B9

• 9.1 Describe the different levels of organisation from individual organisms, populations, communities, to the whole ecosystem

  all the organisms and the environment in which they live form an ecosystem

  
  

  all the organisms that live and interact in an ecosystem form a community

  
  

  the community is made up of populations of different species

  
  

  each population lives in a particular habitat within the ecosystem

  
  

  a habitat includes the other organisms that affect the population and the local environment
• 9.2 Explain how communities can be affected by abiotic and biotic factors, including: temperature, moisture levels, CO2 levels

  -affects rate of photosynthesis

  -both plants and animals need water to survive

  -CO2 affects the rate of photosynthesis in plants
• 9.2 Explain how communities can be affected by abiotic and biotic factors:

  b competition, predation

  -food availability: more food means more organisms can breed more successfully, therefore population increases in numbers

  -new predators

  -new pathogens: when a new pathogen arises the population has no resistance to it so they can be wiped out quickly

  -competition: if one species is better adapted to the environment than another, then it will outcompete it until the numbers of the lesser adapted species are insufficient to breed
• 9.2 Explain how communities can be affected by abiotic and biotic factors, including: light


  -light intensity required for photosynthesis

  -the rate of photosynthesis affects the rate at which a plant grows

  -plants can be food sources or shelter for many organisms
• 9.3 Describe the importance of interdependence in a community

  interdependent species depend on each other for resources

  
  

  organisms need resources to stay alive (for example, animals need food and water). this means that organisms are constantly interacting with each other and their environment

  
  

  If the population of one organism rises or falls, then this can affect the rest of the ecosystem (can be shown in a food web, where food is used to predict changes in an ecosystem)
• 9.4 Describe how the survival of some organisms is dependent on other species, including parasitism and mutualism

  parasitism is where one organism (parasite) benefits by feeding off a host organism, causing harm to the host. the organism lives in or on the host and they may survive for a long time and continue to provide for the parasite if limited harm is caused (eg lice and tapeworms)

  
  

  mutualism is when some organisms that live together benefit from the relationship. for example, flowers depend on insects for pollination (flower benefits as is now able to produce fertilised egg cells, and the insect can collect nectar or pollen from the flower, which is used for food)
• 9.5 Core Practical: Investigate the relationship between organisms and their environment using field-work techniques, including quadrats transects

  Core Practical: Investigate the relationship between organisms and their environment using field-work techniques, including quadrats

  • place on ground to sample area and count all organisms of specific species you're interested in• repeat and work out mean
• 9.5 Core Practical: Investigate the relationship between organisms and their environment using field-work techniques, including belt transects

  Core Practical: Investigate the relationship between organisms and their environment using field-work techniques, including belt transect

  • mark out line in area you want to study• collect data along line using quadrats at regular intervals• repeat and find mean
• 9.6 Explain how to determine the number of organisms in a given area using raw data from field-work techniques, including quadrats and belt transects

  • plot graphs to see if there is a correlation between changing abiotic factor and distribution change
• 9.9 Explain the positive and negative human interactions within ecosystems and their impacts on biodiversity, including:

  a) fish farming


  a) 17% of the protein eaten by people globally comes from fish, and as the human population increases, we need more of it. overfishing wild fish stocks has damaged some water ecosystems, however fish farming aims to produce more fish and so reduce overfishing of wild fish

  
  

  problems caused as so many fish kept in a relatively small space. uneaten food and feces sinks to the bottom of the water, which can change conditions. this may harm wild organisms, and also mean parasites and disease spread more easily between fish in pens
• 9.9 Explain the positive and negative human interactions within ecosystems and their impacts on biodiversity, including:

  b) introduction of non-indigenous species


  some species are introduced in order to affect an ecosystem, such as reduce the numbers of another species that has got out of control (often happens when humans have changed the ecosystem, affecting the food web).

