1. Biodiversity & Species Interactions
Chapter 5

2. How Do Species Interact?
Five types of species interactions—
1. competition
2. predation
3. parasitism
4. mutualism SYMBIOSIS
5. commensalism
All of these affect the resource use and population sizes of the species in an ecosystem.

3. Most Species Compete with One Another for Certain Resources
Competition Intraspecific
(within SAME species)
vs.
Interspecific
(between DIFFERENT species)
Competitive exclusion principle: Two species needing the same resource cannot coexist indefinitely in the same ecosystem when not enough of a given resource is available

4. Some Species Evolve Ways to Share Resources
Resource partitioning – the dividing up of scarce resources
Reduce niche overlap
Use shared resources at different
Times
Places
Ways

5. Competing Species Can Evolve to Reduce Niche Overlap

6. Sharing the Wealth: Resource Partitioning

7. Most Consumer Species Feed on Live Organisms of Other Species
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
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
(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.
(e) Poison dart frog
(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.
Fig. 5-2, p. 103

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

11. Coevolution: A Langohrfledermaus Bat Hunting a Moth

12. Some Species Feed off Other Species by Living on or in Them
Parasitism: (+, - ) one species benefits (parasite) at the expense of the other (host)
Parasite-host interaction may lead to coevolution

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

14. In Some Interactions, Both Species Benefit
Mutualism:(+, +) both organisms benefit
Nutrition and protection relationship
Gut inhabitant mutualism

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

16. In Some Interactions, One Species Benefits and the Other Is Not Harmed
Commensalism: (+, 0) one organism benefits and the other is unaffected
Epiphytes
Birds nesting in trees

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

18. Primary versus Secondary
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.
Primary versus Secondary

19. 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 (mosses & lichens)
Midsuccessional plant species = herbs, grasses, shrubs
Late successional plant species = mostly trees

20. Primary Ecological Succession

21. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession
Some soil remains in a terrestrial system therefore much faster!!
Some bottom sediment remains in an aquatic system
Ecosystem has been
Disturbed
Removed
Destroyed
(Natural disasters, mining, logging, etc.)

22. Natural Ecological Restoration of Disturbed Land

23. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession
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

24. Science Focus: How Do Species Replace One Another in Ecological Succession?
Facilitation : “help” - one species makes it suitable for the next
Inhibition: “hinder” – some early species inhibit the growth of others
Tolerance: “unaffected” - late successional species not affected by early ones

25. Succession Doesn’t Follow a Predictable Path
Traditional view
Balance of nature and a climax community
Current view
Ever-changing mosaic of patches of vegetation
Mature late-successional ecosystems
State of continual disturbance and change