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Ecology
Ch 3, 4, 5, 6
Organization of Life
 Molecules – carbohydrates, nucleic acids,
proteins, lipids, water, and other molecules
necessary for life
 Cells – basic building block of life.
 Tissues – similar cells with similar functions
grouped together.
 Organs and Organ systems – Tissues that
form a specific function for the organism.
Organization of Life - Ecology
 Individual – one organism
 Population – one species in a defined area
 Community – all biotic factors in a defined
area
 Ecosystem – all biotic and abiotic factors in a
defined area
 Biosphere – all biomes and ecosystems
(EARTH)
Ecosystem Structure
An ecosystem is based on energy and
nutrients available. One way flow.
Inputs: sun, dissolved minerals
Outputs: heat, loss of minerals
Order of feeding relationships: trophic
levels.
Some organisms are in one specific level,
others can be multilevel.
Ecosystem Structure
Main Energy Source: Sunlight
1) Primary Producers (Autotrophs):
Photosynthesizing Organisms convert
radiant energy to chemical energy.
CO2 + H2O  C6H12O6 + O2
Ecosystem Structure
1)Primary Producers:
Chemiosynthesis – a process of
generating organic molecules from
inorganic substances (Nitrogen and
Sulfur compounds)
Few bacteria: nitrogen fixing bacteria
and archaebacteria
Ecosystem Structure
2) First Level Consumers
(heterotrophs):
herbivores – animals
that eat plants
(gophers, squirrels)
parasites – insects that
harm plants (grubs)
detrivores – animals
that eat decaying
organic matter.
(earthworms)
!
decomposers –
fungi and bacteria
that eat on dead
material
All feed on
producers
Ecosystem Structure
3) Second Level
Consumers
(heterotrophs):
Carnivores –
Omnivores –
Parasites –
Detritivores –
Decomposers –
All feed on first level
consumers!
Ecosystem Structure
4) Third Level
Consumers
(heterotrophs):
Carnivores –
Omnivores –
Parasites –
Detritivores –
Decomposers –
All feed on Second
Level Consumers!
Ecosystem Structure
5) Fourth Level Consumers
(heterotrophs):
Top Carnivores –
Parasites –
Detritivores Decomposers –
All feed on Third Level Consumers!
Food Web VS. Food Chain?
 Food Chain – A straight sequence from
producer to 4th level consumer.
 Food Web – several food chains cross –
connecting with each other.
Energy Flow
Energy flows from producers to top level
carnivores.
Energy transfer is never 100%. Some is
lost as heat.
Ecosystems will never be more than 4 or
5 trophic levels.
Energy transfers are only one way.
Warm – Up
1.
Give an example of an organism in each
trophic level:
1.
2.
3.
Primary producer, primary consumer, secondary,
tertiary, and quartinary consumers
Explain how decomposers, detrivores, and
parasites fit into the ecosystem.
What is the primary source of energy and is
it cyclic or one-way flow?
Ecological Pyramids
Biomass – depicts the mass of
organisms at each trophic level for an
ecosystem.
Can be an upside down in an aquatic
ecosystem due to primary producers
having less biomass (algae or
phytoplankton)
Ecological Pyramids
Energy – shows how energy changes
from each trophic level. Only 10% of
energy will be transferred. The rest is
lost as heat. Always a traditional
pyramid shape.
Numbers – shows how many organisms
are at each level. Will not always be a
traditional pyramid shape.
Energy Pyramid
Biomass Pyramid
Numbers
Biogeochemical Cycles
Biogeochemical Cycles
Water Cycle
Carbon Cycle
Nitrogen Cycle
Sedimentary Cycles
Success of an Ecosystem
Primary Productivity
Limiting Nutrients
Example: Nitrogen –
cause algal blooms
Community Interactions and
The Biosphere
Ecosystem
 Biotic Factors – all living organisms in
an ecosystem.
 Abiotic Factors – all nonliving
substances in an ecosystem
 These determine survival and growth of
an organism and the productivity of the
ecosystem.
Warm-UP
 Describe a commenalistic, parasitic,
and mutualistic relationship
 Habitat – place where an organism
lives.

Several organisms may have the same habitat.
 Niche – activities, relationships, and
resources needed for survival and
reproduction.

EX: temperature needed, pH levels, place in the
food web, competition, time of the year it
reproduces, time of the year it hibernates or
migrates, and any other characteristic for the
survival of the organism.
Competition
When organisms of the same or different
species attempt to use the same
ecological resource.
