Ecology
What is Ecology?
•=
“The environment”
• Abiotic –
Levels of organization in Nature
Subatomic particle
•
•
•
•
•
•
•
protons
electrons
neutrons
tachyons
baryons
mesons
etc.
Subatomic Particles
Atom
p
p
n
e-
e-
atoms
Subatomic Particles
Molecule
H
H C
COOH
H2O
NH 2
NH2
N
Cl2
OH
OH
OH
HO P
O P
O P
O
O
O
N
O
CH2
H
O
N
N
H
H
H
HO
OH
Molecules
atoms
Subatomic Particles
N2
O2
Organelle
• Sacs or their compartments that separate
different activities inside the dell
Organelle
Molecules
atoms
Subatomic Particles
Cell
• (smallest living unit) May live independently or
part of a multicellular organism
Cell
Organelle
Molecules
atoms
Subatomic Particles
Tissue
• A group of cells and surrounding substances
functioning together in a specialized
activity.
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Organ
• A group of tissues working together to perform a
common task.
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Organ system
• Two or more organs
interacting to contribute to
the survival of the whole
organism.
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
multicellular organism
• An individual composed of
specialized interdependent cells
arrayed in tissues, organs, and
often organ systems
Multicellular Organism
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Population:
• A group of individuals of the…
Population
Multicellular Organism
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Community
Community
• = a group of organisms of
different species (i.e. many
populations)….
Population
Multicellular Organism
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Ecosystem
Ecosystem
Community
Population
Multicellular Organism
Organ System
Organ
• All biotic and abiotic components of
a certain area
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Biome
Biome
Ecosystem
Community
• Major types of ecosystems
on earth, occupying large
geographic regions
Population
Multicellular Organism
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Biosphere
Biome
Biosphere
Ecosystem
Community
• Those regions of the earth’s
waters, crust and atmosphere in
which organism can exist.
Population
Multicellular Organism
Organ System
Organ
Tissue
Cell
Organelle
Molecules
Atoms
Subatomic Particles
Is life uniformly distributed?
Is Life uniformly distributed?
•
Why isn’t all life everywhere?
Factors affecting distribution of
organisms (biogeography)
1. Dispersal limitations
–
Not all areas are accessible – geographic
isolation
2. Habitat selection
•
Animals
3. Biotic Factors
4. Abiotic Factors
3. Biotic Factors
• Absence of symbioses
• Lack of pollinators
• Competition
Competition
• Whenever the quantity of useful matter or energy
falls below the level needed for the maximal
growth of two or more organisms which must
draw on the same supply, a contest begins.
• Competition from introduced species can shrink an
organism’s actual range
What do plants compete for?
4. Abiotic Factors
• Vary from place to place, season to season.
• Each organism has an optimum environment
needed for maximum growth.
……Thus scientists predict that global
warming may radically alter the distribution
of organisms/ecosystems on earth
Fig 50.18
Effects of climate on biogeography
• Solar radiation creates wind currents, ocean
currents, and precipitation (from
evaporation
Fig 50.10
Fig 50.10
Effects of climate on biogeography,
continued
• Local climate
–.
–.
–.
– S slope drier than N slope (thus different plant
communities)
• Microclimate
–.
– Under a log
– Within the litter layer
Your ecosystem type: coastal temperate rainforest
Fig. 50.12
Terrestrial Biomes
•
Locations of the earth’s biomes due to:
1. .
2. .
• One biome type may occur in different areas of the
world
– Different plant species but same:
– Physiognomic structure –
–
Similarities due to convergent evolution –
similar phenotypes due to similar selection
pressures over time
• Similar climate, soils, disturbance patterns,…
Fig. 50.19
1. Tropical rainforest
• Very diverse!
• Large vertical stratification due to competition for
light
2. Savanna
• Rainy & dry season
• Fire adapted
3. Desert
• CAM plants
• Unique plants with adaptations to harsh
environment
4. Chapparal
• Fire-dependent! – seeds germinated after fire,
roots fire-resistant
5. Temperate grassland
• Occasional fire
• Fertile soils
6. Temperate deciduous forest
• 4 seasons (cold winter – dormant)
• Open forests
7. Coniferous Forest
• 4 seasons, large amounts of snowfall
8. Tundra
• No trees or tall plants
• 20% of land area on earth
• Low annual precipitation
4 types of ecological investigation:
1. Organismal ecology
• “plant autecology”
• organism’s response to environment – ability to
exist/adapt
2. Population ecology
• Population size, distribution
3. Community ecology
• Community structure, organization
• Competition
• Diversity
• Disturbance
• Succession
4. Ecosystem ecology
• Energy flow/nutrient cycling
• Interactions of biotic & abiotic components
Plant Population Ecology
Characteristics of Populations
1. Dispersion –
2. Size –
3. Density - the number of individuals living in a
specified area
1. Dispersion
• Patterns of Dispersion:
– Clumped –
– Uniform – evenly spaced due to:
• Competition for resources
• Allelopathy –
– Random – unpredictable; position of one
individual cannot be predicted from position of
another.
