Basic Terms And Concepts

Question 1

ecosystem

Answer 1

community of biotic and abiotic components which are linked by nutrient and energy cycles and interacting as a system

Question 2

food web

Answer 2

the totality of interacting food chains in an ecosystem. It describes how the energy flows in the system.

Food web A diagram or model that shows the feeding connections between all major groups of organisms in an ecosystem.

Question 3

population

Answer 3

group of individuals of the same species, which live in the same demographic region, time and are genetically connected over generations

Question 4

abundance

Answer 4

density of organisms per unit of area/volume

Question 5

biomass

Answer 5

mass of organisms per unit of area/volume, includes all parts of living organisms but not dead organisms or parts thereof

Question 6

production

Answer 6

characteristic of the community, rate of C/energy is fixed, or new biomass is built over time

Question 7

productivity

Answer 7

characteristic of the habitat, says how great the production could be (not community or population)

Question 8

excretion

Answer 8

the elimination of waste products produced by the metabolism (e.g. urine, faces)

Question 9

exudation

Answer 9

diffusive excretion of small molecular compounds (e.g. amino acids, monosaccharides) by plants or phytoplankton

Question 10

ingestion

Answer 10

uptake of material into the digestive system I= A+E

Question 11

assimilation

Answer 11

the incorporating of nutrients into the individual; A=R+P

Question 12

gross growth efficiency

Answer 12

to quantify the efficiency with which organisms convert the energy they acquire through feeding into new biomass. It represents the ratio of the increase in biomass (growth) to the total energy assimilated.

relation between production and ingestion; K1=P/I

higher values indicate more efficient energy conversion and allocation to growth, while lower values suggest a greater proportion of energy is utilized for other purposes.

Question 13

net growth efficiency

Answer 13

to assess the efficiency with which organisms convert assimilated energy into new biomass after accounting for energy losses through respiration and other metabolic processes.

often expressed as a percentage and reflects the effectiveness of an organism in utilizing energy for growth and reproduction

relation between production and assimilation; K2=P/A

higher values indicate a higher proportion of assimilated energy being allocated to net growth, lower values suggest a larger portion of energy is lost through metabolism

Question 14

efficiency of energy transfer between trophic levels

Answer 14

refers to the amount of energy that is transferred from one trophic level to the next in a food chain or food web.

between 0-30%,
Generally, energy transfer becomes less efficient as it moves up the trophic levels, resulting in a pyramid-shaped energy distribution with higher energy levels at lower trophic levels.
the higher organised an organism is, the lower the TTE → lower TL – higher TTE (very generalised)
𝑇𝑇𝐸 = 𝑃𝑝𝑟𝑒𝑑𝑎𝑡𝑜𝑟/𝑃𝑝𝑟𝑒𝑦
(P- Production)

Question 15

efficiency of assimilation

Answer 15

assimilation efficiency AE=A/I

to quantify the proportion of ingested energy (I) that is assimilated by an organism. it is calculated by dividing the assimilated energy (A) by the ingested energy (I).
Assimilated energy represents the portion of ingested energy that an organism is able to digest, absorb, and utilize for metabolic processes, growth, and reproduction. In contrast, the energy that is not assimilated is typically lost as undigested material or through metabolic processes such as respiration or excretion.

Question 16

necromass

Answer 16

mass of dead organic matter, that accumulates within an ecosystem (bark, hardwood…)

• Included as a component of biomass

Question 17

primary production (PP)

Answer 17

rate at which C is fixed (photosynthetically) (=GPP) or new biomass built (=NPP)

forms the foundation of energy flow and nutrient cycling in ecosystems

Question 18

secondary production

Answer 18

rate of production of heterotrophic organisms per unit of area/volume per time
(can be used for somatic growth/ reproduction)

Question 19

P:B ration

Answer 19

production per biomass: growth rate at population or community level.

