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Chapter 24
Ecosystem Structure & Function
Questions to Answer
 Based on the vegetation in the picture on 632, what
inference can you make about the climate there?
 How have plants adapted to that environment?
 How are those adaptations different from costal
plants in Savannah or the environmental factors of
Dexter?
Interactions & Interdependence
 The environment changes organisms and
organisms also change the environment
 This relationship is a product of evolution
through natural selection
Section 1: Abiotic Factors
 What are abiotic factors?
 Climate and other physical conditions limit the
geographical range of many species.
 Ex. Bacteria in hot springs have enzymes that have
evolved to function best at high temperatures where as
our enzymes and other proteins begin to denature
around 105o .
Other limiting abiotic factors
 Water availability
 Adaptations include:
 Active transport in ocean fish
 Thick cuticles in cacti
 Nocturnal behaviors
 Sunlight
 Larger leaves in understory
Other limiting abiotic factors
Physical Structures
pH
Soil composition
Adaptations include symbiotic relationships
Abiotic Catastrophes
 Floods, fires, avalanches, etc. can cause changes in
ecosystems.
 Specifically they can lead to secondary succession
and at times primary succession
Biotic affect on Abiotic
 Plants roots help break down rocks into soil and
also help prevent erosion.
 Decaying organic materials contribute to the
fertility of the soil and its composition.
 Transpiration from forest contributes to the
humidity of the surrounding environment.
Plants & Salt Tolerance pg. 636
 Plants growing in coastal areas must adapt to the high
levels of potentially toxic sodium(Na), chloride(Cl
already ionized) and carbonate (CO3).
 Adaptation for survival: specialized cells that
concentrate the sodium and chloride that are absorbed
 The accumulated salt is stored externally in bladders
maintaining normal levels internally.
 Example plant saltbush
Section 2: Energy in Food Webs
 Autotrophs vs Heterotrophs
 Photosynthesis ultimately determine the amount of
energy available for most ecosystems (terrestrial and
photic)
 What would provide energy to the aphotic ecosystems?
 Nutritional relationships among the producers and
consumers in an ecosystem form its trophic
structure.
What are some primary and
secondary consumers in terrestrial
and aquatic ecosystems?
What organisms would be primary
decomposers?
(how do they breakdown the
material?)
 Just as available energy declines near the peak of
the energy pyramid, the biomass at each
trophic level also decreases.
 The Productivity of an ecosystem is highest
among the producers and declines at higher
trophic levels
Section 3: Relationships in Ecosystems
 Symbiosis and Predation
Competitive exclusion
 The more two species resemble one another in
their patterns of resource use, the more they will
compete with each other.
 Adaptations that enable competing species to
divide and share the resources reduce competition
 Adaptive radiation also helps reduce competition
Section 4: Nutrient Cycles
 Please refer to text for details and enjoy the
handout for a summary 
 Chemical elements in the ecosystems are
limited and must be recycled.
 You need to know the parts to each cycle. How the
elements “move” through the biosphere
Section 5: limiting factors
 Various factors limit the productivity of
ecosystems.
 Limiting Factors include but are not limited to:
 Water
 Soil Composition (amt. of nitrogen)
 Temperature
 Predators
 Producers
Section 6: Population Dynamics
 Types of population growth:
 Logistic
 Exponential
 Population growth-limiting factors include:
 Food availability
 Space
 Mate options
 Competition
 Reduced reproduction rates and increased death
rates can slow population growth.
 When population growth approaches a stable
maximum it has reached its carry capacity
 Terms to review:
 Carrying Capacity and Population Density
Boom-and- bust cycle
 When a population grows exponentially and
quickly exceeds the carrying capacity causing
a rapid decline in reproduction and sharp
increase in the death rate.
Final Thoughts
 Variations in population size of one species can
ripple through and ecosystem causing changes
in many other populations.
 Populations are always changing making it
difficult to accurately determine the cause of
the change.
 Ecosystems are complex fluctuating systems
Learning Objectives
 LO 4.13 Student is able to predict the effects
of change in the community’s populations on
the community
 LO 4.16 Student is able to predict the effects
of a change in matter or emery availability on
communities.