2.2. communities and ecosystems
TRANSCRIPT
2.2. Communities and Ecosystems
Miltiadis Kitsos
Platon school IB diploma
https://goo.gl/forms/7Gm5lnMCEi161eaz1
Significant ideas
• The interactions of species with their environment result in energy and nutrient
flows.
• Photosynthesis and respiration play a significant role in the flow of energy in
communities.
• The feeding relationships of species in a system can be modelled using food chains,
food webs and ecological pyramids.
Knowledge and understanding
• A community is a group of populations living and interacting with each other in a
common habitat.
• An ecosystem is a community and the physical environment with which it interacts.
• Respiration and photosynthesis can be described as processes with inputs, outputs
and transformations of energy and matter.
• Respiration is the conversion of organic matter into carbon dioxide and water in all
living organisms, releasing energy. Aerobic respiration can be represented by the
following word equation.
glucose + oxygen → carbon dioxide + water
Knowledge and understanding
• During respiration, large amounts of energy are dissipated as heat, increasing the
entropy in the ecosystem while enabling organisms to maintain relatively low entropy
and so high organization.
• Primary producers in most ecosystems convert light energy into chemical energy in
the process of photosynthesis.
• The photosynthesis reaction is can be represented by the following word equation.
carbon dioxide + water → glucose + oxygen
• Photosynthesis produces the raw material for producing biomass.
• The trophic level is the position that an organism occupies in a food chain, or the
position of a group of organisms in a community that occupy the same position in food
chains.
• Producers (autotrophs) are typically plants or algae that produce their own food using
photosynthesis and form the first trophic level in a food chain. Exceptions include
chemosynthetic organisms that produce food without sunlight.
• Feeding relationships involve producers, consumers and decomposers. These can be
modelled using food chains, food webs and ecological pyramids.
Knowledge and understanding
• Ecological pyramids include pyramids of numbers, biomass and productivity and are
quantitative models that are usually measured for a given area and time.
• In accordance with the second law of thermodynamics, there is a tendency for
numbers and quantities of biomass and energy to decrease along food chains;
therefore, the pyramids become narrower towards the apex.
• Bioaccumulation is the build-up of persistent or non-biodegradable pollutants within
an organism or trophic level because they cannot be broken down.
• Biomagnification is the increase in concentration of persistent or non-biodegradable
pollutants along a food chain.
• Toxins such as DDT and mercury accumulate along food chains due to the decrease
of biomass and energy.
• Pyramids of numbers can sometimes display different patterns; for example, when
individuals at lower trophic levels are relatively large (inverted pyramids).
• A pyramid of biomass represents the standing stock or storage of each trophic level,
measured in units such as grams of biomass per square meter (g m–2) or Joules per
square meter (J m-2)(units of biomass or energy).
Knowledge and understanding
• Pyramids of biomass can show greater quantities at higher trophic levels because
they represent the biomass present at a fixed point in time, although seasonal
variations may be marked.
• Pyramids of productivity refer to the flow of energy through a trophic level, indicating
the rate at which that stock/storage is being generated.
Knowledge and understanding
• Pyramids of productivity for entire ecosystems over a year always show a decrease
along the food chain.
Applications and skills
• Construct models of feeding relationships—such as food chains, food webs and
ecological pyramids—from given data.
• Explain the transfer and transformation of energy as it flows through an ecosystem.
• Analyse the efficiency of energy transfers through a system.
• Construct system diagrams representing photosynthesis and respiration.
• Explain the relevance of the laws of thermodynamics to the flow of energy through
ecosystems.
• Explain the impact of a persistent or non-biodegradable pollutant in an ecosystem.
Community & Ecosystem
A community is a group of populations living and interacting with each other in a
common habitat whereas,
An ecosystem is a community and the physical environment with which it interacts.
Species 1 Species 2
Species 3
Abiotic environment
Some notes on ecosystems
Ecosystems are units of study thus, the size is delimited by the investigator. Hence, they
may be of varying sizes, ranging from a drop of water to a pot with a flower to a rainforest.
Ecosystems do not exist independently but interact to make up the biosphere.