Clumped lupine
Random trees
Uniform dispersal of sagebrush
2. Population Size
• Demography = study of factors that affect the growth
& decline of populations
• Life Histories = events from birth through
reproduction to death
– Trade-offs between investments in reproduction &
survival when there are limited resources
Controls at every stage of life history
death
reproduction
mature plant
growth
seedling
Seed rain
from mature
plants
Dormancy (seed bank)
Herbivory, disease,
competition,
drought, flood,
freeze
Seeds washed
away, eaten,
decomposed
Demography
• Change in Population size = (B + I) – (D + E)
Exponential Growth
• occurs when resources are abundant or when an
important constraint has be removed.
• Ex.
The j-shaped curve
Number of
Individuals
Time
Biotic Potential (r)
• = Intrinsic/ maximum rate of natural
increase, given:
• Habitat is free of predators and
pathogens.
Limits on Population Growth
• Given their biotic potential what keeps organisms
from filling up the planet?
Limits on Population Growth
• Density & competition for resources will cause
reproduction rates to decline or stabilize
Any essential resource that is in short supply
is a limiting factor on population growth.
• living space
• pollution-free environment
• Environmental resistance affects the number of individuals
of a given species that can be sustained indefinitely in a
particular area.
Naturalization
K
Number of
Colonization
Individuals
Introduction
Time
Carrying Capacity (K)
• =
• Is not fixed - K may decrease when a large
population damages or depletes its own resource
supply.
Logistic growth
Initial carrying capacity
Number of
Individuals
New carrying capacity
Time
3. Density-Dependent Control of
Population Size
• When population density is low, a population
grows rapidly.
• When density is high, populations may grow
slowly, remain stabile (zero growth) or decline –
why?.
• High density puts plants at greater risk of …..
Density-Independent Control of
Population Size
• = events that cause more deaths or fewer births
regardless of population density
• Examples?
Plants have developed adaptations to
population density
• At low density, population is limited only by
intrinsic rate of growth (r)
• At high density, population is limited by carrying
capacity (K)
• R selection and K selection
High density
Naturalization
Pop. Size
Colonization
Low density
introduction
Time
r - selection
• Disturbance creates low-density conditions, frees
resources (fire, flood, volcano)
• Biotic potential (r) limits population size
• Adaptations that are successful for these
conditions:
K-selection
• High density, population size close to K
• Not much “new” space – competition for
resources
• Adaptations that are successful for these
conditions:
• K & r selected species exist together because
small-scale disturbances create space (exposed
soil) for r species (colonizers)
– Ex. Downed tree, badger holes, grazing
disturbance
Plant Community Ecology
Review: definition of community
• Group of organisms of different species living
together in a particular habitat
Characteristics of communities
•
Diversity – composed of:
1. Richness –
2. Evenness –
• Relative abundance = # individuals of
species X divided by total # of individuals
in the community
Which community is more diverse?
What factors determine the plant species
composition & the relative of abundance of
different species in a community?
• Biotic & abiotic components of the habitat
Abiotic components of habitat & their
effect on community structure:
• Each species has a tolerance range –
•
•
•
•
Climate – temp, moisture
Soil – types, pH
Latitude & altitude
Disturbance
Disturbance
• = decrease or total elimination of the biotic components of
the habitat
• Results: decrease in biomass, diversity
• Natural events –
• Human-caused –
• Frees resources, creating opportunities for new species,
different composition
• All communities have evolved with some type of
disturbance, varying in type, frequency, & severity
Small-scale, frequent disturbance
• Ex. Trees downed in wind storm
• Can prevent large-scale disturbance – fire!
– Ex. Yellowstone fire of 1988
– Fire suppression in fire-dependent ecosystem
caused massive, stand-replacing fire
Human - caused disturbance +
introduced species = disaster
•
Ex. Cheatgrass – wildfire cycle
1. Overgrazing in ecosystem that did not evolve
with large herbivores
2. Cheatgrass introduction
3. Decrease in fire frequency (100 yr to 5 year
cycle)
4. Conversion of ecosystem with tremendous
loss of diversity
• These types of problems creating mass
extinction worldwide
Biotic components of habitat & their
effect on community structure
1. The plant itself
•
•
Benefit ex: beech/oak forest creates shade
needed for other young beech & oak to grow
Detriment ex: pine forest creates shade but
pines need lots of light to grow (succession)
2. Other plant species
• Theory of competitive exclusion: when two species
compete for the same limiting resource (occupy the
same niche), the species that is less adapted will be
excluded from the community by the superior
competitor
• One will become extinct or evolve to use a slightly
different set of resources
Species B
Species A
A
low
B
C
Light intensity 
D
high
Species A
A
Species B
B
C
D
• If this theory is true, then actually very little
competition in nature, because each plant occupies
a niche.