Adaptations occur to help organisms
compete in the same ecosystem. Ex:
Resource Partitioning.
Can suppress growth of populations.
Competitive Exclusion
Principle
No two species can
occupy the same
niche in the same
habitat at the
same time.
Interactions
Commensalism – one species benefit, the
other neither helped or harmed.
Mutualism – both species benefit
Parasitism – one species benefit, the
other is harmed.
Interactions
Predator / Prey: one consumer hunts
another
May control population size of prey.
Unique defense adaptations of prey.
Unique adaptations of predators.Horned
Toad (Short-Horned Lizard) -- Animal
Videos -- National Geographic
Succession
Ecosystems change in response to
natural and human disturbances.
Ecosystems begin with pioneer species:
colonizers of vacant habitats, high
dispersal rates, grow fast, and have
high reproduction rates. Ex: Lichens
Stronger competitor species come to
replace pioneer species.
Succession
Primary Succession – pioneer species inhabit
a barren habitat. Ex: new volcanic island, new
land after glacier retreat.
Pioneer species break rock, release nutrients to
make way for grasses and flowering plants.
Soon more species of seeds arrive some with
nitrogen fixing bacteria.
Over time wastes and dead material
accumulate to add nutrients.
Mt. St. Helen’s after disaster and during
recovery.
Succession
Secondary Succession – a disturbed
area within a community recovers and
moves toward a climax state. Ex:
abandoned fields, burned forests.
Climax – pattern model: a community is
adapted to many environmental factors
– topography, climate, soil, wind,
interactions, common disturbances.
Populations
How Populations Grow
 There are three important
characteristics of a population
 1. Geographic Location
 2. Density
 3. Growth rate
How Populations Grow
 Population Density  the number of
individuals per unit area
 Geographic location  where are they
 Growth rate  how fast are they
growing
Population Growth
 Three factors that affect population size
 1. The number of births
 2. The number of deaths
 3. And the number of individuals that
enter or leave the population
Population Characteristics
 Immigration  the movement of
individuals into an area
 Emigration  the movement of
individuals out of an area
Types of Growth
 Exponential Growth  occurs when the
individuals in a population reproduce at
a constant rate.
 Under ideal conditions with unlimited
resources, a population will grow
exponentially
 J - curve
Types of Growth
 Logistic growth  occurs when a
population’s growth slows or stops
following a period of exponential growth
 As resources become less available,
the growth of a population slows or
stops
 S - curve
Types of Growth
 Carrying capacity  the largest number
of individuals that a given environment
can support
Population Characteristics
 Limiting – Factor: something that
causes populating growth to decrease.
 Two types: density dependent factors
and density independent factors.
Density Dependent Factors
 These factors are limiting only when the
population density reaches a specific
level. (too many for ecosystem to
support)
 Competition, predation, parasitism, and
disease
Density – Independent Factors
 These factors are limiting on all
populations regardless of size.
 Unusual weather, natural disasters,
seasonal cycles, human activity.
Human Population Growth
 Increases over time – yet showing
exponential growth
 Most advanced countries have shown
demographic transition – death rate and
birth rate are equal – no population
growth
 Can analyze a population using an age
structure diagram.
Humans and the Biosphere
Biodiversity
 All different organisms of this biosphere.
 Human activity can reduce biodiversity
by altering habitats, hunting species to
extinction, introducing toxic compounds
into food webs, and introducing foreign
species to new environments.
Habitat Alteration
 Land development destroys habitats.
 Habitat fragmentation – splits
ecosystems to several sections.
Reduces number and variety of
organisms that can survive.
Pollution
 Organism can ingest toxic compounds if
they are introduced into the water or soil
of an ecosystem
 Biological magnification –
concentrations of a harmful substance
increases in organisms at higher trophic
levels in a food chain or food web.
 DDT,
Hg
Introduced Species
 Invasive species – rapidly reproducing
species of organisms that are not
indigenous to the ecosystem.
 Has no natural predators to keep them
in check.
 Nutrias,
zebra mussels, leafy spurge
Conservation Biology
 The application of wise management of
natural resources, including the preservation
of habitats and wild life.
 Protecting entire ecosystems as well as
individual species.
 Focus on ‘hot spots’ places where large
numbers of habitats and species are in
immediate danger of extinction due to
humans
Questions for thought.
What is our role as a species in this
biosphere?
Do we have the right to use the natural
resources and destroy ecosystems?
Find an article that deals with
conservation Biology