IB Biology Ecology Optional Topic C 2015

Essential idea: The continued survival of living organisms
including humans depends on sustainable communities.
4.1 Species, communities and ecosystems

The Earth as seen from Saturn's rings
The Earth

Understandings
Statement Guidance
4.1 U.1 Species are groups of organisms that can potentially interbreed to produce
fertile offspring.
4.1 U.2 Members of a species may be reproductively isolated in separate
populations.
4.1 U.3 Species have either an autotrophic or heterotrophic method of nutrition (a
few species have both methods).
4.1 U.4 Consumers are heterotrophs that feed on living organisms by ingestion
4.1 U.5 Detritivores are heterotrophs that obtain organic nutrients from detritus by
internal digestion.
4.1 U.6 Saprotrophs are heterotrophs that obtain organic nutrients from dead
organisms by external digestion.
4.1 U.7 A community is formed by populations of different species living together
and interacting with each other.
4.1 U.8 A community forms an ecosystem by its interactions with the abiotic
environment.
4.1 U.9 Autotrophs obtain inorganic nutrients from the abiotic environment.
4.1 U.10 The supply of inorganic nutrients is maintained by nutrient cycling.
4.1 U.11 Ecosystems have the potential to be sustainable over long periods of time.

Applications and Skills
Statement Guidance
4.1 S.1 Classifying species as autotrophs, consumers,
detritivores or saprotrophs from a knowledge of
their mode of nutrition.
4.1 S.2 Setting up sealed mesocosms to try to establish
sustainability. (Practical 5)
Mesocosms can be set up in open tanks, but
sealed glass vessels are preferable because
entry and exit of matter can be prevented but
light can enter and heat can leave. Aquatic
systems are likely to be more successful than
terrestrial ones.
4.1 S.3 Testing for association between two species
using the chi-squared test with data obtained by
quadrat sampling
To obtain data for the chi-squared test, an
ecosystem should be chosen in which one or
more factors affecting the distribution of the
chosen species varies. Sampling should be
based on random numbers. In each quadrat
the presence or absence of the chosen species
should be recorded.
4.1 S.4 Recognizing and interpreting statistical
significance.

• BiosphereBiosphere
• EcosystemEcosystem is a compilation of both biotic and
abiotic factors, how organisms interact with
their environment.
• CommunityCommunity of different species in the same area
which are interacting
• PopulationPopulation group of organisms of the same
species who live in the same area at the same
time
• Individuals speciesIndividuals species
HabitatHabitat is the environment in which a species
normally lives or the location of a living organism

Distinguish between
autotroph and heterotroph.
• Autotrophs are capable of making their
own organic molecules from inorganic
molecules as a food source (a.k.a.
producers); Examples?
• Heterotrophs – cannot make their own
food and must obtain organic molecules
from other organisms (a.k.a. consumers);
Examples?

Consumers ingest organic matter which is living or recently killed
food chains show the flow of energy through the trophic levels of a
feeding relationship.

Decomposers
Two Types
• Detritivores (Ingest, then digest) ingests non-living organic
matter
• Saprotrophs (Digest first, then absorb) live in or on non-
living matter, secreting digestive enzymes into it and
absorbing digestive products
SaprotrophsDetritivores

Trophic Levels of Feeding Groups
• Ecologists divide the species in a community or
ecosystem into trophic levels based on their main source
of nutrition.
• Primary producers- autotrophs- produce their own
energy source.
• Photoautotrophs- derive energy via
photosynthesis- plants
• Chemoautotrophs- use energy stored in chemical
bonds- Sulfur

Trophic Levels
Consumers- heterotrophs- derive energy from consuming
other organisms
• 1° consumer- eat producers
• 2° consumer- eats herbivores- 1° consumer
• 3° consumer- eats 2° and 1° consumers
Decomposers- consume dead material- recycle nutrients back
to the environment- Saprotroph

Overview of energy & nutrient dynamics

• Energy cannot be recycled  must be constantly
supplied to an ecosystem (mostly by SUNSUN)
• The autotrophs (“self feeders”) are the primary
producers, and are usually photosynthetic (plants
or algae).
– They use light energy to synthesize sugars and other
organic compounds.
4.2 U.2 Light energy is converted to chemical energy in carbon
compounds by photosynthesis.

Heterotrophs are at
trophic levels above the
Primary producers and
depend on their photosynthetic
output.
4.2 U.3 Chemical energy in carbon compounds flows through food
chains by means of feeding

Energy transfer between trophic levels is typically
only 10% efficient
• Production efficiency: only
fraction of E stored in food
• Energy used in respiration
is lost as heat
• Energy flows (not cycle!)
within ecosystems
4.2 U.4 Energy released from carbon compounds by respiration is used
in living organisms and converted to heat.

Trophic Levels
Notice that only 10% is moved to the next level.
Where does the rest go?

THE 10% RULE
and
ECOLOGICAL
PYRAMID

Energy Flow Through Ecosystems

• Shows more complex interactions
between species within a community/
ecosystem
• More than one producer supporting a
community
• A consumer may have a number of
different food sources on the same or
different trophic levels
Food webFood web

What are the factors that effect an ecosystem?
• Abiotic (nutrients and energy)
• Biotic individual organisms that live in that
ecosystem

Factors controlling and ecosystem
I. Nutrients (Closed System)
II. Energy (Open System)
III. Interactions between species

4.3 Carbon cycling
• Essential idea: Continued availability of carbon in
ecosystems depends on carbon cycling.

Understandings
Statement Guidance
4.3 U.1 Autotrophs convert carbon dioxide into carbohydrates and other
carbon compounds.
4.3U.2 In aquatic ecosystems carbon is present as dissolved carbon dioxide and
hydrogen carbonate ions.
4.3 U.3 Carbon dioxide diffuses from the atmosphere or water into autotrophs.
4.3 U.4 Carbon dioxide is produced by respiration and diffuses out of organisms
into water or the atmosphere.
4.3 U.5 Methane is produced from organic matter in anaerobic conditions by
methanogenic archaeans and some diffuses into the atmosphere or
accumulates in the ground.
4.3 U.6 Methane is oxidized to carbon dioxide and water in the atmosphere.
4.3 U.7 Peat forms when organic matter is not fully decomposed because of
acidic and/or anaerobic conditions in waterlogged soils.
4.3 U.8 Partially decomposed organic matter from past geological eras was
converted either into coal or into oil and gas that accumulate in porous
rocks.
4.3 U.9 Carbon dioxide is produced by the combustion of biomass and fossilized
organic matter.
4.3 U.10 Animals such as reef-building corals and mollusca have hard parts that
are composed of calcium carbonate and can become fossilized in
limestone.