The P:B ratio provides insights into the productivity and growth efficiency of organisms or ecosystems and can vary depending on factors such as environmental conditions, species composition, and resource availability.

Question 20

autochthonous

Answer 20

materials produces within the system (einheimisch/ortsständig)

Question 21

allochthonous

Answer 21

material produced outside the system and transported into it (i.e. definition depends on system boundaries)
e.g. leaves or organic matter from trees falling into a freshwater ecosystem from the surrounding terrestrial environment.

Question 22

gross primary production

Answer 22

(GPP) total amount of energy or biomass produced by autotrophic organisms via photosynthesis or chemosynthesis in an ecosystem

total of C fixed

Question 23

net primary production

Answer 23

(NPP) = gross primary production (GPP) - losses due to respiration + exudation/excretion

the amount of energy or biomass that remains after autotrophic organisms have used some of the energy for their own metabolic needs through respiration, representing the available energy for consumption by heterotrophic organisms and for storage in an ecosystem.

Question 24

gross population growth rate (µ)

Answer 24

The gross population growth rate (µ) represents the overall rate of increase or decrease in the size of a population over a specific time period, without accounting for factors such as births, deaths, immigration, or emigration.

Question 25

Which factors determine the trophic transfer efficiency how and why?

Answer 25

(The higher an organism is organised, the higher are the losses due to respiration. Good food quality raises the TTE, because the needed quantity shrinks.

Trophic transfer efficiency: The fraction of total production at a given trophic level that is converted to production at the next trophic level.)

Trophic transfer efficiency (TTE) is influenced by multiple factors. Firstly, TTE generally decreases with higher trophic levels due to energy losses at each transfer. Additionally, prey quality, foraging efficiency of predators, metabolic rates of organisms, temperature, and environmental conditions such as resource availability all play a role in determining TTE. These factors collectively shape the efficiency of energy transfer between trophic levels, impacting the flow of energy and nutrients within ecosystems.

Question 26

osmotrophy

Answer 26

a form of nutrition in which organisms obtain nutrients by absorbing dissolved organic matter or particulate organic matter through osmosis or active transport across their cell membranes.

used by certain protist and fungi

Question 27

mixotrophy

Answer 27

ability to assimilate carbon dioxide (photosynthesis and chemosynthesis) and ingest and digest organic particles (phagotrophy) and dissolved material (osmotrophy).
Mixotrophic organisms have the ability to switch between autotrophy and heterotrophy depending on environmental conditions and resource availability

Question 28

omnivory

Answer 28

Ability of organism to consume both plant matter (as a herbivore) and animal matter (as a carnivore).

the trophic position of omnivores is dynamic and can vary based on their diet and the specific ecosystem they inhabit

examples of omnivorous animals include humans, bears, raccoons, and pigs

Question 29

allometry

Answer 29

body size correlates with weight specific metabolic rates (ingestion, production, respiration, excretion)

larger organisms generally have lower metabolic rates per unit of body mass compared to smaller organisms (“negative allometry”)

Question 30

Metabolic Theory of Ecology (MTE)

Answer 30

Very short: the metabolic rate of organism serve as the fundamental biological rate, which is the base for the most observed pattern in ecology

Question 31

grazing chain/ Grazer food chain

Answer 31

Components of a food web that begin with photoautotrophs (in pelagic systems: cyanobacteria, algae, aquatic vascular plants) and pass through herbivores to carnivores.

Question 32

detritus chain/ Detrital food chain

Answer 32

Food-web components that begin with particulate organic matter (detritus/dead biodegradable material) or dissolved organic matter, and pass through detritivores (detritus eating bacteria and other microorganisms) to other consumers.

Question 33

grazing vs detritus chains in pelagic/terrestrial habitats

Answer 33

• pelagic: grazing chain more important, because the majority of the NPP is consumed by herbivores (usually complete swallowing of the prey) – less detritus occurs

*terrestrial: detritus chain is more important, because herbivores consume only a small part of the NPP, especially in forests, more detritus occurs. (after beraking it down and releasing nutriets back in the soil, these nutrients are used by the NPPs again.)

