IB ESS Topics 2.2, 2.3 & 1.3

Species

A group of organisms that are capable of interbreeding

and have fertile offspring

Population

A group of organisms of the same species living in the same area at the same time 

Community

A group of populations living and interacting with each other in a common habitat. It involves biotic interactions only

Ecosystem

A community of interdependent organisms and the physical environment they inhabit. It includes the interactions of communities with the abiotic habitat

Biosphere

The part of the Earth inhabited by organisms. It extends from the atmosphere to the Earth's crust

Producers

Make their own food from compounds found in environment. All other organisms depend one way or another on biomass that was assimilated by producers.

Consumers

Consists of herbivores (primary consumers), carnivores (secondary or higher level consumers) and omnivores (plant and meat eaters). Consumers either directly or indirectly (several steps removed) gain energy from the producer level. About 10% of the energy from one trophic level is passed on to the next level

Decomposers/Detritivores

Organisms that feed off of dead and decomposing organic material. They recycle organic matter by biodegrading detritus to get their nutrients. They then release simple inorganics into the environment for use by producers

Assimilation

Process by which living organisms integrate nutrients from external resources to their body

Biomass

 Total mass of living organisms in a given area

Carnivore

Consumers that eat other animals

Omnivore

Consumers that eat both plants and animals

Herbivore

Consumers that eat only plants

Abiotic factors required to do photosynthesis

Carbon dioxide, water, chlorophyll, and light

Respiration

Sugars gained through photosynthesis or feeding are used to provide energy during respiration

Anaerboic Respiration

Process of cellular respiration that occurs in the absence of oxygen, leading to the breakdown of glucose into energy and producing lactic acid or ethanol as a byproduct

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The break down of organic material in a landfill relies on anaerobic respiration

Productivity

The rate at which energy is added to the bodies of a group of organisms in the form of biomass

Primary Productivity

The rate at which solar energy (sunlight) is converted into organic compounds via photosynthesis (producers). Measured in units of energy per unit area per unit time.

Gross productivity

The total gain in energy; total biomass produced

Gross Primary Productivity (GPP)

the gross productivity specifically of producers. It is the total rate of photosynthesis in a given area. 

Factors that affect GPP

Amount of light, CO2 and H2O available, nutrient availability, temperature, and herbivory

GPP can be measured through

the rate of oxygen production, CO2 consumption rate & glucose production rate

Net Primary Production

the rate of energy storage by photosynthesizers in a given area after subtracting the energy lost to respiration

NPP formula

NPP = Photosynthesis (GPP) - Respiration (R)

What does negative NPP mean?

Loss in biomass

What does positive NPP mean?

Growth, gain in biomass

What does zero NPP mean?

No change

Methods to measure NPP

* CO2 Assimilation (use probe to measure GP and to measure the amount of CO2 released during R)
* O2 production

The gross primary productivity of a meadow in southeastern Kansas is found to be **40,000 kcal/m²**. Respiration, which is measured by the amount of CO₂ released, is **15,000 kcal/m²**, what is the net primary productivity for this ecosystem, in kcal/m² per year?

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1. 25,000 kcal/m2/yr
2. 55,000 kcal/m2/yr
3. -25,000 kcal/m2/yr
4. -55,000 cal/m2/yr

The net annual primary productivity of a particular wetland ecosystem is found to be 6,000 kcal/m² per year. If respiration by the aquatic producers is 12,000 kcal/m² per year, **what is the gross annual primary productivity** for this ecosystem, in kcal/m² per year?

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1. 6,000 kcal/m2/yr
2. 18,000 kcal/m2/yr
3. -6,000 kcal/m2/yr
4. 12,000 kcal/m2/yr

Gross Productivity of a consumer

equal to the NP of the trophic group before it

* Producer: GPP - R = NPP

Gross Secondary Productivity

GSP is the total energy or biomass assimilated by consumers

GSP formula

GSP = food eaten - fecal loss

Net Secondary Productivity

NSP = GSP - R

Bottle Method

Food Webs

Show the feeding relationships with multiple species per trophic level and multiple energy pathways (multiple arrows).

Food Chains

Show one feeding interaction that depicts how one species per trophic level gets energy from the previous level. It depicts one energy arrow per trophic level.

Trophic Level

Is the position an organism occupies in a food chain. In a food web, omnivores may occupy more than one trophic level.

Ecological Pyramids

Is the position an organism occupies in a food chain. In a food web, omnivores may occupy more than one trophic level.

First Law of Thermodynamics

Energy cannot be created or destroyed but it may be changed to other forms.

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Second Law of Thermodynamics

Energy is always degraded (lost to an unwanted form) during a transfer of energy. This means the entropy of the universe is always increasing.

Pyramid of numbers

Compares the number of organisms at each trophic level

Pyramid of biomass

Compares the mass of biological material at each trophic level

Pyramid of energy/productivity

Compares the amount of energy passing through each trophic level over a period of time

Inverted Pyramids - why?

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1. **Producer is large in size**--Leads to inverted pyramid of numbers


1. Ex. 1 tree may support many small primary consumers
2. **Seasonal Changes**


1. **Ex. After a seasonal fire, a grassland has less biomass in the producer level**
3. **Reproduction/Migration/Feeding Habits** 


1. Ex. When a meadow blooms it attracts a large number of pollinators who may not always stay in that area

Bioaccumulation

the process in which a non-biodegradable toxin that has been released into the environment ends up stored in the body tissue of an organism

Biomagnification

the process in which a non-biodegradable toxin becomes more concentrated in higher trophic level organisms.

Why are DDT and mercury bad?

*In the environment, insects would encounter DDT and absorb some of it into their bodies. Often, they would receive a sub-lethal dose, enough to impair them but perhaps not kill them. In any event, it stands to reason that insects either dying or merely slowed down by pesticide intake would become easy targets for birds. Upon ingestion, the DDT in the insect bodies is released and makes its way into the tissues of the bird's body, particularly the fat deposits. Because an individual bird eats many insects, and because the DDT does not leave the bird's body, and because DDT resists breaking down (either in the environment or the body), it accumulates to higher levels in the bird's tissues. In other words, the DDT that was spread out over, say 1,000 crickets will be concentrated in one bird.*