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

Species Richness ?

Relative Abundance ?

Species Diversity

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

Chthamalus vs Balanustwo 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

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





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





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





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


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

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

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

Mycorrhizae fungi living in plant roots

Mycorrhizae fungi increase absorption of nutrients by plants

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

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

• 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 ???

ecosystem ecosystem = community (all biotic elements) plus physical environment (all abiotic...

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