Statement Guidance
4.3 A.1 Estimation of carbon fluxes due to processes in
the carbon cycle.
Carbon fluxes should be measured in
gigatonnes.
4.3 A.2 Analysis of data from air monitoring stations to
explain annual fluctuations.
4.3 S.1 Construct a diagram of the carbon cycle.

Essential idea: Soil cycles are
subject to disruption.
C.6 The nitrogen and phosphorus cycles (AHL)
http://www.agricorner.com/wp-content/uploads/2013/09/urea-caf.jpg

Understandings, Applications and Skills
Statement Guidance
C.6 U.1 Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.
C.6 U.2 Rhizobium associates with roots in a mutualistic relationship.
C.6 U.3 In the absence of oxygen denitrifying bacteria reduce nitrate in the soil.
C.6 U.4 Phosphorus can be added to the phosphorus cycle by application of
fertilizer or removed by the harvesting of agricultural crops.
C.6 U.5 The rate of turnover in the phosphorus cycle is much lower than the
nitrogen cycle.
C.6 U.6 Availability of phosphate may become limiting to agriculture in the future.
C.6 U.7 Leaching of mineral nutrients from agricultural land into rivers causes
eutrophication and leads to increased biochemical oxygen demand.
C.6 A.1 The impact of waterlogging on the nitrogen cycle.
C.6 A.2 Insectivorous plants as an adaptation for low nitrogen availability in
waterlogged soils.
C.6 S.1 Drawing and labelling a diagram of the nitrogen cycle.
C.6 S.2 Assess the nutrient content of a soil sample.

I. Nutrient Cycles ThroughI. Nutrient Cycles Through
EcosystemsEcosystems
Biogeochemical cyclesBiogeochemical cycles are cycles of matter between the
abiotic and the biotic components of the environment
• The carbon, nitrogen, and phosphorus cycles are
central to life on Earth
• Carbon and nitrogen cycles have atmospheric
components, and cycle on a global scale
• Phosphorus has no atmospheric component, and
cycles on a local scale

Very few types of organism play a role
in the cycling of nutrients
Saprotrophic Bacteria
cycle Nitrogen
Fungi Cycle Carbon

Carbon Cycle
• Is exchanged of the element carbon among the
biosphere. Or geosphere, hydrosphere, and
atmosphere of the Earth.
• Carbon interconnected by pathways of exchange with
these reservoirs is mainly through plants .

Carbon Cycle
Carbon cycle diagrams vary greatly in the detail they contain. This one shows not only the sinks
and the flows, but also estimates carbon storage and movement in gigatons/year.

You need to be able to produce a simplified carbon cycle. Use the
following sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere
and hydrosphere
(oceans)
Carbon
compounds in
fossil fuels
Carbon compounds
in producers
(autotrophs)
Carbon
compounds in
consumers
Carbon compounds
in dead organic
matter
Key:
Sink
Flux
n.b. some of the fluxes will need to be used more than once.
Cell respiration
Photosynthesis
Combustion
FeedingEgestion
Death
Incomplete
decomposition &
fossilization

You need to be able to produce a simplified carbon cycle. Use the following
sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere and
hydrosphere (e.g. oceans)
Carbon compounds
in fossil fuels
Carbon compounds in
producers (autotrophs)
Carbon compounds
in consumers
Carbon compounds in
dead organic matter
Key:
Sink
Flux
Cell respiration
Photosynthesis
Combustion
Feeding
Egestion
Death
Incomplete
decomposition &
fossilisation
Cellrespiration
Combustion
Cellrespiration
Feeding
Death
Feeding

You need to be able to produce a simplified carbon cycle. Use the following
sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere and
hydrosphere (e.g. oceans)
Carbon compounds
in fossil fuels
Carbon compounds in
producers (autotrophs)
Carbon compounds
in consumers
Carbon compounds in
dead organic matter
Key:
Sink
Flux
Cell respiration
Photosynthesis
Combustion
Feeding
Egestion
Death
Incomplete
decomposition &
fossilisation
Cellrespiration
Combustion
Cellrespiration
Feeding
Death
Feeding
Use the video to help practice
your drawing skills*
*this is a good resource, but there is one mistake in the video –
carbon is egested, when not digested by an organism, not excreted.

Extend your understanding:
1.Between which sinks would you add a flux showing volcanoes
and the weathering of rocks?
2.What additional sink would you add to show the role of corals
and shellfish? What additional flux would be needed?
3.In some environments water is unable to drain out of soils so
they become waterlogged and anaerobic. This prevents the
decomposition of dead organic matter forming peat deposits
[4.3.U7]. Peat can be dried and burnt as a fuel. Suggest how peat
could be added to the carbon cycle.
4.Explain why fossil fuels are classified as non-renewable
resources when the carbon cycle indicates they are renewed
(hint: refer to the pictorial carbon cycle).
5.Diffusion is a flux that moves CO2 from the atmosphere to the
hydrosphere and back again. Taken together these fluxes are
largest in the cycle suggest why.

