Transcript Introduction to Ecology

Introduction to Ecology
Chapters 52
Figure 50.3 Rachel Carson
Ecology
• Ecology – the study of interactions
between organisms and the
environment
• Biotic – living components of an
ecosystem (ex. animals and plants)
• Abiotic - nonliving components of
an ecosystem (ex. soil, air, and
water)
Species distribution
• Interactions between organisms and the
environment limit the distribution of species.
• What affects the distribution of species?
– Dispersal limits (range expansions and species
transplants)
– Behavior and habitat selections
– Biotic factors (other species)
– Abiotic factors (temperature, water, sunlight, wind,
rocks/soil, and climate)
Figure 50.7 Spread of the African honeybee in the Americas since 1956
Figure 50.11 Solar radiation and latitude
Figure 50.12 What causes the seasons?
Figure 50.14 How mountains affect rainfall
Figure 50.18 Zonation in a lake
Figure 50.22 Zonation in the marine environment
Figure 50.24 The distribution of major terrestrial biomes
Figure 50.10 A climograph for some major kinds of ecosystems (biomes) in North
America
POPULATION ECOLOGY
CHAPTER 53
POPULATION CHARACTERISTICS
• Population – organisms of the
same species in the same area
• Density – number of individuals
in a given area (example:
1200/m2)
• Dispersion – pattern of spacing
among individuals
Measuring Size
• Quadrant method used for
stationary organisms
• Mark and recapture used for
mobile organisms
Patterns of Dispersion
• Clumped – individuals
aggregated in patches (most
common)
• Uniform – evenly spaced
individuals
• Random – unpredictable,
patternless
Patterns of dispersion within a population’s geographic range
DEMOGRAPHY
• Demography is the study of factors that affect
populations
• Age structure – relative number of individuals of
each age
• Birthrate or fecundity – number of offspring
born during a certain time period
• Death rate – number of individuals who die in a
certain time period
• Generation time – average span between birth
of individuals and the birth of their offspring
• Sex ratio – proportion of individuals of each sex
• Life tables – used to determine
how long, on average, an individual
of a given age could be expected to
live
• Cohort – group of individuals of
same age
• Survivorship curve – a plot of the
numbers in a cohort that are alive
at each age
Life Table for Belding Ground Squirrels (Spermophilus beldini) at Tioga Pass, in the
Sierra Nevada Mountains of California
Idealized survivorship curves
LIFE HISTORIES
• Life history – traits that affect an organism’s
schedule of reproduction and death
• Life histories vary greatly
– Salmon travel to ocean to mature and then
back to stream to reproduce
– Some oaks cannot reproduce until they are
at least 20 years old
• Semelparity or big bang reproduction –
produce numerous offspring and then die
• Iteroparity or repeated reproduction –
produce fewer offspring over many seasons
An example of big-bang reproduction: Agave (century
plant)
• There is a trade-off between
reproduction and survival
–Female red deer who are
reproductive have a greater
chance of dying
–Larger brood sizes increase
mortality rate
Cost of reproduction in female red deer on the Island
of Rhum, in Scotland
Probability of survival over the following year for European
kestrels after raising a modified brood
POPULATION GROWTH
ΔN = Change in population size
B = # births during time interval (birth rate)
D = # deaths during time interval (death rate)
Δt = time interval
ΔN/Δt = B – D
Per capita birthrate (b)= # offspring produced per time by an
average member of population
Ex. 46 births/year in pop of 1000 so b = 46/1000 = 0.046
Birth rate = Expected # births/year for pop (B):
B=bN
Ex. B = 0.046 x 500 = 23 births/year (where N = 500)
Per capita death rate (m)= # deaths per time by an average
member of population
Ex. 22 deaths/year in pop of 1000 so m = 22/1000 = 0.022
Death rate = Expected # deaths/year for pop (D):
D=mN
Ex. D = 0.022 x 500 = 11 deaths/year (where N = 500)
Maximum per capita growth rate (rmax)
ΔN/Δt = bN – mN (birthrate – death rate)
r=b–m
ΔN/Δt = rmaxN (exponential growth rate)
dN/dt = rmaxN (calculus version)
•
•
•
•
If a population is growing, r is positive.
If a population is declining, r is negative.
Zero population growth occurs when r = 0
Exponential growth – maximum population
growth rate
• Intrinsic rate of increase is the maximum
population growth rate, rmax
• Exponential growth is:
• dN/dt = rmax N
Population growth predicted by the exponential model
Example of exponential population growth in nature
• Carrying capacity (K) –
maximum population size that a
particular environment can
support with no net increase or
decrease
• Logistic Growth – incorporates
the effect of population density on
rmax, allowing it to vary from rmax
under ideal conditions to zero as
carrying capacity is reached.
