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Chapter 5
Ecological Concepts
Environment:
– abiotic
– biotic
Ecosystems are the most complex level of
biological organization:
– cells, tissues, organs, organisms, populations,
communities, ecosystems.
• Limiting Factors
• range of tolerance
• acclimation
Chapter 5
Habitat and Niche
• The “Where” and the “How”.
• Habitat:
• “Where” organisms lives.
• Niche:
• Includes space, food, temperature, conditions
for mating, etc.
• Also takes into account behavior at various
seasons or times of day.
• Niche is not synonymous with habitat
Chapter 5
Natural Selection & Evolution
• Within species  speciation
• Charles Darwin
• Organisms change relative to one another over
time.
• Browsing plants evolve in relation to
herbivores.
• Herbivores adapt for food.
• Pesticides and Insects
Chapter 5
Organismal Interactions
• Competition:
• intraspecific competition:
– competition between individuals of a single species.
• interspecific competition:
– competition between two different kinds of
organisms.
• Competitive Exclusion Principle
– “No two species can occupy exactly the same niche
indefinitely”
Chapter 5
Predation:
• Predation limits size of populations.
• Prey must survive in at least small
numbers or predator becomes extinct.
• Prey evolves to have unique defenses
against predator.
Chapter 5
Symbiotic Relationships:
• Two different species (partners) live in physical
contact with each together.
• Parasitism:
• one partner benefits, other is harmed (special
form of predation).
– parasite - benefits
– host – harmed
“ecto” & “endo” parasites:
• internal parasites are more specialized
Chapter 5
Commensalism:
• One partner benefits, other neither benefits nor
is harmed.
• Individuals of one species physically attached
to individuals of other species.
Mutualism:
• both partners benefit.
– example: ants and acacia
– example: mycorrhizae fungi and plant roots
Chapter 5
Community & Ecosystem Interactions
Ecosystem Roles:
• Producers
• Consumers
– primary
– secondary
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carnivores
omnivores
scavenger
parasite
• Decomposers
Chapter 5
Ecosystem Energetics
• trophic levels
– Each step in the flow of energy through an
ecosystem is known as a trophic level
– analogous to ecosystem roles
• energy at each level can be estimated by
measuring biomass
Food Chain/Food Web
producer (convert about 1% of suns energy to
organic energy)
• consumer(90% loss of that energy at each step)
• decomposer
Chapter 5
Biogeochemical Cycles
• All substances in organisms cycle through
ecosystems.
• Bulk of substances are not contained within the
bodies of organisms.
• Organisms must be able to move these
substances from abiotic into biotic
systems.
Chapter 5
Carbon Cycle
• Based on atmospheric carbon dioxide. (0.03%
of air)
• Plants (and some bacteria) make 70 billions
tons of organic compounds yearly.
• CO2 released back into atmosphere from
respiration.
– In the beginning…lots of CO2,Planet inhospitable to
people, plants ruled, carbon sequestered as coal/oil,
oxygen created, climate more hospitable to human.
Cycle balanced for millennia. Now burning fossil
fuels, cutting of forests, etc means carbon is released
back to atmosphere…impacts?
Chapter 5
Nitrogen Cycle
• Protein is an organic compound with nitrogen
(e.g. amino acid).
• Nitrogen constitutes about 78% of air.
• Very few organisms can convert nitrogen gas
into biologically useful forms.
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Humans use lots-o-energy to make fertilizer
nitrogen-fixers
free living and symbiotic bacteria
N2  ammonia
Decomposers break other N-compounds into
ammonia as well
Chapter 5
Nitrogen Cycle (cont’d)
• Nitrifiers
– two different groups of bacteria working in
sequence
– ammonia  nitrite  nitrate
• Plants then use nitrate
• Denitrifying Bacteria
– Take nitrite to N2 gas—goes back to
atmosphere
• Nitrogen is essential to life—require
micro-organisms and bacteria to cycle
Chapter 5
Phosphorous Cycle
• Originates in rock, dissolution of rock
releases into water and soil.
– Bat/bird guano harvested for P content
• Needed in life for nucleic acids and ATP.
– Plants take it in through roots.
– Animals eat plants.
– Decomposers return it to soil.