4.3 U.1 Autotrophs convert carbon dioxide into carbohydrates and
other carbon compounds.
http://www.earthtimes.org/newsimage/photosynthesis-dream-renewable-energy_1_02842012.jpg
n.b. Although most autotrophs fix
carbon by photosynthesis. A few are
Chemoautotrophs and fix carbon by
utilising the energy in the bonds of
inorganic compounds such as hydrogen
sulfide.
All autotrophs however convert carbon dioxide (from the atmosphere or
dissolved in water) or into organic compounds.
Plant initially synthesis sugars
(e.g. glucose) which are then
converted into other organic
compounds such as:
•complex carbohydrates e.g.
starch, cellulose
•lipids
•amino acids

4.3 U.2 In aquatic ecosystems carbon is present as dissolved carbon
dioxide and hydrogen carbonate ions.
CO2 + H2O → H2CO3 → H+
+ HCO3
–
Both dissolved carbon dioxide and hydrogen
carbonate ions are absorbed by aquatic plants
and other autotrophs that live in water.
H+
ions explains how
carbon dioxide reduces
the pH of water.
Some CO2 will directly
dissolve in water, but most
will combine with water to
become carbonic acid.
CO2 + H2O → H2CO3 → H+
+ HCO3
–

4.3 U.3 Carbon dioxide diffuses from the atmosphere or water into
autotrophs
http://www.kbg.fpv.ukf.sk/studium_materialy/morfologia_rastlin/webchap10epi/web10.3-6.jpg
Transverse section of parsnip leaf (Pastinaca sativa)
CO2 from outside the leaf
diffuses down the concentration
gradient into the leaf
Photosynthesis uses CO2 keeping the
concentration of CO2 inside the leaf low
High
CO2Concentration
gradient
CO2Concentration
gradient
Low
CO2 moves through stomata openings
in the leaves of land plants*
atmosphere or water
Inside the leaf
atmosphere or water
Plants must have a constant supply of carbon dioxide (CO2) to continually photosynthesize

4.3 U.4 Carbon dioxide is produced by respiration and diffuses out of
organisms into water or the atmosphere.
In terms of the carbon cycle three main categories of organisms carry out
respiration:
•autotrophs, e.g. plants
•heterotrophs, e.g. animals
Organisms carry out respiration to release energy in the form of ATP.
Carbon dioxide is a waste product of cell respiration
http://ib.bioninja.com.au/_Media/cell_respiration_summary.jpeg

4.3 U.7 Peat forms when organic matter is not fully decomposed
because of acidic and/or anaerobic conditions in waterlogged soils.
Partially decomposed organic matter can be compressed to form brown
soil-like peat. Once dried peat burns easily and can be used as a fuel.
Peat is a highly effective carbon sink, it is
estimated that the world’s peat contains
550 Gt of carbon (International Mire
Conservation Group, 2007-01-03) http://commons.wikimedia.org/wiki/File:Peat-bog-Ireland.jpg
http://commons.wikimedia.org/wiki/File:Toppila_power_plant.JPG
Toppila Peat-Fired Power Plant in Oulu, Finland

• In soils organic matter, e.g.
dead leaves, are digested by
saprotrophic bacteria and
fungi.
• Saprotrophs assimilate some
carbon for growth and release
as carbon dioxide during
aerobic respiration (requiring
O2).
• Waterlogged soils are an
anaerobic environment leaving
these organisms unable to
complete the process.
• Large quantities of (partially
decomposed) organic matter
build up. The organic matter is
compressed to form peat

4.3.U7 Peat forms when organic matter is not fully decomposed
because of acidic and/or anaerobic conditions in waterlogged soils.
Saprotrophs assimilate some carbon for
growth and release as carbon dioxide during
aerobic respiration.
Aerobic respiration
requires oxygen
Waterlogged soils are an
anaerobic environment
Partial
decomposition
causes acidic
conditions
saprotrophs and
methanogens [4.3.U5] are
inhibited
Organic matter is only
partially decomposed
Large quantities of
(partially decomposed)
organic matter build up.
The organic matter is
compressed to form peat
http://commons.wikimedia.org/wiki/File:Peat-bog-Ireland.jpg
Organic matter

http://commons.wikimedia.org/wiki/File:Coal_lump.jpg
Coal is formed when deposits of peat are buried under other sediments.
The peat is compressed and heated over millions years eventually
becoming coal.

http://commons.wikimedia.org/wiki/File:Coal_lump.jpg
4.3 U.8 Partially decomposed organic matter from past geological eras was converted
either into coal or into oil and gas that accumulate in porous rocks.
The cycle of sea-level changes that happened during the Carboniferous period caused costal
swamps to be buried promoting the formation of coal.

Carboniferous
• Extended from 359 million years ago, to the about 299.
• A time of glaciation, low sea level and mountain building. With many
beds of coal were laid down all over the world during this period.

Carboniferous period
• The world’s large coal deposits
occurred during this time
period
Two factors
1. The appearance of bark-
bearing trees (containing bark
fiber lignin).
2. Lower sea levels
• Development of extensive
lowland swamps and forests.
• Large quantities of wood were
buried during this period.
• Animals and decomposing
bacteria had not yet evolved
that could effectively digest
the new lignin.

