Topic 9: Ecosystems

• Community - all the organisms of different species in a habitat

  Population - all the organisms of one species in a habitat

  Habitat - a place where animals, plants and microorganisms live
• All organisms in an environment form an ecosystem and they're a community as they live and interact. Each population lives in a certain habitat
• Interdependence - when organisms depend on each other for things like food/shelter to survive and reproduce

  This means that a population change in one species can have massive effects for other species in that community
• Abundance - a measure of how common something is in an area like population which can be estimated by taking samples using a quadrat
• Quadrat/Belt Transect Practical:

  1. Place a 1m2 quadrat at a random point in the first sample area
  2. Count all interesting organisms within then repeat steps multiple times
  3. Multiply known quadrat areas to match the sample area after finding the mean for a population estimate
  4. Placing the quadrats in a row creates a belt transect which can be used to form a graph with a gradient showcasing if a changing abiotic factor is correlated to distribution in a habitat
  5. Other data such as mean height and light intensity can be recorded
• The sun is the source of energy for almost all life on Earth.

  Plants and algae are producers as they create their own organic nutrients using sunlight (energy used in respiration while rest is stored in biomass)
• Primary consumers (usually herbivores) eat the producers, then the secondary consumers (usually carnivorous) eat the primary consumers and so forth
• Biomass is passed through the food chain but energy is lost:

  • respiration
  • transferred to surroundings by heat
  • not all of the organism is eaten (e.g. bones)
  • undigested material is lost by faeces

  This is why food chains hardly have over 5 tropic levels, the number of organisms decreasing as the level increases
• A pyramid of biomass shows the total weight of the organisms at each tropic level and the amount of energy.

  Each time you go up a tropic level, the mass of organisms decrease as biomass/energy is lost each time
• Abiotic factors are non-living:

  • temperature
  • amount of water
  • pH
  • light intensity
  • levels of pollutants
• Each species has adaptations meaning a change in abiotic factors could:

  • change the distribution of populations (cannot survive droughts)
  • increase/decrease population size (whole community is affected if polar bears are driven out by temperature changes)
  • harm their habitats (pollutants poisoning area)
• Biotic Factors - the organisms in an ecosystem that affect other organisms such as through competition and predation
• Competition - when organisms compete with other and their own species for the same resources meaning populations can decrease depending on what is available
• Predation - when a predator species is dependent on a prey species population and vice versa, meaning as predators decrease prey increases as they are eaten less which can increase competition
• Predation in small communities mean the numbers are similar in a predator-prey cycle and controlling this can increase biodiversity:

  • reintroduction of wolves to Yellowstone Park USA rapidly reduced elk populations
  • increased beaver populations as there was less competition from elks
  • dams created by beavers allowed new species to grow in the habitats
• Indicator species - organisms that are sensitive to environmental changes and so their presence/absence can be used to monitor pollution
• Water pollution can be shown through 4 invertebrate indicators:

  • Stonefly Larvae/Freshwater Shrimps - good indicators for clean water as they're sensitive to the concentration of dissolved oxygen
  • Bloodworms/Sludge worms - adapted to live in polluted conditions so indicate high water pollution levels
• Air pollution can be indicated through a plant and fungus:

  • Lichen - very sensitive to sulfur dioxide concentrations meaning its presence indicates clean air, especially if bushy
  • Blackspot Fungus - found on rose leaves and has the same principles as lichen
• Advantages of Indicator Species:

  • simple
  • cost-effective
  • quick
  • numerical value allows comparison
  • shows long-term health
• Disadvantages of Indicator Species:

  • doesn't show exact pollution values (inaccurate)
  • other factors can effect species
• Indictor Species Solutions:

  • dissolves oxygen meters and chemical tests for water pollution
  • electronic meters/lab tests for air pollution
• Parasitism - when one organism benefits by feeding off a host organism, causing harm to the host
• Parasites live in or on the host which can survive for a long time, feeding the parasite, if limited harm is caused.

  For example, roundworms absorb nutrients from human body fluids which will block the flow and cause extreme swelling
• Mutualism - when some organisms that live together both benefit from the relationship like clownfish (provide nutrients/chase predators) and sea anemones (provide protection)
• Parasitism Examples:

  • tapeworms (human intestine)
  • head lice (hair/skin)

  Mutualism Examples:

  • flowers (provides pollen/nectar) and bees (pollination)
  • polyps (provides protection) and algae (provides food)
• Eutrophication - when an excess of nutrients in water (fertilisers) causes the algae to grow rapidly on the water surface
• Eutrophication blocks light so plants can't photosynthesise causing them to die and decompose.

  Microorganisms increase and use up oxygen which kills organisms that require aerobic respiration (fish die so biodiversity decreases)
• Non-indigenous species don't naturally occur as they're introduced intentionally or unintentionally (food/stowaway) and can cause problems for indigenous species.

  Non-indigenous species compete with indigenous species for recourses and sometimes outcompete them and introduce new diseases which decreases biodiversity
• Fish farms reduce biodiversity and was made to combat overfishing:

  • food in nets produce waste which can leak into open water and cause eutrophication
  • breeding ground for parasites that can kill wild species
  • kill predators trapped in nets
  • fish could escape to cause problems for indigenous species
  • very low biodiversity
• Conservation - when an effort is made to protect rare/endangered species or habitats which can be done through reforestation and animal conservation schemes
• Reforestation - when a cut-down area is replanted to form a new forest to restore biodiversity after deforestation

  It must be carefully planned so that the forest has a high biodiversity that provides lots of food/shelter for different animal species
• Animal Conservation Schemes protect biodiversity by preventing species from extinction through:

  • protecting a natural habitat
  • seed banks to store and distribute endangered plants
  • protecting species in safe areas outside their natural habitat (zoos)
  • captive breeding programmes to increase populations
• There are lots of benefits to wildlife and humans on a local and global scale: (1)

  • Protecting Human Food Supply - overfishing greatly reduced fish stocks and future generations need to eat
  • Ensuring Minimal Damage to Food Chains - species are interdependent in a food chain so helping one species will help others
  • Providing Future Medicines - undiscovered plants may contain new medicinal chemicals
• There are lots of benefits to wildlife and humans on a local and global scale: (2)

  • Cultural Aspects - individual species may be a symbol of a nation or area cultural heritage
  • Ecotourism - brings money into biodiverse areas and educates people about the environment
  • Providing New Jobs - employment opportunities for local people
• Food Security - having access to enough safe and healthy food at all times

  Our rapidly growing population meaning more food must be grown to meet rising demand
• Pests and pathogens can damage crops/livestock which decreases yield.

  As wealth increases, more meat and fish is consumed which can lead to overfishing/deforestation even though more biomass is taken in through crops than animals
• Fossil fuels release carbon dioxide which is a greenhouse gas that contributes to climate change.

  Global warming may lead to soil pollution which affects crop growth and decreases yield
• To become sustainable, biofuels are renewable alternatives but they take up crop land and have high input costs, making it too expensive for farmers to maintain food production and continue farming
• The Water Cycle:

  1. Energy from the sun evaporates water into water vapour (transpiration)
  2. Water vapour rises and condenses to form clouds
  3. Water precipitates (rain, snow, hail, sleet) to provide fresh water for land plants and animals before draining back to a large body of water
• Desalination can be used during droughts to produce potable water (removes mineral ions like salts from salt water) through methods like thermal desalination and reverse osmosis