• When N is small compared to K, the
per capita rate of increase is high. (N
= pop size)
• When N is large and resources are
limiting, the per capita rate of
increase is small.
• When N = K, pop stops growing.
• For logistic growth:
ΔN/Δt = rmaxN (K-N/K)
Population growth predicted by the logistic model
How does the logistic curve fit
real populations?
• Some populations closely follow
the S-shaped curve.
• Other populations do not.
–Low numbers may hurt a
population (rhinos)
–Populations may overshoot the
carrying capacity and then drop
below K.
How well do these populations fit the logistic population
growth model?
Strategies
• K-selected populations (density dependent)
– organisms that are likely to be living at density near
the limit imposed by the environment (K)
• r-selected populations (density indepedent)
– organisms that are likely to be living in variable
environments in which populations fluctuate or in
open habitats where individuals are likely to face
little competition
Characteristics
r-selected
K-selected
Maturation time
Short
Long
Lifespan
Short
Long
Death rate
Often high
Usually low
#offspring/episode
Many
Few
# reproductions/
lifetime
Timing 1st reproduction
Usually one
Often several
Early in life
Late in life
Size of offspring/eggs
Small
Large
Parental care
none
Often extensive
POPULATION LIMITING FACTORS
• Limiting factors – factors that limit population growth
• Density dependent factors – death rate rises or birth
rate falls with increasing pop density
• Disease
• Predation
• Competition
• Lack of food
• Lack of space
• Density independent – birth rate or death rate that
does not change with pop density
• Climate
Decreased survivorship at high population densities
Long-term study of the moose (Alces alces) population
of Isle Royale, Michigan
Extreme population fluctuations
Population cycles in the snowshoe hare and lynx
Human population growth
Demographic transition in Sweden and Mexico, 1750-1997
Age-structure pyramids for the human population of Kenya
(growing at 2.1% per year), the United States (growing at 0.6%
per year), and Italy (zero growth) for 1995
Annual percent increase in global human pop
(data from 2005). Sharp dip in 1960 due mainly
to famine in China that killed 60 million people.
Infant mortality and life expectancy (from 2005)
COMMUNITY ECOLOGY
CHAPTER 54
COMMUNITIES
• Communities – different populations
living within the same area
• What factors are most significant in
structuring a community?
INTERACTIONS
• Interspecific interactions –
occur between different
populations within a community
• Coevolution – a change in one
species acts as a selective
force on another species, and
counter-adaptation by the
second species, which may
cause a selective force on the
1st species.
• Predation (+/-)
– Lion hunting, killing, and eating a zebra
• Parasitism (+/-)
– Ticks sucking blood of human
• Competition (-/-)
– Fighting over resources
• Commensalism (+/0)
– Birds feeding on insects which bison flush out of
grass
• Mutualism (+/+)
– Legumes with nitrogen fixing bacteria
• Herbivory (+/-)
– Insects eating plants
• Disease (pathogens) (+/-)
– Bacteria, viruses, protists, fungi, and prions
Figure 53.x2 Parasitic behavior: A female Nasonia
vitripennis laying a clutch of eggs into the pupa of a
blowfly (Phormia regina)
Figure 53.9
Mutualism between
acacia trees and ants.
The ants live in the
hollow thorns and
sting other pests.
Predation
• Cryptic coloration –
camouflage
• Aposematic coloration –
when animals with effective
chemical defenses are brightly
colored as a warning
Figure 53.5 Camouflage: Poor-will (left), lizard (right)
Figure 53.6 Aposematic (warning) coloration in a
poisonous blue frog
Figure 53.x1 Deceptive coloration: moth with
"eyeballs"
• Mimicry – an organisms mimic
another
–Batesian mimicry – a
harmless species mimics a
harmful or unpalatable
species
–Mullerian mimicry – two or
more aposematically species
resemble each other
Figure 53.7 Batesian mimicry: the hawkmoth larva
resembles a snake
Figure 53.8 Müllerian mimicry: Cuckoo bee (left),
yellow jacket (right)
Competition
• Competitive exclusion principle –
two species with similar needs for the
same limiting resources cannot
coexist in the same place.
–Could lead to extinction of one species
• Ecological niche – ecological role;
the sum total of the organism’s use of
biotic and abiotic resources
• Resource partitioning – sympatric
(geographically overlapping) species
consume slightly different foods or use
resources in slightly different ways.
• Character displacement – characteristics
are more divergent in sympatric populations
compared to geographically isolated
(allopatric) populations
Figure 53.3a Resource partitioning in a group of
lizards
Figure 53.2 Testing a competitive exclusion
hypothesis in the field
Figure 53.3bc Anolis distichus (left) perches on sunny
areas and Anolis insolitus (right)
perches on shady branches.
