Bio 203 Ecology And Evolution

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Parasitism (Exploitation)

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non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.

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Mutualism

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An interaction involving mutual benefits between two speciesthrough the exchange of resources or services.

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Herbivory

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An interaction that involves a species that consumes a plant species.

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Coevolution

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Reciprocal evolutionary change in two species.Key Points:

1) Reciprocity

2) Evolution occurs in response to another species

3) Specific sequence of events

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What factors can influence the outcome and strengthsof species interactions?

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1) Abiotic context: levels of resources and/or environmental conditions

2) Biotic Context: other types of species interactions

3) Disturbance

4) Evolution

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Zero Population Growth Isoclines:

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The population does not increase or decrease in size for any combination of V and P that lies on these lines.

Why?

Zero growth isoclines can determine the conditionsunder which each species will increase or decrease.

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Victim Isocline:

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number of predators that will maintain prey (victims) at zero growth rate (dV/dt = 0)

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Predator Isocline:

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number of victims (prey) that will maintain predators at zero growth rate (dP/dt = 0)

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Predator-prey functional responses:

Type 1

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Rate of consumption is directly proportional to prey density.

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Predator-prey functional responses:

Type 2:

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Prey consumption decreases at high prey density

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Predator-prey functional responses:

Type 3:

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Predators become more efficient as prey become more common

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Succession

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The change in species composition orstructure at a specific place over time

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Clements

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- Deterministic

- Community assuperorganism

- Climax (endpoint)

- Plants rule

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Elton

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- Context-dependent

- Interactions amongorganisms and theenvironment shapecommunity

- Role of animals

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Gleason

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- Stochastic

- Community as collectionof individuals

- No climax community

- Plants rule

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Primary Succession

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- occurs on an area where no soilexists and has not been occupied previously by life.

ORIGIN: Begins with no life

PIONEER: Lichen and moss come first Weeds, grasses or woody plants

RATE: Slow

EXAMPLE: e.g. Glacial retreat

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Secondary Succession

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begins in a previouslyvegetated area where soil remains after a disturbance

ORIGIN: Follows removal of existing biota No soil present Soil already present

PIONEER: Weeds, grasses or woody plants

RATE: Fast

EXAMPLE: e.g. Forest fire

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Abiotic agents of change

Stress:

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An abiotic condition that reduces the growth or reproduction of individuals.

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Abiotic agents of change

Disturbance:

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Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability or the physical environment

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Why is Disturbance Important?

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•Resets succession

•Creates a diversity of conditions

•Provides opportunity for a diversity ofspecies

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Community

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•An association of populations ofdifferent species living in the same area

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• Total Abundance:

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total number of individuals of all species

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•Relative Abundance:

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abundance of a species divided by the total abundance

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• Species Richness:

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count of the total number of species

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Abundance

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the number of individualsof a species in a community

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Species Richness:

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number of species in thecommunity

For example, a community with 100 species has greater species richnessthan a community with 10 species

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Species Evenness:

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relative abundance ofspecies that occur in a community

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Intermediate Disturbance Hypothesis (Connell 1978):

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justifies that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent.

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Biogeography:

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the study of this variation.

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Local diversity (alpha)

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Species diversity in a small area of homogeneous habitat

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Beta diversity

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Difference (or turn over) in species diversity from one habitat toanother

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Regional diversity (gamma)

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Species diversity observed across all habitats within a geographic area

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The distribution of species

General Patterns

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(1) Species richness increases as we move toward the equator.

(2) Rainfall and temperature increase towards the equator.

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The distribution of species

Species-Area Relationships Typically Demonstrate:

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1) A positive relationship between area and species richness

2) Island communities have steeper slopes than mainland communities

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What are three hypotheses for whydiversity is highest in the tropics?

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•Stability/Productivity Hypothesis: Stable climate with warm temperature andsufficient precipitation -> niche differentiation/speciation

•Area Hypothesis: Larger area -> more habitat -> increased speciationLarger area -> larger populations -> decreased extinction

•Museum Hypothesis: Uniform and stable abiotic environment -> lowerextinction rates -> “old” species remain

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Biogeographic island’s species richness:

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1. increases with area (more area, more habitat,greater number of niches)

2. decreases with isolation (greater distance fromsource of colonists, so more difficult to colonize)

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Island Biogeography Theory

Sequilibrium = I x P / I + E

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S = Equilibrium number of species on an island

I = Maximum immigration rate of new species

P = maximum number of species that can immigrate to theisland

E = maximum rate of extinction

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Immigration declines with number of species present.

Why?

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- individuals that arrive are morelikely to already be present

- individuals that arrive willcompete with species alreadypresent and not establish

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Extinction increases with number of species present.

Why?

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- Niche overlap andcompetition ismore intense withmore species

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Regional diversity – influence of area

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Extinction is higher in small areas dueto small population sizes

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Regional diversity – influence of distance

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Immigration is slower for far islandsdue to greater dispersal distance

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Energy

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the most basic requirement for allorganisms.

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Autotrophs

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are organisms that assimilate energy fromsunlight (photosynthesis) or from inorganic compounds(chemosynthesis).

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Net Primary Production

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is the total chemical potentialenergy input into the ecosystem(growth, consumption, storage of carbon)

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Heterotrophs

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obtain their energy by consumingenergy-rich organic compounds from other organisms.

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Net Ecosystem Production (NEP)

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is the total energy inthe system when we account for energy loss from bothautotrophs and heterotrophs

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Descriptive vs. Functional Food Webs

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Descriptive: Embracescomplexity, illustrating alltrophic interactions, nomatter how strong or weak.

