BIOL 208 FInal

Community

an association of potentially interacting species inhabiting some defined area, at some particular scale, over some particular span of time

Community structure

attributes of a community, such as the number of species or the distribution of individuals among species within the community

Species diversity

a measure of diversity that increases with species evenness and species richness

Species richness

the number of species in a community

Species evenness

the relative abundance of species in a community

What are the 3 types of species diversity

1. Gamma

2. Alpha

3. Beta

Gamma

diversity within a region or landscape

Alpha

diversity within a locality within a region or landscape

Beta

the difference between the diversity of a region or landscape, and a locality within the region or landscape. A measure of the diversity among locations within a region

Guilds

Guilds are groups of similarly functioning organisms

Species Dominance

More often than not, communities include a dominant species, one that is more common than all others.

Most species in the community will occur in ________________________ abundances

moderate

True or False: Diversity makes communities more stable

True

Rank abundance curve

Plot of relative abundance of species against their rank in abundance. In other words, another way to assess dominance and diversity in community

If the slope of the line is less in a rank abundance curve it has ___________________ eveness

less

Describe the relationship between environmental complexity and species diversity?

In general, the more complex or heterogeneous, the environment, the greater species diversity

Simple Homogeneous Environment

1. Few factors that influence organisms

2. Few niches

3. Ex. the poles

Complex Heterogenous Environment

1. Many factors that influence organisms

2. Many niches

3. Equator

Species composition

The species that occur in a given community at a given time

Why is species composition important?

Shifts in species composition to non-native species often leads to changes (usually decreases) in species richness and evenness

True or False: Generally, the more diverse a population is genetically, the more resilient it is

True

Species Composition Shifts: Non-native species, invasive species

Species that establish a new range in which they proliferate, spread, and persist to the detriment of the environment

Biodiversity

The sum of all organisms in an area, taking into account the diversity of species, their genes, their populations, and their ecosystems

Food webs

Are trophic networks

Trophic level

Position within a food web

trophic position in the ecosystem

Primary Producer = trophic level ______

1

Primary Consumer = trophic level _________

2

Secondary Consumer = trophic level _______

3

Trophic Interaction

Transfer of energy from one trophic level to another, aka, eating

10% Rule

10% of biomass in each trophic level is available for processing in further trophic levels. Therefore it should be 10% smaller in each increasing trophic level

True or False: The 10% rule is a bit more efficient in aquatic systems than in terrestrial ones, thus there are more trophic levels

True

Keystone species

species that, despite low biomass (=low population density), exert strong effects on the structure of the community they inhabit

Why/how do keystone species affect the ecosystem?

1. Reduce competitive exclusion between other species (through predation)

2. Are mutualists, and perform important functions (parasite removal, movement of seeds)

Trophic cascades

When a change in the population size of a species in one trophic level changes/alters populations in the other trophic levels

Top-down Trophic Cascade

Trophic cascade caused by consumers

bottom up trophic cascade

Trophic cascades caused by primary producers

True or False: Most communities are controlled by both top-down and bottom-up trophic cascades

True

Primary Production

The fixation of energy by autotrophs in an ecosystem

What are the biggest sources of primary production?

Biggest source of primary production is photosynthesis, by plants, phytoplankton, and cyanobacteria

True or False: Primary production can also occur through chemosynthesis by some species of bacteria

True

The rate of primary production in an ecosystem is called ____________ ___________________

primary productivity

Primary productivity

It is the amount of energy fixed by autotrophs over an interval of time. In the case of photosynthesis, how much energy from the sun is used to make sugars by plants.

What is the Redfield Ratio

C:N:P -- 106C:16N:1P

What are other reactions used to supplement sunlight if there is a lack of sunlight?

1. Ammonium oxidation (NH4+)

2. Methane oxidation (CH4)

3. Reduced sulfur oxidation (H2S)

What are the two measures of primary productivity

1. Gross Primary Production

2. Net Primary Production

Gross Primary Production (GPP)

The total amount of energy fixed by all the autotrophs in the ecosystem, regardless of the cost associated with its fixation (Photosynthesis)

Net Primary Production (NPP)

The total amount of energy fixed by all the autotrophs in the ecosystem, minus the cost associated with its fixation, it is the amount of energy available to consumers in an ecosystem (Photosynthesis-Respiration)

Primary production in terrestrial ecosystems is mainly limited by ___________________ and __________________

temperature and moisture

Actual Evapotranspiration (AET)

The total amount of water that evaporates and transpires off a landscape during a given time period, measured in mm water. Great for accounting for both temperature and precipitation, as AET is affected by both

How does soil fertility effect primary production

Adding fertilizers nearly doubled primary production (because amount of nutrients available can often be the limiting factor in plant growth)

Aquatic primary production is mainly limited by ______________ ______________

nutrient availability

Eutriphication

nutrient enrichment of a water body through natural processes or pollution, generally causing rapid algal growth and reduced dissolved oxygen levels

How is primary production determined in marine waters?

