Ecology Section two notes Anna Morrison

Ecological Succession Succession: the sequence of biotic changes that regenerate a damaged community or create a community in a previously uninhabited area Primary Succession: the establishment and development of an ecosystem an area that was previously uninhabited; starts with bare rock Examples: when a glacier retreats or when lava cools Pioneer Species: the first organisms that live in a previously uninhabited area (examples: lichens and some mosses)

Ecological Succession Secondary Succession: the reestablishment of a damaged ecosystem in an area where the soil was left intact Examples: after a fire or hurricane Starts with dirt and leftover plant life Climax community: a stable community formed after primary OR secondary succession once little or no change occurs

Cycling of Matter Hydrologic cycle: aka the water cycle: the circular pathway of water on Earth from the atmosphere to the surface below ground, and back Biogeochemical cycle: the movement of a particular chemical through the biological and geological, or living and nonliving, parts of an ecosystem Carbon Cycle Nitrogen Cycle Phosphorus cycle

The Water Cycle Water is constantly moving between the atmosphere & Earth.

The Carbon Cycle Carbon plays many roles-4 main processes move carbon: Biological processes- such as photosynthesis, respiration and decomposition Burial and decomposition of dead organisms and their conversion under pressure (fossil fuel) Geochemical processes- such as erosion and volcanic activity release CO2 Mining, cutting and burning fossil fuels

The Nitrogen Cycle The atmosphere is the main reservoir of nitrogen; it also cycles through the soil and tissues of living organisms.

The Phosphorus Cycle Phosphorus in biosphere cycles among the land, ocean, sediments and living organisms.

Competitive Exclusion When two species are competing for the same resources, one species will be better suited to the niche, and the other species will be pushed into another niche or become extinct Results Niche partitioning The two squirrel species could have naturally divided different resources based on competitive advantages, If one type of squirrel ate nuts from the tops of trees while others ate nuts from the ground, the niche would have been divided. Evolutionary response The two species of squirrel could have experienced divergent evolution. Selection for larger teeth might have allowed one type of squirrel to become better at cracking large nuts, while selection for smaller teeth might have allowed the other to eat small seeds.

Ecological Equivalents Species that occupy similar niches, but live in different geographical regions. Never compete for the same resources.

Population Density Population density: a measurement of the number of individuals living in a defined space

Population Dispersion Population Dispersion: the way in which individuals of a population are spread in an area or a volume Random: individuals are spread randomly within an area or volume Uniform: territoriality and intraspecies competition for limited resources lead to individuals living at specific distances from one another Clumped: individuals may live close together in groups in order to facilitate mating , gain protection, or access food resources

Survivorship Curve Survivorship Curve: a generalized diagram showing the number of surviving members over time from a measured set of births Type I: shows a low level of infant mortality and a population that will generally survive until old age (example: large mammals) Why? Organisms in this group demonstrate parental care for their young Type II: at all times, these species have equal chances of living or dying, whether from disease or as a result of predation (examples: birds, small mammals, and some reptiles) Type III: shows a very high birth rate and also a very high infant mortality rate (examples: invertebrates, fish, amphibians, and plants) Why? Many die from predation

Population Growth Patterns Factors affecting the size of a population: Immigration: the movement of individuals into a population from another population (INCREASE) Births (INCREASE) Emigration: the movement of individuals out of a population and into another population (DECREASE) Deaths (DECREASE)

Exponential Growth Exponential Growth: occurs when a population size increases dramatically over a period of time (J-shaped curve)

Logistic Growth Logistic Growth: a population begins with a period of slow growth followed by a brief period of exponential growth before leveling off at a stable size (S- shaped curve) Carrying capacity: the number of organisms of one species that can be supported in an environment Population crash: a dramatic decline in the size of a population over a short period of time

Limiting Factors The factors that has the greatest effect in keeping down the size of a population Density-dependent limiting factors: limiting factors affected by the number of individuals in a given area Competition Predation Parasitism and disease

Limiting Factors Density-independent limiting factors: the aspects of the environment that limit a population's growth regardless of the density of the population Unusual weather Natural disasters Human activity