Functional: focuses only oninteractions that influencecommunity structure.Ignores weak interactions.

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Food web structure describes

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1) how many trophic levels there are in acommunity

2) how much biomass and productivity at eachtrophic level

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What determines how many trophic levels are in afood web?

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Most likely, the level of net primary productivity determineshow many trophic levels can be supported in a given community.

This is referred to as ‘bottom-up’ control.

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(Eltonian Productivity Pyramids)

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Hypothesis:more productivity more trophic levels(Bottom-Up Control)

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What factors control energy flow through ecosystems?

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Nutrients:Nutrient availability can affect local productivity in terrestrial,freshwater, and marine ecosystems:N, P, K, Ca, Fe, Mg…

Species Composition:Species vary in their capacity to respond to abiotic conditionsand resources (e.g., fertilizer).

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Keystone species

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is one whose influence on community(or ecosystem) structure and processes is disproportionatelylarger than its biomass”

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Trophic Cascades

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occur when top predators have an influenceall the way down the food chain.

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Ecosystem

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•All the organisms in a given area as well as thephysical environment in which they live.

•An ecosystem can include one or morecommunities

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Macronutrients

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• Nitrogen: amino acids, proteins, enzymes.

• Phosphorous: ATP, DNA, RNA, phospholipids,

• Sulfur: amino acids, proteins, enzymes.

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Other key macronutrients

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• Mg: in chlorophyll molecule, cofactor for some enzymes

• K: enzyme cofactor, osmoregulation

• Ca: plant cell walls, signal transduction in animals

• Si: plant cell walls.

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Biogeochemical cycle

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The path an elementtakes as it moves fromabiotic pools throughproducers and consumersand back to abiotic pools.

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Biogeochemical cycle

Key Points:

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1) Sources: Nutrients enter ecosystems through thechemical breakdown of minerals in rocks……and through fixation of gases in the atmosphere.

2. Transformations: Chemical and biologicaltransformations in the ecosystem alter the chemicalform and supply of nutrients.

3. Controls: Abiotic and biotic factors control therate of biogeochemical processes.

4. Export and/or import can occur with otherlocations/sources and links cycles globally.

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Why is cycling faster in warmer and wetterenvironments?

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•Better plant growth environment; GPP is higher•Decomposition occurs faster; nutrients in deadorganisms are made available faster

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What causes sea level to rise?

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• Increasing run-off

• Warming ocean

• Subsidence of river deltas

• Land-based glacial melt

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How have humans impacted the water, N, and C cycles?

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1. Reduced PercolationIncreased run-off rather than percolation Barriers to percolation (e.g.,asphalt)

2. Depletion of WaterAgriculture Industry

1) Nfixation (chemical, for fertilizer), 2) river runoff to oceans, 3)denitrification, 4) N deposition.

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GPP (Gross Primary Production)

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Total amount of C fixed through photosynthesis by plants in an ecosystem.

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Emission Scenarios

B1 Scenario - LOW

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• Population peaks midcentury

• Rapid economic changes

• Rapid technological change

• End of Century TempIncrease:

• Global mean 1.8°C (3.2°F)

• Range 1.1-2.9°C

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Emission Scenarios

A2 Scenario - HIGH

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• High population growth

• Slow economicdevelopment

• Slow technological change

• End of Century TempIncrease:

• Global mean 3.4°C (6.1°F)

• Range 2.0-5.4°C

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Phenology

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the science of appearance

• Timing of biological events

– Flowering

– Leaf out

– Insect emergence

– Animal migration

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Phenology and ClimateChange

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• Mismatch in timing of biological events:

– Physical damage

– Decreased reproductive rates

– No pollinators present

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Invasive Species:

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Survive, Reproduce, Cause Harm

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Habitat Fragmentation

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1) Reduces habitats to a sizethat is too small to supportsome species.

2) Reduces the ability ofindividuals to disperse,leading to genetic inbreeding.

3) Creates large amounts ofpoor-quality “edge” habitat.

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endemic species

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one whose habitat is restricted to a particular area.

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commensalism

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an association between two organisms in which one benefits and the other derives neither benefit nor harm.

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exploitation

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A form of competition where in organisms indirectly compete with other organisms for resources by exploiting resources to limit the resources availability to other organisms.

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competition

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is an interaction between organisms or species in which the fitness of one is lowered by the presence of another.

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Batesian mimicry

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is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both.

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Mullerian mimicry

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is a natural phenomenon in which two or more distasteful species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals.

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mission-oriented crisis discipline

– Michael Soulé (1986)

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• Two central goals:

– Evaluate human impacts on biological diversity– Develop practical approaches to prevent theextinction of species

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Endemic Species

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• A species found in a particular location andnowhere else

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Values of Biodiversity

Increased diversity can enhance:

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1) Productivity

2) Resource Use (Conversion) Efficiency

3) Resistance/Resilience to Disturbance

4) Ecosystem Services

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Resistance

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is a measure of how much a community is affected by a disturbance.

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Landscape Ecology

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• Focuses on the nature and ecological consequences of heterogeneity, or‘patchiness’ in landscapes

• Has major conservation applications!

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Landscape

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a heterogeneous area composed of several ecosystems

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Landscape element

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ecosystems within a landscape forming distinctpatches

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Landscape structure

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describes the size, shape,composition, number, and position of differentecosystems within a landscape.

influences the susceptibility of localpopulations to extinction.

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Fractals

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are patterns that reiterateon different scales

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metapopulation

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is a group of populations of an organism occupyingspatially isolated patches with individuals that migrate between patches

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landscape fragmentation

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– decrease in mean patch size due to humanactivity (e.g., building roads) – is a major source of change in landscapestructure