Community Ecology. Community interactions: Community Ecology.
Ecology
description
Transcript of Ecology
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EcologyB. Species Interactions
1. Intraspecific competition• Ex – Competition for algae by sea urchins• Ex – Competition for shells by hermit crabs
2. Interspecies competition
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EcologyB. Species Interactions
2. Interspecific competition – Competitive exclusion
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EcologyB. Species Interactions
3. Predation• Natural selection favors increased predation efficiency• Predators can control prey populations (Top-down)
• Reduce competition/competitive exclusion• Prey can control predator populations (Bottom-up)
• Prey = food• Some prey have evolved defense mechanisms
• Ex – Spines in plankton• Ex – Poisonous chemicals in algae and mollusks
• Some defenses are inducible• Ex – Barnacles grow upright when predatory snails absent and horizontally when snails present• Ex – Algae produce more bad-tasting chemicals after being damaged
• Coevolution – Evolutionary “arms race”
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EcologyB. Species Interactions
3. Predation• Natural selection favors increased predation efficiency• Predators can control prey populations (Top-down)
• Reduce competition/competitive exclusion• Prey can control predator populations (Bottom-up)
• Prey = food
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EcologyB. Species Interactions
3. Predation• Some prey have evolved defense mechanisms
• Ex – Spines in plankton• Ex – Poisonous chemicals in algae and mollusks
• Some defenses are inducible• Ex – Barnacles grow upright when predatory snails absent and
horizontally when snails present• Ex – Algae produce more bad-tasting chemicals after being damaged
• Coevolution – Evolutionary “arms race”
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EcologyB. Species Interactions
4. Symbiosis• Relationship between host and symbionta. Commensalism
• One partner benefits, other unaffected• Ex – Barnacles living on whale
b. Parasitism• One partner benefits at expense of other• Common in marine environment• Ex – Tapeworm in whale
c. Mutualism• Both partners benefit• Ex – Cleaner wrasses and shrimps on coral reefs• Ex – Anemonefishes and anemones
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EcologyC. Trophic Structures
• Energy and matter flow through ecosystems can be described through trophic relationships
• Relationships between producers and consumers = food chain
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EcologyC. Trophic Structures
• Food chains are often simplistic – alternative is a food web
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EcologyC. Trophic Structures
• Food chains are often simplistic – alternative is a food web
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EcologyC. Trophic Structures
• Energy transfer between trophic levels not 100% efficient• Matter consumed by metabolism• Energy released as heat• Matter released as waste• Transfer efficiency ~ 10% (5-20%)
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EcologyC. Trophic Structures
• Energy transfer can be illustrated as pyramid of energy• Higher levels contain progressively less energy
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EcologyC. Trophic Structures
• Energy transfer can be illustrated as pyramid of energy• Higher levels contain progressively less energy
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EcologyC. Trophic Structures
• Decomposers – break down waste products
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Marine ResourcesA. Fisheries
• Seafood is ~1% of all food eaten worldwide• Seafood especially important in poor coastal nations with
low protein availability• World seafood catch stabilized by late 1980s
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
1. Clupeoid fishes• Herrings, sardines, anchovies, menhadens, shads• Feed on plankton (use gill rakers)• Form large schools over continental shelves and in upwelling zones
• Caught with purse seines• Industrial fisheries
- Fish meal (protein supplement in animal feed) - Fish oil (margarine, cosmetics, paint) - Fish flour (protein supplement for humans) - Fertilizers - Pet food
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Marine ResourcesA. Fisheries
1. Clupeoid fishes
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
2. Cods and related fishes• Cods, pollock, haddock, hakes, whiting• Demersal and benthopelagic cold-water fishes
• Caught with bottom trawls• Grand Banks (Newfoundland), Georges Bank (New England) and North Sea supported
extensive cod fisheries until 1992, 1994, and 2001, respectively• Cod populations crashed; catches plummeted• Ex – North Sea catch• 1971 – 277,000 tonnes • 2001 – 59,000 tonnes
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
3. Tunas• Skipjack, yellowfin, albacore, bigeye, bluefin• Primarily eaten in affluent countries
• Can be very expensive (up to $40,000 for a choice bluefin in Tokyo)• Highly migratory species
• Caught with purse seines, longlines, gill nets, rod and reel• Often associate with floating objects, dolphin schools• Juveniles caught in purse seines may be finished in net pens (aquaculture)
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Marine ResourcesA. Fisheries
3. Tunas
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Marine ResourcesA. Fisheries
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Marine ResourcesA. Fisheries
4. Other species• Flatfishes, rockfishes, mackerels, salmon• Mostly coastal• Threatened by coastal pollution, damming of rivers (salmon), overfishing• Flatfishes and rockfishes harvested extensively in US• Salmon farmed heavily in Canada, Chile• Non-finfish
• Squid, octopus• Clams, oysters, scallops• Crabs, lobsters• Sea urchin, sea cucumber• Barnacles, jellyfish• Sea turtles, seals, whales
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Marine ResourcesA. Fisheries
5. Fishery Yields
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Marine ResourcesA. Fisheries
5. Fishery Yields• Overfishing leads to
1) Stock depletion2) Reduced catch rate3) Capture of smaller individuals4) Unsustainable harvest
• Biological – Can’t reproduce fast enough• Economic – Can’t catch enough to make a profit
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Marine ResourcesA. Fisheries
5. Fishery Yields