Exam 4

Biogeography

Geography of biodiversity, past and present

What 2 things does biogeography contain?

1. History of taxonomic lineages across space and time

2. Global and continental scales

Landscape Ecology

Influence of the composition and arrangement of habitats across a large spatial area

Habitat Heterogeneity

The reflection of recent and historical events caused by natural and human forces

Legacy Effects

Long-term effects of past events on current ecology (ex. glaciation, ancient human settlements)

Species richness (1) from local to regional scales due to (2) habitat heterogeneity

1. Increases

2. Increasing

What are the 3 types of diversity?

1. Alpha diversity

2. Beta diversity

3. Gamma diversity

Alpha Diversity

# of species in a relatively small area; local

Beta Diversity

# of species differing between two (local) habitats

Gamma Diversity

# of species in all habitats of a large geographic area; regional

(1) diversity combines (2) and (3) diversity

1. Gamma

2. Alpha

3. Beta

Ecosystem Engineers

Species that have a disproportionate effect (relative to their biomass) on landscapes

Name an example of ecosystem engineers

Humans

What are the 2 effects of human-made fragmentation?

1. Decreases in patch/habitat area

2. Increases in patch number, amount of edge, and patch isolation

(1) habitats have (2) populations, which are more likely to go extinct

1. Small

2. Small

Island Biogeography Theory

Larger areas contain more species

Who are the 2 people that came up with the Island Biogeography Theory?

MacArthur and Wilson

Species-area curves are often presented on what type of scale?

Log-scale to create a straight line

What is the equation for the species-area relationship?

S = c*A^z

- S: number of species

- A: area

What is the y-intercept for the species-area equation?

Log(c) = y-intercept

What is the line slope for the species-area equation?

z = line slope

The line slope has consistent ranges around what values?

approximately between 0.20-0.35

Near islands contain (1) species than far islands

1. More

Equilibrium Theory of Island Biogeography

Number of species on an island reflects a balance between colonization and extinction rates that are impacted by island isolation and size

Why do colonization rates decrease with species number?

With more species on an island, there are fewer new species to add; species with strong dispersal abilities tend to arrive quickly

Why do extinction rates increase with species number?

With more species on an island, there are more species at risk of extinction; also more interspecific competition

Where is the equilibrium point (for equilibrium theory of island biogeography)?

Species richness (S-hat) where the 2 lines (rate of colonization and rate of extinction) cross

Why do smaller islands have higher extinction rates?

Because smaller islands support smaller populations and smaller populations are at higher risk for extinction

Do smaller islands have a lower or higher S-hat value?

Lower

Why do islands closer to the source habitat have higher colonization rates?

Being nearer means that more species are capable of dispersing that far and, by chance, more individuals will disperse successfully

Do nearer islands have a lower or higher S-hat value?

Higher

Based on the model that includes the effects of isolation and size on S-hat, which types of islands would have the most and least number of species at equilibrium?

Most: large and near islands

Least: small and far islands

What was the florida keys experiment? What were the 2 results"?

Tents were built and fumigated on selected islands.

Results:

1. more insects re-colonized nearer islands

2. final richness similar to initial richness

What are the 6 global biogeographic regions?

1. Nearctic

2. Neotropic

3. Afrotropic

4. Palearctic

5. Indomalaya

6. Australasia

Pangea

A single landmass from 250 MYA

Pangea split into what 2 things?

1. Gondwana (includes South America, Africa, Antarctica, Australia, and India)

2. Laurasia (includes North America, Europe, and Asia)

What has allowed individual continents to independently involve groups of organisms for long periods?

Continental Drift

What are the 2 important ecological consequences of the movement of major continental plates?

1. Continental drift creates and breaks barriers to dispersal

2. Positions of continents and ocean basins influence climate

Vicariance

Splitting of a widely distributed ancestral population by continental drift

What joined North and South America ~3 MYA?

The Isthmus of Panama

What were the 3 effects that the joining of North and South America had on the world?

1. Triggered exchanges and extinctions

2. Diverted ocean currents

3. Transformed global climate

How long ago were the poles covered by oceans extending to tropical regions?

50-30 MYA; caused warmer polar climates

What were the 3 effects that drifting continents had on global distribution of heat and ocean circulation?

1. Antarctic circumpolar current

2. Cooler, drier high latitudes

3. Greater stratification of temperate and tropical organisms

How long ago was the gradual cooling of earth?

2 MYA

Gradual cooling of earth does what to climate?

Causes climate oscillations known as Ice Ages

What effect did the Ice Ages have on the hemispheres?

Glacial advances in Northern Hemisphere drove temperate species southward

What are 3 proposed explanations for the latitudinal diversity gradient?

1. Solar radiation: higher energy sites should be able to support more species

2. Longer evolutionary history

3. Climate stability

What are the 3 aspects of the longer evolutionary history hypothesis?

1. Tropics are persistent over geologic time

2. No glaciation

3. Large land area

(all of these indicate more time and space for evolutionary diversification of tropical species to occur)

Climate Stability Hypothesis

Fewer species can tolerate climatically unfavorable or variable conditions (more can tolerate climatically favorable conditions)

Energy

The ability to do work

1 calorie (cal)

Can raise the temperature of 1g of water by 1C

1 Joule is how many calories?

1 J = 0.239 cal

Conservation of Energy

Energy is neither created nor destroyed, only tranformed

Primary Productivity

Rate at which energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis

Most energy enters the biosphere via what?

