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Transcript
Ecology and Food
CENV 110
Topics
• Ecology: what is it?
• The difference between ecology and the
environment
• Elements of ecology
• The balance of nature
• Food webs: currencies, biomass, energy
• Succession
• Ecology and Food
Youtube video
• Ecology - Rules for Living on Earth: Crash
Course Biology #40
What is ecology?
• It is a process –
• The study of the interaction of living organisms
with one another and their environment
• Ecology is a scientific discipline
• Environmental studies is broader – includes
hydrology, soils, energy, climate etc.
• Environmentalism is a form of activism, seeking
to change politics, laws and institutions
Related disciplines
• Evolution, genetics, physiology, behavior,
biogeography, natural history, conservation
biology
Key questions ecologists ask
• What determines the distribution and
abundance of species and biodiversity?
• The movement of mass and energy through
living systems – food webs etc.
• Succession of ecosystems
• The processes of interaction between species
and their environments
Ecological concepts
• Habitat: the biotic and physical environment
• Niche: the specific habitats and biotic requirements of a species
• Population: a self sustaining group of individuals from the same
species
• Community: the combination of species that interact in the same
place
• Ecosystem: the biotic community and the physical environment
• Biome: a distinct group of plants, animals and physical
environments that are characterized by the dominant plant forms.
For example the boreal forest, the continental shelf
• Biosphere: the part of the earth and its atmosphere that are
capable of supporting life – the oceans, soil, rivers, lakes, terrestrial
habitats and the lower atmosphere
Specialties
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Population Ecology:
Community Ecology:
Evolutionary Ecology
Physiological Ecology
Behavioral Ecology:
Food webs
Key concepts: Energy flow
• 80-90% of energy is lost as it flows from one
trophic level to another, through metabolism
of the consumers. Thus the pyramid of energy
will narrow rapidly as you move to higher
trophic levels.
• Top predators will always be rare compared to
their prey, which will be rare compared to the
food the prey consume.
Key concepts biomass
• The pyramid of biomass is also unpredictable,
since some species at low trophic levels, such
as phytoplankton, turn over very rapidly, very
high birth and predation rates.
• Other long lived low energy species may have
high biomass but low energy flow.
Food production and food webs
• Agriculture has so much impact on ecosystems
because we take away the primary producers,
thus removing the base of the food web
Succession
• The sequence of changes to a community
following disturbance or colonization that
leads to a long term stable community
Old Field Succession
Receding glaciers
Mt. St. Helens
Agriculture and succession
• Rebuilding ecosystems after agriculture
primarily involves letting the process of
succession take place
• The time it takes to restore the original
community depends greatly on the kind of
ecosystem
– In east coast forests it may be less than 100 years
– In west coast rain forest it could be 500+ years
Theories of the climax community
• Original theory was that there was a single
community, the climax, that was resistant to
invasion
• Later it was recognized that the nature of the
climax will differ based on local physical
conditions: there is no single climax community
• Growing evidence that there may be different
climax communities, perhaps due to chance, and
that they are not necessarily resistant to invasion
Views of ecological stability and the
balance of nature
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Balance of Nature
Randomness: nature as a joker
Spatial patterns
Multiple Stable states
Ecology and food production
• Applied ecology: pest control
• Applied ecology: fish and wildlife harvesting
• Landscape ecology: transformation of
ecosystems
Pest control
• Chemical control is simply blasting crops with
pesticides
• Biological control is looking at the ecology of
the pest
Biological control
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Introduction of diseases
Introduction of predators or parasites
Sterile males
Integrated pest management
– Uses both biological control and other techniques
such as chemicals
Failures of biological control
• Mongoose in Hawaii
– Introduced to kill rats, had terrible effect on native
birds. Not planned with ecology in mind
• Cane toads in Australia
– Introduced to control sugar cane beetles – did not
control beetles but became major pest eating lots
of other things and poisoning animals that eat the
toads
Key points
• Ecology is different from environmental
studies and environmentalism.
• It seeks to understand the interaction
between individuals and their environment
• There are a number of central concepts in
ecology that are relevant to food production
and understanding the impact of food
production.
Study questions
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Distinguish between ecology, environmental studies and environmentalism.
Ecology is a scientific discipline
Environmental studies is a broader scientific discipline – includes hydrology, soils, energy, climate etc.
Environmentalism is a form of activism, seeking to change politics, laws and institutions
What are some of the key questions ecologists ask of nature?
What determines the distribution and abundance of species and biodiversity?
How does mass and energy move through living systems
How do communities change in response to disturbance
The processes of interaction between species and their environments
What is the biosphere?
the part of the earth and its atmosphere that are capable of supporting life – the oceans, soil, rivers, lakes, terrestrial habitats and the lower atmosphere
What is a food web?
It is a description of the way that mass and energy flow between species in an ecosystem.
What is the difference between an autotroph and a heterotrophy?
An autotroph produces energy from natural abiotic sources, primarily sunlight. A heterotrophy gets its energy from other individuals through feeding.
Why are top predators usually rare?
Because energy is lost at each trophic level as you move up the food chain. So by the time you get to the top predators there is much less energy available and smaller populations can be
supported.
What does the “top” mean in top predator?
It refers to the predators being of high trophic level and sitting “on top” of the food chain or the trophic pyramid.
Give an example of how there might be few individual autotrophs but many individuals that feed on it.
You might have a few large trees in an ecosystem, or you could have many small insects or other herbivores feeding on an individual plant.
How does most agriculture affect the food web?
It eliminates the plant community and replaces it with species that produce food products. Thus often totally changing the species in the food web. Agriculture also removes much of the
primary production for human consumption, leaving less production for higher trophic levels.
What species are the first to colonize in the sequence of plant succession that follows a disturbance?
Usually they are annual plants with highly dispersive seeds that can land on the disturbed ground.
What is “old field succession?”
It is the sequence of plant communities that follow the abandonment of a farm field.
What is a climax community?
The theoretically stable community that is the end product of succession.
How does biological control differ from integrated pest management?
Biological control refers to using biological agents rather than chemical agents to control pests. Integrated pest management uses a range of tools that may include both biological
control and chemicals.