Ecosystem Interactions Honors Biology Chapter 14
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Ecosystem Interactions
Honors Biology Chapter 14
Where & how organisms liveRange- geographical reach
Habitat- where
Ecological Niche- how
Niche includes food, abiotic conditions, behavior
• Competition results when species, in the same community, overlap in use of resources– Strong selective force– Competitive exclusion
• Banishment/extinction
• Evolution• Niche partitioning
Niche (resource) partitioning
Ecological Equivalents – same niche…different communities
Convergent evolution’s fingerprint
Predation – Another interaction with highly selective outcomes
Symbiosis – a kinder interaction, tho’ not without an evolutionary punch
Mutualism – both benefit
Parasitism – parasite benefits, host harmed
Commensalism – one benefits, the other unaffected
Population Dynamics
• Population: all the individuals of a species that live together in an area
• Demography: the statistical study of populations, make predictions about how a population will change
Population Dynamics
• Three Key Features of Populations
• Size
• Density
• Dispersion
• (spatial distribution)
Three Key Features of Populations
1. Size: number of individuals in an area
Influences on Population SizeSurvivorship Reproductive Strategies
1. R Strategists short life span, small
body, reproduce quickly, many young, little parental care
2. K Strategists long life span, large
body, reproduce slowly, few young, parental care,
Three Key Features of Populations
2. Density: measurement of population
per unit area or unit volume
Formula: Dp= N/S
Pop. Density = # of individuals ÷ unit of space
Human Population Density
Three Key Features of Populations
3. Dispersion: describes their spacing relative to each other
• clumped
• uniform
• random
Clumped for protection, resources,mating or social interaction
Uniform dispersion due to intraspecies competition / territoriality
3. Dispersion: describes their spacing relative to each other
Three Key Features of Populations
Random dispersion implies absence of interaction - rare. Mature communities.
Patterns of Dispersion
Population Growth Patterns• Growth Rate: Birth Rate (natality) -
Death Rate (mortality)
• How many individuals are born vs. how many die
• Birth rate (b) + Immigration rate (i) − death rate (d) = rate of natural increase (r).
• Total Growth must add immigration & subtract emigration statistics
Population Growth Patterns
Exponential – J shaped curve Logistic – S curve
Population Growth PatternsThe “Boom Bust” Curve
World Human Population Growth
Other Factors Affecting Population Growth
• Age Structure
POST-REPRODUCTIVE
REPRODUCTIVEPRE-REPRODUCTIVE
Age Demographics for Three Countries
Immigration and Emigration Can Strongly Effect Population Dynamics
Estimated rates of US population growth with or without immigration.
Immigration & Emigration Influences on Total Rate of Growth
Demographic TransitionThe move from “Developing” to “Developed”
Country
Other Factors Affecting Population Growth
• Carrying Capacity- the maximum population size that can be supported by the available resources
– There can only be as many organisms as the environmental resources can support
Carrying Capacity
Carrying Capacity (k)
Time
J-shaped curve (exponential growth)
S-shaped curve (logistic growth)
#
Other Factors Affecting Population Growth
• Limiting Factors - any biotic or abiotic factor that restricts the existence of organisms in a specific environment.
Two Types of limiting Factors
1. Density-dependent factors- increase effect as population size increases. (disease, competition, parasites)
4. Density-independent factors- affecting populations regardless of
their density (temperature, storms, habitat destruction, drought)
Gradual, sequential change in an area that regenerates or creates a community an area
Succession at Mt. St. Helens.
Ecological Succession
Succession after the Yellowstone fires.
Primary succession: occurs where life has not previouslyexisted
Retreating Glaciers at Glacier Bay Alaska
Primary Succesion – Very Slow
Secondary Succession – Faster (soil already present)
Mount St. Helens
Succession• Climax Community theoretical end-point of
succession. Stable community.
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