Biosphere is the part of the Earth and its atmosphere where living organisms exist, including
parts of the lithosphere, the hydrosphere and the atmosphere. Also called ecosphere.
http://www.tabletsmanual.com/img/wiki/drop_of_water.jpg
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Types of ecosystems
There are three main types of ecosystems:
• Marine
• Terrestrial
• Freshwater
http://www.laboratoryequipment.com/sites/laboratoryequipment.com/files/legacyimages/Resources/Laboratory_News/032612_fisheries.jpg
http://danielisland.com/wp-content/uploads/2017/03/Salt-Marsh.jpg
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Types of ecosystems
There are three main types of ecosystems:
• Marine
• Terrestrial
• Freshwater
http://blogs.dctc.edu/laht/files/2009/12/csprairietwolg.jpg
http://danielisland.com/wp-content/uploads/2017/03/Salt-Marsh.jpg
http://cdn-image.travelandleisure.com/sites/default/files/styles/1600x1000/public/1498168552/el-yunque-national-rainforest-tropical-puerto-rico-TROPICALPLANTS0617.jpg?itok=AY97tSbV
Prairie
Taiga
Rain
forest
Types of ecosystems
There are three main types of ecosystems:
• Marine
• Terrestrial
• Freshwater
http://justfunfacts.com/wp-content/uploads/2016/05/yangtze-river.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Ugandan_fishing_boats.jpg/1280px-Ugandan_fishing_boats.jpg
http://cdn-image.travelandleisure.com/sites/default/files/styles/1600x1000/public/1498168552/el-yunque-national-rainforest-tropical-puerto-rico-TROPICALPLANTS0617.jpg?itok=AY97tSbV
Yangtze
River, China
Lake Victoria,
Uganda
Lake Victoria,
Uganda
Respiration and photosynthesisPrimary producers in most ecosystems convert light energy into chemical energy in the process of
photosynthesis.
Photosynthesis produces the raw material for producing biomass.
Photosynthesis is a biological process, carried out by autotrophs (e.g., plants) which use
solar energy to synthesize complex biological molecules such as glucose, from simpler
molecules that is, carbon dioxide and water.
https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3A3a8b868ced61d4b45f5c32edabc96e70bb5f8878a26a806286eed92c%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1
For this purpose, photosynthetic pigments
such as chlorophyll are used which have the
ability to “trap” the sunlight and convert it to
chemical energy.
https://media1.shmoop.com/images/biology/biobook_photosyn_6.png
Respiration and photosynthesisThe photosynthesis reaction can be represented by the following word equation. carbon
dioxide + water → glucose + oxygen
6C02 + 6H2O C6H1206 + 6O2
chlorophyll
Carbon dioxide + water glucose +oxygen
Reactants Products
Photosynthesis
Respiration and photosynthesis can be described as processes with inputs, outputs and transformations of
energy and matter.
Solar energy is transformed in stored chemical energy.
Respiration and photosynthesisRespiration is the conversion of organic matter into carbon dioxide and water in all living organisms,
releasing energy.
Cellular respiration is a biological process where complex biological molecules are broken
down to carbon dioxide and water, releasing energy which is used for the energy
requirements of the organisms.
Energy is required for processes like movement, nutrition, excretion etc.
https://www.exploringnature.org/graphics/biology/cellular_respiration2_72.jpg
The process is carried in the cell’s
mitochondria.
https://media1.shmoop.com/images/biology/biobook_photosyn_6.png
Respiration and photosynthesisAerobic respiration can be represented by the following word equation.
glucose + oxygen → carbon dioxide + water
6C02 + 6H2OC6H1206 + 6O2
Carbon dioxide + waterglucose +oxygen
Reactants Products
Cellular respiration
Respiration and photosynthesis can be described as processes with inputs, outputs and transformations of
energy and matter.
Cellular respiration
The coupling between photosynthesis and respiration
Producers Primary producers in most ecosystems convert light energy into chemical energy in the process of
photosynthesis.
Producers have a key role in any ecosystem since they have the ability to trap the solar
energy and utilize it in order to convert simple inorganic molecules into living matter.
