Download trophic level

What is it?
Ecology
Ecology
• Hierarchy of Organization
- Individual
- Population - # of individuals in given area
- Community – all biota in an area
- Ecosystem – all biota & abiotic factors
- Landscape – multiple ecosystems over
large area
- Biosphere – all life on Earth
Ecology
Autecology: study interrelations of
individuals with environment
Synecology: study of communities
Basic Scientific Principles
• Law of Conservation of Matter
Matter cannot be created nor destroyed,
rather it can only be transformed
• 1st Law of Thermodynamics (Energy)
Energy cannot be created nor destroyed,
rather it can only be converted in form
Basic Scientific Principles
• 2nd Law of Thermodynamics
When converting energy, always lose
some energy as heat
Major Ecosystem Processes
1) Energy Flow = energy moves through
system
2) Nutrient Cycling = chemical elements
recycled in system
Energy Flow
• Solar energy – primary energy source
(fig 3.5, p. 42)
Of incoming solar radiation:
66% absorbed
34% reflected (albedo)
Solar Energy
• Of solar radiation absorbed:
- ~22%
water cycle
- nearly all
transform to heat &
radiates
emissivity: relative ability of Earth to
release energy (e.g., radiate heat into
space; link to global warming)
Solar Energy
• Tiny amount of solar energy into
photosynthesis (< 0.1%)
photosynthesis (PNS): use solar energy to
convert CO2 & H2O into sugar; by-product
= O2
primary production: all organic matter
resulting from PNS; raw material for other
organisms (gross production vs. net
production)
Energy Flow in Communities
food chain: sequence of organisms linked
by energy & nutrient flow
trophic level: feeding level/position of
organism in food chain
Trophic Levels
Producer: (autotrophs) anchor of chain;
produce all organic matter for other
organisms
Heterotrophs (consumers)
Primary consumer: directly consume
producers = herbivores
Secondary consumer: consume herbivores
Tertiary & Quaternary consumers: consume
secondary & tertiary consumers,
respectively
Trophic Levels
Decomposers: (detritus feeder) consume
and convert dead material for use by
producers
Food Webs
food web: interconnected food chains; all
trophic interactions in community
Human Impacts
Ecosystem simplification: elimination of
species from food webs via human
alterations to land
Example: vertebrate communities in ag.
landscapes
Energy Flow Between Trophic
Levels
Does 100% of energy transfer from 1
trophic level to another?
No. Remember 2nd Law of Thermodyn.
Range 5-20% transference (usually ~10%)
Graphical representation of energy
transference in food web = energy
pyramid
Energy Flow Between Trophic
Levels
Why such low efficiency?
Three Reasons:
1) Escape behavior/protective
coloration/unavailable material
2) Indigestible material
3) Cellular respiration
Bioaccumulation = Biomagnification
Nutrient Cycles
What does the Law of Conservation of
Matter state?
• circular flow of chemicals = recycling
• Inputs & relationship to energy flow?
• Water, Carbon (C), Nitrogen (N),
Phosphorus (P), Sulfur (S)
Carbon Cycle
• Carbon = building block of life
• Reservoirs = atmosphere, ocean,
organisms
• High rate of exchange in/out reserves
• Any relation to global warming?
Nitrogen Fixation
Types
1) atmospheric fixation via lightening
or sunlight; NO3 as precipitation (ppt)
2) biological fixation* via soil & water
bacteria (blue-green algae); NH3;
legumes & root nodules
Water Quality & Nitrates
Soil Condition & Fertilizers
Phosphorus Cycle
• Water Quality & Phosphorus
• Eutrophication: increase in nutrient
content of lakes
Some Ecological Principles
Individual
• Law of Tolerance: organisms can
tolerate a range of conditions beyond
which they die
• e.g., temperature, nutrients
• age-dependent, DNA
Where does habitat fit?
Habitat: home; area having necessary
resources (food, water, cover) and
environmental conditions (temp., ppt) that
allows organism to live & reproduce
Your habitat = ?????
What if habitat is drastically changed or
destroyed?
• Move, Adapt, or Die
Properties of Communities
1) Species Richness = # species in a comm.
2) Species Evenness = relative abundance of
different species
3) Species Diversity = richness & evenness
e.g., Four species (A,B,C,D) in 2 different
communities
Comm 1 – 25A 25B 25C 25D
Comm 2 – 97A 1B 1C 1D
What Happens in a
Community?
1) Competition: individuals contest over a
resource (food, space, water, mates…) –
major factor determining structure
http://fr.truveo.com/The-Raccoon-and-Two-House-Pets/id/2429116624
What Happens in a
Community?
