1. Chapter 38
Community and
Ecosystem
Ecology
Lecture Outline
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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
38-3

4. Figure 38.1A
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Competition only
P.aurelia grown occurs between
separately
Population two species of
Density Paramecium when
they are grown
together
P.caudatum grown
separately
When one species
Population
fed on the bottom
Density
and the other fed
on suspended
food, resource
partitioning
Both species
occurred and
Population
grown together
Density
competition
decreased
Time
38-4

5. Figure 38.1C Niche specialization occurs among five
species of coexisting warblers
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cape May
warbler
Black-throated
greenwarbler
Bay-breasted
warbler
Blackburnian
warbler
Yellow-rumped
warbler
38-5

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
38-6

7. Figure 38.2A
Predator-prey interaction between a snowshoe hare and a lynx
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
140
hare
lynx
120
100
Number (thousands)
80
60
40
20
1845 1855 1865 1875 1885 1895 1905 1915 1925 1935
© Alan Carey/PhotoResearchers, Inc.
38-7

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
38-8

9. Figure 38.2B Antipredator defenses
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Camouflage
© Gustav Verderber/Visuals Unlimited
38-9

10. Figure 38.2B Antipredator defenses (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Warning coloration
© Zig Leszczynski/Animals Animals
38-10

14.  Viceroy
 Monarch

15. Figure 38.2C Mimicry: All of these insects have the same coloration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
flower fly longhorn beetle
bumble bee yellow jacket
(flower fly,longhorn beetle, yellow jacket): © Edward S. Ross; (bumblebee): © James H.Robinson/Photo Researchers, Inc. 38-15

16. Parasitism
 Parasitism – a parasite infects a host
 A symbiotic relationship – at least one of the
species is dependent on the other
38-16

17. 38-17

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
38-18

19. Figure 38.4 A clownfish living among a sea anemone’s tentacles
38-19

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
38-20

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
38-21

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.
38-22

23. Figure 38.6A Primary succession begins on areas of bare rock.
Secondary succession begins at the grass stage
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rock lichens/mosses grass low shru b high shru b shrub-tree low tree high tree
primary succession
secondary succession
38-23

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
38-24

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
38-25

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
38-26

27. Figure 38.8A Energy flow and chemical cycling in an ecosystem
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
solar
energy heat
producers
consumers
inorganic
nutrient pool
heat
energy
heat decomposers 38-27
nutrients

28. Figure 38.8B Energy balances for an herbivore
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Heat to
environment
Energy to
growth and reproduction
carnivores
Energy
to detritus
feeders
38-28
© George D. Lepp/Photo Researchers, Inc.

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
38-29

30. Figure 38.9 Grazing food web (top) and detrital food web (bottom)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Autotrophs Herbivores/Omnivores Carnivores
owls
nuts
4
birds hawks
1
2 leaf-eating
insects
deer
3
foxes
5
leaves
3 chipmunks
rabbits
skunks
detritus snakes
3 mice
mice
death
death
death
38-30
fungi and bacteria in detritus invertebrates carnivorous invertebrates salamanders shrews

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
38-31

32. Figure 38.10 This ecological pyramid based on the
biomass content of bog populations could also be used to
represent an energy pyramid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
top carnivores
1.5 g/m2
carnivores
11g/m2
herbivores
37g/m2
autotrophs
809 g/m2
38-32

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
38-33

34. Figure 38.12 The phosphorus cycle

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
38-35

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
38-36

37. Figure 38.13 The nitrogen cycle

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
38-38

39. Figure 38.14 The carbon cycle

40. Connecting the Concepts:
Chapter 38
 Competition leads to resource partitioning
 Prey use various defenses against predators
 3 examples of symbiotic relationships
 Primary vs. Secondary Ecological Succession
 Trophic levels exist within food chains & food
webs (10% energy conservation between levels)
 Nutrients cycle (Phosphorous, Nitrogen &
Carbon)
38-40