- Define ecology and describe the major sub-disciplines: behavior, population ecology, community ecology
- Explain the physical forces that lead to atmospheric and ocean circulation patterns and predict the local, regional, and global effects if forces change
- Predict how changes in temperature and precipitation patterns (climate) can alter species ranges and biome locations
Ecology and its sub-disciplines
Ecology is the study of how organisms interact with their environment. These interactions range from how an individual responds to a stimulus (behavior), how individuals of the same species interact with each other (population ecology), different species interact (community ecology), and how organisms interact with non-living components of the environment (ecosystem ecology). The entire set of interactions on a planet is called the biosphere.
Climate Patterns affect where communities live in the biosphere
Where organisms live on the planet is governed by global scale processes caused by the orientation of the earth’s axis toward the sun, heat retention versus loss in the atmosphere, and by the rotation of the earth. The atmosphere-ocean system is a very, very large heat engine (refer to the Hadley Cell Cross-Section figure below). Sunlight input at the equator heats the water and air along the equator. Water becomes water vapour and rises with the heated air to up into the atmosphere (1). The rising air cools, causing precipitation in equatorial regions. The warm but dry air is pushed out of the way by the expanding hotter air below (2). Once it cools, the air falls back to earth, this time without accompanying moisture (3). The high pressure created by the falling air redistributes to locations of lower pressure (4), such as the equator, establishing an air conveyor.
Scaled up to the entire, spherical planet, the Hadley cell and it’s companion cells at mid-latitudes and the poles establish significant north-south air and precipitation gradients. Because the earth is rotating on it’s axis, the north-south patterns become disrupted by the Coriolis effect to establish the prevailing wind patterns seen as trade winds and westerlies in the figure below.
Based on where these patterns of heat, wind, and precipitation, where do you predict the world’s deserts should be?
Deserts are one of many common communities, which are classified according to temperature and precipitation profiles into biomes. Biomes can be terrestrial (shown below), aquatic, or marine.
This view of biomes arranged by their location on the planet allows us to see global community patterns, such as how deserts or forest communities are organized with respect to latitude. Interruptions to the this pattern occur when major geologic features run counter to latitude. For example, the Andes in South America set up north-to-south biomes along the west coast, disrupting the east-to-west patterns evident in Africa.
Alternatively, if we categorize biomes along axes of temperature and precipitation then we can use the graphical organization to predict how environmental changes can alter the biome found in a specific location.
If a wet tundra biome experiences an increase in average annual temperature, what biomes would you predict the community in that location to shift to over time?
In biomes governed by water, precipitation matters less while temperature and winds take on a more dominant role. One example of this is ocean upwelling, depicted in the figure below.
In smaller freshwater aquatic systems, seasonal temperature change causes the greatest fluctuations in water temperature and water movement, called turnover. In winter, a lake or pond covered by surface ice has stratified temperature layers, and nutrients slowly settle to the bottom in the still waters. Water remains liquid to 0 degrees C, but it’s most dense at 4 degrees C, so once the air temperatures rise in spring, the surface waters warm slightly and become more dense than the colder layer below. The dense surface waters sink, pushing the deeper, nutrient rich waters to the surface, and turning over the nutrients from bottom to top. Waters stratify again in the summer, and experience turnover again in the fall as surface temperatures drop down, making surface water more dense.
How would you relabel the temperatures in the diagram above so that they more accurately reflect the turnover process?