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

2. What is Community Structure?
Physical appearance
Relative sizes, stratification, and distribution of its populations and species.
Species diversity and richness
The number of different species
Species abundance
The number of individuals of each species
Niche structure
The number of ecological niches, their resemblance, and how they interact

3. Mosaic of vegatation patches
100 30
Mosaic of vegatation patches
Ecotones – transition zones between ecosystems
Edge Effects - differences in the physical structure and physical properties between two ecosystems 20 50 10 ft m
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Thorn
scrub
Tall-grass
prairie
Short-grass
prairie
Desert
scrub
Types, sizes, and stratification of plant species in terrestrial communities

4. What determines the number of species in an isolated ecosystem?
Island Ecosystems
Size of the ecosystem
Degree of isolation

5. Species Equilibrium Model or Theory of Island Biogeography (MacArthur and Wilson)
Number of species found on an island determined by balance between:
Rate of immigration
Rate of extinction
Immigration and extinction rates affected by:
Size of island
Distance from nearest mainland

6. Distance from New Guinea (kilometers)
100 50 25
12.5
6.25
2,000
4,000
6,000
8,000
10,000
Distance from New Guinea (kilometers)
Number of species (percentage of sample studied)
NEW GUINEA
© 2004 Brooks/Cole – Thomson Learning
Species diversity decreases with increasing distance

7. Number of amphibian and reptile species
100 1 10
1,000
10,000
100,000
Area (square miles)
Number of amphibian and reptile species
SABA
MONTSERRAT
CUBA
© 2004 Brooks/Cole – Thomson Learning
Hispaniola
Cuba
Puerto Rico
Jamaica
Montserrat
Saba
Species diversity increases with increasing island size
Redonda

8. Species Interactions competition predation parasitism mutualism
commensalism

9. Competition
Intraspecific competition – competition between members of the same species
Gain a competitive advantage (Plants)
Chemical inhibitors
Seed dispersal
Territoriality (Animals)
Patrol or mark an area
Defend an area

10. Competition
Interspecific competition – competition between members of two or more different species
Abundant commonly used resources (food, sunlight, water, soil nutrients, space, nesting sites)
Fundamental niche
Limited resources
Overlap of fundamental niches

11. Interspecific Competition
Interference competition
One species limits another’s access to some resources
Exploitation competition
Competing species have equal access to resources but differ in how fast or efficiently they exploit it

12. Competitive Exclusion Principle
The niches of two species cannot overlap completely or significantly for very long.

13. Resource Partitioning
Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species.

14. Predator – Prey Relationship
Predation – members of one species (predator) feed directly on all or part of a living organism of another species (prey).
Benefits from reducing prey population
Gives remaining prey greater access to food supply
Can improve the genetic stocks of the prey population

15. Predator Tactics Pursuit Cheetah Eagle Wolves
Ambush Preying Mantis Snowy Owls Humans

16. Prey Tactics Run, swim, or fly fast
Highly developed sense of sight or smell
Protective shells
Thick bark
Spines or thorns
Chemical defenses
Camouflage
Warning coloration
Mimicry
Behavioral strategies

17. Symbiotic Species Interactions
Symbiosis – relationship in which species live together in an intimate association.
Parasitism
Mutualism
Commensalism

18. Parasitism
One species (parasite) feeds on part of another organism (host) by living on or in the host.
Smaller than the host
Remains closely associated with host and may weaken host over time
Rarely kills its host

19. Mutualism Two species interact in ways that benefit both
Nutritional mutualism
Pollination, lichens, rhizobium, coral, bacteria
Nutrition and protection
Birds and large animals, clownfish and anemones, mycorrihizae and plants

20. Commensalism
symbiotic relationship that benefits one species but neither harms nor helps the other species

21. POPULATION DYNAMICS AND CARRYING CAPACITY
Most populations live in clumps although other patterns occur based on resource distribution.
Figure 8-2

22. Changes in Population Size: Entrances and Exits
Populations increase through births and immigration
Populations decrease through deaths and emigration

23. Age Structure: Young Populations Can Grow Fast
How fast a population grows or declines depends on its age structure.
Prereproductive age: not mature enough to reproduce.
Reproductive age: those capable of reproduction.
Postreproductive age: those too old to reproduce.

24. Limits on Population Growth: Biotic Potential vs
Limits on Population Growth: Biotic Potential vs. Environmental Resistance
No population can increase its size indefinitely.
The intrinsic rate of increase (r) is the rate at which a population would grow if it had unlimited resources.
Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat.

26. Exponential and Logistic Population Growth: J-Curves and S-Curves
Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off.
Figure 8-4

27. Exponential and Logistic Population Growth: J-Curves and S-Curves
As a population levels off, it often fluctuates slightly above and below the carrying capacity.
Figure 8-4

28. Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size
Over time species may increase their carrying capacity by developing adaptations.
Some species maintain their carrying capacity by migrating to other areas.
So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans.

29. Population Density and Population Change: Effects of Crowding
Population density: the number of individuals in a population found in a particular area or volume.
A population’s density can affect how rapidly it can grow or decline.
e.g. biotic factors like disease
Some population control factors are not affected by population density.
e.g. abiotic factors like weather

30. Types of Population Change Curves in Nature
Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically.
Stable: fluctuates slightly above and below carrying capacity.
Irruptive: populations explode and then crash to a more stable level.
Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles.
Irregular: erratic changes possibly due to chaos or drastic change.

32. ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITION
New environmental conditions allow one group of species in a community to replace other groups.
Ecological succession: the gradual change in species composition of a given area
Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment.
Secondary succession: series of communities develop in places containing soil or sediment.
Succession involves species competing for enough light, nutrients and space which will influence its trajectory.

33. Primary Succession: Starting from Scratch
Primary succession begins with an essentially lifeless area where there is no soil in a terrestrial ecosystem
The trajectory cannot be precisely predicted.
Figure 7-11

34. Secondary Succession: Starting Over with Some Help
Secondary succession begins in an area where the natural community has been disturbed.
Figure 7-12

35. ECOLOGICAL STABILITY AND SUSTAINABILITY
Living systems maintain some degree of stability through constant change in response to environmental conditions through:
Inertia (persistence): the ability of a living system to resist being disturbed or altered.
Constancy: the ability of a living system to keep its numbers within the limits imposed by available resources.
Resilience: the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

36. ECOLOGICAL STABILITY AND SUSTAINABILITY
Having species diversity appears to increase the sustainability of many communities.
Human activities are disrupting ecosystem services that support and sustain all life and all economies.