Since they rely entirely on themselves for meeting their energy needs they are called
autotrophs (the self-feeders)
http://www.goldiesroom.org/Multimedia/Bio_Images/05%20Nutrition/01%20Photosynthesis.gif
https://med-algae.com/wp-content/uploads/2017/08/algae-types.jpg
https://c1.staticflickr.com/3/2235/2401285296_57f4963b2d_b.jpg
Plants, algae and bacteria belong to this
groups
Photoautotrophs vs chemoautotrophsProducers (autotrophs) are typically plants or algae that produce their own food using
photosynthesis Exceptions include chemosynthetic organisms that produce food without
sunlight.
http://1.bp.blogspot.com/-RaE_tt57MT4/TiM0-w5wKwI/AAAAAAAADV0/Rn9TF20Z1Qk/s1600/hydrothermal+vents1.jpg
https://userscontent2.emaze.com/images/223af43b-4931-477f-bfc3-5c372ab39bfc/a046d5deeb2c0a8ca143815a44ab180f.jpg
http://www.marine-biotechnologie.de/files/images/riftia_1.gif
Most autotrophs are photoautotrophs meaning they use
solar energy are they main source of energy
Some bacteria are chemoautotrophs, meaning they use
chemical energy to convert simple molecules into
sugars.
A very good example are the chemosynthetic bacteria
living in a symbiotic relationship with giant tube worms
in deep sea vents.
ConsumersConsumers are heterotrophs that feed on living things by ingestion. They take in indigestedorganic material from consumers or producers.
Organisms that are unable to produce their own food and need other organisms to obtain energy and matter.
This is the reason they are called heterotrophs.
https://www.youtube.com/watch?v=xd8r9pf27v0
https://www.youtube.com/watch?v=79RvGRUdnwE
Limpet (Patella vulgata) foraging on kelp. Limpets belong to consumers.
DecomposersDecomposers obtain food and nutrients from the breakdown of dead organic matter
The decomposition of dead organic material releases nutrients which are again available in the ecosystem, mainly to the producers.
http://ww2.rspb.org.uk/Images/earthworms_tcm9-91592.jpg?width=768&height=432&crop=auto
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiX65imnInYAhUEOJoKHTCVAKUQjRwIBw&url=https%3A%2F%2F8ksfdeciduousforest.weebly.com%2Fsoil.html&psig=AOvVaw0F_t1xHF4DdEJCryU-eQRC&ust=1513331222736340
Thus decomposers have a major role in the recycling of matter to the ecosystems
They also contribute to the formation of the humus layer (decomposed organic matter)which retains:• nutrients in the soil.• humidity
Food chainsThe trophic level is the position that an organism occupies in a food chain, or the position of a group of
organisms in a community that occupy the same position in food chains.
A food chain is a graphical representation of the trophic relations between certain
species in an ecosystem. The arrows indicated the unidirectional flow of energy and
matter.
Eaten byEaten byEaten by
Food chains always begin with the producers (usually photosynthetic organisms),
followed by primary consumers (herbivores), secondary consumers and so one
Trophic levelThe trophic level is the position that an organism occupies in a food chain, or the position of a group of
organisms in a community that occupy the same position in food chains.
Food websFood webs are a more realistic representation of the feeding relations
The diets of most species are not limited to only one species. Quite the opposite,
since:
• They are seasonal changes in a diet.
• Most species do not belong to only one trophic level.
• There are developmental changes in diets.
In this image, identify the number of
food chains
and comment on the trophic level that
humans belong.
http://schoolbag.info/biology/humans/humans.files/image469.jpg
Food websFood webs are a more realistic representation of the feeding relations
Thus, food webs are complex networks of interrelated food chains.
You need to be able to:
Identify the length of all food
chains
Identify the trophic level of all
species involved
New equilibrium points if the
population of one or more
species change.
Efficiency of energy transfers within an ecosystem
Analyse the efficiency of energy transfers through a system.
All ecosystems on earth are open ecosystems supported by solar energy. The energy
is transformed to chemical energy by producers and then it flows through the living
components.