What controls community
structure?
•
•
•
•
•
Species diversity
Food webs
Dominant species
Keystone species
Foundation species
Figure 53.21 Which forest is more diverse?
Species Diversity
• Species diversity – considers the
following:
–Species richness – number of
different species
–Species relative abundance –
proportion each species
represents of the total individuals
in community
• Dominant species – most abundant or highest
biomass
– Ex. American Chestnut was dominant before
1910, but chestnut blight killed all in N.
America
– Invasive species can become dominant
• Keystone species – a predator that makes an
unusually strong impact on community structure
– Keystone predators maintain higher species
diversity by reducing the densities of strong
competitors, such that the competitive
exclusion of other species does not occur
– Ex. Removing Piaster decreased species
diversity. Without piaster, mussels
overpopulated and excluded other species,
Figure 53.14b Testing a keystone predator hypothesis
Figure 53.14a Testing a keystone predator hypothesis
Figure 53.15 Sea otters as keystone predators in the
North Pacific
Without sea
otters, sea
urchins do
well and eat
kelp. Kelp
forests are
being
destroyed.
Otters are
being eaten
by killer
whales.
• Foundation species - cause physical
changes to environment
– Ex. beaver dam, black rush (grass) helps
prevent salt build up in soil of marshes
Bottom-up or Top-down
Controls
• Bottom-up = influence from lower to
higher trophic levels
– Mineral nutrients control the plants, which
control the herbivores, which then controls
the predators
• Top-down = influence from higher to
lower trophic levels
– Predators limit herbivores, which in turn
limits plants, which affects soil nutrients
DISTURBANCES
• Disturbances are events such as fire, storms,
drought, or human activities that damage
communities.
– Can create opportunities for other species
– Human disturbance is not always negative
• Yellowstone fire in 1988 killed old forest,
but new plants quickly grew in its wake
• Dynamic equilibrium hypothesis – species
diversity depends on the effect of disturbance
on the competitive interactions of populations.
Figure 53.16 Routine disturbance in a grassland
community
Figure 53.18x2 Forest fire
SUCCESSION
• Ecological succession – transitions in
species composition over time
• Primary succession – when succession
begins in an area that is virtually lifeless
and has no soil.
• Lichens and mosses are usually the first
macroscopic photosynthesizers
–Can slowly dissolve rock to make soil,
which takes thousands of years
Figure 53.18x1 Large-scale disturbance: Mount St.
Helens
Figure 53.19 A glacial retreat in southeastern Alaska
Table 53.2 The Pattern of Succession on Moraines in
Glacier Bay
• Secondary succession –
occurs where an existing
community has been cleared by
some disturbance that leaves
soil intact (example fire or
volcanoes erupting)
–Typically pioneer species are
r-selected (high birthrates and
dispersal)
Figure 53.18 Patchiness and recovery following a
large-scale disturbance
ECOSYSTEMS
Chapter 55
FOOD WEBS and TROPHIC LEVELS
• Autotrophs
– Producers make own food
• Heterotrophs
– Primary consumers = herbivores = eat
producers
– Secondary consumers = carnivores = eat
primary consumers
– Tertiary consumers = carnivores = eat
secondary consumers
– Detritivores (decomposers) = eat detritus
(nonliving organic material and dead
remains)
Figure 54.1 An overview of ecosystem dynamics
A Food Web
Section 3-2
Figure 54.2 Fungi decomposing a log
• Production – rate of
incorporation of energy and
materials into the bodies of
organisms
• Consumption – metabolic use
• Decomposition – breakdown of
organic material into inorganic
ENERGY FLOW IN
ECOSYSTEMS
• Most solar radiation is absorbed,
reflected, or scattered in the
atmosphere of Earth.
• Only a very small portion of sunlight
is used by algae, bacteria, and
plants for photosynthesis
• Primary productivity – amount of light
energy converted to chemical energy by
autotrophs in an ecosystem in a given time
period
• Gross primary productivity (GPP) – total
primary productivity (not all of this energy is
stored in autotrophs because autotrophs use
energy for respiration)
• Net primary productivity (NPP)
NPP = GPP – R
Where R = the amount of energy used in
respiration
Respiration
C6H12O6 + 6O2
6CO2 + 6H2O
Photosynthesis
• Gross primary productivity results
from photosynthesis
• Net primary productivity is the
difference between the yield of
photosynthesis and the consumption
of fuel in respiration
• Primary productivity
–J/m2/yr (energy measured per
area per unit time)
–g/m2/yr (biomass added per
area per unit time)
• Seasonal changes and
available nutrients can limit
primary productivity
Figure 54.3 Primary production of different
ecosystems
Figure 54.4 Regional annual net primary production
for Earth
• Limiting nutrient – the nutrient
that must be added to increase
primary productivity
–Example: nitrogen or phosphorus
are often limiting in aquatic
systems (especially in the photic
zone)
• Secondary productivity – rate at
which an ecosystem’s consumers
convert chemical energy into their
own new biomass
Figure 54.9 Nutrient addition experiments in a Hudson
Bay salt marsh
Figure 54.11 An idealized pyramid of net production
ECOLOGICAL PYRAMIDS
• Pyramid of productivity
–~10% rule - ~10% of energy at
one level transfers to next level
–Where does the energy go?