Via photosynthesis

- Exception: chemosynthesis near deep ocean vents

Great Oxygenation Event

2.3 billion years ago by photosynthetic cyanobacteria, caused extinction of >90% of earth’s species at the time

What is the percent of photosynthetic efficiency?

1% - only 1% of solar energy is captured by photosynthesis (gross primary productivity)

What percent of gross primary productivity is respired?

60%

What percent of gross primary productivity is used for producer growth and reproduction? (net primary productivity)

40%

Gross Primary Productivity (GPP)

Total energy acquired via photo- or chemosynthesis

Respiration (R)

Using oxygen to release chemical energy to drive cellular processes

Net Primary Productivity (NPP)

Energy converted to producer biomass

What is the equation for NPP?

NPP = GPP - R

Assimilated Energy / Gross Secondary Production (GSP)

Energy that a consumer digests and absorbs (consumed - egested)

Net Secondary Production

Energy converted to consumer biomass (assimilated energy left after respiration by the first order consumer)

What is the equation for NSP?

NSP = GSP - R

What 3 things can be used to estimate primary production?

1. Change in producer biomass

2. CO2 exchange

3. Remote-sensing

Change in Producer Biomass (PP prediction)

Can estimate NPP by harvesting plants to determine mass of growth over a period of time

- Underestimation due to herbivory, below-ground biomass, and mutualistic exchanges

CO2 Uptake (PP prediction)

Light/dark bottle experiments can be used to measure NPP and GPP

- Light: measure net CO2 uptake (NPP

- Dark: measure CO2 released by respiration

Remote Sensing (PP prediction)

To estimate NPP, you can measure the absorption of blue and red light and reflection from green light from satellite images to calculate indices indicating vegetation biomass

-NDVI is a commonly used index

What gives you information on seasonal and annual variation?

Changes in spectral reflectance over time

Productivity varies with what 2 things?

1. Latitude

2. Biomes

Up to what percent of variation in NPP on a global scale can be explained by precipitation and temperature alone?

Up to 89%

How do food chains describe energy tranfer?

Energy flows from producers through successive trophic levels; energy is lost at each level but the amount lost depends on transfer efficiency

What is the equation for consumption efficiency?

Consumption efficiency = (consumed energy)/(net production energy of the next lower trophic level)

Assimilation Efficiency

Of the food that is consumed, some is assimilated and the rest is egested (defecated, regurgitated)

What is the equation for assimilation efficiency?

Assimilation efficiency = (assimilated energy)/(consumed energy)

What has lower assimilation efficiencies, primary consumers or secondary consumers? Why?

Primary consumers have lower assimilation because plant matter is less digestible

Net Production Efficiency

Of food assimilated, some of it is used for growth and reproduction (net production) and the rest is lost through respiration

What is the equation for net production efficiency?

Net production efficiency = (net production energy)/(assimilated energy)

Is net production efficiency higher or lower in homeothermic / mobile animals compared to poikilothermic / sedentary animals?

Net production efficiency is lower for homeothermic and mobile animals

Ecological Efficiency

Net production from one trophic level compared to the next lower trophic level

Ecological Efficiency incorporates what 3 things?

1. Consumption efficiency

2. Assimilation efficiency

3. Net production efficiency

What is the equation for ecological efficiency?

Ecological efficiency = (net production energy of a trophic level) / (net production energy of the next lower trophic level)

Ecological efficiency is usually around what %?

Generally around 5-20%, 10% used as “rule of thumb” (this means that ~90% is lost with each trophic level)

Trophic Pyramids

Illustrates distribution of energy or biomass among trophic groups in an ecosystem

What is the limit of trophic levels for aquatic and terrestrial species?

Aquatic: ~5

Terrestrial: ~3 or 4

Why are biomass pyramids often inverted in aquatic systems?

Because primary producers may be eaten as quickly as they grow (small standing crop)

Food energy available to humans depends on their what?

Trophic level

How much more land does a meat-based diet require compared to a plant-based diet? Why?

~7x more land needed, this is because the higher an individual is on the food chain, the more energy that is needed to support its diet

Decomposer / “Brown” Food Webs

Food web involving a wide variety of organisms ranging from microscopic, to small visible animals and fungi, to larger organisms

Nutrients

Elements required by organisms for metabolism and growth

Biogeochemistry

Physical, chemical, and biological factors that influence the movements and transformation of elements

Assimilation

Requires energy, inorganic to organic

Dissimilation

Releases energy, organic to inorganic

What are the 2 abiotic sources of nutrients?

1. Minerals in rocks

2. Gases in the atmosphere

Minerals in rocks contain what 4 elements?

1. Potassium

2. Calcium

3. Magnesium

4. Phosphorus

How are minerals in rocks turned into soluble nutrients?

Weathering

What 4 elements (and their %) make up the gases in the atmosphere?

1. N2 (78%)

2. O2 (21%)

3. Argon (0.9%)

4. CO2 (0.039%)

What are 2 ways for atmospheric gases to be turned into soluble nutrients?

1. Atmospheric deposition

2. Chemical fixation