Ecology and Environment
Table of Contents
- Basic Chemistry, Organic Molecules and Enzymes
- Cells, Membranes and Viruses
- Cellular Respiration and Photosynthesis
- DNA Replication and Protein Synthesis
- Genetics and the Cell Cycle
- Evolutionary Biology
- Diversity of Organisms
- Plant Structure and Function
- Circulation, Respiration, Digestion, and Excretion
- The Immune, Lymphatic, and Endocrine Systems
- Development and Behavior
- The Musculoskeletal and Nervous Systems
- Ecology and Environment
This section covers the following topics
- Levels of ecology
- Different biomes
- The water, carbon and nitrogen cycles
- The ecological pyramid
- Exponential and logarithmic population growth
- Ecological succession
- Current issues in ecology
Section Summary
Ecology can be studied on four different levels. Scientists examine the entire biosphere, individual ecosystems, communities or populations.
Aquatic environments are divided into layers. Photosynthesis is possible in the trophic layer, but impossible in the deeper atrophic layer. The benthic layer is the sediment at the bottom of an ocean or lake, and is populated by organisms collectively called the benthos. Detritus, or organic material that falls from the trophic layer, feeds much of the benthos. Thermoclines, or sharp changes in temperature at a certain depth, are often present in lakes. Turnover refers to the mixing of water in lakes.
Water, carbon and nitrogen go through different cycles. Energy enters the Earth via light from the sun and exits as heat. The ecological pyramid, which shows the relative numbers of different types of organisms in a community, is made up of producers and different types of consumers. Only about 10% of the energy taken in by an organism can be passed to the next highest tropic level. Decomposers digest and eat the dead bodies of organisms from every level of the pyramid. Toxins tend to collect in higher concentrations at higher tropic levels in a phenomenon called biological magnification. Common interactions between organisms include mutualism, commensalism, parasitism, competition and predation.
Populations are measured based on their density, dispersion and demographics. Life tables and survivorship curves show the rates at which organisms reproduce and survive, respectively. In terms of reproductive strategy, organisms can exhibit semelparity (big-bang reproduction) or iteroparity (repeated reproduction) and can be influenced by R-selection or K-selection.
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