7.4 Ecology and Populations

• What is ecology?

  This is the study if relationships between organisms and their environment.
• What is an environment?

  The biotic and abiotic factors that affect organisms.
• What is interdependence?

  This is how a species within an ecosystem depend on each other, like food and shelter.
• What is an ecosystem?

  This is an area in which a community of organisms interact with each other and their physical environment.
• A population looks at all the organisms of one species in the same habitat at one time.
• A community looks at all the organisms of all populations of species in the same habitat at one time.
• A habitat is the physical environment of an organism or population, including the biotic and abiotic factors.
• A niche is the position that a species occupies within a habitat, governed by biotic and abiotic factors.
• What does the overlap of this graph signify?

  It signifies where the competition occurs for the given niche.

  
• Label these as biotic or abiotic factors:

  Grazing (Eating plants) = Biotic

  Light = Abiotic

  Temperature = Abiotic

  Disease = Biotic

  Competition = Biotic

  Predation = Biotic

  Inorganic ions = Abiotic

  Water availability = Abiotic
• What is the effect of the abiotic factor: temperature?

  Kinetic Energy, Enzymes, rate of reaction, oxygen solubility in water.
• What is the effect of the abiotic factor: humidity/water availability?

  Reactions that take place in a solution, metabolite, evaporation and turgidity.
• What is the effect of the abiotic factor: light intensity?

  The rate of photosynthesis in plants, which in term effects plant biomass (growth).
• What is the effect of the abiotic factor: pH?

  Enzymes, enzyme substrate complexes and rates of reaction.
• Within a habitat, a species occupies a niche governed by adaptation to both abiotic and biotic conditions. An ecosystem supports a certain size of population of a species, called the carrying capacity. Because of this, organisms in one species (intraspecific) and between species (interspecific) will compete for resources and to survive.
• Different species will compete for; food sources, mineral ions (plants), water, living spaces, etc.
• What is interspecific competition?

  This is competition between two different species. Different species try to avoid competition by occupying different niches, allowing coexistence.
• Describe and explain the effects of a reduction in food supply on the populations of two competing species.

  Interspecific competition will occur between these two species causing the niches to overlap and the number of niches to reduce. As a result, the population of the poorer competing species decreases and the population of the better competing species increases.
• What is intraspecific competition?

  This occurs within one species when the conditions change and a resource (e.g. food) becomes limited, causing the population size to be limited.
• Predation is a relationship between two animal species, and it affects the population size of both. The predator hunts kills & eats the prey. Also making predation a form of interspecific competition.
• What are the two types of succession?

  Primary and secondary succession.
• What is primary succession?

  This is the colonisation of bare rock or barren land, e.g. sand dunes.
• What is secondary succession?

  This is the succession on pre-existing soil after an event that has reduced an already established ecosystem occurs, e.g. forest fire.
• Why is succession important?

  Succession is important for land that has been effected by a disaster, like a volcano eruption, which has resulted in a change in conditions and destroyed vegetation can redevelop.
• What is succession?

  Succession is a change in the ecological community over time due to a change in environmental conditions.
• What are pioneer species?

  Pioneer species are resilient species that are first to colonise barren environments, or to repopulate disrupted ecosystems as part of succession.
• What are the features of pioneer species?

  • Reproduce a-sexually.
  • Produce lots of wind-dispersed seeds/spores.
  • Germinate rapidly.
  • Can photosynthesise.
  • Can fix nitrogen levels.
  • Tolerant to extreme conditions - xerophytes.
• What are climax communities?

  These are communities with the same species or a stable community, which have constant abiotic factors and stable populations.
• What are conifer climax communities?

  Conifer climax communities are a less diverse community compared to climax communities due to lots of shading which prevents light from reaching the floor, resulting in less photosynthesis and therefore fewer niches.
• Describe this succession table.

  The pioneer of the succession is Baetis quilleri.

  The pioneer would have changed an abiotic condition (e.g. nutrient levels of plants) which allows a new species (cryptolabis paradoxa) to colonise with a more suitable environment.

  This new species outcompetes the pioneer and the new species (cryptolabis paradoxa and leptohyphes packeri) exist in a climax community, increasing biodiversity.

  
  

  Names written out: Baetis quilleri, Leptohyphes packeri, Helicopsyche mexicana, Cryptolabis paradoxa, Pentaneurini guttipennis, Micropsectra klinki.

  
• How can sampling succession be measured?

  It can be measured by using a belt transect and placing quadrats at regular intervals then recording the percentage cover of the desired species.
• What could you do to conserve a grassland habitat?

  Coppicing (remove) woody plants at regular intervals, e.g. every two years.

  Control the grazing of animals in the habitat.

  Remove competing plant species.
• What is conservation?

  It is the maintenance and protection of the species in a habitat.
• Woods can be coppiced (cut) to provide a continuous supply of useful log and poles. Coppicing involves cutting down some trees in a woody area to leave stumps, where new shoots will grow from. After about 15 years these trees can be coppiced again. Because this produces wood with patches of light and shade, the diversity of plants and animals in a coppiced wood area is high.
• Describe how to sample with quadrats along a belt transect.

  1. Create transects by laying measuring tapes along the habitat.
  2. Collect a large number of samples at regular intervals along the belt transect line.
  3. Count (frequency) all organisms in each quadrat and record abiotic data, e.g. light intensity.
  4. Repeat with a further parallel transect.
  5. Add up organism numbers from equal distance up the transects and divide by number of transects to calculate the mean.
  6. Test for a significant correlation and the probability that the result is due to chance.
• Why do we use statistical tests?

  1. It enables a null hypothesis to be accepted or rejected.
  2. It determines whether a correlation or a difference is significant.
  3. A statistical test determines the probability of the result being due to chance.