AP Biology Unit 8: Ecology

Ecology

The scientific study of the interactions between organisms and their environment.

Abiotic components

Nonliving chemical and physical factors such as temperature, light, water, and nutrients.

Organismal ecology

Concerned with the behavioral, physiological, and morphological ways individuals interact with the environment.

Population

A group of individuals of the same species living in a particular geographic area.

Population ecology

Examines factors that affect population size and composition.

Community

Consists of all the organisms of all of the species that inhabit a particular area.

Community ecology

Examines the interactions between species and considers how factors such as predation, competition, disease, and disturbance affect community structure and organization.

Ecosystem

Consists of all the abiotic factors in addition to the entire community of species that exist in a certain area.

Ecosystem ecology

Studies energy flow and cycling of chemicals among the various abiotic and biotic components.

Landscape/seascape

Consists of several different ecosystems linked by exchanges of energy, materials, and organisms.

Landscape ecology

Deals with arrays of ecosystems and their arrangement in a geographic region. Focuses on factors controlling the exchanges of energy, materials, and organisms among patches.

Patchiness

Each landscape consists of a mosaic of different types of patches.

Biosphere

The global ecosystem, or the sum of all of the planet’s ecosystems. It includes the entire portion of Earth inhabited by life (atmosphere, ocean, etc.).

Biogeography

The study of past and present distributions of individual species in the context of evolutionary theory.

Dispersal

The movement of individuals away from centers of high population density or from their area of origin. It is crucial to understanding geographic isolation in evolution.

Transplant

One way to determine if dispersal is a key factor limiting distribution.

Successful transplant

The organisms must not only survive in the new area but also reproduce there. It means that the potential range of the species is larger than its actual range.

Limitations of transplants

Species introduced to new geographic locations may disrupt the communities and ecosystems to which they are introduced and therefore are rarely conducted in experiments today.

Habitat selection

Sometimes organisms do not occupy all of their potential range but select particular habitats and limits distribution.

Biotic factors that limit distribution

Negative interactions with other organisms (predation, parasitism) that limit the ability of organisms to survive and reproduce.

Absence of other species can limit distribution (ex: absence of prey or a specific pollinator).

Abiotic factor limiting distribution: environmental temperature

Very few organisms can maintain an active metabolism at very high or very low temperatures.

Some organisms have adaptations to allow them to live outside the temperature range habitable for most others.

Abiotic factor limiting distribution: water variability

Most aquatic organisms are restricted to either freshwater or marine environments.

Terrestrial organisms face a constant threat of desiccation and have to obtain and conserve water.

Abiotic factor limiting distribution: sunlight

Intensity of light is not extremely important in limiting plant growth in terrestrial environments, though shading by a forest canopy makes competition intense.

Light intensity limits distribution in photosynthetic organisms because water absorbs so much light. Therefore, most photosynthesis occurs near the surface.

Photoperiod

The relative length of daytime and nighttime, and is a reliable indicator of seasonal events and is an important cue for the development or behavior of many organisms.

Abiotic factor limiting distribution: wind

Amplifies the effects of temperature by increasing heat loss due to evaporation and convection.

Increase water loss by increasing the rate of evaporative cooling/transpiration.

Abiotic factor limiting distribution: structure/composition

The physical structure, pH, and mineral composition of soil and rocks that limit the distribution of plants and thus the animals that feed upon them.

Substrate composition can affect water chemistry and the ability for organisms to attack or burrow into those habitats.

Climate

The prevailing weather conditions in an area. Determines the makeup of biomes.

Four abiotic factors: climate

Temperature, water, sunlight, and wind are the major components of climate. They have a major influence on the distribution of organisms.

Macroclimate

Patterns on a global, regional, or local level.

Microclimate

Very fine patterns such as the conditions experienced by a community of organisms under a fallen log.

Global climate patterns

Determined by sunlight and Earth’s movement in space.

The sun’s warming effect on the atmosphere, land, and water establishes the temperature variations, air movement and evaporation of water that leads to latitudinal variations in climate.

How do bodies of water and topographic features affect climate?

Bodies of water and topographic features such as mountain ranges create regional climatic variations, while smaller features of the landscape affect local climates.

How do ocean currents influence climate?

They heat or cool overlying air masses, which may pass over land. In certain areas, cool, dry ocean breezes are warmed when they move over land, absorbing moisture and creating a hot, rainless climate slightly inland.

Coastal regions are generally moister than inland areas at the same latitude.

How do mountains influence climate?

They have a significant effect on the amount of sunlight reaching an area, as well as local temperature and rainfall (Ex: south-facing slopes receiver more sunlight than north-facing slopes, and are warmer and dryer).

How does temperature change with altitude/latitude?

Air temperature declines 6 degrees Celsius for every 1,000m increase in elevation. Similarly, 6 degrees Celsius of temperature is decrease for every 880km increase in latitude.

Rainfall in mountains

Moist, warm air approaches a mountain, rises and cools, and releases moisture on the windward side of the peak. On the leeward side, cool, dry air descends, absorbing moisture and producing a rain shadow.