  
  

  can affect the indigenous or native species. for example, cane toads from south america were introduced to australia to control the numbers of cane beetle which ate sugar cane crops. however, these toads are poisonous and kill native animals, which is a problem
• 9.9 Explain the positive and negative human interactions within ecosystems and their impacts on biodiversity, including:

  c) eutrophication

  addition of more nutrients to an ecosystem than it normally has. for example, when too much too much fertiliser is added to a field

  
  

  fertilisers help crop plants grow better, however will also increase the growth of other plants and algae. can cause forms of pollution and aquatic animals such as fish to die due to lack of oxygen from photosynthesis, as teh algae blocks sunlight from reaching them
• 9.10 Explain the benefits of maintaining local and global biodiversity, including the conservation of animal species and the impact of reforestation


  reforestation is where trees are planted on mostly moorland areas, which increases the range of habitats and number of species living in the area. now, this can be home to species that are rare in other parts of the uk

  
  

  conservation is when an effort is made to protect a rare or endangered species or habitat (for example, red squirrels are becoming endangered due to grey squirrels, therefore if any grey squirrel is spotted, it will be killed)

  
  

  areas with greater biodiversity can recover faster from natural disasters such as flooding, we can use plants and animals for food and a source of medicine, and as conditions change, we may need new varieties of plants and animals to provide what we need
• 9.12 Describe how different materials cycle through the abiotic and biotic components of an ecosystem

  biotic - water makes up around 60% of your body and much of the cell cytoplasm. we are continuously losing water to the environment so we need to take in more water to replace it

  
  

  abiotic - living organisms need different substances from their environment to stay alive, such as water and carbon and nitrogen compounds. there are only limited amounts of these substances on earth, so they must be recycled through organisms and the environment in order to support life
• 9.13 Explain the importance of the carbon cycle, including the processes involved and the role of microorganisms as decomposers

  Carbon enters the atmosphere as carbon dioxide from respiration and combustion

  
  

  Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis

  
  

  Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die

  
  

  Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion

  
  

  important, as our planet has only a limited stock of chemical elements and they are constantly being recycled in different ways
• 9.14 Explain the importance of the water cycle, including the processes involved and the production of potable water in areas of drought including desalination

  water evaporates from oceans, lakes and rivers to form water vapour. as air rises it cools, so water vapour in it condenses to form clouds. as water droplets get too large and heavy they fall as rain or snow in rivers and lakes. this eventually returns to the ocean

  
  

  to make water portable (safe to drink), it must be treated with chemicals and filtered, to remove dirt, pathogens and any toxic substances (eg metal ions). also may be treated to improve taste, by removing other non toxic substances
• 9.15 Explain how nitrates are made available for plant uptake, including the use of fertilisers, crop rotation and the role of bacteria in the nitrogen cycle (nitrogen cycle)


  • precipitation occurs and enters soil, finds bacteria on plant's root

  • birdied

  nitrogen w/ hydrogen = ammonia = nitrogen fixation

  • ammonia w/ oxygen = nitrification

  • nitrogen now called "nitrite" (NO2)• more bacteria convert nitrite to nitrates (NO3).

  • absorb nitrates w/ assimilation

  • some nitrates can escape to bacteria

  • release nitrates to atmosphere = denitrifying and cycle repeats
• 9.15 Explain how nitrates are made available for plant uptake, including the use of fertilisers, crop rotation and the role of bacteria in the nitrogen cycle (crop rotation)


  • farmers grow peas and beans bc they have nitrogen-fixing bacteria to make nitrate

  • makes soil fertile and full of nitrate

  • crops take in nitrate to make protein for growth

  • diff. crops grown in the same cycle = CR
• 9.15 Explain how nitrates are made available for plant uptake, including the use of fertilisers, crop rotation and the role of bacteria in the nitrogen cycle (fertilisers)

  • natural fertilisers e.g manure and compost to provide nitrate source for crop supply

  • expensive artificial fertilisers e.g ammonia nitrate can be applied to fields for crop supply
• desalination


  obtaining fresh water from the sea or salty water

  
  

  desalination is where the water is evaporated and then condensed under a cover, where it trickles to the bottom of the slope and can be collected