Transcript ecology - TeacherWeb

ECOLOGY
Introduction
I. WHAT IS ECOLOGY?
• study of interactions between organisms &
the environment
• leads to evaluating of environmental
issues
A. Important Abiotic Factors
1.
2.
3.
4.
5.
6.
environmental temp.
water
sunlight – drives nearly all
wind – effects temp.
rocks & soil (structure, pH & minerals)
periodic disturbances (fire, hurricanes,
volcanoes)
III. The cost & benefits of
homeostasis
• Regulators: maintain homeostasis
through behavioral & physiological
mechanisms
• Conformers: allow internal conditions to
vary w/ external
• Principle of allocation: each organism has
a limited amount of energy that can be
allocated for obtaining nutrients, repro.
escaping; so too much for homeo….
IV. BIOMES – often name for
predominant vegetation
Tropical Forest
• near equator
• temp. varies little
• rainforest = greatest
diversity
Savanna
• grassland w/
scattered trees
• S. America & Africa
(central & south)
Desert
• low & unpredictable
precipitation (not
temp.)
• central Asia & N.
Africa
Chaparral
• dense, spiny shrubs
w/ tough evergreen
leaves (along coasts)
• periodic fires
Temperate Grasslands
• similar to savannas
but with cold winters
(plains & prairies of
U.S.)
• soil deep & rich
Temperate Deciduous Forest
• midlatitude regions
with sufficient
moisture to support
large, broad-leaved
dec. trees
Taiga
• coniferous forest
• soil thin & acidic
Tundra
• permafrost
• northern-most limits
of plant growth (low
shrubby, mat-like
vegetation)
• not a lot of animals
V. Aquatic Biomes – occupy the
largest part of the biosphere
• Freshwater – (less than 1% salt) closely
linked to terrestrial biomes they are near
• Marine – (more than 3% salt) 75% of
Earth; algae make most oxygen
Ponds & Lakes
• standing bodies of
water
• vertical stratification in
light (aphotic vs.
photic) & temperature
(thermocline)
• oligotrophic = deep,
nutrient poor (clear)
• eutrophic = shallow,
nutrient rich (murky)
Streams & Rivers
• bodies of water that
move continuously in
1 direction
• change in structure &
life from headwaters
to mouth
Wetlands
• covered by water that
support aquatic
vegetation
• hydrophytes live here
Estuaries
• area where fresh
water stream or river
merges with ocean
• very productive due to
nutrients from rivers
• salinity varies
The Intertidal Zone
• where land & sea
meet; alternately
submerged &
exposed by tides
• Rocky – vertically
stratified (attached to
harsh)
• Sandy – no clear
stratification (pred. &
scavengers)
Coral Reefs
• warm, tropical water
where sunlight
penetrates to ocean
floor (diverse &
productive)
Oceanic Pelagic Biome
• open waters far from
shore
• nutrient content low
• plankton & nekton
prevalent
Benthos
•
•
•
•
ocean bottom
nutrients from detritus
diverse
low light & temp.
POPULATION ECOLOGY
I. Important Characteristics
A. Density = number of individuals per unit
area or volume
B. Dispersion = clumped, uniform or
random
III. Mathematical model for
exponential growth describes an
idealized population in unlimited
environment
• Change in population size over time =
births – deaths
• ZPG = death & birth rates are equal (births
& deaths still occur)
• Carrying capacity = maximum stable
population size that the environment can
support over long time period
IV. Factors affecting population
growth
A. Density-dependent
* nutrients
* territory
* accumulation of waste
B. Density-independent
* weather, climate
* natural disasters
COMMUNITY ECOLOGY
I. Predation & parasitism (+ - )
interactions
A. Predation
1. Plant defenses against: thorns,
hooks, spines, bad taste, hormones
causing abnormal development
2. Animal defenses: hide, escape,
coloration
3. Mimicry: to scare or lure prey
II.
Interspecific competitions are
(- -)
• Inference competition – fighting
• Exploitative competition – consumption or
use
• Niche: how it “fits into” an ecosystem (the
organism’s role)
V. Factors that structure
communities
• Competition
• Predation
• Environmental patchiness: more
heterogeneous the habitat = more diverse
community
VI. Succession is the sequence of
changes in a community after a
disturbance
• Ecological succession: transition in
species composition over ecological time
• Primary succession: begins in areas
essentially barren of life due to lack of
formed soil or on rubble
• Secondary succession: if an existing
community has been cleared by some
disturbance that leaves soil intact
• Climax community: relatively stable state
after transitional stages
• Disturbances can have positive impact on
community: species diversity
ECOSYSTEMS
* Involves energy flow & chemical
cycling
I. Trophic structure determine an
ecosystem’s routes of energy flow
& chemical cycling
• Food chain – pathway along which food is
transferred from trophic level to trophic
level
• Food web – relationships actually woven &
elaborate
• Trophic levels:
1. primary producers
2. primary consumers
3. secondary consumers
4. tertiary consumers
5. decomposers
II. An ecosystem’s energy budget
depends on primary productivity
• Primary productivity: amount of light
energy converted to chemical energy by
autotrophs of an ecosystem
gross: total converted
net: total – energy used for respiration
• Factors determining productivity:
temperature, precipitation, light intensity
• As energy flows through an ecosystem,
much is lost at each level (85-95% of
energy available never transfers to next
level)
• Only 3-5 trophic levels can be supported
• Predators highly susceptible to extinction if
ecosystem disturbed
Water Cycle
• Sun causes evaporation from ocean --water rises, cools --- falls as precipitation
• Primarily physical
Carbon Cycle
• Carbon dioxide into leaf – into biomass –
out with respiration
• Some carbon diverted in wood, coal,
petroleum
Nitrogen Cycle
• Atmosphere 80% N2
• Nitrogen only available NH4 (ammonium)
& NO3 (nitrate)
• Enters ecosystems by atmospheric
deposition (5-10% dissolved by rain) or
nitrogen fixation
Phosphorus Cycle
• Weathering rocks adds P to soil –
producers absorb & incorporate –
transferred to consumers – back to soil by
excretion & decomposition