Types of Competition
A) Interspecific: competition between
different species, e.g., blue jay & chickadee
compete for sunflower seed at feeder
What Happens in a
Community?
Types of Competition
B) Intraspecific: competition within the same
species, e.g., 2 oryx bobcats compete for
space
Principle of Competitive
Exclusion (Gause’s experiments)
• Two species which compete for same
resource cannot coexist in same place at
same time
• Implications = different locations or
different times
• Relates directly to niche concept
Niche Concept
Niche: functional role (“occupation”) &
position (spatial & temporal) of a species in
its community
• Principle of Competitive Exclusion = 2
species cannot occupy the same niche
What Happens in a
Community? (cont.)
2) Predation: one species consumes another
species
Some Ecological Principles
Community
• Biological Succession: temporal
sequence of one community replacing
another; predictable
• Primary vs. Secondary
Terrestrial Biomes
• Biomes - distinguished primarily by their
predominant plants and associated with particular
climates.
– Geographic and seasonal variations in temperature and
precipitation are fundamental components.
•
Soil : Foundation of Terrestrial
Biomes
Soil is a complex
mixture of living and
non-living material.
– Classification based
on vertical layering
(soil horizons)
• Soil Profile =
snapshot of soil
structure in a constant
state of flux
Soil Horizons
• O horizon: Organic Layer freshly fallen
organic material - most superficial layer
• A horizon: Mixture of minerals, clay, silt
and sand
• B horizon: Clay, humus, and other materials
leached from A horizon - often contains
plant roots
• C horizon: Weathered parent material
Tropical Rainforests
• Little temperature variation
between months
• Organisms add vertical
dimension
• Harbor staple foods and
medicines for world’s human
populations - increasingly
exploited
Tropical Dry Forest
• Climate more
seasonal than
tropical rainforest
• Heavily settled by
humans with
extensive clearing
for agriculture
Tropical Savanna
• Climate alternates
wet / dry seasons
– Fire dependent
Desert
~ 20% of earth’s land
surface
• Water loss usually
exceeds precipitation
• Human intrusion
increasing
Mediterranean Woodland &
Shrubland (Chaparral)
• All continents
except Antarctica
• Climate cool &
moist in fall,
winter, and spring;
hot & dry in
summer
• Fire-resistant
plants due to fire
regime
Temperate Grassland
• Periodic droughts
• Soils tend extremely
nutrient rich and deep
• Dominated by
herbaceous vegetation
• Warm season grasses
(tall grass vs. short
grass)
• Large roaming
ungulates
– Bison vs. cattle
Temperate Forest
• Fertile soils
– Long growing
seasons dominated
by deciduous
plants
– Short growing
seasons dominated
by conifers
• Many major human
population centers
Boreal Forest (Taiga)
• Northern Hemisphere
– ~ 11% of earth’s
land area
• Thin, acidic soils low
in fertility
• Generally dominated
by evergreen conifers
• Historically, low
levels of human
intrusion
• Covers most of lands
north of Arctic Circle
– Climate typically
cool & dry; short
summers
• Low decomposition
rates
• Human intrusion
historically low, but
increasing as resources
become scarce
– What type of
increased use?
Tundra
dN
 rN
dt
dN
 N
 rN 1  
dt
 K
Density-dependent Effects
Who Cares?
Why bother discussing these models?
Metapopulations & Source-sink Populatons
highlight the importance of:
• habitat & landscape fragmentation
• connectivity between isolated
populations
• genetic diversity
Habitat Fragmentation
• Process of breaking contiguous unit into
smaller pieces; area & distance
components
• Leads to:
< remnant patch size
> edge:interior ratios
> patch isolation
< connectivity
• Community & Ecosystem processes
altered
Habitat Fragmentation
• First-Order Effects: fragmentation leads
to change in a species’ abundance and/or
distribution
• Higher-Order Effects: fragmentation
indirectly leads to change in a species
abundance and/or distribution via altered
species interactions
Habitat Fragmentation
• area-sensitive species: species that
require minimum patch size for daily
life requirements
• Edge effects: influence of factors from
outside of a patch
Edge Effects
• Habitat surrounding a patch can:
- change abiotic conditions; e.g., temp.
- change biotic interactions, e.g.,
predation
Example of nest predation = edge effect of
approximately 50 m into forest patch
Conservation Implications
• All habitats are “islands”
• The “internal external threat”
• Develop & manage reserve as
landscapes/ecosystems linked by
movement of species (metapop.
concepts)
• Develop strategies for countering edge
effects……predator control?????