ecology

• levels of organisation in an ecosystem : individual -> population -> community -> ecosystem
• an ecosystem is the interaction of a community of living organisms with the abiotic and biotic parts of their environment
• organisms which need the same resource compete for it:

  • interspecific competition - organisms from different species compete for the same resources
  • intraspecific competition - organisms from the same species compete for a resource
• plants may compete for: light, space, water and mineral ions
• animals may compete for: mating partners, territory / space, food and water
• to survive and reproduce organisms require a supply of materials from their surroundings and from the other living organisms there
• • interdependence describes how organisms in a community depend on each other for vital services
  • these include:
  • food
  • shelter (birds take shelter in trees)
  • reproduction (flowers are pollinated with the help of bees)
• the removal or addition of one species can affect the whole community as it changes predator or prey numbers
• a stable community is one where all the species and environmental factors are in balance, so population sizes remain roughly constant
• the predator-prey cycle:

  1. when predator numbers are lower, the prey population starts to grow
  2. as the prey population increases, the predator population increases because there is more food
  3. the number of prey reduces because there are more predators
  4. so the predator population decreases because there is less prey
• abiotic factor -- light intensity:

  • light is required for photosynthesis
  • the rate of photosynthesis affects the rate at which the plant grows
  • plants can be food sources or shelter for many organisms
  • light intensity also affects rate of decay
• abiotic factor -- temperature:

  • temperature affects the rate of photosynthesis (increased temp means increased photosynthesis)
  • rate of photosynthesis affects the rate at which the plant grows
  • and plants can be food sources and shelter for many organisms
• abiotic factor -- moisture levels:

  • both plants and animals need water to survive
• abiotic factor -- soil pH and mineral content:

  • soil pH affects the rate of decay and therefore how fast mineral ions return to the soil, which are then taken up by other plants, used for growth)
  • different species of plants thrive in different nutrient concentration levels
• abiotic factor -- wind intensity and direction:

  • wind affects the rate of transpiration in plants
  • transpiration affects the temperature of the plant and the rate of photosynthesis because transpiration transports water and mineral ions to the leaves
• abiotic factor -- carbon dioxide levels:

  • carbon dioxide affects the rate of photosynthesis in plants
  • it also affects the distribution of organisms as some thrive in high carbon dioxide environments (extremophiles)
• abiotic factor -- oxygen level (aquatic animals):

  • oxygen levels in the ocean can vary greatly
  • most fish need high oxygen concentrations to survive
• biotic factors -- food availability:

  • more food means organisms can breed more successfully and therefore population numbers can increase
• biotic factors -- new predators:

  • increased competition between predators means predator populations can decrease
  • prey population decreases
• biotic factors -- new pathogens:

  • when a new pathogen spreads, populations have no resistance or immunity so populations can be wiped out quickly
• biotic factors -- competition:

  • if one species is better adapted to the environment than another, it will outcompete it until the numbers of the lesser adapted species are insufficient to breed
• organisms have features (adaptations) that enable them to survive in the conditions they normally live in
• a structural adaptation is a feature that helps an organism survive:

  • sharp teeth of a carnivore to tear meat apart
  • camouflage
  • thick layer of fat as insulation for species in a cold environment
• a behavioural adaptation is a behaviour that helps an organism survive:

  • courting behaviour to attract a mate
  • penguins huddling
• a functional adaptation is a biological process within an organism that helps it survive:

  • snake producing venom
• extremophiles are organisms that live in environments that are very extreme, such as in high temperatures, pressures or salt concentrations
• bacteria living in deep sea vents are extremophiles
• examples of adaptations -- cold climates:

  • smaller surface area to volume ration to reduce heat loss, thick insulating layer of fat
• examples of adaptations -- dry climates:

  • adaptations to kidneys to produce highly concentrated urine, large surface are to volume ratio, being active early morning and late at night when its cooler
• photosynthetic organisms are the producers of biomass for life on earth
• relationships are shown by food chains
• all food chains begin with a producer (usually a green plant or algae) which is always a photosynthetic organism. Through photosynthesis they produce glucose, which is used to make up other biological molecules in the plant, and this makes up biomass
• producer -> primary consumer -> secondary consumer -> tertiary consumer
• energy is transferred through organisms in an ecosystem when one is eaten by another
• in a stable community, the numbers of predators and prey rise and fall in cycles
• consumers that kill and eat other animals are predators, and those eaten are prey
• many different materials cycle through the biotic and abiotic components of an ecosystem
• all material in the living world are recycled (broken down into their base materials, and then those base materials are reused) to provide the building blocks for future organisms
• the carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis
• carbon is a finite resource meaning there isn't an endless supply of carbon, but all complex biological molecules are made up from carbon, so it needs to be recycled to sustain life and allow new organisms to be made and grow