Question 34

trophic cascade (HSS)

Answer 34

A trophic cascade is a phenomenon in which changes in the abundance or behavior of organisms at one trophic level in a food chain or food web can have cascading effects on multiple other trophic levels. This can occur when the manipulation of top predators or primary producers leads to indirect effects that propagate through the trophic levels, altering community structure and ecosystem dynamics.

Question 35

trophic level

Answer 35

integer, says how often substance got assimilated since the last fixation by the primary production

A group of organisms that obtain their food from sources of equal distance from the original source. Autotrophs equal level 1, herbivores equal level 2, primary carnivores equal level 3, and secondary carnivores equal level 4. Species feeding from more than one level may be assigned a fractional trophic level called trophic position based on their diet composition.

Question 36

trophic position

Answer 36

determined by the TL/TP the population is feeding on, doesn’t have to be an integer

a species must be assigned to fractional trophic levels, called trophic positions that reflect their diet. For example, an omnivore (e.g., a bear or a crayfish) feeding 50% on level 1 (e.g., autotrophs) and 50% on level 2 (e.g., herbivores) would be assigned a trophic position of 2*0.5 + 3 *0.5=2.5. Thus, models can take into account proportionate differences in the diet composition.

warum trophic level 2 und 3?

Question 37

bottom-up-control

Answer 37

regulation of higher trophic levels by the abundance or productivity of lower trophic levels.

Question 38

top-down-control

Answer 38

regulation of lower trophic levels by the abundance or activity of higher trophic levels
(many predators → little prey, negative correlation)

Question 39

upper limit to the size ratio between predator and prey

Answer 39

max ratio terrestrial: 1000:1,
pelagic: 1.000.000:1 (This larger ratio is partly due to the different dynamics and energy availability in aquatic environments, where smaller prey items, such as plankton or microorganisms, can sustain larger predators through more efficient energy transfer and the abundance of prey resources.)

If the predator is getting to big, the uptake of the prey is not energetically worthwhile anymore

Question 40

„stability” of an ecological system

Answer 40

There isn’t one definition of THE stability in ecology. There are just stability properties like persistence, resistance and resilience.
The stability of an ecological system refers to its ability to maintain its structure, function, and overall dynamics in the face of internal or external disturbances. A stable ecosystem can resist and recover from perturbations, maintaining relatively constant population sizes, species composition, and ecological processes over time. Stability can be measured through various indicators, such as resilience (the ability to bounce back after a disturbance) and resistance (the ability to withstand disturbances without significant changes). A more stable ecosystem is generally characterized by balanced trophic interactions, robust food webs, and efficient nutrient cycling, promoting long-term sustainability and biodiversity.

Question 41

Persistence

Answer 41

Outlast/Survival of an ecological system over time, including e.g. preservation of the species inventory

Beständigkeit

Question 42

Resistance

Answer 42

remain essentially unchanged despite potential disorders/ in response to disturbance or cahnged enviromental conditions

Resistenz

Question 43

Resilience

Answer 43

return to the initial/stable state after a change due to temporary disturbances (subsumes elasticity (=speed of return to the initial state) & area of attraction (= all the states from which the initial state is reached again)

Resilienz

Question 44

taxonomic diversity

Answer 44

‘Simpson-Index:’

𝐷=1−Σ𝑝𝑖^2𝑠𝑖 =1 (p…proportion of specie)
𝐷𝑚𝑎𝑥=1−𝐷𝑠 (s…specie number)
𝐸=𝐷/𝐷𝑚𝑎𝑥 (E…evenness)
Simpson – relies more on evenness than specie number

‘Shannon-Wiener:’

𝐻′=−Σ(𝑝𝑖log(𝑝𝑖))𝑠𝑖=1
𝐻′=log (𝑠)
E = 𝐻′/𝐻′𝑚𝑎𝑥
SW relies more on species number than evenness

Therefore, the Simpson Index focuses on evenness in species proportions, while the Shannon-Wiener Index places greater importance on the number of species present in the calculation of diversity.