Figure 54.10 Energy partitioning within a link of the
food chain
• Pyramid of biomass – standing
crop biomass (total dry weight)
–Some aquatic systems show
inverted pyramids because
zooplankton consume
phytoplankton quickly
–Productivity still upright
Figure 54.12 Pyramids of biomass (standing crop)
Figure 54.13 A pyramid of numbers
NUTRIENT CYCLING
• Biogeochemical cycles – involve both abiotic
and biotic components
Figure 54.16 The water cycle
Figure 54.17 The carbon cycle
CARBON CYCLE
• Carbon dioxide in
atmosphere is lowest in
summer in N. hemisphere
and highest in winter. More
plants in summer = less CO2
in atmosphere
• Dissolved CO2 makes
carbonic acid (H2CO3)
• Increased burning of fossil fuels
has increased CO2 levels, which
leads to global warming.
–Carbon dioxide absorbs much
of the reflected infrared
radiation = greenhouse effect.
•Without the greenhouse
effect, temperature would be
–18°C.
Figure 54.26 The increase in atmospheric carbon dioxide and
average temperatures from 1958 to 2000 (readings taken from
Mauna Loa, Hawaii)
Global Warming
• A number of studies predict CO2 will double
by end of 21st century.
• Will cause a predicted 2ºC average global
temp increase
• Historically, a 1.3 ºC would make world
warmer than any time in past 100,000 years.
• Poles probably most affected and polar ice
melting may change our coastlines!
Figure 54.18 The nitrogen cycle
NITROGEN CYCLE
• Plants cannot use N2 (gas).
• Nitrogen fixing bacteria convert nitrogen gas
into a form of N that plants can use:
ammonium (NH4+) or nitrate(NO3-).
• Nitrogen fixing bacteria can live in the soil or
in plants called legumes (mutualism).
• Legumes include beans, alfalfa, and soy.
• Denitrifying bacteria convert nitrate back into
nitrogen gas.
• Without nitrogen fixing bacteria, plants could
not get the nitrogen they need and would die.
All life on earth depends on these bacteria.
Figure 54.19 The phosphorous cycle
PHOSPHORUS CYCLE
• Phosphorus is often the limiting nutrient
in lakes.
• Sewage and runoff provide excess
phosphorus. This can cause
eutrophication. This is when a lake
develops a high productivity, which is
supported by high rates of nutrient
cycling. This leads to algal blooms,
which can suffocate the lake.
Figure 54.8 The experimental eutrophication of a lake
Figure 54.24 We’ve changed our tune
BIOLOGICAL MAGNIFICATION
• Nonbiodegradable substances become
more concentrated in increasing,
successive trophic levels.
• The biomass at any given level is
produced from a much larger biomass
ingested from the level below.
• Example: DDT caused birds of prey to lay
eggs with thin shells.
Figure 54.25 Biological magnification of DDT in a food
chain
Chlorinated Hydrocarbons
• Include DDT, agent orange, PCBs
(polychlorinated biphenyls)
• They are persistent (i.e., they persist in the
environment for several years)
• They are non-polar (i.e., water-hating)
• They bioaccumulate (i.e., they concentrate
in the fat of organisms, and their
concentration increases as one moves up the
food chain)
• They are causing a toxic effect at low
concentrations
• Agent Orange was a defoliant used during
the Vietnam War.
• Agent Orange is an herbicide that was used
during the Vietnam War to strip the land of
vegetation making it easier for the US troops
to see the opposing forces and also to
deplete their food supply.
• Dioxin is a very toxic chemical within Agent
Orange.
• Dioxin is believed to be the cause of so much
damage and has been linked to many
cancers and birth defects.
Dioxin (part of Agent Orange)
OZONE DEPLETION
• Ozone (O3) provides a protective barrier
to UV light.
• Chlorofluorcarbons react with O3 and
reduce it to O2, which makes holes in the
layer.
• Largest hole over Antarctica.
• Chlorofluorcarbons come from
refrigerants, propellants in aerosol cans,
and in some manufacturing processes.
Figure 54.27a Erosion of Earth’s ozone shield: The
ozone hole over the Antarctic
Figure 54.27b Erosion of Earth’s ozone shield:
Thickness of the ozone layer