Ecology

• Ecosystem


  The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
• Abiotic factors


  • Temperature
  • Light intensity
  • Carbon dioxide level
  • Wind intensity and direction
  • Oxygen level
  • Salinity and mineral content
• Biotic factors


  • New predators
  • Competition
  • New pathogens
  • Availability of food
• Organisms need things from their environment and from other organisms in order to survive and reproduce
• Plants need light, space, water and minerals from the soil
• Animals need space, territory, food, water and mates
• Organisms compete with other species and members of their own species for the same resources
• A change in any environment

  Can have knock-on effects
• In a community, each species depends on other species for things such as food, shelter, pollination and seed dispersal - this is called interdependence
• The interdependence of all the living things in an ecosystem means that any major change in the ecosystem (such as one species being removed) can have far-reaching effects
• Effects of loss of stonefly larvae

  • Algae increase
  • Blackfly larvae decrease
  • Water spider decrease
  • Stickleback decrease
• Stable communities include tropical rainforests and ancient oak woods
• A decrease in light intensity, temperature or carbon dioxide level


  Decreases the rate of photosynthesis in plants
• A decrease in mineral content of soil

  Causes nutrient deficiencies in plants
• A new predator


  Causes a decrease in the prey population
• Grey squirrels


  Outcompete red squirrels, so red squirrel population decreases
• Adaptations


  • White fur for camouflage
  • Thick blubber layer
  • Thin fat layer and large surface area
  • Producing little sweat and concentrated urine
  • Hibernating and lowering metabolism
• Extremophiles


  Microorganisms adapted to live in very extreme conditions like high temperatures, high salt concentrations or high pressure
• Using quadrats to study distribution

  1. Place quadrat at random location

  2. Count organisms within quadrat

  3. Repeat in multiple locations

  4. Calculate average density
• Quadrats give quantitative data on the distribution of organisms
• In the playing field, you might find that debies are not common in the open than under trees, because there's min light available in the open
• To study the distribution of an organism

  1. Measure how common an organism is in two sargiemas ng using saduts and compare them

  2. Study how the distribution charan across an area, eg, by placing quadam along at 158
• Both of these methods give quantitative data inamben about the distribution
• Use Quadrats to Study The Distribution of Small Organisms

  1. Place a quadrat on the ground at a random paint within the fint sample area

  2. Count all the organisms within the quadrat

  3. Repeat steps 1 and 2 as many smes as you can

  4. Work out the mean number of organisms per quadrat within the first sample area

  5. Repeat steps 1 to 4 in the second sample area

  6. Compare the two means
• To Work Out the Population Size of an Organism in One Area

  1. Work out the mean number of organisms per m²

  2. Then multiply the mean by the total area (in m) of the habitat
• Use Transects to Study The Distribution of Organisms

  1. Mark a starting point in the area you want to study

  2. Then collect data along the line

  3. You can do this by counting all the organisms u counted in for each the nets

  4. You can also collect data by using Quadrats placed next to each other along the line
• Estimate the Percentage Cover of a Quadrat

  1. Count the number of squares covered by organism A

  2. Make this into a percentage-divide the number of squares covered by the organism by the total number of squares in the quadrat (100, then multiply the result by 100

  3. Do the same for organism B
• You don't need fancy kit to study the distribution of ani
• The amount of water on Earth is pretty much constant-but where it is changes
• The Water Cycle


  1. Energy from the Sun males water esaposate from the land and sea, turning it into water vapour

  2. The warm water vapour is carried upwards and cools down and farm clouds

  3. Water falls from the clouds as peecipitation usually rain, but sometimes snow or hall onto land, where at provides fresh water for plans and animals

  4. It then drains into the sea before the whole process starts again
• All the nutrients in our even are constantly being recycled- there's a nice balance between what goes in and what goes out again
• The Carbon Cycle


  1. CO, is removed from the atmosphere by green plants and algae during photosynthesis

  2. When the plants and algae are eaten by animals, some carbon becomes part of the fats and proteins in their bodies

  3. When plants, algae and animals die, other animals (called detritus feeders) and microorganisms feed on their remains

  4. The combustion (burning) of wood and fossil fuels also releases CO, back into the air
• Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem
• Importance of biodiversity


  • High biodiversity makes sure that ecosystems are stable because different species depend on each other for things like shelter and food
  • For the human species to survive it's important that a good level of biodiversity is maintained
• Lots of human actions, including waste production and deforestation as well as global warming are reducing biodiversity
• The population of the world is currently rising very quickly, and it's not slowing down
• Reasons for population growth

  Modern medicine and farming methods have reduced the number of people dying from disease and bunge
• Our increasing population puts pressure on the environment as we take the resources we need to survive
• People around the world are also demanding a higher standard of living, which means we use more raw materials and energy for manufacturing processes
• Many raw materials are being used up quicker than they're being replaced