Question 45

The recycling of resources from dead org. material occurs mostly via bacteria and fungi (almost only relevant in terrestrial systems → why?!)

Answer 45

• The most fungi are obligate aerobe
• There is more dead organic matter in terrestrial systems
• In terrestrial system fungi are the main decomposers of lignin, in open water ecosystems there isn’t lignin, → white rot

Lignin: phenolisches Makromolekül aus verschiedenen Monomerbausteinen, ein fester, farbloser Stoff, der in die pflanzliche Zellwand eingelagert wird und dadurch die Verholzung der Zelle bewirkt

Question 46

Define biodiversity. How is it measured?

Answer 46

Biodiversity is the variety or richness of genes, species, populations and their interactions.
You can measure it with different indices (Simpson, Shannon-Wiener etc.) to compare different ecosystems, habitats etc…

Question 47

How does biodiversity influence ecosystem functions and their spatial-temporal variability? What are the mechanisms?

Answer 47

Stability of ecosystem function increases with diversity, at first linear, then weaker → high biodiversity → low variability of ecosystem functions

The reasons are buffer mechanisms:
Compensatory mechanism between individual populations, positive covariance → less stable; negative covariance → more stable

Portfolio effect: the more individual populations the higher the probability of asynchronous fluctuations → negative covariance

Insurance Hypothesis: with high diversity the probability of an occurrence of different species with the same functions increases (negative covariance)

Facilitation: one species benefits from another

Complementarity: different niches

Jansen-Cornell effect: Probability of survival for seedlings of a plant (this hypothesis was postulated for tropic trees) increases with the distance to the next adult individual… one reason for the species richness in the tropes

Question 48

factors influencing biodiversity: latitude

Answer 48

diversity is decreasing from the tropics to the poles

Question 49

factors influencing biodiversity: extreme habitats

Answer 49

extreme habitats are low on species number, but (with enough productivity) rich in individuals and vice versa, temperate habitats are more diverse and often have fewer individuals per species

Question 50

factors influencing biodiversity: productivity

Answer 50

productivity of the habitat: unimodal curve, maximum at medium productivity, with low productivity only specialist survive, with high productivity strong competition for light → plants grow very big → fewer individuals/area, with medium productivity the diversity is the highest, because different species are limited by different resources (Tilman model)

Question 51

factors influencing biodiversity: IDH (Intermediate Disturbance Hypothesis)

Answer 51

IDH suggests that ecosystems experiencing intermediate levels of disturbance will have higher species diversity compared to ecosystems with low or high disturbance levels

the diversity is highest (measured by the duration of the generation) at mean interference frequency and Interference intensity;

very frequently and strong disturbances → r-strategists;
very seldom and weak disturbances → K-strategists;
mediate frequency and intensity → both strategists are alternating, new niche dimensions arise

R-strategists are characterized by high reproductive rates and minimal parental care
K-strategists exhibit slower reproduction, extended parental care, and higher investment in fewer offspring

Question 52

factors influencing biodiversity: Temporal fluctuations

Answer 52

caused by external influences like seasons, weather, climate; or endogenous processes like predator-prey cycles; change competitive relationships, create new niche dimensions trough adaption

Question 53

factors influencing biodiversity: spatial heterogeneity

Answer 53

spatial heterogeneity and unequal access to resources: gradients in resource availability, resource concentration can differ on very small spatial scales → strong building of niches

Question 54

factors influencing biodiversity: Patchiness

Answer 54

metapopulation dynamics or source-sink-dynamics; regional coexistence, while local competitive exclusion; migration inhibits extinction