Basidiomycetes (fungi)
• Appear 290 million years ago. They can degrade it Lignin. The
substance is insoluble, to heterogeneous because of specific
enzymes, and toxic, they are one of the few organisms that can.
http://andreas-und-angelika.de/galleries/andreas/2014-
05_Autumn_Colours/photos/aka-Autumn-Colours-2014-04-
19__D8X7633.jpg

4.3 U.8 Partially decomposed organic matter from past geological eras was converted either into
coal or into oil and gas that accumulate in porous rocks.
http://commons.wikimedia.org/wiki/File:Oil_well.jpg
http://www.agiweb.org/education/energy/images/oildrill.png
Conditions are anaerobic
and so decomposition is
only partial.
Methane forms the
largest part of natural
gas.
The mixture of different
types of oil and gas is
the result of complex
chemical changes.
oil and gas formation occurred in ancient oceans

4.3 U.10 Animals such as reef-building corals and Mollusca have hard parts that are
composed of calcium carbonate and can become fossilized in limestone.
http://commons.wikimedia.org/wiki/File:Fossils_in_a_beach_wall.J
When the animals die the soft body parts decompose, but the calcium carbonate remains to
form deposits on the ocean floor.

4.3 U.10 Animals such as reef-building corals and Mollusca have hard parts that are
composed of calcium carbonate and can become fossilized in limestone.
• Some animals secrete calcium
carbonate (CaCO3) structures to
protect themselves:
 Shells of mollusks
 Hard corals exoskeletons
• When the animals die the soft
body parts decompose, but the
calcium carbonate remains to form
deposits on the ocean floor.
• The deposits are buried and
compressed and eventually form
limestone rock
• Imprints of the hard body parts
remain in the rock as fossils.
• Limestone rock is a huge carbon
sink

Essential idea: Soil cycles are subject to disruption.
Nitrogen cycle

C.6 U.1 Nitrogen-fixing bacteria convert atmospheric nitrogen to
ammonia.
Nitrogen gas Ammonia (NH3)
Nitrites (NO2
-
)nitrates (NO3
-
)
Rhizobium & Azotobacter
Nitrobacter*
*Bacteria can be chemoautotrophs deriving
energy (for carbon fixation) from the bonds in
the compounds they convert.
Nitrosomonas*
The roles of
bacteria in
nitrogen fixation
http://en.wikipedia.org/wiki/File:Azotobacter_cells.jpg
Plants cannot directly
absorb and assimilate
nitrogen. It must be first
converted to
compounds such as
nitrates and ammonia.
http://on.be.net/1arnCUH
nitrogen fixation
Nitrification is the process of
converting ammonia into nitrates

http://commons.wikimedia.org/wiki/File:French_bean_plant_from_lalbagh_2336.JPG
• Mutualism describes
relationships between
organisms in which both
organisms benefit.
• The legume supplies
carbohydrates to the
bacteria. The bacteria use
the carbohydrates for
processes such as
respiration.
• The bacteria supply
ammonia (fixed from
atmospheric nitrogen) to
the legume.
• The legume requires
ammonia for the synthesis
of amino acids.

http://commons.wikimedia.org/wiki/File:Nitrogen-fixing_nodules_in_the_roots_of_legumes..JPG
• Azotobacter are
free-living in the
soil whereas
bacteria of the
genus Rhizobium
are often not free-
living but live in a
close symbiotic
association in the
roots of plants
such as the legume
family.
• Legumes and the
Rhizobium grow
together to form
nodules on the
roots of the
legume.

C.6 U.3 In the absence of oxygen denitrifying bacteria reduce nitrate in
the soil.
• Electron transport is a key process in
cellular respiration
• Oxygen or nitrate can be used as an
electron acceptor in electron
transport.
• Though oxygen is preferred in oxygen
poor conditions nitrate is used and
the process releases nitrogen gas a
product.
Denitrification reduces the availability of nitrogen compounds to plants.
Nitrate (NO3
-
) Nitrogen (N2)
A chemical reduction process
carried out by bacteria
e.g. Pseudomonas sp.
http://microbewiki.kenyon.edu/index.php/File:P._Cloroaphis.jpg

C.6 A.1 The impact of waterlogging on the nitrogen cycle.
http://www.hampshirecam.co.uk/feb909_2.html

http://soer.justice.tas.gov.au/2009/image/1076/lan/id1076-p-SoilDegradationWaterlo-l.Jpg
• Soil can become inundated by water, waterlogged, through flooding or
irrigation with poor drainage.
• Waterlogging reduces the oxygen availability in soils.
• This encourages the process of denitrification by bacteria, e.g. Pseudomonas
sp.
• n.b. excess water in the soil also leads to greater leaching of nutrients, which leads
to nutrient enrichment of rivers and lakes and therefore to eutrophication.

C.6 A.2 Insectivorous plants as an adaptation for low nitrogen
availability in waterlogged soils.
http://botany.org/Carnivorous_Plants/
Drosera sp. - the Sundews
Find out more
• Modified leaves have evolved to trap insects.
• Enzymes are secreted to (extracellular) digest
the animal.
• The products of digestion are absorbed by the
modified leaves.
“Carnivorous plants have the most bizarre
adaptations to low-nutrient environments.
These plants obtain some nutrients by
trapping and digesting various invertebrates,
and occasionally even small frogs and
mammals. Because insects are one of the
most common prey items for most
carnivorous plants, they are sometimes called
insectivorous plants. It is not surprising that
the most common habitat for these plants is
in bogs and fens, where nutrient
concentrations are low but water and
sunshine seasonally abundant.”

http://i.telegraph.co.uk/multimedia/archive/01464/plant-5_1464520i.jpg
Insectivorous plants cannot be truly considered carnivorous as only nitrogen compounds
are absorbed. The plant still obtains it’s energy from light via photosynthesis.

