B6

• Biodiversity


  The variety of different species of organisms on Earth or within an ecosystem
• High biodiversity


  • The ecosystem will be stable, as species would be less dependent on each other for things such as food and shelter
• Quadrats


  1. Used to study ecology, make it easier to estimate distribution and abundance of organisms within a large area by looking at a few smaller representative samples

  2. A transect is a defined area where the samples will be taken and is used to estimate the number of organisms across the whole area, such as across a whole field

  3. The quadrats are placed along the transect and the amount of each organism is counted

  4. The quadrats can also be randomly placed across the whole area, rather than using a transect

  5. Percentage cover can also be estimated but this is subjective and less accurate than counting which gives a quantitative value

  6. The accuracy of the quadrat estimations can be improved by doing more samples, repeat testing or completing the sampling over larger transects
• Nets


  1. Useful for collecting flying insects, such as butterflies

  2. The nets are swept through long grass and counted

  3. This is repeated over different areas to get an estimate of population
• Pooters


  1. A small jar used to collect animals

  2. One tube goes over the insect and you suck into the other tube in order to apply suction

  3. There is a mesh covering to stop insects being swallowed
• Pitfall traps


  1. Used to sample small insects, such as beetles or spiders

  2. A container is buried in the ground and the top is covered by a piece of wood with a gap to allow insects to climb in

  3. The sides of the container are high and smooth to stop the insects crawling out again

  4. The traps are checked regularly to make sure that the insects are not eaten

  5. The capture-recapture method is usually used for this

  6. Insects that fall into the trap are marked harmlessly and then a few days later the trap is set up again. The number of marked animals in the second sample are recorded and if there are few or none marked then it indicates a large population size

  7. You have to assume that there is no death or movement of animals to other habitats in between the time the two samples are taken and that the marking did not affect the survival rate (e.g. markings did not make them more visible to predators)
• Temperature


  Climate change may lead to insects migrating to places in the world which are becoming hotter
• Water availability


  Populations will migrate to find water
• Atmospheric gas composition


  Certain pollutants can affect the distribution of organism, e.g lichen cannot grow in places where sulfur dioxide is present
• An increasing human population means that it is becoming difficult to ensure that everyone is able to have food (food security)
• Sustainability is an issue because more of the population is becoming wealthy and so their diet changes to an increase in meat and fish consumption, which are less energy efficient than eating plants and they use a lot more space than crops do
• Global warming may lead to droughts which will make it more difficult to grow crops
• New pests and pathogens are constantly entering but the genetic modification and selective breeding of certain crops and animals means increased vulnerability to new pathogens
• Hydroponics


  Growing crops in glasshouses by replacing soil with a mineral solution, allowing for careful control of growth by adjusting temperature etc.
• Biological control


  Release a natural predator into the area where the crops are being grown
• Gene technology


  Modifying crops or animals to have better yields, e.g. plants producing bigger fruits
• Herbicides


  Used to get rid of competing plants so that the maximum amount of energy and mass is conserved
• Insecticides and pesticides


  Gets rid of animals that eat the crops so that the maximum amount of energy and mass is conserved
• Selective breeding


  1. When humans breed certain plants or animals which have desirable characteristics

  2. Select individuals with desirable characteristics and breed together

  3. Choose the best offspring and breed them together

  4. Repeat process over many generation until all the offspring have the desired characteristic
• Genetic engineering


  1. A process where the genome of an organism is modified by introducing desirable characteristics

  2. Genes from chromosomes are 'cut out' using restriction enzymes leaving 'sticky ends'

  3. A virus or bacterial plasmid is cut using the same restriction enzyme to also create sticky ends. This also contains an antibiotic marker gene

  4. The loop and gene sticky ends are then joined together by DNA ligase enzymes

  5. The combined loop is placed in a vector, such as a bacterial cell, and then allowed to multiply as it will now contain the modified gene. As the bacteria grows we can see which ones are resistant to antibiotics. The colonies that are will be the bacteria that are also producing the modified gene, as they were inserted together
• Crops can be genetically modified in order to contain nutrients in countries where it may be difficult to obtain these nutrients naturally. For example, Golden Rice was created with beta-carotene from a daffodil, in order to make vitamin A in the body. In countries where the climate means that a large variety of crops cannot be grown this is a good solution to ensure that less people get deficiencies in nutrients
• Health


