populations in ecosystems

• Habitat


  The place where an organism lives, e.g. a rocky shore or a field
• Population


  All the organisms of one species in a habitat
• Community


  Populations of different species in a habitat make up a community
• Ecosystem


  A community, plus all the non-living (abiotic) conditions in the area in which it lives. Ecosystems can be small, e.g. a pond, or large, e.g. an entire ocean
• Abiotic conditions


  The non-living features of the ecosystem, e.g. temperature and availability of water
• Biotic conditions


  The living features of the ecosystem, e.g. the presence of predators or food
• Niche


  The role of a species within its habitat, e.g. what it eats, where and when it feeds
• Adaptation


  A feature that members of a species have that increases their chance of survival and reproduction, e.g. giraffes have long necks to help them reach vegetation that's high up. This increases their chances of survival when food is scarce
• Every species has its own unique niche - a niche can only be occupied by one species
• If two species try to occupy the same niche, they will compete with each other. One species will be more successful than the other, until only one of the species is left
• Common pipistrelle bat


  • Lives throughout Britain on farmland, open woodland, hedgerows and urban areas. Feeds by flying and catching insects using echolocation (high-pitched sounds) at a frequency of around 45 kHz
• Soprano pipistrelle bat


  • Lives in Britain in woodland areas, close to lakes or rivers. Feeds by flying and catching insects using echolocation, at a frequency of 55 kHz
• It may look like both species are filling the same niche (e.g. they both eat insects), but there are slight differences (e.g. they use different frequencies for their echolocation)
• Adaptations


  Features that increase an organism's chance of survival and reproduction
• Types of adaptations


  • Physiological (internal body)
  • Behavioural (way an organism acts)
  • Anatomical (structural features of the body)
• Organisms with better adaptations


  Are more likely to survive, reproduce and pass on the alleles for the adaptations
• Every species is adapted to use an ecosystem in a way that no other species can
• Niche


  An organism's unique way of using an ecosystem
• Organisms are adapted to both the abiotic conditions (e.g. how much water is available) and the biotic conditions (e.g. what predators there are) in their ecosystem
• Adaptations to abiotic conditions

  • Otters have webbed paws
  • Seals have a thick layer of blubber
  • Hedgehogs hibernate
• Adaptations to biotic conditions

  • Sea otters use rocks to smash open shellfish and clams
  • Male frogs produce mating calls to attract females
  • Some bacteria produce antibiotics
• Population size


  The total number of organisms of one species in a habitat
• Carrying capacity


  The maximum population size of a species that an ecosystem can support
• Carrying capacity


  • Varies as a result of both abiotic and biotic factors
  • Depends on the chemical composition of the surroundings
• When abiotic conditions are ideal for a species

  Organisms can grow fast and reproduce successfully
• When abiotic conditions are not ideal for a species

  Organisms can't grow as fast or reproduce as successfully
• Interspecific competition


  Competition between different species for the same resources
• Interspecific competition


  • Can reduce the resources available to both populations
  • Can lead to one species out-competing the other
• Intraspecific competition


  Competition within a species for the same resources
• Population changes over time

  1. Population increases when resources are plentiful

  2. Population declines when resources become limiting

  3. Population starts to grow again when competition for resources decreases
• As prey population increases


  Predator population grows
• As predator population increases


  Prey population begins to fall
• As prey population falls

  Predator population decreases
• Predator-prey relationships are usually more complicated than this because there are other factors involved, like availability of food for the prey
• Random Sample


  A sample taken in a way that gives each individual in the population an equal chance of being selected
• You need to take a Random Sample from the Area You're Investigating
• Quadrats and Transects are used to Investigate Non-Motile Organisms
• Using Quadrats


  1. Choose an area to sample

  2. Place quadrats randomly within the area

  3. Count the number of individuals of each species in the quadrat

  4. Measure the percentage cover of each species
• Using Transects


  1. Place quadrats next to each other along a transect line

  2. Measure species frequency and percentage cover along the transect
• Mark-Release-Recapture


  A method used to measure the abundance of more motile species