differences between organisms > understanding how they're related and how they interact (evolutionary relationships and ecological relationships)

  • Evolutionary: Species with similar characteristics > similar genes > share recent ancestor > closely related > similar habitats
  • Genetically different species may look similar > adapted to same habitat (not closely related, evolved from dif. ancestors)
  • Evolutionary trees show common ancestors & relationships. The more recent the ancestor, the more closely related the 2 species
  • Ecological: Organisms in same environment with similar characteristics (eg. dolphins & sharks) > suggests competition (eg. food source)
  • Differences can show predator-prey relationships
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Evolution (2)

Natural Selection - Charles Darwin

  • Individuals within a species show variation because of differences in their genes
  • Individuals with better adapted characteristics to their environment > better chance of survival > more likely to breed successfully
  • Genes are responsible for useful genes being passed onto future generations

Evolution can occur due to Mutations

  • A mutation is a change in an organism's DNA
  • Most of the time they have no effect but occasionally they can be beneficial by producing a useful characteristic > increasing chance of survival and reproduction
  • Beneficial mutation more likely to be passed on by natural selection
  • Over time the mutation will accumulate in a population
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Evolution (3)

Darwin's Idea was Controversial at the time

  • Went against religious beliefs about how life on earth developed (didn't involve God)
  • Darwin couldn't give an explanation for how useful genes/mutations appeared. Weren't discovered until 50 years later
  • Wasn't enough evidence to convince scientists

Lamarck 1744-1829

  • He argued that if a characteristic was used a lot by an organism, it would become more developed during its lifetime (eg. if a rabbit ran a lot, its legs would get longer)
  • Lamarck believed that these characteristics would pass on to next generation
  • Only way to find out whose hypothesis was right > find evidence to prove/disprove
  • Lamarck's theory was eventially rejected > experiments didn't support it
  • The discovery of genetics supported Darwin's idea > it provided an explanation of how organisms born with beneficial characteristics could pass them on
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