As you remember from topic 1, these transformations of energy are never 100%
efficient so much of the energy is transformed into heat.
Efficiency of energy transfers within an ecosystem
Analyse the efficiency of energy transfers through a system.
Describe the main transfers and transformations in this system’s diagram.
Ecological pyramidsEcological pyramids include pyramids of numbers, biomass and productivity and are quantitative
models that are usually measured for a given area and time.
These graphical models
demonstrate the feeding
relationships in an ecosystem
in a quantitative manner.
The surface area of each
square is indicative of the
energy, biomass, or, population
numbers.
KJ m-2 y-2Producers
Primary consumers
Secondary consumers
Tertiary consumers
Mind the units
Quantitative data for each trophic level are
drawn to scale as horizontal bars arranged
symmetrically around a central axes.
Pyramids of numbers Ecological pyramids include pyramids of numbers, biomass and productivity and are quantitative models that
are usually measured for a given area and time.
Each trophic level represents the number of individuals coexisting in an
ecosystem. Following the second law of thermodynamics the number of
individuals will be decreasing and hence, the pyramid would be narrower towards
the apex.
Producers
Prim. consumers
Sec. consumers
Tert. consumers
Number of individuals
Inverted pyramids of numbers. In
certain ecosystems, the number of
individuals at the producer level is
much lower that at the next trophic
level (e.g., in a woodland ecosystem
the number of trees is much lower than
the number of herbivorous insects)
resulting in a pyramid being upside-
down.
Pyramids of biomassEcological pyramids include pyramids of numbers, biomass and productivity and are quantitative models that
are usually measured for a given area and time.
Pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass
present at a fixed point in time, although seasonal variations may be marked
A pyramid of biomass represents the amount of (dry) organic material at each
trophic level.
Units: g m-2 or kg m-2
Producers
Prim. consumers
Sec. consumers
The usual shape is pyramid but with some exceptions, as for example, in marine ecosystems where phytoplankton (producers) is usually represented by small biomass at each time interval. Thus, at ant specific time interval x, phytoplankton may have a smaller biomass than zooplankton (secondary consumers)
340
17
0.85
173 Phytoplankton
Zooplankton
Pyramids of productivityEcological pyramids include pyramids of numbers, biomass and productivity and are quantitative models that
are usually measured for a given area and time.
A pyramid of productivity does not represent the standing stock but the rate at
which biomass or energy flow in the ecosystem.
They are always pyramid shaped .
Units are J m-2 yr-1 or gr m-2 yr-1
They are a better tool for comparing the energy flow in two ecosystems.
https://qph.ec.quoracdn.net/main-qimg-dd3e8f2c464a21ca080ffc4e47a3117f
An example from stores Pyramids of productivity refer to the flow of energy through a trophic level, indicating the rate at which that
stock/storage is being generated.
You can not compare the sales of two supermarkets by just looking at their
shelves.
The turnover rate, that is the speed by which a shop sell its products in relation to
stocks needs to be known.
This shop (image) may have already sold
the stocked products but to the eyes of
An observer it may be a shop having a very
low rate of sales.
Likewise, a pyramid of biomass depicts the
standing stock of organic mater at a given time,
while a pyramid of productivity describes the
turnover rate.
https://qph.ec.quoracdn.net/main-qimg-dd3e8f2c464a21ca080ffc4e47a3117f
https://upload.wikimedia.org/wikipedia/commons/5/5b/Empty_supermarket_shelves_before_Hurricane_Sandy%2C_Montgomery%2C_NY.jpg
173 Phytoplankton
Zooplankton
Constructing an ecological pyramid Pyramids of productivity refer to the flow of energy through a trophic level, indicating the rate at which that
stock/storage is being generated.
Producers 500 x 103 J m-2 yr-1
1st class consumers
50 x 103 J m-2 yr-1
2nd class consumers
5 x 103 J m-2 yr-1
1. Draw a rectangle for the the producers,
found at the bottom; indicate trophic
level and values with appropriate units.
