Download Lecture 9 Ecosystems W12 - Spokane Community College

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
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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
Species Diversity
Species Richness ?
Relative Abundance ?
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
Competitive Exclusion Principle
Chthamalus vs Balanus
two species of barnacles
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
Chthalamus stellatus
Mean Low Water Neap Tide
Balanus balanoides
Mean Low Water Spring Tide
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
Test Hypothesis #1: Chthamalus distribution
is determined by physical factors
(1) Moved rocks with Chthamalus
to regions throughout intertidal
Rock
Settled Chthamalus
Mean High Water Spring Tide
Mean High Water Neap Tide
Chthamulus stellatus
Mean Low Water Neap Tide
Balanus balanoides
Mean Low Water Spring Tide
In absence of Balanus, Chthamalus enjoyed
high survival throughout intertidal zone
physical factors not important
Test Hypothesis #2: Chthamalus distribution is
determined by predation by the snail, Thais lapillus
Performed a snail exclosure experiment
Snail exclosure
Mean High Water Spring Tide
Mean High Water Neap Tide
Chthamalus stellatus
Mean Low Water Neap Tide
Balanus balanoides
Mean Low Water Spring Tide
Snail exclosure had no affect on Chthamalus survival
snail predation not important
Test Hypothesis #3: Chthamalus distribution is
determined by space competition with Balanus
On rocks settled by both species,
partitioned rock in ½ and removed all
Balanus from one side.
Rock
Settled Chthamalus and Balanus
Mean High Water Spring Tide
Mean High Water Neap Tide
Chthamalus stellatus
Mean Low Water Neap Tide
Balanus balanoides
Mean Low Water Spring Tide
Balanus removal greatly enhanced Chthamalus survival
competition 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;
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Size of food
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Type of food
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Habitat usage
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Feeding times
lions hunt large prey,
leopards smaller prey
Resource Partitioning
hawks hunt in daytime, owls at night
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
Mutualism
Examples;
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
Mycorrhizae fungi living in plant roots
Mycorrhizae fungi increase
absorption of nutrients by plants
Commensalism
In 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
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
Hyphae grow longer, not thicker – WHY?
Production of antibiotic by Penicillium fungus
What type of
relationship?
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
Fungal Life Cycle
Mycelium can live a LONG time in the soil
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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
Coevolution
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
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
Coevolution
Adaptation = 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 highpitched 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 ???