Environmental Science: Toward a Sustainable Future Richard T. Wright - PowerPoint PPT Presentation

1 / 30
About This Presentation
Title:

Environmental Science: Toward a Sustainable Future Richard T. Wright

Description:

Environmental Science: Toward a Sustainable Future Richard T. Wright Chapter 4 Ecosystems: How They Change PPT by Clark E. Adams (modified) Factors That Contribute to ... – PowerPoint PPT presentation

Number of Views:719
Avg rating:3.0/5.0
Slides: 31
Provided by: Cla1158
Category:

less

Transcript and Presenter's Notes

Title: Environmental Science: Toward a Sustainable Future Richard T. Wright


1
Environmental Science Toward a Sustainable
Future Richard T. Wright
Chapter 4
  • Ecosystems How They Change
  • PPT by Clark E. Adams (modified)

2
Factors That Contribute to Ecosystem Change
  • Dynamics of natural populations
  • Mechanisms of population equilibrium
  • Ecosystem response to disturbance

3
Dynamics of Natural Populations
  • Population growth curves
  • Biotic potential versus environmental resistance
  • Density dependence and critical number

4
Population Equilibrium
A dynamic balance between births and deaths.
  • Births

Deaths
5
Population Growth Curves
6
Population Growth Curves
  • Reproductive strategies

Not really- think insects, fish, frogs
Many offspring with low parental care
Maybe, maybe not
Few offspring with high parental care
J-shaped growth curve
S-shaped growth curve
R strategists
K strategists
7
Population Dynamics
  • Environmental resistance combination of biotic
    and abiotic factors that may limit population
    increase
  • Predators, competitors, disease
  • Adverse weather, limited food/nutrients

8
Biotic Potential and Environmental Resistance
9
Density Dependence and Critical Numbers
  • Factors of environmental resistance are either
  • density-independent effect does not vary with
    population density e.g., adverse weather
  • density-dependent effect varies with population
    density e.g., infectious disease
  • Critical number the lowest population level for
    survival and recovery

10
Mechanisms of Population Equilibrium
  • Predatorprey dynamics
  • Competition
  • Interspecific
  • Intraspecific
  • Introduced species

11
PredatorPrey Balance Wolves and Moose
12
Lessons to Be Learned about PredatorPrey Balance
  • Absence of natural enemies allows a herbivore
    population to exceed carrying capacity, which
    results in overgrazing of the habitat.
  • The herbivore population subsequently crashes.
  • Predators reduce the herbivore population it is
    maintained so that overgrazing or other overuse
    does not occur.

13
PlantHerbivore Dynamics
Reindeer on St. Matthew Island
  • No regulatory control (predation) on herbivores
  • Went into exponential growth pattern
  • Overgrazed habitat
  • Massive die-off of herbivores

14
Mechanisms of Population Equilibrium
PlantHerbivore
  • Compare the predatorprey with plantherbivore
    methods of controlling the size of the herbivore
    population.
  • How would the herbivore population growth curve
    look if diseases or predators were used as the
    control mechanism?

15
Keystone Species
  • A single species that maintains biotic structure
    of the ecosystem
  • Pisaster ochraceus a starfish that feeds on
    mussels, keeping them from blanketing the rocks

http//www.marine.gov/
16
Competition- an overview
  • Interspecific competition- different species
    compete for the same resource- my tomatoes and
    sheep sorel in my garden!
  • It is often less of a problem because or specific
    habitats and niches, until an invader appears-
    zebra mussel, ruffe, etc.
  • Intraspecific competition- competition within a
    species- songbirds sing mainly to warn other
    songbirds to stay out!

17
Ecosystem Responses to Disturbance
  • Ecological succession
  • Disturbance and resilience
  • Evolving ecosystems

18
Succession and Disturbance
  • 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

19
Primary Succession
20
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.

21
Secondary Succession
22
Aquatic Succession
23
Disturbance and Resilience
  • Removes organisms
  • Reduces populations
  • Creates opportunities for other species to
    colonize

24
Disturbance and Resilience
  • Removes organisms
  • Reduces populations
  • Creates opportunities for other species to
    colonize

25
Fire and Succession
http//www.fs.fed.us/photovideo/
26
Ground Fire
27
Fire and Succession
  • Fire climax ecosystems dependent upon fire for
    maintenance of existing balance e.g.,
    grasslands, pine and redwood forests
  • What significance does this have for humans and
    where they live?

28
Resilience in Ecosystems
29
Resilience Mechanisms after a Forest Fire
  • Nutrient release to soil
  • Regrowth by remnant roots and seeds
  • Invasions from neighboring ecosystems
  • Rapid restoration of energy flow and nutrient
    cycling

30
What you should know from Ch. 4Population growth
curves- J vs SBiotic potentialEnvironmental
ResistanceDensity dependent and independent
resistance factorsK vs R strategistsKeystone
speciesInter intraspecific competitionSuccessi
on- primary secondaryDisturbance and resilience
Write a Comment
User Comments (0)
About PowerShow.com