1. Biodiversity, Species Interactions, and Population Control
Chapter 5

2. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?
Habitat
Hunted: early 1900s
Partial recovery
Why care about sea otters?
Ethics
Keystone species
Tourism dollars

3. Southern Sea Otter

4. 5-1 How Do Species Interact?
Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

5. Species Interact in Five Major Ways
Interspecific Competition
Predation
Parasitism
Mutualism
Commensalism

6. Most Species Compete with One Another for Certain Resources
Competition
Competitive exclusion principle

7. Most Consumer Species Feed on Live Organisms of Other Species (1)
Predators may capture prey by
Walking
Swimming
Flying
Pursuit and ambush
Camouflage
Chemical warfare

8. Most Consumer Species Feed on Live Organisms of Other Species (2)
Prey may avoid capture by
Camouflage
Chemical warfare
Warning coloration
Mimicry
Deceptive looks
Deceptive behavior

9. (b) Wandering leaf insect
(a) Span worm
(b) Wandering leaf insect
(c) Bombardier beetle
(d) Foul-tasting monarch butterfly
(e) Poison dart frog
(f) Viceroy butterfly mimics
monarch butterfly
Figure 5.2
Some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
(h) When touched,
snake caterpillar changes
shape to look like head of snake.
Stepped Art
Fig. 5-2, p. 103

10. Science Focus: Why Should We Care about Kelp Forests?
Kelp forests: biologically diverse marine habitat
Major threats to kelp forests
Sea urchins
Pollution from water run-off
Global warming

11. Purple Sea Urchin

12. Predator and Prey Species Can Drive Each Other’s Evolution
Intense natural selection pressures between predator and prey populations
Coevolution

13. Coevolution: Orchid mimics a female wasp

14. Some Species Feed off Other Species by Living on or in Them
Parasitism
Parasite-host interaction may lead to coevolution

15. Parasitism: Tree with Parasitic Mistletoe, Trout with Blood-Sucking Sea Lampreys

16. In Some Interactions, Both Species Benefit
Mutualism
Nutrition and protection relationship
Gut inhabitant mutualism

17. Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish

18. In Some Interactions, One Species Benefits and the Other Is Not Harmed
Commensalism
Epiphytes
Birds nesting in trees

19. Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree

20. 5-2 How Can Natural Selection Reduce Competition between Species?
Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

21. Some Species Evolve Ways to Share Resources
Resource partitioning
Reduce niche overlap
Use shared resources at different
Times
Places
Ways

22. Competing Species Can Evolve to Reduce Niche Overlap

23. Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler
Blackburnian Warbler
Black-throated Green Warbler
Cape May Warbler
Bay-breasted Warbler
Yellow-rumped Warbler
Figure 5.8
Sharing the wealth: resource partitioning of five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition for food with the others by spending at least half its feeding time in a distinct portion (shaded areas) of the spruce trees, and by consuming different insect species. (After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,” Ecology 36 (1958): 533–536.)
Fig. 5-8, p. 107

24. Specialist Species of Honeycreepers

25. 5-3 What Limits the Growth of Populations?
Concept 5-3 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

26. Populations Have Certain Characteristics (1)
Populations differ in
Distribution
Numbers
Age structure
Population dynamics

27. Populations Have Certain Characteristics (2)
Changes in population characteristics due to:
Temperature
Presence of disease organisms or harmful chemicals
Resource availability
Arrival or disappearance of competing species

28. Most Populations Live Together in Clumps or Patches (1)
Population distribution
Clumping
Uniform dispersion
Random dispersion

29. Most Populations Live Together in Clumps or Patches (2)
Why clumping?
Species tend to cluster where resources are available
Groups have a better chance of finding clumped resources
Protects some animals from predators
Packs allow some to get prey
Temporary groups for mating and caring for young

30. Populations Can Grow, Shrink, or Remain Stable (1)
Population size governed by
Births
Deaths
Immigration
Emigration
Population change =
(births + immigration) – (deaths + emigration)

31. Populations Can Grow, Shrink, or Remain Stable (2)
Age structure
Pre-reproductive age
Reproductive age
Post-reproductive age

32. Populations Can Grow, Shrink, or Remain Stable (3) Which type of growth?

33. No Population Can Grow Indefinitely: J-Curves and S-Curves (1)
Biotic potential
Low
High
Intrinsic rate of increase (r)
Individuals in populations with high r
Reproduce early in life
Have short generation times
Can reproduce many times
Have many offspring each time they reproduce

34. Environmental resistance
Carrying capacity (K)
Population stabilizes
Population size
Exponential
growth
Figure 5.11
No population can continue to increase in size indefinitely. Exponential growth (left half of the curve) occurs when resources are not limiting and a population can grow at its intrinsic rate of increase (r) or biotic potential. Such exponential growth is converted to logistic growth, in which the growth rate decreases as the population becomes larger and faces environmental resistance. Over time, the population size stabilizes at or near the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped) population growth curve. Depending on resource availability, the size of a population often fluctuates around its carrying capacity, although a population may temporarily exceed its carrying capacity and then suffer a sharp decline or crash in its numbers. See an animation based on this figure at CengageNOW. Question: What is an example of environmental resistance that humans have not been able to overcome?
Biotic
potential
Time (t)
Fig. 5-11, p. 111

35. No Population Can Grow Indefinitely: J-Curves and S-Curves (2)
Size of populations limited by
Light
Water
Space
Nutrients
Exposure to too many competitors, predators or infectious diseases

