This document is an outline for Chapter 38 of an ecology textbook. It covers several key topics:
1) Competition can lead to resource partitioning between species to decrease competition. Predator-prey interactions also affect population numbers of both species.
2) Antipredator defenses in prey include camouflage, warning coloration, and mimicry. Parasitism involves a parasite infecting a host, while commensalism benefits one species without affecting the other.
3) Mutualism benefits both participant species, like the relationship between plants and pollinators. Ecological succession is the replacement of species over time after a disturbance.
2. Ridding the World of Waste
 http://www.youtube.com/watch?v=I1RHmSm36aE
3. 38.1 Competition can lead to resource
partitioning
 Competition is rivalry between populations for
the same resources, such as light, space,
nutrients, or mates
 Competitive Exclusion Principle – no two species
can occupy the same niche at the same time
 Ecological niche – the role organism plays in its
community, including its habitat (where the organism
lives) and its interactions with other organisms and
the environment
 Resource partitioning – decreases competition
between the two species
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6. 38.2 Predator-prey interactions affect
both populations
 Predation occurs when one organism (the
predator) feeds on another (the prey)
 Predator – Prey interactions affect both
populations
 Numbers of one species dictates numbers of the
other species
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8. Prey Defenses
 Prey Defenses
 Camouflage – ability to blend into the background
 http://www.youtube.com/watch?v=3WHUTL4fujo
 Warning coloration tells the predator that the prey is
potentially dangerous
 Mimicry – when one species resembles another that
possesses a defense
 Batesian mimicry-a mimic lacks the defense of the organism
it resembles
 Mullerian mimicry-species have the same defense and
resemble each other
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16. Parasitism
 Parasitism – a parasite infects a host
 A symbiotic relationship – at least one of the
species is dependent on the other
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18. Commensalism
 Commensalism is a symbiotic relationship
between two species in which one species is
benefited and the other is neither benefited nor
harmed
 Example: Spanish moss grow in the branches of
trees, where they receive light, but they take no
nourishment from the trees
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19. Figure 38.4 A clownfish living among a sea anemone’s tentacles
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20. Mutualism
 Mutualism – symbiotic relationship in which
both members benefit
 Example: Bacteria in the human intestinal tract
acquire food, but they provide us with vitamins
 Relationship between plants and their pollinators
is a good example of mutualism
 Mycorrhizae & Lichens
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21. Figure 38.5B
Cleaning symbiosis occurs when small fish clean large fish
Cleaning symbiosis –
symbiotic relationship in
which crustaceans, fish,
and birds act as cleaners
for a variety of vertebrate
clients
Large fish in coral reefs
line up at cleaning
stations and wait their
turn to be cleaned by
small fish that even enter
the mouths of the large
fish
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22. Primary & Secondary Succession
 Ecological Succession – series of species
replacements in a community following a
disturbance (flood, tornado, volcanic eruption,
fire, clear-cutting forest)
 Primary succession occurs in areas where no soil is
present. Can take thousands of years.
 Secondary succession begins in areas where soil is
present. Much shorter time span than primary
succession.
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24. 38.7 Ecosystems have biotic
and abiotic components
Abiotic (nonliving) components:
 Sunlight, inorganic nutrients, type of soil, water,
temperature, wind
Biotic (living) components:
 Producers, consumers, scavengers (detritus feeders),
decomposers
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25. Autotrophs
 Biotic Components of an Ecosystem
 Autotrophs
 Called producers because they produce food
 Photoautotrophs, also called photosynthetic organisms,
produce most of the organic nutrients for the biosphere
 Exs: Algae, green plants
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26. Heterotrophs & Decomposers
 Heterotrophs need a preformed source of organic nutrients
 Called consumers because they consume food
 Herbivores are animals that graze directly on plants or algae
 Carnivores feed on other animals
 Omnivores feed on both plants & animals
 Scavengers (detritus feeders) feed on the dead remains of
animals and plants that have recently begun to decompose
 Detritus refers to organic remains in the water and soil that are
in the final stages of decomposition
 Bacteria and fungi, including mushrooms, are the decomposers
that use their digestive secretions to chemically break down
dead organic matter
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29. Food Webs & Food Chains
 Food web, a diagram that describes trophic
(feeding) relationships, common in nature
 Trophic Levels
 Diagram that shows a single path of energy flow in an
ecosystem are called Food Chain (rare in nature)
 Trophic level is composed of organisms that occupy
the same position within a food web or chain
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31. 38.10 Ecological pyramids are
based on trophic levels
 Ecological pyramid
 10% rule – only about 10% of the energy of one
trophic level is available to the next trophic level
because of energy loss
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33. 38.12 The phosphorus cycle
 Phosphorus
 On land, the very slow weathering of rocks places phosphate
ions in the soil
 Some of these become available to plants, which use phosphate
to make ATP, and nucleotides that become DNA and RNA
 Human Activities and the Phosphorus Cycle
 Human beings boost the supply of phosphate by mining
phosphate ores for producing fertilizer and detergents
 Results in eutrophication (overenrichment) of waterways
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35. 38.13 The nitrogen cycle
 Ammonium (NH4+) Formation and Use
 Nitrogen fixation occurs when nitrogen gas (N2) is converted to
ammonium (NH4+), a form plants can use
 Cyanobacteria and bacteria living on some roots can fix
atmospheric nitrogen
 Formation of Nitrogen Gas
 Denitrification is the conversion of nitrate back to nitrogen gas,
which then enters the atmosphere
 Denitrifying bacteria living in the anaerobic mud of lakes, bogs, and
estuaries carry out this process as a part of their own metabolism
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36. 38.13 The nitrogen cycle is gaseous
 Human Activities and the Nitrogen Cycle
 Humans significantly increase transfer rates in nitrogen cycle by
producing fertilizers from N2
 Nearly doubles the fixation rate
 Fertilizer, which also contains phosphate, runs off into lakes and
rivers and results in an overgrowth of algae and rooted aquatic
plants
 Acid deposition occurs because nitrogen oxides (NOx) and
sulfur dioxide (SO2) enter the atmosphere from the burning of
fossil fuels
 Combine with water vapor to form acids that eventually
return to the Earth
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38. 38.14 The carbon cycle
 Human Activities & the Carbon Cycle
 More CO2 is being deposited in the atmosphere than
is being removed due to burning of fossil fuels and
destruction of forests to make way for farmland
 Greenhouse gas – allows solar radiation to pass
through but hinder the escape of heat back into
space, called the greenhouse effect
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