adapted from: http://commons.wikimedia.org/wiki/File:Nitrogen_Cycle.jpg#mediaviewer/File:Nitrogen_Cycle.svg
On this diagram the pools (boxes) and fluxes (arrows) have been drawn on already. Add in the
processes and state the bacteria related to the some of the processes.
Rhizobium
free-living
nitrogen-fixing
bacteria in the
soil
Azotobacter
Mutualistic nitrogen-fixing
bacteria in root nodules
Nitrification (x2)
Nitrosomonas
Nitrobacter
Uptake (by active transport)
and assimilation by plants
Natural nitrogen
fixation by lightning
Application of fertilizers
containing nitrogen (fixed
by the Haber process)
Transfer by
the food
chain
Denitrification
Pseudomonas
Death &
decomposition
Ammonification
Excretion

free-living nitrogen-
fixing bacteria in the soil
Azotobacter
Mutualistic
nitrogen-fixing
bacteria in
root nodules
Nitrification
Nitrobacter
Uptake (by active
transport) and
assimilation by
plants
Natural
nitrogen
fixation by
lightning
Application of
fertilizers
containing
nitrogen (fixed by
the Haber process)
Transfer by
the food
chain
Denitrification
Pseudomonas
Death &
decomposition
Ammonification
Excretion
Nitrification
Nitrosomonas
Rhizobium

Essential idea: Soil cycles are subject to disruption.
We consume phosphorus through food produced with fertilizers. The women above is spreading
phosphorus by hand in her rice paddy to increase production..
Phosphorus cycles
http://www.futureearth.org/blog/2014-oct-16/can-we-build-sustainable-phosphorus-governance

C.6 U.5 The rate of turnover in the phosphorus cycle is much lower than
the nitrogen cycle.
http://commons.wikimedia.org/wiki/File:Phosphorus_cycle.png

C.6 U.5 The rate of turnover in the phosphorus cycle is much lower than
the nitrogen cycle.
The phosphorous cycle shows the various different forms in which phosphorous can
naturally be found.
•Certain rocks, e.g. Phosphorite, contains high levels of phosphate minerals.
Weathering of these rocks releases phosphates into the soil. Phosphates are a form
of phosphorus that can is easily be absorbed by plants entering the food chains.
•The rate of turnover is relatively slow, compared with Nitrogen, as phosphate is only
slowly released to ecosystems by weathering.
•Organisms have a variety of uses for phosphate
 ATP
 DNA and RNA
 cell membranes
 skeletons in vertebrates

C.6 U.4 Phosphorus can be added to the phosphorus cycle by application of fertilizer
or removed by the harvesting of agricultural crops.
• Phosphate is mined and converted to
phosphate-based fertilizer – this increase
the rate of turnover.
• The fertilizer is then (transported great
distances and) applied to crops . The
processes remove phosphorus from the
cycle in one location and adds it to
another.
http://commons.wikimedia.org/wiki/File:Agriculture_in_Volgograd_Oblas
http://commons.wikimedia.org/wiki/File:Phosphate_Mine_Panorama.jpg

C.6 U.6 Availability of phosphate may become limiting to agriculture in the future.
• The demand for artificial fertilizer
in modern intensive farming is very
high.
• Consequently phosphate mining is
being carried out at a much faster
rate than the rocks can be
naturally formed and hence
replenished.
Impacts to agriculture of reduced
phosphate production are
potentially great.
• There are no sources of phosphate
fertilizer other than mining
minerals.
• There is no synthetic way of
creating phosphate fertilizers*,
though this may change in the
future.
*Yields per unit of farmland
would plummet without the
*Unlike ammonia which can be created by the
industrial conversion of plentiful supplies of
atmospheric nitrogen.
http://commons.wikimedia.org/wiki/File:Crop_spraying_near_
St_Mary_Bourne_-_geograph.org.uk_-_392462.jpg

http://commons.wikimedia.org/wiki/File:Phosphateproductionworldwide.svg
The graph is based on US Geological Survey data and shows world phosphate
production from mining.
World production has
varied greatly, but
overall there have been
smaller increases to
production after than
before 1980.
As the reserves of phosphate rock are depleted the production of phosphorous is likely to
peak and then decline. Though some sources the peak is likely to occur in in the next 30 years
it is difficult to judge particularly due to the fact new phosphate mineral deposits are still being
discovered.
millions of
Metric tons
C.6 U.6 Availability of phosphate may become limiting to agriculture in
the future.

http://commons.wikimedia.org/wiki/File:Potomac_green_water.JPG
An increase in nutrients in aquatic ecosystems leads to eutrophication

http://nroc.mpls.k12.mn.us/Environm
• Rainfall leaches water-soluble
nutrients (e.g. phosphates,
ammonia and nitrates) from the
soil and carries them into rivers
and lakes.
• The nutrients can come either
from artificial fertilizers, natural
fertilizer such as manure or the
urine of livestock.
• Poorly drained, or waterlogged
soils encourages leaching of these
materials.
• An increase in nutrients in aquatic
ecosystems leads to
eutrophication a negative
environmental effect that could
include hypoxia, the depletion of
oxygen in the water, which may
cause death to aquatic animals.

In summary:
•Algal growth is normally limited by the availability of nutrients such as
nitrates and phosphates
•Rapid growth in the algal populations occurs, these increases are called ‘algal
blooms’ also leading to an increase so naturally does the numbers of dead
algae
•the numbers of (saprotrophic) bacteria and microbes that feed on the dead
algae also increase
•an increase in biochemical oxygen demand (BOD) by the saprotrophic
bacteria results in deoxygenation of the water supply (reduced dissolved O2)
The consequences to organisms of low levels of dissolved oxygen:
•death or emigration of oxygen sensitive organisms (e.g. fish)
•proliferation of low dissolved O2 tolerant organisms
•reduction of biodiversity
•decrease in water transparency, i.e. an increase in turbidity stresses
photosynthetic organisms …
•… this in turn will affect the whole food chain
•increased levels of toxins and greater numbers of pathogens means affected
water is no longer suitable for bathing or drinking

Red tide on Long Island has lead to eutrophication.

