1. Biodiversity, Species Interactions, and Population Control5
Biodiversity, Species Interactions, and Population Control

2. Core Case Study: Southern Sea Otters - A Species in Recovery
Live in giant kelp forests
By the early 1900s they had been hunted almost to extinction
Partial recovery since 1977
Why care about sea otters?
Ethics
Tourism dollars
Keystone species

3. Southern Sea Otter
Figure 5.1 An endangered southern sea otter in Monterey Bay, California (USA) uses a stone to crack the shells of clams that it feeds on (left). It lives in a giant bed of seaweed called kelp (right).
Fig. 5-1, p. 102

4. 5-1 How Do Species Interact?
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. Most Species Compete with One Another for Certain Resources
Five basic types of interactions
Interspecific Competition
Predation
Parasitism
Mutualism
Commensalism
Interspecific competition
Compete to use the same limited resources

6. Some Species Evolve Ways to Share Resources
Resource partitioning
Species may use only parts of resource
At different times
In different ways

7. Sharing the Wealth Blackburnian Warbler Black-throated Green Warbler
Cape May Warbler
Bay-breasted Warbler
Yellow-rumped Warbler
Figure 5.2 Sharing the wealth: Resource partitioning among five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species spends at least half its feeding time in its associated yellow-highlighted areas of these spruce trees.
Stepped Art
Fig. 5-2, p. 103

8. Insect and nectar eaters
Specialist Species of Honeycreepers
Fruit and seed eaters
Insect and nectar eaters
Greater Koa-finch
Kuai Akialaoa
Amakihi
Kona Grosbeak
Crested Honeycreeper
Akiapolaau
Figure 5.3 Specialist species of honeycreepers: Through natural selection, different species of honeycreepers have shared resources by evolving specialized beaks to take advantage of certain types of food such as insects, seeds, fruits, and nectar from certain flowers. Question: Look at each bird’s beak and take a guess at what sort of food that bird might eat.
Maui Parrotbill
Apapane
Unkown finch ancestor
Fig. 5-3, p. 104

9. Consumer Species Feed on Other Species
Predator – feeds directly on all or part of a living organism
Carnivores
Pursuit and ambush
Camouflage
Chemical warfare

10. Consumer Species Feed on Other Species (cont’d.)
Prey can avoid predation
Camouflage
Chemical warfare
Warning coloration
Mimicry
Behavioral strategies

11. Predator-Prey Relationships
Figure 5-4: Predator-prey relationship: This brown bear (the predator) in the U.S. state of Alaska has captured and will feed on this salmon (the prey).
Fig. 5-4, p. 104

12. Predator-Prey Relationships
Figure 5-6 These prey species have developed specialized ways to avoid their predators: (a, b) camouflage, (c, d, e) chemical warfare,
(d, e, f) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
Fig. 5-6, p. 106

13. Interactions between Predator and Prey Species
Intense natural selection pressures between predator and prey populations
Coevolution
Interact over a long period of time
Changes in the gene pool of one species can cause changes in the gene pool of the other
Bats and moths
Echolocation of bats and sensitive hearing of moths

14. Coevolution
Figure 5-7: Coevolution: This bat is using ultrasound to hunt a moth. As the bats evolve traits to increase their chance of getting a meal, the moths evolve traits to help them avoid being eaten.
Fig. 5-7, p. 107

15. Some Species Feed off Other Species by Living on or inside Them
Parasitism
Parasite is usually much smaller than the host
Parasite rarely kills the host
Parasite-host interaction may lead to coevolution

16. Parasitism
Figure 5-8: Parasitism: This blood-sucking, parasitic sea lamprey has attached itself to an adult lake trout from the Great Lakes (USA, Canada).
Fig. 5-8, p. 107

17. In Some Interactions, Both Species Benefit
Mutualism
Nutrition and protective relationship
Gut inhabitant mutualism
Not cooperation – mutual exploitation

18. Mutualism
Figure 5-9: Mutualism: Oxpeckers feed on parasitic ticks that infest animals such as this impala and warn of approaching predators.
Fig. 5-9, p. 108

19. In Some Interactions, One Species Benefits and the Other Is Not Harmed
Commensalism
Benefits one species and has little affect on the other
Epiphytes
Birds nesting in trees

20. Commensalism
Figure 5-10: In an example of commensalism, this pitcher plant is attached to a branch of a tree without penetrating or harming the tree. This carnivorous plant feeds on insects that become trapped inside it.
Fig. 5-10, p. 108

21. 5-2 Responding to Changing Environmental Conditions
How do communities and ecosystems respond to changing environmental conditions?
The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession

