Pyramid Models  Used to show amount of matter and energy in an ecosystem  Shows the general flow of energy from producers to consumers and the amount of organisms at each trophic level  Each level of a food chain contains less energy than the one below it.

Transfer of Energy  Only 10% of available energy is transferred from one trophic level to the next  90% of energy is lost as heat  Energy pyramid:  Shows how available energy is distributed among trophic levels in an ecosystem  Unit of measurement is kcal (kilocalories)

Energy Pyramid

Biomass Pyramids  Shows the total amount of living tissue within a given trophic level (biomass) Represents the amount of potential food available for each trophic level

Pyramid of Numbers  Shows the number of individual organisms at each trophic level in an ecosystem  Can be used to show the vast number of producers and consumers needed to support an ecosystem

Habitat and Niche  Habitat: all the biotic and abiotic factors in the area where an organism lives Example: A lions habitat might include shade trees, tall grasses and watering holes  Niche: the way an organism interacts with its environment; composed of all the physical, chemical and biological factors a species needs to survive, stay healthy and reproduce

Habitat and Niche  Think of a habitat as where as a species lives and a niche as how it lives within the habitat.  A niche includes: Food: the type it eats, how it competes with others, where it fits in the food web Abiotic Conditions: range of conditions such as temperature and amount of water available Behavior: time of day the species is active and where and when it reproduces

Community Interactions 1. Competition: when organisms attempt to use the same ecological resource at the same time 2. Predation: one organism captures and feeds on the other 3. Symbiosis: any relationship in which organisms live closely together

Community Interactions: Types of Symbiosis 1. Mutualism: both species benefit from the relationship - Ex. flowers and many insects: flowers provide food, insects help flowers reproduce 2. Commensalism: one organism benefits and the other is neither helped or hurt - Ex. barnacles on whales 3. Parasitism: one organism lives on or in another and harms it - Ex. tick on a dog

Population Density and Distribution  Population Density: a measurement of the number of individuals living in a defined space Example: rural area vs. city  Population Dispersion: the way individuals in a population are spread in an area Clumped dispersion: live close together Uniform dispersion: live at specific distances from each other Random dispersion: individuals spread randomly

Population Growth  Affected by: Number of births (increase) Number of deaths (decrease) Number of individuals that enter or leave a population ○ Immigration: movement of individuals into an area ○ Emigration: movement of individuals out of an area

Exponential Growth  Occurs when the individuals in a population reproduce at a constant rate Occurs under ideal conditions with unlimited resources

Logistic Growth  Occurs when a population’s growth slows or stops following a period of exponential growth Most common type of growth As resources become less available, the growth of a population will slow or stop Reaches carrying capacity: largest number of individuals that a given environment can support

Limits to Growth  Limiting factors: factors that cause a populations growth to decrease Competition Predation Parasitism and disease Drought and other climate extremes Human disturbances

Density-Dependent Factors  Limiting factors that depends on population size ○ Affect mostly large populations ○ Do not really affect small, scattered populations ○ Include: competition, predation, parasitism and disease

Density-Independent Factors  Limiting factors that affect all populations in similar ways, regardless of population size Unusual weather, natural disasters, seasonal cycles, human activities

Ecological Succession  Ecosystems are constantly changing Natural and human disturbances Older inhabitants die out, new organisms move in  Ecological Succession: phases of growth from barren rock to a climax forest.

Primary Succession  Succession that occurs where no soil exist Ex. After volcanic eruption, retreating glacier  Pioneer species: first to appear in area (usually lichens) Mosses Grasses Shrubs and trees

Primary Succession

Secondary Succession  Disturbance of some kind changes an existing community without moving the soil Ex. Abandoned farmland, after wildfires