1. Environmental Science: Chapter 4
Ecosystems: How they change

2. Biotic Potential Vs. Environmental Resistance

3. Predator-prey Balance:Wolves and Moose

4. Steps in predation
Encounter
Attack
Capture
Ingestion

5. Encounter
Ambush: Wait for prey to come to you. Burst speed. Pike, muskie, barracuda, gar
Lepisosteus osseus
Rover: Actively search for food. Constant motion. Bass, yellow perch

6.  forward (most fish) or sideways (gar) lunge
Attack:
 forward (most fish) or sideways (gar) lunge
 special grasping organs
Odonate larvae mentum extends to grasp prey
Capture:
 prey have adaptation to avoid capture
 piscivores have lots of teeth

7. predator – prey sizes ~ 1mm Blue Whale 100 ft, up to 220 tons
~ 1mm
Blue Whale 100 ft, up to 220 tons

8. Other factors effect population levels; ex. parasitism, weather
predation
parasitism
Time
population size
Time
population size

9. Mechanisms of Population Equilibrium: Plant-Herbivore

10. Livestock grazing in western US
-Livestock grazing occurs on more federal public lands than any other commercial use
-Affects more than 260 million acres – an area the size of Texas and California combined
-Water diversions, predator control, vegetation manipulation and fencing
-In the US, livestock grazing has contributed to the listing of 22 percent of federal threatened and endangered species (almost equal to logging (12 percent) and mining (11 percent) combined)

11. =
Selective feeders
Migratory
Non-selective
Non-migratory

12. Interactions between species: competition vs predation
resource
consumer +
predation - + -
competition - - +

13. intraspecific competition: between members of same spp
 density dependent population regulation
 evolutionary change
resources scarce, competition
K= # that resources can support
population size
Time

14. interspecific competition: occurs between members of different species
 negative effect on both populations
 depends on adaptations of each population
spp 1 niche
spp 2 niche
realized niche
competition

15. Dry habitat, trees can’t compete w/ grass
Expect to find different kinds of vegetation types at different places in the landscape
Different types will affect the passage of water and its chemical composition differently
Chemical composition of water entering lake affect the biota (living things) in the lake

16. Territoriality: defense of a resource against individuals of the same species
-Examples: wolves, songbirds, bluegill
-Means habitat supports fewer individuals and less competition is result

17. Tipping the Balance: Introduced Species

18. Chestnut Blight
-Fungus which entered US on Asian nursery stock imported to New York ~ 1900
-Spread by wind, rain, birds etc…, enters through cracks or wounds, multiplies rapidly, making sunken cankers which expand and kill everything above the canker
-American chestnut was devastated throughout the natural range, the Appalachian hills and highlands from Maine to Georgia
-By 1940, three and a half billion American chestnuts had perished.
-American chestnut stock advertised as "blight free", means it was grown in an area where no blight is present, outside the natural range or inside a greenhouse.

19. Introduced Species
Why have these introductions resulted in a degradation of the ecosystems? (Think in terms of environmental resistance and biotic potential.)

20. Disturbance and Succession
Equilibrium = No change

21. Ecological succession: transition between biotic communities
Primary- no previous biotic community
Secondary- previously occupied by a community
Aquatic- transition from pond or lake to terrestrial community

22. Primary Succession
Mosses invade an area and provide a place for soil to accumulate.
Larger plants germinate in the new soil layer resulting in additional soil formation.
Eventually shrubs and trees will invade the area.

23. Dramatic examples: HI lava flows
Relies on adjacent ecosystems
Rain of organic material, seeds, and spores accumulates in cracks
Some pockets moist enough to support scattered `ohi`a seedlings and a few hardy ferns and shrubs
Accumulation leaves, bark… converted by soil organisms into a thin but rich organic soil
A forest can develop in wet
regions in less than 150 years

24. Aquatic Succession

25. Ecosystems can show resilience during a disturbance
Fire

26. Disturbance Removes organisms, favors tolerant spp.
Reduces populations
Creates opportunities for other species to colonize

27. Fire and Succession
Fire climax ecosystems: maintained by fire; e.g., grasslands, pine and redwood forests
What significance does this have for humans and where they live?

28. Resilience Mechanisms After A Forest Fire
Nutrient release to soil
Re-growth by remnant roots and seeds
Invasions from neighboring ecosystems
Rapid restoration of energy flow and nutrient cycling

29. Ecosystem management: thinking about the entire system rather than trying to maximize harvest of few populations
Adaptive management: 1) be prepared to chance policy 2) bring in stakeholders 3) do experiments