22. Communities and Ecosystems Change over Time: Ecological Succession
Gradual change in species composition
Primary succession
In lifeless areas
Secondary succession
Areas of environmental disturbance
Examples of natural ecological restoration

23. Primary Ecological Succession
Figure 5.11 Primary ecological succession: Over almost a 1,000 years, these plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in western Lake Superior. The details of this process vary from one site to another.
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. 5-11, p. 109

24. Natural Ecological Restoration
Animated Figure 5.12 Natural ecological restoration of disturbed land: This diagram shows the undisturbed 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.
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. 5-12, p. 110

25. Ecological Succession Does Not Follow a Predictable Path
Traditional view
Balance of nature and climax communities
Current view
Ever-changing mosaic of patches of vegetation in different stages of succession

26. Living Systems Are Sustained through Constant Change
Inertia
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

27. What Limits the Growth of Populations
No population can grow indefinitely because of limitations on resources and because of competition among species for those resources

28. Most Populations Live in Clumps
Group of interbreeding individuals of the same species
Population distribution
Clumping
Species cluster for resources
Protection from predators
Ability to hunt in packs

29. A School of Anthias Fish
Figure 5-13: A population, or school, of Anthias fish on coral in Australia’s Great Barrier Reef.
Fig. 5-13, p. 111

30. Populations Can Grow, Shrink, or Remain Stable
Population size governed by:
Births and deaths; immigration and emigration
Population change = (births + immigration) – (deaths + emigration)
Age structure
Pre-reproductive age
Reproductive age
Post-reproductive age

31. Some Factors Can Limit Population Size
Range of tolerance
Variations in physical and chemical environment
Individuals may have different tolerance ranges

32. Some Factors Can Limit Population Size
Limiting factor principle
Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance
Precipitation, nutrients, sunlight
Populations density
Number of individuals in a given area

33. Zone of physiological stress Zone of physiological stress
Trout Tolerance of Temperature
Lower limit
of tolerance
Higher limit
of tolerance
No organisms
Few organisms
Few organisms
No organisms
Abundance of organisms
Population size
Figure 5.15 Range of tolerance for a population of trout to changes in water temperature.
Zone of intolerance
Zone of physiological stress
Zone of physiological stress
Zone of intolerance
Optimum range
Low
Temperature
High
Fig. 5-13, p. 113

34. Different Species Have Different Reproductive Patterns
Some species:
Have many small offspring
Little parental involvement
Other species:
Reproduce later in life
Have small number of offspring

35. No Population Can Grow Indefinitely: J-Curves and S-Curves
There are always limits to population growth in nature
Environmental resistance – factors that limit population growth
Carrying capacity
Maximum population of a given species that a particular habitat can sustain indefinitely

36. No Population Can Grow Indefinitely: J-Curves and S-Curves (cont’d.)
Exponential growth
At a fixed percentage per year
Logistic growth
Population faces environmental resistance

37. Growth of a Sheep Population
Population overshoots carrying capacity
Environmental resistance
2.0
Carrying capacity
1.5
Population recovers and stabilizes
Number of sheep (millions)
Population runs out of resources and crashes
1.0
Exponential growth
Animated Figure 5.16 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 and few predators. 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. .5
1800
1825
1850
1875
1900
1925
Year
Fig. 5-16, p. 115

38. 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 deer population explosion
Spread Lyme disease
Deer-vehicle accidents
Eating garden plants and shrubs
How can we control the deer population?

39. White-Tailed Deer Populations
Figure 5-17: White-tailed deer populations in the United States have been growing.
Fig. 5-17, p. 115

40. When a Population Exceeds Its Carrying Capacity It Can Crash
A population exceeds the area’s carrying capacity
Reproductive time lag may lead to overshoot
Subsequent population crash
Damage may reduce area’s carrying capacity

41. Population Crash Population overshoots carrying capacity 2,000 1,500
Population crashes
Number of reindeer
1,000
Figure 5.18 Exponential growth, overshoot, and population crash of reindeer introduced onto the small Bering Sea island of St. Paul in 1910.
500
Carrying capacity
1910
1920
1930
1940
1950
Year
Fig. 5-18, p. 116

42. Humans Are Not Exempt from Nature’s Population Controls
Ireland
Potato crop in 1845
Bubonic plague
Fourteenth century
AIDS
Current global epidemic

47. Three Big Ideas Certain interactions among species
Affect their use of resources and their population sizes
Changes in environmental conditions
Cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession)
There are always limits to population growth in nature

48. Tying It All Together – Southern Sea Otters and Sustainability
Before European settlers in the U.S., the sea otter ecosystem was complex
Settlers began hunting otters
Disturbed the balance of the ecosystem
Populations depend on solar energy and nutrient cycling
When these are disrupted biodiversity is threatened