C.6 S.2 Assess the nutrient content of a soil sample.
Guidance on proper use of tests
and limitations of simple home
test kits:
http://www.ext.colostate.edu/mg/ga
Garden supply companies commonly sell soil quality assessment kits. The kits involve adding a
chemical to a sample of soil that reacts with the nutrient in question, if present. A colour is
produced that can be visually compared to a key.
An example kit from Urban Farmer:
http://www.ufseeds.com/Premium-Soil-Test-Kit.item

Essential idea: Ecosystems require a continuous supply of
energy to fuel life processes and to replace energy lost as heat.
4.2 Energy flow

Understandings
Statement Guidance
4.2 U.1 Most ecosystems rely on a supply of energy
from sunlight.
4.2 U.2 Light energy is converted to chemical energy
in carbon compounds by photosynthesis.
4.2 U.3 Chemical energy in carbon compounds flows
through food chains by means of feeding
The distinction between energy flow in ecosystems
and cycling of inorganic nutrients should be stressed.
Students should understand that there is a continuous
but variable supply of energy in the form of sunlight
but that the supply of nutrients in an ecosystem is
finite and limited.
4.2 U.4 Energy released from carbon compounds by
respiration is used in living organisms and
converted to heat.
4.2 U.5 Living organisms cannot convert heat to other
forms of energy.
4.2 U.6 Heat is lost from ecosystems.
4.2 U.7 Energy losses between trophic levels restrict
the length of food chains and the biomass of
higher trophic levels.
Pyramids of number and biomass are not required.
Students should be clear that biomass in terrestrial
ecosystems diminishes with energy along food chains
due to loss of carbon dioxide, water and other waste
products, such as urea.

Statement Guidance
4.2 S.1 Quantitative representations of energy flow
using pyramids of energy.
Pyramids of energy should be drawn to scale
and should be stepped, not triangular. The
terms producer, first consumer and second
consumer and so on should be used, rather
than first trophic level, second trophic level
and so on.

C.2 Communities and Ecosystems
Essential idea: Changes in community
structure affect and are affected by organisms.

Understandings
Statement Guidance
C.2 U.1 Most species occupy different trophic levels in multiple food
chains.
C.2 U.2 A food web shows all the possible food chains in a community.
C.2 U.3 The percentage of ingested energy converted to biomass is
dependent on the respiration rate.
C.2 U.4 The type of stable ecosystem that will emerge in an area is
predictable based on climate.
C.2 U.5 In closed ecosystems energy but not matter is exchanged with
the surroundings.
C.2 U.6 Disturbance influences the structure and rate of change within
ecosystems.

Statement Guidance
C.2 A.1 Conversion ratio in sustainable food production
practices.
C.2 A.2 Consideration of one example of how humans
interfere with nutrient cycling.
C.2 S.1 Comparison of pyramids of energy from different
ecosystems.
C.2 S.2 Analysis of a climograph showing the relationship
between temperature, rainfall and the type of
ecosystem.
C.2 S.3 Construction of Gersmehl diagrams to show the
inter-relationships between nutrient stores and
flows between taiga, desert and tropical rainforest.
C.2 S.4 Analysis of data showing primary succession.
C.2 S.5 Investigation into the effect of an environmental
disturbance on an ecosystem.
Examples of aspects to
investigate in the ecosystem
could be species diversity,
nutrient cycling, water
movement, erosion, leaf area
index, among others.

II. Energy (Open system on Earth)

Sunlight is the initial energy source for
almost all communities
• Energy flows through the food chain, being lost at each
stage due to respiration.

Pyramids of energy
• Show the flow of energy between trophic levels
• Measured in units of energy per unit area per unit time. KJ m-2
y-1
• The transfer of energy is never 100% efficient

Energy Flow through the Ecosystem

• The conversion of light energy into energy stored in
chemical bonds within plant tissue. Primary
production results in the addition of new plant
biomass to the system.
• Two types
• Net Primary Production
• Gross Primary Production.
Primary ProductionPrimary Production

Primary Productivity
•The most productive terrestrial areas are tropical rain
forests; least productive are deserts

NPP = GPP - R
• Gross Primary Production (GPP)Gross Primary Production (GPP) is the amount of light
energy that is converted to chemical energy by
photosynthesis per unit time.
• Net Primary Production (NPP)Net Primary Production (NPP) is equal to gross primary
production minus the energy used by the primary
producers for respiration (R). Which will be the total
energy available to all the other living things in that
ecosystem

Biomass
• Biomass is the total dry mass of organic matter in
the organisms or ecosystem.
• By measuring biomass of an ecosystem we can
see how productive it is and compare this to
other ecosystems of past data

Pyramids of BiomassPyramids of Biomass

C.2 A.1 Conversion ratio in sustainable food production practices.
In commercial (animal) food production, farmers measure the food conversion ratio
(FCR). It is a measure of an animal's efficiency in converting feed mass into the desired output.
For dairy cows, for example, the output is milk, whereas animals raised for meat, for example,
pigs the output is the mass gained by the animal.
mass of the food eaten (g)
(increase in) desired output (g)
(per specified time period)FCR =
http://en.wikipedia.org/wiki/Feed_conversion_ratio
Animal FCR
Beef Cattle 5 - 20
Pigs 3 - 3.2
Sheep 4 - 6
Poultry 1.4 - 2
Salmon 1.2 - 3
The lower the FCR the more efficient
the method of food production.
It is calculated by:

http://en.wikipedia.org/wiki/Feed_conversion_ratio
Animal FCR
Beef Cattle 5 - 20
Pigs 3 - 3.2
Sheep 4 - 6
Poultry 1.4 - 2
Salmon 1.2 - 3
A good (low) FCR is obtained by
minimizing the losses of energy by
respiration, for example:
•Restricting animal movement
•Slaughtering the animal at a young age
(older animals have higher FCRs as they
grow more slowly)
•Optimizing feed so it is efficiently
digested
How ethical are the practices that lead to a low FCR?
What is more important, efficient food production or the ethical
treatment of animals?
C.2 A.1 Conversion ratio in sustainable food production practices.