It is a gradient based on how far water is from land. NPP is highest in costal areas, lowest in deep ocean

Hypoxia

When water oxygen concentrations

Dead zones

Hypoxic areas in aquatic ecosystems, typically a consequence of pollution, eutrophication, and high rates of decomposition

that are essentially devoid of life

How do dead zones form?

1. During the spring, sun-heated freshwater runoff from the Mississippi River creates a barrier layer in the Gulf, cutting off the saltier water below from contact with oxygen in the air

2. Nitrogen and phosphorus from fertilizer and sewage in the freshwater later ignite huge algae blooms when the algae die, they sink into the saltier water below and decompose, using up oxygen in the deeper water

3. Starved of oxygen and cut off from resupply, the deeper water becomes a dead zone. Fish avoid the area or die in massive numbers. Tiny organisms that form the vital base of the Gulf food chain also die. Winter brings respite, but spring runoff start the cycle anew

The First Law of Thermodynamics

The total amount of energy in the universe is constant. Energy can be transformed

but not created nor destroyed

Second law of thermodynamics

Heat energy will move from a warmer body to a cooler-one. Thus, entropy will increase over time in a closed system

Trophic Level

Position in food web

determined by number of energy transfers from primary producers to that level

Trophic dynamics

The transfer of energy from one part of the ecosystem to another

What are the 3 reasons the 10% Rule exists?

1. Loss of energy as it is transferred is inevitable

2. not all biomass is edible

3. not all biomass is accessible to be eaten

True or False: Because of the 10% rule, pyramids exist

True

What are the other limits (besides the 10% rule) that there are limits to the number of trophic levels?

• of the NPP available to primary consumers, only 4% is passed up and is available to secondary consumers

• Each successive level occurs in lower abundances

True or False: 99% of the solar energy input into the ecosystem was available to primary consumer

True

Allochthonous Inputs

Organic matter derived or created in a community external to the one it is deposited in

Keystone species

Species that despite low biomass (=low population density), exert strong effects on the structure of the community they inhabit (disproportionate to biomass)

Energy _________ through ecosystems

flows

Nutrients ___________ through ecosystems

cycles

Reservoirs

Stores of water or nutrients in a cycle

Nutrients

elements that are required for the development, maintenance, and reproduction of organisms

Macronutrients

Essential elements required in large concentrations in an organism

What are the macronutrients

carbon, hydrogen, oxygen, nitrogen, phosphorus

Micronutrients

essential elements required only in small concentrations in an organism

What are the micronutrients

iron, magnesium, iodine, selenium, zinc

Facts about Phosphorus

1. Essential to energetics, genetics, and structure of living systems (main component of ATP, RNA, DNA, and phospholipid molecule)

2. not very abundant in the biosphere

3. Does not have an atmospheric reservoir

4. Can be a limiting factor for aquatic primary production, not usually for terrestrial primary production

The Phosphorus Cycle

1. Phosphorus is tied up in mineral deposits and marine sediment

2. Phosphorus is usually (naturally) released to ecosystems through weathering of rocks

3. Plants take up phosphate ions from soil or water and incorporate them directly into tissue

4. Animals gain phosphate by eating these tissues, or from tissues of other organisms

5. Animals eliminate excess phosphorus through urine

6. Phosphate in water can sometimes be precipitated into the sediment under the right conditions

Facts about Nitrogen

1. Important to structure and functioning of organisms

2. May limit rates of primary production in terrestrial and marine systems

3. one of the biggest reservoirs is the atmosphere (78% N)

4. Microbes play a BIG role in the nitrogen cycle

What are the forms of N

1. Ammonium

2. Ammonia

3. Nitrite

4. Nitrate

5. Nitrogen gas

6. Nitric oxide

Ammonuium

NH4+

NH4+

Ammonium

Ammonia

NH3

NH3

ammonia

Nitrite

NO2-

NO2-

Nitrite

Nitrate

NO3-

NO3-

Nitrate

Nitrogen gas

N2

Nitric oxide

NO

What are the five transformations of N

1. Nitrogen fixation

2. Immobilization

3. Mineralization (ammonification)

4. Nitrification

5. Denitrification

Nitrogen Fixation

The process of converting atmospheric nitrogen into forms primary producers can use (by microbes and cyanobacteria)

Immobilization

The conversion of mineral forms of nitrogen (ex. ammonia and nitrate) into organic forms (proteins)

Mineralization

The conversion of organic forms of nitrogen (ex. proteins) into mineral forms (ex. ammonia and nitrate)

Nitrification

The conversion of ammonium (NH4+) to nitrite (NO2), and then nitrite (NO2) to nitrate (NO3-)

Denitrification

The process of converting nitrate into nitrogen gas

The Nitrogen Cycle

1)

True or False: Nitrogen can be fixed through nitrogen fixation by certain prokaryotes, it can also be fixed by lightning

True