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Productivity within trophic levels

Productivity within an ecosystem can be defined as the percentage of energy entering the ecosystem incorporated into biomass in a particular trophic level. Biomass is the total mass, in a unit area at the time of measurement, of living or previously living organisms within a trophic level. Ecosystems have characteristic amounts of biomass at each trophic level. For example, in the English Channel ecosystem the primary producers account for a biomass of 4 g/m 2 (grams per meter squared), while the primary consumers exhibit a biomass of 21 g/m 2 .

The productivity of the primary producers is especially important in any ecosystem because these organisms bring energy to other living organisms by photoautotrophy or chemoautotrophy. The rate at which photosynthetic primary producers incorporate energy from the sun is called gross primary productivity    . An example of gross primary productivity is shown in the compartment diagram of energy flow within the Silver Springs aquatic ecosystem as shown ( [link] ). In this ecosystem, the total energy accumulated by the primary producers (gross primary productivity) was shown to be 20,810 kcal/m 2 /yr.

Because all organisms need to use some of this energy for their own functions (like respiration and resulting metabolic heat loss) scientists often refer to the net primary productivity of an ecosystem. Net primary productivity is the energy that remains in the primary producers after accounting for the organisms’ respiration and heat loss. The net productivity is then available to the primary consumers at the next trophic level. In our Silver Spring example, 13,187 of the 20,810 kcal/m 2 /yr were used for respiration or were lost as heat, leaving 7,632 kcal/m 2 /yr of energy for use by the primary consumers.

Ecological efficiency: the transfer of energy between trophic levels

As illustrated in [link] , large amounts of energy are lost from the ecosystem from one trophic level to the next level as energy flows from the primary producers through the various trophic levels of consumers and decomposers. The main reason for this loss is the second law of thermodynamics, which states that whenever energy is converted from one form to another, there is a tendency toward disorder (entropy) in the system. In biologic systems, this means a great deal of energy is lost as metabolic heat when the organisms from one trophic level consume the next level. In the Silver Springs ecosystem example ( [link] ), we see that the primary consumers produced 1103 kcal/m 2 /yr from the 7618 kcal/m 2 /yr of energy available to them from the primary producers. The measurement of energy transfer efficiency between two successive trophic levels is termed the trophic level transfer efficiency (TLTE)    and is defined by the formula:

TLTE  =   production at present trophic level production at previous trophic level  × 100

In Silver Springs, the TLTE between the first two trophic levels was approximately 14.8 percent. The low efficiency of energy transfer between trophic levels is usually the major factor that limits the length of food chains observed in a food web. The fact is, after four to six energy transfers, there is not enough energy left to support another trophic level. In the Lake Ontario example shown in [link] , only three energy transfers occurred between the primary producer, (green algae), and the apex consumer (Chinook salmon).

Questions & Answers

Mendel experiment when years ago in work
Biruk Reply
what is the smallest unit in an organism
Neimar Reply
what is endoplasmic
Fatou Reply
If Jane was in room(B) while her mother Stella was in room (Y). Jane was cooking fish, her mother came to smell the good scent, By what process did her mother came to smell the scent
Neimar Reply
Is it a serious question?
Ehsan Reply
what's the question
Joseph
how many days do a bean seed take to germinate
Nando
what is DNA
Yahaya Reply
genetic information
MG
Deoxyribonucliec acid (DNA) is the cell's hereditary material that contains instructions for growth, development and reproduction.
Joseph
ok
oly
what's different between sex and gender
oly
Are there differences between sex and gender?
Theo
lol
Andrew
describe an experiment to show that plants require light for photosynthesis
Diyara Reply
uuh... putting a plant in a dark closet... and another in a light enviroment?
Anastasiya
wow! awesome explanation Anastasiya.
Joseph
please can you explain why air is homogenous
Joseph
Because each layer of the Earth's atmosphere has a different density, each layer of air is it's own homogenous.
MG
tell me about big bang
Mustafa
what's DNA
Mustafa
What's an amoeba
Bigger Reply
An amoeba is a cell or an organism that has the ability to ulter it's shape.
Joseph
An amoeba has an irregular shape and it changes constantly,it's a unicellular organism belong to a group called protists it has a pseudopodia used for locomotion and ingestion...
Emmanuel
amoeba is an organism that has an inregular shape which changes constantly
Cashizz
amoeba is an unicellular organism that uses pseudopodia,it does not have a constant shape
Alohan
what is the difference between DNA and RNA
Alohan
DNA with oxygenated but RNA without oxygenated
qax
what is the mode of nutrition of fungi
Survive
asexual
qax
amoeba are protozoa with one cell and no fixed shape
James
heterotrophic and outrotrophic
qax
what is the between arteries and capillary
qax
arteries>arterioles>capillaries. decrease in size and thus pressure
Anastasiya
DNA deossoribonucleic acid. RNA ribonucleic acid. The difference between the two lies in a lack of one oxygen on the sugar in DNA. Also: in DNA the azotate bases are Guanine, Citosine, Adenine and TIMINE base, the latter is replaced by URACILE in RNA. DNA formes a double helix structure...
Anastasiya
... while RNA form is usually a single stand line, but it can form loops etc
Anastasiya
what is a zygote?
Darius Reply
zygote is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual.
MG
A zygote is an organism formed after fertilization
Neimar
how do plants form a zygote
Paclina Reply
What is zygote
Van
what is zygote
Darius
Zygote is located inside the ovule, which is present in the ovary.
MG
zygote is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual.
MG
Okay
Van
what is biology?
Aadan Reply
biology is the study of living n non living organism
Kelsia
what is procotist?
Kelsia
Biology is the branch of science that deals with the study of living and non living things
Neimar
Describe at least two major changes to the animal phylogenetic tree that have come about due to molecular or genetic findings.
Tamala Reply
what is herbarium sheet
Ramreichon Reply
Which of the following is not a characteristics of all living organisms? A. Excretion B. Photosynthesis C. Reproduction D. Respiration
Abel
B.
Anastasiya
B photosynthesis
Survive
general equation for photosynthesis
Ojasope Reply
6CO2 + 6H2O + solar energy= C6H1206+ 6O2
Anastasiya
meaning of amino Acids
AJAYI Reply
An aminoacid is a base unit molecule for proteins. It s formed by a central Carbon, to which are attached: an amminic Group, a carbossilic Group, an H hydrogen, and an R group ( which varies for each different aminoacid). Glycin is the only aminoacid to have for an R group a simple H hydrogen.
Anastasiya
H NH2-C-COOH R this is the not ionized form but usually they are ionized, with NH+ and COO-
Anastasiya
The R group, the lateral Chain, is responsible for the characteristics of the aminoacid.
Anastasiya
* NH2+
Anastasiya
J=1 jar daq
Van

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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