2. On top of producers draw a rectangle
for 1st class consumers. Size should be
proportionate to value differences.
3. Continue with rest of trophic levels.
producers
50 x 103 J m-2 yr-1
500 x 103 J m-2 yr-1
1st class consumers
2nd class consumers 5 x 103 J m-2 yr-1
Bioaccumulation across trophic levels Bioaccumulation is the build-up of persistent or non-biodegradable pollutants within an organism or trophic
level because they cannot be broken down.
Biomagnification is the increase in concentration of persistent or non-biodegradable pollutants along a food
chain.
Toxins such as DDT and mercury accumulate along food chains due to the decrease of biomass and energy.
Biomass DDT mass
Concentration
2nd class consumers
1 kg 1 mg 1 mg/kg
1st class cons
100 kg 1 mg 1 x 10-2 mg/kg
Producers 10,000 kg 1 mg 1 x 10-5 mg/kg
Consider this food chain
Since the biomass decreases and the mass of the non-biodegradable substance remains unchanged, the concentration of the non-biodegradable substance will increase up the food chain (biomagnification)
http://www.clker.com/cliparts/4/4/8/4/11954413581415126884johnny_automatic_generic_fish.svg.hi.pnghttps://teara.govt.nz/files/di-5137-enz.gif
Case study: The Bald eagle
The bald eagle (Haliaetus leucocephalus), once common throughout
most of North America, was reduced to as few as 400 nesting pairs
in the lower 48 United States by the 1960s.
The decline of the bald eagle was caused primarily by habitat loss
and widespread use of the pesticide DDT.
Toxins accumulated in the fatty tissues of adult eagles and caused
the females to lay eggs with shells too thin to survive.
Eggs were usually crashed by hutching mothers.
This is a very good example of a top predator (top of the food chain)
suffering from the biomagnification of a non-biodegradable pesticide.
The bald eagles were consuming smaller preys for long periods of
time thus accumulating DDT in their fatty tissues.
http://www.bagheera.com/wp-content/uploads/2014/01/bald_eagle_2011.jpg
https://goo.gl/images/uSVAfg
Case study: Minamata bay
• Minamata is a small town in Japan, known for the Chisso
factory producing fertilizers and plastics.
• Between 1932 and 1968, Chisso factory released more
than
• 20 tones of mercury and methylmercury in Minamata Bay.
• In the early 50s, people in the Minamata area started
suffering from mercury poisoning, due to the consumption
of seafood, mainly shellfish, that had been accumulating
mercury.
https://www.google.gr/maps/place/Minamata,+Kumamoto+Prefecture,+Japan/@32.6115314,130.619745,5z/data=!4m5!3m4!1s0x353fa336b868fd75:0xbcbb57ce5b5109de!8m2!3d32.2145158!4d130.4073698?hl=en
https://www.canada.ca/content/dam/eccc/migration/main/mercure-mercury/D721AC1F-4446-4E44-A13E-3845A7FAF7D7/i-f-bom-e.jpg
http://america.aljazeera.com/content/ajam/articles/2014/8/29/grassy-narrows-mercuryminimata/jcr:content/headlineImage.adapt.1460.high.minamata_japan_ontario_082914.1411404893479.jpg
Top carnivores
• In any food chain, top carnivores usually have small numbers due to the limited available energy
and thus, biomass.
• Furthermore, their diets are usually limited and thus any change in their food prey has a strong
effect on their survival rates. Thus, top carnivores are less resilient to change.
• Bioaccumulation and biomagnification also pause the populations of the top predators to a risk.
• Case study: Crash of the peregrine falcon populations in the UK during the 50s due to the
extensive use of DDT. After the non-biodegradable chemical were banned in the 60s the
populations started to recover.
https://res.cloudinary.com/dk-find-out/image/upload/q_80,w_1920,f_auto/Food_web_keclt8.jpg
https://youtu.be/QTV3XFHzvT4
References
Andrew, Davis, et al. Pearson Baccalaureate Environmental Systems And Societies For The Ib Diploma.
Rutherford, Jill. Environmental Systems and Societies. Oxford University Press, 2015.