Comprehensive Notes on Population Ecology and Biomes

The study of population ecology focuses on a core question: how the interactions between individuals within populations assist in maintaining relatively consistent numbers of organisms.

Biological systems are organized in a hierarchy from simple atoms to the entire biosphere: - Atoms - Molecules - Macromolecules - Organelles - Prokaryotic Cell - Eukaryotic Cell - Tissue - Organ - Organ system - Organism - Population - Community - Ecosystem - Biome - Biosphere
The "organism" level of organization is inclusive of prokaryotes, single-celled eukaryotic organisms, and multicellular organisms.

Exponential Growth: - Characterized by unlimited resources. - The growth curve is J-shaped. - Bacteria frequently demonstrate this specific kind of standard exponential growth curve.
Human Population Growth: - The human population has historically shown periods of exponential growth. - Because resources are finite on Earth, human population growth is currently starting to level off.
Logistic Growth: - Occurs when resources are limited. - The resulting curve is S-shaped. - Growth stabilization occurs at the point where the number of births equals the number of deaths: \text{# Births} = \text{# Deaths}.

Carrying capacity is defined as the largest population that a specific environment can support.
Variations and Overshoots: - Populations may oscillate over and under the carrying capacity. - If a population overshoots the capacity and the environment is consequently degraded, the carrying capacity of that environment will drop.

Population Size is denoted as $N$ .
Population Density: - Defined as the number of individuals per unit area. - There is a common correlation where density decreases as the physical size of the organisms increases.
Population Distribution Types: - Uniform: Each individual organism is equally spaced out. - Random: There is no discernable pattern to the spacing. - Clumped: Organisms are found in groups, or offspring settle in close proximity to their parents.

Density Dependent Factors: - The effect of these factors is contingent upon the density of the population. - These are mostly biotic factors. - Primary examples include competition, predation, and disease.
Density Independent Factors: - These factors affect a population regardless of its current density. - These are mostly abiotic factors. - Primary examples include natural disasters, weather/climate, and pollution.

Populations that are linked through predation can show oscillations over time.
In these dynamic cycles, one population typically lags behind the other in growth or decline.
Example: The populations of Lynx and Hares are classic examples of predator-prey dynamics.

A biome is a large geographical area characterized by similar ecosystems, including similar plants, animals, and climate (temperature and precipitation).
Determinants of Biomes: - Mean annual precipitation (measured in $\text{cm}$ ). - Mean annual temperature (measured in $^\circ\text{C}$ ).
Major Biome Categories: - Tundra - Coniferous Forest - Deciduous Forest - Desert - Grassland - Tropical Rainforest
Regional Example: Virginia is categorized as part of a temperate deciduous forest biome, where many trees shed their leaves annually.