1. Ecology Section two notes
Anna Morrison

2. 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)

3. 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

4. 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

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

6. 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

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

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

9. 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.

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

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

12. 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

13. 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

14. 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)

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

16. 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

17. 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

18. 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