• Niche
• =
• Includes all aspects of a species’ use of biotic &
abiotic resources (microclimate, rooting zone,
pollinators, etc)
3. Other (non-plant species)
• Interactions with animals, insects, fungi, bacteria
• Mutualism –
– Ex.
– Ex. Pollinator gets nectar and plant gets pollen
transfer
– Ex. Animals eat fruit (nutrition) and seeds are
dispersed
– Ex. Acacia trees get defense from herbivores &
ants get home, food
• Commensalism – one species benefits &
other is not affected
• Competition –
• Predation – one harmed, other benefits
– Herbivory
– pathogens
Controls on community structure
• Dominant species = species with the highest
abundance or biomass in the community
– Controls occurrence & distribution of other
species
– If eliminated, other species take over
– Ex. Douglas fir
• Keystone species
– Ex. Sea otter – reduction in populations caused
boom in sea urchin population, destroying kelp
forests (drastic decline in diversity)
Succession
Succession
• =
• Species replacement continues until the
composition of species becomes relatively steady
under prevailing climatic conditions & disturbance
regimes (dynamic equilibrium, not climax).
Two major types of succession
• Primary Succession
• Secondary Succession
1. Primary succession
• Sequence:
1..
2.As these decay, acids weather the rock & primitive
soil forms
3.Pioneer plants establish (r-selected)
4.Pioneers replaced by K-selected species
The Nature of Pioneer Species
• typically small plants, short life cycles, producing an
abundance of small seeds which are quickly dispersed
(wind & water)
• can grow in N-poor soil because of their mutualistic
interactions with nitrogen-fixing bacteria.
Example of primary succession: glacial
retreat
Fig 53.23
Fig 53.20
Mosses, lichens, fireweed
Dryas stage
.
Alders & cottonwoods dominate
Spruce enter forest and replace alders/cottonwoods
Hemlock slowly replace Spruce. Hemlock is “climax”
What Pioneers Do: Facilitation
• accumulation of their wastes and remains adds
volume to the soil and enriches it with nutrients
that allow other species to take hold.
2. Secondary Succession
• Plant community is destroyed but soil remains/
new soil exposed
• Examples?
• Typical progression: small herbs & grasses
shrubs trees
Pioneer species
• Sometimes these opportunistic species (especially
invasive weeds!) inhibit the growth of the native
climax species changing the structure and type of
climax community forever.
• Ex. cheatgrass
Ecosystem Ecology
Ecosystems
• An ecosystem is an association of organisms and
their physical environment,
Structure of Ecosystems
1. Physiognomic structure
• =
• Relative abundance of trees, shrubs, herbs,
mosses, etc.
• Phenotypes, physical characteristics
• Vertical & horizontal stratification
http://www.mightytrees.com/science/foreststrat.html
2. Temporal Structure
• Diurnal (Daily) patterns
• Seasonal changes
3. Species composition
• Determined by soil resources, climate
tolerance ranges, stresses (ex. Competitive
interactions, herbivory)
4. Trophic levels
• = Feeding levels
• Autotrophs
– First level of all food webs---- primary
producers
• Heterotrophs – consumers - depend directly or
indirectly on energy stored in tissues of primary
producers.
Types of Heterotrophs
• Herbivores
• Parasites
• Detritivores
• Carnivores – eat herbivores & other carnivores –
secondary consumers
• Omnivores partake of a variety of edibles
• Decomposers - extract energy and recycle nutrients
from organic matter.
Decomposition
links all trophic
levels
Fig 54.2
• Some organisms like man extract energy from more
than one trophic level so it is hard to assign them to a
specific trophic level.
• Actual feeding relationships in an ecosystem are
complex –.
Energy Flow Through
Ecosystems
Primary Production
• =
• How much energy actually get stored depends on:
• 1) how many plants are present and
• 2) the balance between photosynthesis and aerobic
respiration.
• Ecosystems differ in their PP:
Fig 54.4
Fig 54.5
• Other organisms tap into the energy that is
conserved in plant tissues, remains, or
wastes.
• They, too, lose heat to the environment.
• All of these heat losses represent a one-way
flow of energy out of the ecosystem.
Secondary Production
• =
• Ex. Caterpillar eating a plant:
– 50% loss to feces (energy transfer to detritus)
– 34% to respiration (heat loss)
– 16% to growth
Trophic efficiency
• =
• Thus 85-90% of available energy at one level is
not transferred to the next
– Instead lost as heat, not consumed, or
transferred to detritus
Fig 54.11:
Energy pyramid
Fig 54.12 Biomass pyramid
Fig. 54.13 Pyramid of numbers