Question 55

factors influencing biodiversity: Insular biogeography

Answer 55

Insular biogeography (on near and big islands – highest diversity)

Question 56

factors influencing biodiversity: seed dormancy

Answer 56

Seed dormancy, can raise diversity, because of the outlast of bad periods, resettlement after extinction

Question 57

factors influencing biodiversity: predation

Answer 57

Predation can increase diversity (parasitism) or decrease it (predator-mediated completion, intraguild predation)

Question 58

Why do we find typically a unimodal relationship between the productivity of a habitat (e.g. determined by nutrient concentrations, precipitation) and biodiversity but a saturating function between production (of new biomass) and biodiversity?

saturating- sättigend

Answer 58

‘Different objects’: productivity (=characteristic of the habitat, says how great the production could be) and production (= characteristic of the community, rate of C/energy is fixed, or new biomass is built over time)
‘Different scales’: In experiments we measure the production, there is a positive relationship between biomass production and diversity (complementary mechanism, dominance mechanism and facilitation → overyielding)
Observation of the productivity over different locations get averaged
‘Different dependency’: experiments – total production depends on diversity
observations - diversity depends on abiotic factors and the competition relationships

long story short: they are different things
Unimodal relation between productivity and biodiversity because: with medium productivity the diversity is the highest, because different species are limited by different resources (e.g. Tilman model)
Saturating function between production and biodiversity because: Stability of ecosystem function increases with diversity, at first linear, then weaker → high biodiversity → low variability of ecosystem functions

Question 59

What do bacteria feed on in soil and open water?

Answer 59

open water: bacterioplankton - osmotrophy of organic content from other organisms, play an important role in the microbial loop and remineralisation of organic compounds (C, N)

some bacteria are autotrophs, or mixing energy sources (mixotrophs)

soil: decomposers, feed on plant material,
lithotrophs & chemoautotrophs, obtain energy from N, S, FE, H,
many of them are nitrogen fixing bacteria, important for N- cycle

Question 60

Trophic guild

Answer 60

A group of organisms that share common food sources and common predators

Question 61

Trophic transfer efficiency

Answer 61

The fraction of total production at a given trophic level that is converted to production at the next trophic level.

Question 62

Ecological stoichiometry

Answer 62

Study of element ratios within biomass in relation to element ratios within food or in the surrounding environment.

study of the balance and flow of elements, particularly carbon, nitrogen, and phosphorus, in ecological systems and how their ratios influence ecological processes, nutrient cycling, and the structure and functioning of ecosystems.

Question 63

Different shape of the trophic pyramid (pelagic vs. terrestrial)

Answer 63

When based on biomass, such a diagram takes a pyramidal shape for terrestrial environments whereas it resembles more a column for pelagic ecosystems at least for the lower trophic levels. That is, the laws of nature do not require the pyramidal shape, and a higher trophic level may have the same or even more biomass than a lower trophic level adjacent to it.

In both terrestrial and pelagic ecosystems, exceptions to the pyramidal shape can occur, with higher trophic levels potentially having comparable or even greater biomass than adjacent lower trophic levels.

pelagic: higher biomass in higher TL, terrestrial: higher in lower TL

adjacent- angrenzend

Question 64

POM

Answer 64

particulate organic matter (POM, detritus)

also designated as particulate organic carbon (POC)

Question 65

DOM

Answer 65

dissolved organic matter (DOM)

also designated dissolved organic carbon (DOC)

Question 66

efficiency of consumption

Answer 66

Consumtion Efficiency = In / Pn-1 (n=Trophic level)

calculated by dividing the ingested energy at a particular trophic level (In) by the production at the previous trophic level (Pn-1).
A higher consumption efficiency value suggests that a larger proportion of energy produced at the lower trophic level is being consumed and utilized by organisms at the higher trophic level.

Question 67

I = A + E = P + R + E

Answer 67

Ingestion( I ) = Assimilation A + Excretion E = Production P + Respiration R + Excretion E