36. No Population Can Grow Indefinitely: J-Curves and S-Curves (3)
Environmental resistance
Carrying capacity (K)
Exponential growth
Logistic growth

37. Number of sheep (millions)
2.0
Population
overshoots
carrying
capacity
Carrying capacity
1.5
Population recovers
and stabilizes
Population
runs out of
resources
and crashes
Number of sheep (millions)
1.0
Exponential
growth .5
Figure 5.12
Logistic growth of a sheep population on the island of Tasmania between 1800 and After sheep were introduced in 1800, their population grew exponentially, thanks to an ample food supply. By 1855, they had overshot the land’s carrying capacity. Their numbers then stabilized and fluctuated around a carrying capacity of about 1.6 million sheep.
1800
1825
1850
1875
1900
1925
Year
Fig. 5-12, p. 111

38. Population Size of Southern Sea Otters Off the Coast of So
Population Size of Southern Sea Otters Off the Coast of So. California (U.S.)

39. Science Focus: Why Are Protected Sea Otters Making a Slow Comeback?
Low biotic potential
Prey for orcas
Cat parasites
Thorny-headed worms
Toxic algae blooms
PCBs and other toxins
Oil spills

40. When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash
Carrying capacity: not fixed
Reproductive time lag may lead to overshoot
Dieback (crash)
Damage may reduce area’s carrying capacity

41. 2,000 Population overshoots carrying capacity 1,500 Population crashes
Number of reindeer
1,000
500
Carrying
capacity
Figure 5.13
Exponential growth, overshoot, and population crash of reindeer introduced to the small Bering Sea island of St. Paul. When 26 reindeer (24 of them female) were introduced in 1910, lichens, mosses, and other food sources were plentiful. By 1935, the herd size had soared to 2,000, overshooting the island’s carrying capacity. This led to a population crash, when the herd size plummeted to only 8 reindeer by Question: Why do you think this population grew fast and crashed, unlike the sheep in Figure 5-12?
1910
1920
1930
1940
1950
Year
Fig. 5-13, p. 112

42. Species Have Different Reproductive Patterns
r-Selected species, opportunists
K-selected species, competitors

43. Carrying capacity K K species; experience K selection
Number of individuals
r species;
experience
r selection
Figure 5.14
Positions of r-selected and K-selected species on the sigmoid (S-shaped) population growth curve.
Time
Fig. 5-14, p. 112

44. Genetic Diversity Can Affect the Size of Small Populations
Founder effect
Demographic bottleneck
Genetic drift
Inbreeding
Minimum viable population size

45. Under Some Circumstances Population Density Affects Population Size
Density-dependent population controls
Predation
Parasitism
Infectious disease
Competition for resources

46. Several Different Types of Population Change Occur in Nature
Stable
Irruptive
Cyclic fluctuations, boom-and-bust cycles
Top-down population regulation
Bottom-up population regulation
Irregular

47. Population Cycles for the Snowshoe Hare and Canada Lynx

48. Humans Are Not Exempt from Population Controls
Ireland
Potato crop in 1845
Bubonic plague
Fourteenth century
AIDS
Global epidemic

49. Case Study: Exploding White-Tailed Deer Population in the U.S.
1900: deer habitat destruction and uncontrolled hunting
1920s–1930s: laws to protect the deer
Current population explosion for deer
Lyme disease
Deer-vehicle accidents
Eating garden plants and shrubs
Ways to control the deer population

50. 5-4 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
Concept 5-4 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

51. Communities and Ecosystems Change over Time: Ecological Succession
Natural ecological restoration
Primary succession
Secondary succession

52. Some Ecosystems Start from Scratch: Primary Succession
No soil in a terrestrial system
No bottom sediment in an aquatic system
Early successional plant species, pioneer
Midsuccessional plant species
Late successional plant species

53. Balsam fir, paper birch, and Jack pine, white spruce black spruce,
Figure 5.16
Primary ecological succession. Over almost a thousand years, plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern Lake Superior. The details of this process vary from one site to another. Question: What are two ways in which lichens, mosses, and plants might get started growing on bare rock?
Balsam fir,
paper birch, and
white spruce
forest community
Jack pine,
black spruce,
and aspen
Heath mat
Small herbs
and shrubs
Lichens and
mosses
Exposed
rocks
Time
Fig. 5-16, p. 116

54. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1)
Some soil remains in a terrestrial system
Some bottom sediment remains in an aquatic system
Ecosystem has been
Disturbed
Removed
Destroyed

55. Mature oak and hickory forest Young pine forest
Figure 5.17
Natural ecological restoration of disturbed land. Secondary ecological succession of plant communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance, such as deforestation or fire, would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. Questions: Do you think the annual weeds (left) would continue to thrive in the mature forest (right)? Why or why not? See an animation based on this figure at CengageNOW.
Mature oak and hickory forest
Young pine forest
with developing understory of oak and hickory trees
Shrubs and
small pine
seedlings
Perennial
weeds and
grasses
Annual
weeds
Time
Fig. 5-17, p. 117

56. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2)
Primary and secondary succession
Tend to increase biodiversity
Increase species richness and interactions among species
Primary and secondary succession can be interrupted by
Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species

57. Living Systems Are Sustained through Constant Change
Inertia, persistence
Ability of a living system to survive moderate disturbances
Resilience
Ability of a living system to be restored through secondary succession after a moderate disturbance
Tipping point