Ecosystem Ecosystem = community (all biotic elements) plus physical environment (all abiotic...
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Transcript of Ecosystem Ecosystem = community (all biotic elements) plus physical environment (all abiotic...
Ecosystem
Ecosystem = community (all biotic elements) plus
physical environment (all abiotic elements)
Ecology = study of interrelationships between biotic and abiotic elements in an ecosystem
Habitat
Habitat = any part of the Earth where a species can live, temporarily or permanently
= organism’s physical surroundings
= where an organism lives
Ecological Niche
Ecological Niche = functional role of a species in the community, including habitat, activities & relationships
= what an organism does, its occupation
Abiotic Factors
• Sunlight• Water• Air• Climate (Temperature, precipitation, wind)• Soil & Rocks• Periodic disturbances
Key Properties of Communities
1) Diversity = variety of different organisms
2) Prevalent Form of Vegetation
3) Stability = ability to resist change
4) Trophic Structure
Species Diversity
Species diversity evaluated based on two factors;
1) Species Richness = total number of different species
2) Relative Abundance or Evenness = number of fairly common or noticeable species
Interspecific Interactions in a Community
1) Competition
2) Predation
(predator-prey or herbivore-plant)
3) Symbiosis
Competition
Interspecific Competition = between different species
VS
Intraspecific Competition = within the same species
Competitive Exclusion Principle
Competitive Exclusion Principle = no two species can occupy the same niche at the same time
OR
= two species so similar that they compete for the same limiting resources cannot coexist in the same place
- G. F. Gause
Intertidal Ecology: Foundations of Experimental Community Ecology
Joseph Connell, 1961
The Pattern: Barnacle distributions in rocky intertidal zones
Mean High Water Spring Tide
Mean High Water Neap Tide
Mean Low Water Neap Tide
Mean Low Water Spring Tide
Chthalamus stellatus
Balanus balanoides
Range of weak (neap) tide
What causes distribution pattern of Chthamalus?
Three Different Hypotheses:
Chthamalus distribution is determined by;
1. physical factors
2. predation by the snail, Thais lapillus
3. space competition with Balanus
Mean High Water Spring Tide
Mean High Water Neap Tide
Mean Low Water Neap Tide
Mean Low Water Spring Tide
Chthamulus stellatus
Balanus balanoides
Rock
Settled Chthamalus
(1) Moved rocks with Chthamalus to regions throughout intertidal
Test Hypothesis #1: Chthamalus distribution is determined by physical factors
In absence of Balanus, Chthamalus enjoyed high survival throughout intertidal zone
physical factors not important
Mean High Water Spring Tide
Mean High Water Neap Tide
Mean Low Water Neap Tide
Mean Low Water Spring Tide
Chthamalus stellatus
Balanus balanoides
Snail exclosure
Performed a snail exclosure experiment
Test Hypothesis #2: Chthamalus distribution is determined by predation by the snail, Thais lapillus
Snail exclosure had no affect on Chthamalus survivalsnail predation not important
Mean High Water Spring Tide
Mean High Water Neap Tide
Mean Low Water Neap Tide
Mean Low Water Spring Tide
Chthamalus stellatus
Balanus balanoides
Rock
Settled Chthamalus and Balanus
On rocks settled by both species, partitioned rock in ½ and removed all Balanus from one side.
Test Hypothesis #3: Chthamalus distribution is determined by space competition with Balanus
Balanus removal greatly enhanced Chthamalus survivalcompetition for space is important
Competitive Exclusion Principle
Loser must adapt or be eliminated
One possibility is Resource Partitioning,
they use the same resource at different times, ways, or places (at least one difference between the two organism’s niches)
What was the difference between the barnacles niches?
Resource Partitioning
Competitors segregate to avoid competition based on;
• Size of food
• Type of food
• Habitat usage
• Feeding times
lions hunt large prey, leopards smaller prey
Predation
Predation = consumption of one species “prey” by another “predator”, also includes herbivores eating plants
What are some adaptations that have evolved in predators and in prey?
Adaptations
Predators = speed & quickness, eyesight, camouflage, larger brain, sharp claws & teeth, stingers, and poisons
Prey = speed & quickness, hiding, live in groups, porcupine quills , turtle shell, camouflage, chemicals (skunk, poisons), distraction displays, and mimicry
Plants = spines, thorns, tough leathery leaves, protective chemicals (strychnine, morphine, nicotine, & distasteful)
Selective Pressures
Selective pressures are elements of an organism’s environment that make an adaptation advantageous.
