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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 ecosystemUnit of measurement is kcal (kilocalories)
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 livesExample: 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 webAbiotic 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 Symbiosis1. 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 spaceExample: rural area vs. city
Population Dispersion: the way individuals in a population are spread in an area Clumped dispersion: live close togetherUniform dispersion: live at specific
distances from each otherRandom 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 rateOccurs under ideal
conditions with unlimited resources
Logistic Growth Occurs when a
population’s growth slows or stops following a period of exponential growthMost common type of
growthAs 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 decreaseCompetitionPredationParasitism and diseaseDrought and other climate extremesHuman 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 sizeUnusual weather, natural disasters,
seasonal cycles, human activities
Ecological Succession
Ecosystems are constantly changingNatural and human disturbancesOlder 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 existEx. After volcanic eruption, retreating glacier
Pioneer species: first to appear in area (usually lichens)Mosses GrassesShrubs and trees
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