C.2 S.1 Comparison of pyramids of energy from different ecosystems.

source of data: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NetProductivity.html
To
understand
why analyze
the energy
pyramids of
the different
ecosystems.
Net productivity of different ecosystems varies greatly

1. High primary
productivity (by
producers) means
more energy is
available to the
ecosystem.
3. Higher the primary productivity and greater the
efficiency of energy transfer mean that more energy is
available at high trophic levels. This can support longer the
food chains, hence and more trophic levels increasing net
productivity. Ecosystems rarely have more than 4 or 5
trophic levels.
2. The higher the
efficiency of energy
transfer between
trophic levels the
higher the net
productivity. Energy
transfer is typically
10%.
Reasons for high net productivity of an ecosystem
(4 trophic levels)
(5 trophic levels)

http://commons.wikimedia.org/wiki/File:Nutrient_cycle.svg
Gersmehl diagrams were first developed in 1976, by P.F. Gersmehl, to show the
differences in nutrient flow and storage between different ecosystems
Sinks for nutrient storage:
• Biomass (flora and
fauna)
• Litter
• Soil
C.2 S.3 Construction of Gersmehl diagrams to show the inter-relationships between
nutrient stores and flows between taiga, desert and tropical rainforest.

http://commons.wikimedia.org/wiki/File:Nutrient_cycle.svg
Nutrient inputs into the ecosystem:
•Nutrients dissolved in raindrops
•Nutrients from weathered rock
Nutrient outputs (losses) from the
ecosystem:
•Nutrients lost through surface runoff
•Nutrients lost through leaching

When used to analyze a particular
ecosystem:
•Diameter of sinks are proportional to
the mass of nutrients stored in each
sink
•the thickness of the arrows are
proportional to the rate of nutrient
flow
Flows between the sinks:
•Littering (including withering, defoliation,
excretion, unconsumed parts left over, dead
bodies of animals, and so on) *
•Decomposition of the litter into inorganic
nutrients, which are then stored in the soil
•Nutrient uptake by plants
Human interactions are not considered – do not confuse
littering with dropping trash
*

C.2 S.3 Construction of Gersmehl diagrams to show the inter-
relationships between nutrient stores and flows between taiga, desert
and tropical rainforest.
• Litter (pine needles) is
the main store
• Slow rate of nutrient
transfer between
stores
• Soil is the main store
• Slow rate of nutrient
transfer between
stores (except for the
transfer from biomass
to litter)
• Biomass is the main
store (soil is nutrient
poor)
• Fast rate of nutrient
transfer between
stores
tagia
(temperate forest)
desert tropical rainforest
Image source: Allott, A. (2014). Biology: Course companion. S.l.: Oxford University Press.

C.2.U3 The percentage of ingested energy converted to biomass is dependent on the respiration
rate.

Ecosystems are not fixed, but constantly change with time. This change
is called succession. Imagine a lifeless area of bare rock. There are two
types of succession Primary and Secondary

Changes over time in total plant species
richness over time at select sites on Mount
Saint Helens, WA
http://www.nature.com/scitable/knowledge/libra
Use the examples to analyze data showing
primary succession
http://wps.pearsoncustom.com/wps/media/objects/2128/2179441/28_03.html

Secondary successionSecondary succession
•Starts with soil, but no (or only a few)
species, such as in a forest clearing,
following a forest fire, or when soil is
deposited by a meandering river
After a forest fireAfter a forest fire
One year laterOne year later Five years laterFive years later
C.2 U.6 Disturbance influences the structure and rate of change within
ecosystems.

C.2 S.5 Investigation into the effect of an environmental disturbance on
an ecosystem.
http://en.wikipedia.org/wiki/File:NASAburningbrazil.jpg

C.2 S.5 Investigation into the effect of an environmental disturbance on
an ecosystem.
Your investigation should compare a site
undergoing secondary succession
with a primary ecosystem. This can be
extended to look at the various stages of
secondary succession if local sites allow.
Possible opportunities include:
•Abandoned settlements/fields
•Fields recovering after fire damage
•Fire breaks in woodland
•Ways of measuring the affect of
succession include:
•Species diversity
•Stem/Seedling density
•Biomass
•Canopy coverage / light intensity at the
surface
•Depth/Volume of leaf litter
•Soil nutrient levels
http://en.wikipedia.org/wiki/File:NASAburningbrazil.jpg

C.2.U4 The type of stable ecosystem that will emerge in an area is predictable based
on climate.
Biome is a geographical area that has a particular climate and sustains a specific
community of plants and animals (i.e. a type of ecosystem)
Biosphere is the total of
all areas where living things
are found (i.e. the totality of
biomes)
• The main factors affecting the distribution of biomes is temperature and rainfall
• These factors will vary according to latitude and longitude, elevation and proximity to the sea
• Temperature is influential because it affects the rate of metabolism – the phases in the life cycles
of many organisms are temperature dependent
• In the same way, the availability of fresh water (both in the soil and in rivers and lakes) is critical
to the growth and nutrition of organisms
• Rainfall and warmer temperatures are more common near the equator and less common at the
poles
http://ib.bioninja.com.au/options/option-g-ecology-and-conser/g2-ecosystems-and-biomes.html

The six major types of biome/ecosystem are outlined in the table below

The six major types of biome/ecosystem are outlined in the table below
You don’t have to remember the individual biomes …

C.2.S2 Analysis of a climograph showing the relationship between temperature, rainfall and the type
of ecosystem.
http://cispatm.pbworks.com/f/1209212862/biome_graph.jpg
n.b. The biomes in regions within the dashed line are strongly
influenced by other factors (e.g. seasonality of drought, fire,
animal grazing).
A climograph is a diagram which
shows the relative combination of
temperature and precipitation in an
area.
This modified climograph (first
developed by Robert Whittaker)
shows the stable
ecosystems/biomes that arise as a
result of the relative combination
of temperature and precipitation.
It is a graphical representation of
the biome summary table (last
slide).
… but, you do have to be able to analyse a climatograph

C.2.S2 Analysis of a climograph showing the relationship between temperature, rainfall and the type
of ecosystem.
http://cispatm.pbworks.com/f/1209212862/biome_graph.jpg
n.b. The biomes in regions within the dashed line are strongly
influenced by other factors (e.g. seasonality of drought, fire,
animal grazing).
A climograph is a diagram which
shows the relative combination of
temperature and precipitation in an
area.
This modified climograph (first
developed by Robert Whittaker)
shows the stable
ecosystems/biomes that arise as a
result of the relative combination
of temperature and precipitation.
It is a graphical representation of
the biome summary table (last
slide).

