Transcript An Introduction to Ecology and the Biosphere

Ecology
Campbell, Chapters 50-54
Ecology v. Environment
• Hierarchy of
Ecology
– biosphere
– ecosystem
– community
– population
– organismal
Biotic and Abiotic Factors
• components of the environment
• biotic
– other species may affect one species and its
distribution
• abiotic
– temperature
– water
– sunlight
– Wind
– rocks and soil
Population Ecology
• Density
– mark and recapture
method
– line intercept method
– point count method
• Distribution
– clumped
– uniform
– random
Age Distribution
• distribution of males
and females in each
age group of a
population
• used to predict future
population growth
Survivorship
• mirrors mortality
• expressed in survivorship
curves
• plots surviving individuals
at different age groups
• three types of
survivorship curves
• late loss (Type I)
• constant loss (Type II)
• early loss (Type III)
Population Dynamics:
Exponential Model
• population lives in an area with no environmental
limitations
N
 B  D 
t
B = number of births in time period
D = number of deaths in time period
• example
– # of births over one year is 500 and # of deaths over one
year is 50
N
 500  50  450 individual s
t
Population Dynamics:
Exponential Model
• per capita rate of
increase
– average number
of births and
deaths calculated
as rates
• J curve
• exponential growth
r bd
# of births
b
N
# of deaths
d
N
Population Dynamics:
Exponential Model
• example
– 10,000 birds in a population
– 1500 births and 500 deaths per year
– 1500/10,000 - 500/10,000 = .10 or 10%
– expressed by stating there is a 10% increase per bird
per year
Population Dynamics:
Exponential Model
• measures optimal population growth
• rmax = intrinsic rate of increase

 rmax N
t
• example
– if N=500; r=.05 Calculate the intrinsic rate of increase
N
 .05500   25 individual s
t
Population Dynamics:
Logistic Growth Model
• size of a population is limited to:
– intrinsic rate of increase
– environmental resistance
• includes limitations the environment imposes on birth rate
and death rate in a population
–
–
–
–
food
space
predation
Parasitism
• carrying capacity (K) determined by
– renewable resources like water, nutrients, and light
– nonrenewable resources such as space
Population Dynamics: Logistic Growth Model
– logistic population
growth
– r decreases as N
increases
– K-N tells us # of
individuals population
can accommodate
– S curve
N
KN
 rmax (
)N
t
K
Logistic Growth Model and Life Histories
• K-selected
– equilibrial populations
– live at density near limit imposed by resources
• r-selected
– opportunistic populations
– live in environments where little competition is
present
Density Influence on Birth and Death Rates
• density independent
– unrelated to population size
– most important are
• weather
• Climate
• density dependent
– increase effectiveness as population density increases
– especially affects long lived organisms
– include
• predation
• parasitism
• competition
Human Population Growth
• J curve growth
• grows at a rate of about 80
million yearly (r=1.3%)
• Why doesn’t environmental
resistance take effect?
• altering their environment
• technological advances
– the cultural revolution
– the agricultural revolution
– the industrial-medical
revolution
Community Ecology
• competition
• predator-prey
• symbiosis
– mutualism
– commensalism
– parasitism
– amensalism
• species richness
• relative abundance
• species diversity
Competition
• intraspecific
competition
• interspecific
competition
• Competitive exclusion
principle
Predator-prey Interactions
• one species eating another
– herbivory
– carnivory
– parasitism
– cannibalism
• predators are agents of natural selection
• animal defenses against predators
– hiding or escape
– mimicry
– adaptive coloration
Mimicry
• Batesian mimicry
Mimicry
• Müllerian mimicry
Mimicry
• aggressive mimicry
Adaptive Coloration
• cryptic coloration
Adaptive Coloration
• deceptive coloration
Adaptive Coloration
• aposematic coloration
Symbiosis
• involves
– host
– symbiont
• 3 divisions
– mutualism
– commensalism
– parasitism
Mutualism - lichens
Symbiosis
• involves
– host
– symbiont
• 3 divisions
– mutualism
– commensalism
– parasitism
Commensalism –
sea slug and chloroplasts
Symbiosis
• involves
– host
– symbiont
• 3 divisions
– mutualism
– commensalism
– parasitism
Parasitism –
Chagas’ Disease
Coevolution
• reciprocal evolutionary change
– e.g. flower shape and pollination
• creates a “balance of nature”
Moderator of Competition
• keystone species
– removal dramatically
alters the environment
– influences species
diversity
Trophic Structure
• feeding relationships
• trophic levels
– primary producers
– primary consumers (herbivores)
– secondary consumers (primary carnivores)
– tertiary consumers (secondary carnivores)
• detritovores
• omnivores
• food chain vs. food web
Food Chain v. Food Web
Ecological Succession
• structural change in a community and its
nonliving environment over time
• typically occurs as a result of some
environmental disturbance
• 2 forms
– primary succession
• begins in a lifeless area with invaders called pioneers
• may proceed to a stable climax community
• vary according to geography, climate, etc
– secondary succession
• occurs in an existing community where a disturbance has
occurred
Ecosystem Processes
• Production
• Consumption
• Decomposition
Trophic Relationships
exhibit all 3 processes
– autotrophs produce
– heterotrophs consume
– detritovores and
decomposers recycle
and decompose
Production: Energy Flow
• light energy
– about 1% of sun’s energy used for life
– converted via photosynthesis
• How do we measure the amount of
energy incorporated by producers?
– primary production
Consumption: Energy Flow
• ecological efficiency
– 10% on average
• energy pyramid
• biomass pyramid
Nutrient Cycles
• Biogeochemical cycles
– materials move through biotic and abiotic
portions
– reservoir
Biogeochemical Cycles
• Be able to answer the following questions about
each biogeochemical cycle
• 1. What is the reservoir?
• 2. How does the nutrient enter the biotic portion
of
the cycle?
• 3. How is the nutrient returned to the reservoir?
Biological Magnification
• toxic substances
accumulate in higher
concentrations as
trophic levels increase
• toxin is usually not
biodegradable
• result of inefficiency
of energy transfer
Human Impact: Deforestation
Human Impact: Global Warming
Human Impact: Global Warming
Human Impact: Acid Rain
Human Impact: Agriculture
• manipulate ecosystem productivity
– use of herbicides to get rid of unwanted plants
– use of pesticides to get rid of unwanted pests
– fertilization and irrigation
– genetic modification of plants to increase yield