Identify the selective pressure for the following adaptations;
Long, thick fur
Thorns
Fangs
Camouflage
Production of beta lactamase
Symbiotic Relationships
Species #1 Species #2
1) Parasitism benefits harms
2) Mutualism benefits benefits
3) Commensalism benefits neutral
Parasitism
Parasitism is where the parasite gets nourishment from the host, much like predation except host is usually not killed immediately.
Example; Plasmodium vivax invades RBC, causing them to burst and triggering the chills & fever of malaria
MutualismExamples;
Honey bees get nectar while pollinating flowers
Rhizobium, N2- fixing bacteria that provide nitrogen to plants in return for glucose from the plant
Mycorrhizae fungi living in plant roots that increase plant’s absorption of nutrients & fungi get nutrition from the plant
CommensalismIn commensalism the host often provides a home or
transportation
For example; Remoras attached to sharks
Commensalism
Examples of commensalism;• Epiphytes which are plants that
grow on plants
• E. coli bacteria that live in human intestine
Life on a Leaf
A look at the fungal community that grows on healthy new leaves.
Includes examples of
a variety of interrelationships
between organisms.
Fungi
• Heterotrophs
• Digest food externally & absorb small nutrient molecules
• Most are multicellular (yeast = unicellular)
• Form a mycelium, which is a netlike mass of filaments called
hyphae
• Hyphae grow & extend around and through food source
Fungi
Fungi grow FAST – one mycelium can add up to a kilometer of hyphae per day
Hyphae grow through or around plant cells (enzymes digest plant cells)
If fungus grows on dead plant = relationship ??
If fungus grows on live plant = relationship ??
Fungal Reproduction
Yeast is unicellular and reproduces by dividing into two new cells
Sexual or Asexual?
Fungal Reproduction
In multicellular fungi, sometimes two different hyphae fuse together (combining their DNA) and produce a spore
Spore develops into new mycelium
Mycelium can live a LONG time in the soil
• In Northern Michigan one mycelium formed from a single spore about 1500 years ago covers about 30 acres
• In Oregon a single mycelium is 3.4 miles in diameter, covers 2200 acres, weighs 100s of tons and is at least 2400 years old
Coevolution
Coevolution is when the adaptations of two species are closely connected – that is when an adaptation in one species leads to a counter adaptation in a second species.
Coevolution is when two species, with a close ecological relationship, act as selective pressures for each other
Adaptation = the passionflower vines, Passiflora, produce toxic chemicals that protect their leaves
Counter adaptation =
Heliconius butterfly
caterpillars eat the
leaves – they have
enzymes that break
down toxic chemicals
Coevolution
Behavioral adaptation by Heliconius females is not laying eggs on leaves with bright yellow eggs already on them
which would reduce intraspecific competition
Some passionflower vines have sugar secreting glands that mimic the eggs, and attract ants & wasps that prey on Heliconius eggs & larvae
CoevolutionAdaptation = Bats use echolocation to “see” prey
(beams of ultrasonic sound waves, 20-60 kHz, & the returning echoes)
Counter adaptation = some insects (lacewings, praying mantises, most moths) can hear high-pitched sound waves
Bats in search mode send out “clicks” at 10 to 20/sec,
When they get closer to prey the rate increases up to several 100/sec just prior to snatching prey
Bats detect prey over short range – 5 to 10 m
When moths detect clicks 40 m away, they fly away from the slow click rate
If fast click rate is detected they take evasive maneuvers (power dives, barrel rolls, etc)
Counter adaptation = tiger moths generate their own clicks• Warns bat of bad tasting prey (avoid after 1st taste)• Startle the bat (bats do get used to it)• “jam” the sonar = interfere with bats ability to pinpoint
prey• Only works if clicks arrive with 1st returning echo, so
window of opportunity only 1/1,000 sec
Bats still catch >50% of prey they attack
Counter-counter adaptation = tropical “gleaning” bats use ultra high frequency (up to 212 kHz) sound waves that are above the insects ability to detect
Counter-counter-counter adaptation = moths have sensors that detect wind movement created when bats hover for an instant prior to striking prey – gives moth a chance to quickly drop to ground
Right now bats are developing ???