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Ecology
Priority 4
Reviewed
Responses to the environment
Responses to cues
Can be:
phenotypic plasticity
positive or negative feedback
Thermoregulation— organisms manage internal environment by regulating
(endotherm) or conforming (ectotherm)
Photoperiodism— periodic flowering depending on the length of daylight
Phototropism— auxin secreted from light-detecting tip of plant causes
elongation of cells in shade
Osmoregulation— gain or lose water in salt/freshwater
Ecology 1
Taxis
Kinesis
Controlled movement towards or
Gradual increase in random
away from a stimulus
movement
Behavioral responses
ENSURE REPRODUCTIVE SUCCESS:
asserting dominance
acquiring food or territory
Kin selection— more likely to behave altruistically towards relatives
Pack behavior
Communication eg. birdsong
Energy flow
ENERGY FLOWS, MATTER CYCLES.
Matter
matter is cycled through
feeding
absorbing/releasing towards atmosphere
chemical fixing
e.g. carbon and nitrogen cycles
Energy
Ecology 2
ENERGY FLOWS THROUGH TROPHIC
LEVELS
Gross primary production (GPP) =
total primary production of
energy
Net primary production (NPP) =
energy available to consumers
after plants use some for
matabolism
secondary production: amount of
energy in food converted to new
biomass, excluding feces and
metabolism
Factors of energy flow
light limitation: less productivity past oceanic photic zone due to less light
available for photosynthesis
nutrient limitation, often nitrogen or phosphorus for DNA
eutrophication: too much nutrients causing algae bloom
Deconposers perform extracellular digestion (secrete digestive enzymes) and
absorption, therefore they do not belong to any trophic level.
Ecology 3
Population ecology
Population = groupd of individuals of the same species living in the same
general area
Uniform dispersion Random dispersion Clumped dispersion
competition for limited interaction shared resources
resources
uniform resources predator avoidance
territoriality social behavior
Survivorship curve
survivorship curves show the results (survival patterns), while r/k selection
explains the underlying strategies (reproduction and care) that lead to those
results.
1. Type 1 (top red)
a. low mortality during young
life, but increases as
population gets older
2. Type 2 (middle blue)
a. random mortality
3. Type 3 (lower green)
a. high juvenile mortality but
levels off for survivors
r-selection tend to have energy-cheap offspring, small body size, and type 3
survivorship.
Ecology 4
k-selection tend to have energy-expensive offspring, large body size, parental
care, and type 1/2 survivorship.
Density dependence
in DENSITY-DEPENDENT populations, birth rates fall and death rates rise as
density increases
Negative feedback loop
territoriality may pre-req and limit density
competition for resources
diseases can spread more rapidly in dense populations
if prey increase in density predators might prefer that species
in DENSITY-INDEPENDENT populations, birth/death rates do not change
with density
Independent limiting factors
seasonal change
human-driven climate change
Community ecology
a community is a group of populations of different species in an area
interacting.
Interspecific interactions
Interaction Relationships Result
Competition* -/- both sides spend energy
Predation* +/- prey adapt to have camouflage
Herbivory +/-
Symbiosis* TYPES directly affect SURVIVAL of species
Competition
Competitive exclusion principle states that 2 species competing for the same
limited resource CANNOT coexist.
Ecology 5
Resource partition: division of resources to reduce competition
Predation
1. Cryptic (blending) coloration
1. Aposematic (warning) coloration
1. Batesian mimicry: harmless
species mimics a harmful one
Ecology 6
1. Mullerian mimicry: 2 harmful
species mimic each other to
intensify the message
Symbiosis
SYMBIOSIS RELATION
Parasitism -/+
Commensalism +/0
Mutualism +/+
Biodiversity
Richness ≠ Evenness
>> Just because there are many TYPES of species, biodiversity is not
established until there is a roughly EQUAL number of each species.
The Simpson diversity index
∑ n(n − 1)
D =1−( )
N(N − 1
where n = number of individuals in a single species
N = number of individuals in the total population
Biodiversity renders the community MORE RESISTANT TO CHANGE
Ecology 7
TROPHIC CASCADE: loss of one
trophic level magnifies the entire food
web
keystone species: species that
have an OVERWHELMINGLY
large impact on the community
Disruptions to ecosystems
Disturbance
=== any event that changes a community, removes organisms, and alters
resource availability
Human disturbance is the BIGGEST disturbance
Prevents natural disturbances
Removes community structure
e.g. fire, in most terrestrial ecosystems
Ecological succession
=== sequence of changes after a disturbance
1. Primary succession MUTATIONS and ADAPTATIONS
affect successions
a. where no soil is left after the
disturbance mutations do NOT depend on
abiotic factors
2. Secondary succession
adaptations DO depend on
a. where soil remains
abiotic factors
Ecology 8
Invasive species
=== species that are not native and have a tendency to spread
e.g. kudzu vine
>> new niche free of natural
predators or competitors
>> outcompete native species
Plate tectonics
=== lithosphere (crust and mantle) movement
continental drift contributes to biodiversity
Ecology 9