  The state of physical and mental wellbeing
• Disease


  A disorder that affects the body, organs or cells
• Types of diseases


  • Communicable: contagious diseases that can spread between people, caused by a pathogen
  • Non-communicable: non-contagious diseases
• Communicable diseases


  • Chickenpox, malaria, HIV
• Non-communicable diseases


  • Diabetes, heart conditions, neurological diseases, cancer from carcinogens
• Non-communicable diseases are often caused by lifestyle factors, such as diet, stress, lack of exercise, alcohol
• HIV and TB


  • HIV affects the strength of the immune system
  • Tuberculosis (TB) is a common bacterial disease that is found in HIV patients because they are more susceptible to infectious diseases
  • TB mainly affects the lungs
• HPV and cervical cancer


  • Viruses living in cells can trigger cancers
  • Most cervical cancer cases are linked with the HPV virus
• Viral infections


  Viruses infect and live inside a host cell. They replicate their DNA many times and then burst in order to release the virus and infect nearby cells. Viral infections cannot be treated by antibiotics
• HIV


  • Initial flu-like symptoms
  • Spread by bodily fluids, commonly through sexual activities or through injecting drugs and then sharing needles with people infected with HIV
  • Prevention: using condoms, not sharing needles, mothers with HIV bottle-feeding children
  • Complications: HIV can develop into Acquired Immune Deficiency Syndrome (AIDS) which remains dormant for some time after HIV infection and then attacks the person's immune system
  • Treatment: no cure for HIV but people are given antiviral drugs in order to stop its development
• Viruses living in cells can trigger cancers
• Most cervical cancer cases are linked with the HPV virus
• Viral infections


  Viruses infect and live inside a host cell. They replicate their DNA many times and then burst in order to release the virus and infect nearby cells. Viral infections cannot be treated by antibiotics.
• Human Immunodeficiency Virus (HIV)


  • Initial flu-like symptoms
  • Spread by bodily fluids, commonly through sexual activities or through injecting drugs and then sharing needles with people infected with HIV
  • Prevention: using condoms, not sharing needles, mothers with HIV bottle-feeding children
  • Complications: HIV can develop into Acquired Immune Deficiency Syndrome (AIDS) which remains dormant for some time after HIV infection and then attacks the person's immune system
  • Treatment: no cure for HIV but people are given antiviral drugs in order to stop its development into AIDS
• Tobacco Mosaic Virus (TMV)

  • Infects chloroplasts of levels and changes the green to white spots in a mosaic pattern, which means that the tobacco plant cannot photosynthesise properly and will die
  • Spread: transmitted by contact between plants
  • Prevention: good field hygiene, pest control, growing TMV-resistant strains
• Salmonella (food poisoning)


  • Bacteria living in the gut of animals spreading when the meat is ingested by humans
  • Symptoms: fever, stomach cramps, vomiting, diarrhoea
  • Spread: found raw meat and eggs, unhygienic conditions
  • Prevention: keeping raw meat away from cooked food, avoid washing it, wash hands and surfaces when handling it, cook food thoroughly
• Crown gall disease (Agrobacterium tumefaciens)


  • Transfers some of its own DNA to the infected plant's DNA
  • Symptoms: like a cancer and a tumour develops in the stems or roots, plants become stunted
• Athlete's foot


  • Symptoms: rash found between toes, red or white flaky skin
  • Spread: touching infected skin or surfaces, so is commonly found in swimming pool changing rooms
  • Treatment: antifungal medication
• Barley powdery mildew (Erysiphe graminis)


  • Affects grass plants, such as barley. Eventually the plant can no longer make chlorophyll and therefore cannot photosynthesis
  • Symptoms: circular fluffy white growth on leaves, fungus produces spores to reproduce which are spread in the wind, hyphae produced on upper and lower leaf surfaces
  • Spread: common in cool, damp environments
  • Treatment: fungicides, removing infected leaves