1. Species Interactions and Community Ecology
Chapter 6 Part 1
Species Interactions and Community Ecology

2. Zebra Mussels Invade the Great Lakes
Polluted waters Great Lakes became cleaner after the Clean Water Act of 1970 – used again for recreation and fishing
Zebra mussel arrived, native to western Asia and eastern Europe.
Larval stage is well adapted for long-distance dispersal, and it encountered none of the predators, competitors, and parasites it was used to

3. Zebra Mussels (continued)
Zebra mussels can
clog up water intake pipes
damage boat engines, docks, and fishing gear
sink buoys that ships use for navigation
Zebra mussels also have severe impacts on the ecological systems they invade
take large quantities of food (phytoplankton) needed by native molluscs for food
It is being displaced by the quagga mussel, which has a larger niche than even the zebra mussel.

4. Species Interactions Most common interactions Competition Predation
Parasitism
Herbivory
Mutualism

5. Competition Occurs when resources are limited
Intraspecific competition – between members of the same species
Limits population growth
Interspecific competion – among members of at least 2 different species
Affects composition (what is in) of communities
*interstate runs between more than one state

6. Competitive Exclusion
One species is a very effective competitor
Excludes another species from a resource completely
Example: zebra mussel outcompeted the native mussel in the Great Lakes

7. Species Coexistence
When one species does not fully exclude another from resources
State of equilibrium – population size of each species remains constant
Species that use the same resources can minimize competition

8. Minimizing Competition
Use only a portion of the total array of resources (niche) that they are capable of using
Full niche of a species is called its fundamental niche
An individual that plays only part of its role because of competition or other species interactions - displaying a realized niche. (page 143, Fig. 6.2)

9. Minimizing Competition (continued)
Resource partitioning - competing species may evolve to use slightly different resources or to use their shared resources in different ways.
Over time, character displacement may occur as they evolve physical characteristics that reflect their use of a specific portion of the resource
Natural Selection!

10. Exploitative Interactions
Exploitation occurs when one member of an interaction exploits or uses another for its own gain.
Examples:
Predation
Parasitism
Herbivory

11. Predation
Predation - an individual of one species hunts, captures, kills, and consumes an individual of another species, its prey.
Predation can sometimes drive population dynamics, causing cycles in population sizes.
Better predators will leave more and healthier offspring – making them better hunters.
Prey species - evolve defense mechanisms

12. Parasitism
Parasitism - the parasite, depends on the host, for nourishment or some other benefit while doing the host harm.
Many parasites live in close contact with their hosts, such as tapeworms, ticks, and lamprey.
Other types of parasites are free-living and come into contact with their hosts only infrequently (e.g., nest parasites such as cuckoos and cowbirds).

13. Parasitism (contiued)
Some parasites cause little harm, but others may kill their hosts
Examples:
Parasitic wasps
Lay eggs on caterpillars
Larvae burrow into and eat caterpillar’s tissue
Larvae turn into wasps that fly out of dead cateripillar
Sea lampreys (see handout)

14. Herbivory Herbivores exploit (use) plants.
Herbivory occurs when animals feed on the tissues of plants
Plant defenses:
Production of toxic chemicals
Thorns, spines, irritating hairs
Other insects working with plant to attack the predators (ants protect some plants)

15. Mutualism Mutualists help one another.
Mutualism - two or more species benefit from interaction with one another.
Many mutualistic relationships occur between organisms that live in close physical contact; this is called symbiosis.
Bees and flowers engage in mutualism in the process of pollination.

16. Use Your Book!
Use your text to list examples of mutualism – you have 5 minutes.

17. Commensalism Some interactions have no effect on some participants.
Commensalism occurs when one organism benefits and the other is unaffected.
Barnacles – barnacles attach to skin of whales and can be transported to new sources of food
Remora sharks – have an adhesive (sticky) disk on their head and can attach to whales. After the whale eats, the shark detaches and eats the leftovers!

18. Book Work! SAVE THIS PAPER! YOU WILL BE ADDING MORE TO IT!
Page 171, Testing Your Comprehension, numbers 1 – 3
SAVE THIS PAPER! YOU WILL BE ADDING MORE TO IT!

19. Ecological Communities
Energy passes among trophic levels.
As organisms feed on one another - energy moves through the community from one trophic level to another.
Producers are the first trophic level.
Examples:
Grasses, algae, chemosynthetic bacteria

20. Consumers Second trophic level - primary consumers
Most of them consume plants and are called herbivores (deer or grasshoppers eat grass)
Third trophic level - secondary consumers
prey on primary consumers (rodents eat grasshoppers that eat grass)

21. Consumers (continued)
Higher trophic levels –tertiary consumers
hawks eat rodents that eat grasshoppers that eat grass
* Secondary and tertiary consumers are carnivores because they eat animals

22. Consumers (continued)
Animals that eat both plant and animal food are omnivores.
Detritivores (scavengers) and decomposers (break down) consume nonliving organic
These “eat” the dead material from all other trophic levels
Look at page 149, Fig. 6.10
The arrow points to what is doing the “eating”

23. Rule of 10 Think back to our Rule of 10 pyramid!
Only 10% of the usable energy is passed on.
The producers start with the most energy, and it decreases with every step up.
Being a vegetarian, rather than a meat-eater, decreases a person’s ecological footprint. Why?
Page 150, Weighing the Issues

24. Biomass Biomass – organic material that makes up living organisms
Biomass energy – energy harnessed from plant and animal matter
The Rule of 10 applies to
Energy
amount of biomass/biomass energy
and number of organisms

25. Food Webs Show feeding relationships and energy flow Visual map
Shows the many paths by which energy passes among organisms as they consume one another.
Page 151, Fig. 6.12

26. With a Partner: 20 Minutes
Draw a food web that could be found in TN
Use colored pencils
Do not have to have elaborate drawings
Stick drawings (like Mrs. Alred’s drawings) are fine
Must include
Producer (10 points)
Primary consumer (10 points)
Secondary consumer (10 points)
Tertiary consumer (10 points)
Decomposer/Detritivore (10 points)