Biodiversity – variability among living organisms from all sources including diversity between and among
species and ecosystems.
Ecology- the scientific study of the interactions between organisms and their environment.
Early (simplistic and inaccurate) Ecological views:
- There is a balancer of nature in which natural systems are stable and tend to return to an
original state following a disturbance
- Each species has a distinct role to play in maintaining that balance.
View that has stood the test of time:
- Events in nature are interconnected, and most species interact indirectly through resources.
Energy moves through ecosystems in a single direction it is unable to be recycled. Nutrients are
Levels of Organization:
- Individual: single organism
- Population: A group of individuals of the same species
- Community: Multiple populations of different species living in the same geographical area.
- Ecosystem: A biological community of interacting organisms and their physical environment.
Two Types of Scale:
- Spatial Scale: Based on space
- Temporal Scale: based on time
Ecologists evaluate competing hypotheses about natural systems with experiments, observations and
quantitative models. They answer questions by:
- Observations in the field
- Experiments in the field
- Controlled lab experiments
- Quantitative models
- Assign treatments at random
- Statistically analyze to determine effects
Controls are used to account for anything that may affect the result. Experiments have three attributes (n which no experiment can satisfy all of):
No single factor can explain the decline of amphibian populations.
Nitrate concentration when combines with UV light resulted in a decline in tadpole survival.
The physical environment ultimately determines where organisms can live and what resources are
available to them. Climate is the most fundamental characteristic of the physical environment, it
determines geographic distribution of organisms.
There are three global atmospheric circulation cells (which result in three major climatic zones):
- Hadley (tropical)
- Ferrel (temperate)
- Polar (polar)
Regional climate can be affected by topography and water bodies.
Evaportranspiration – the sum of water lost through transpiration by plants and evaporation from the
soil. It transfer energy in the form of latent heat (change of state) and water into the atmosphere,
affecting air temperature and moisture.
Biosphere – zone of life on earth. Between lithosphere and troposphere.
Biomes – large biological communities shaped by the physical environment, particularly climatic
variation. Based on similarities in the morphological responses of organisms to physical environment.
Terrestrial biomes – characterized by the dominant growth forms of vegetation. Classified by the growth
form of most abundant plants. Characteristics of leaves may be used:
- Deciduousness – seasonal shedding of leaves
- Succulence – development of fleshy water storage tissues
Biological Zones in freshwater systems are associated with velocity, depth, temperature, clarity and
chemistry of water.
Benthic zone – ecological zone at the lowest level of a body of water, it includes the sediments. (in
oceans: sparsely populated, freezing temperatures, high pressure)
Littoral zone – nearshore zone where the photic zone reaches the bottom
Photic zone – surface layers of water where there is enough light for photosynthesis (0.5-200m) Pelagic zone – open water Include: Nekton (swimming organisms capable of overcoming ocean
currents), phytoplankton (plants), zooplankton (animals)
Marine biological zone are determined by ocean depth, light availability, and the stability of the bottom
Autotrophs- make energy from photosynthesis or chemosynthesis. Energy stored in carbon-carbon
bonds. Carbon is the currency used for measure of primary production. Primary productivity is the rate
of primary production.
Gross Primary Production – total amount of carbon fixed by autotrophs in an ecosystem. Depends on
the climatic influence on photosynthetic rate and the leaf are index – leaf area per unit of ground area.
LAI = 1 means that 100% of the ground is covered by leaves.
Net Primary Production = GPP – respiration. Energy left over for plant growth and consumption by
detritivores and herbivores. In nutrient poor biomes, over 50% of NPP is allocated to roots, in biomes
where competition for light is important a smaller percentage is allocated to roots.
Normalized difference vegetation index – uses the difference between visible light (VIS) and near
infrared reflectance (NIR) to estimate the absorption of light by chlorophyll. (NIR – VIS) / (NIR + VIS)
Harvesting techniques are not used for phytoplankton instead photosynthesis and respiration are
measured in water samples.
Global NPP ~ 1.05 *10^17g of Carbon per year. 54 % by terrestrial ecosystems. 46% by oceans.
Net primary productivity is constrained by both physical and biotic environmental factors. Nutrients
control NPP in terrestrial ecosystems. In lakes NPP is often limited by phosphorus. In Open Ocean NPP is
limited by nitrogen. In the equatorial Pacific ocean iron is the limiter.