C.2.U5 In closed ecosystems energy but not matter is exchanged with the surroundings.
http://cdn.pickchur.com/wp-content/uploads/2013/02/bottle_ecosystem.jpg
Most natural ecosystems are ‘open
ecosystems’. They can exchange energy and
matter with adjacent ecosystems or
environments. Examples of matter exchange
are:
•migration of animals
•harvesting of crops
•the flow of water or gases
Closed ecosystems, such as mesocosms
(4.1.S2) and the Biosphere 2 project are closed
ecosystems. Although energy can be
exchanged (most commonly through the entry
of light and the loss of heat), matter remains
in the system. Water and nutrients are cycled
within the ecosystem.
Closed ecosystems are of interest
to Scientists as they provide insight
in how extra-terrestrial habitats
can be setup and maintained.
http://upload.wikimedia.org/wikipedia/commons/1/13/Biosphere_2_-_1998_a.jpg

C.2 A.2 Consideration of one example of how humans interfere with nutrient cycling.
Humans practices can accelerate the the flow of matter into and out of ecosystems. This
by implication (and often design) alters the nutrient cycling in ecosystems.
Biomass (including
phosphates and nitrates)
removed from the
agricultural ecosystem
Phosphates and nitrates
removed from
the
agricultural ecosystem
and
added to adjacent aquatic
ecosystems
phosphates added
to
the agricultural
ecosystem
phosphates added to
the agricultural
ecosystem
Phosphate
mined and
converted to
fertiliser.
Nitrate fertiliser
produced from
atmospheric
Nitrogen
(by the Haber
process)
Agriculture
Harvesting
of crops
Water run-off
(leaching) from
agricultural
fields results in
build-up of
phosphates and
nitrates in
waterways and
leads to
eutrophication.

C.1 Species and Communities
Essential idea: Community structure is an
emergent property of an ecosystem.

Understandings
Statement Guidance
C.1 U.1 The distribution of species is affected by limiting factors.
C.1 U.2 Community structure can be strongly affected by keystone species.
C.1 U.3
Each species plays a unique role within a community because of the
unique combination of its spatial habitat and interactions with other
species.
C.1 U.4
Interactions between species in a community can be classified
according to their effect.
C.1 U.5
Two species cannot survive indefinitely in the same habitat if their
niches are identical.

Statement Guidance
C.1 A.1
Distribution of one animal and one plant species to illustrate limits of tolerance
and zones of stress.
C.1 A.2
Local examples to illustrate the range of ways in which species can interact
within a community.
C.1 A.3
The symbiotic relationship between Zooxanthellae and reef-building coral reef
species.
C.1 S.1
Analysis of a data set that illustrates the distinction between fundamental and
realized niche.
C.1 S.2
Use of a transect to correlate the distribution of plant or animal species with an
abiotic variable.

III. Interactions between species

G 1.2a Explain the factors that affect the distribution
of animal species, including temperature, water,
breeding sites, food supply and territory.

Example: Territory
availability and distribution
of animals
•Tigers are solitary animals
that require large territories,
the size of which is
determined mostly by the
availability of prey.
•A tiger’s territory consists of
forest, to shelter their prey,
and access to water.
•Although individuals do not
patrol their territories, they
visit over a period of days or
weeks and mark their
territory with urine and
feces.
http://upload.wikimedia.org/wikipedia/commons/1/16/Indian_Tiger.jpg

Example factors affecting the distribution of species
Oak and Maple trees synthesize ‘antifreeze proteins’ which prevents the formation of
ice crystals inside cells. This enables these species to survive in temperatures as low as
-40 o
C.
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/BrockenSnowedTrees.jpg/1024px-BrockenSnowedTrees.jpg

Migration for food supply in animals
“Southern right whales migrate from their Antarctic feeding areas to temperate breeding areas
along the costs of Chile and Argentina, southern Africa, and Australia and New Zealand, covering
2,500 km each way.
http://www.nature.com/scitable/knowledge/library/animal-migration-13259533
http://upload.wikimedia.org/wikipedia/commons/c/c2/Southern_right_whale6.jpg

G 1.1a Outline the factors that affect the distribution
of plant species, including temperature, water, light,
soil pH, salinity and mineral nutrients.

G 1.2b Explain the factors that affect the distribution

G 1.2c Explain the factors that affect the distribution

Temperature - plant can only survive in a range of temperatures to which they are adapted
•Metabolic pathways are controlled by enzymes, which have optimal temperatures, too high
and the enzymes will denature
•High temperatures increase the rate of evaporation (and hence transpiration)
Water availability limits plant growth in most terrestrial ecosystems
•Needed to maintain cell turgor
•Needed for photosynthesis and respiration to occur
•Xerophytes, e.g. Cacti are adapted to low water conditions, hydrophytes, e.g. rice, are
adapted to waterlogged soils
Light (intensity/wavelength) limits the plants ability to carryout photosynthesis.
•Plants that grow in shade (lower light intensity) contain more chlorophyll, they have darker
green leaves
•Plants, e.g. Kelp (algae), appear brown, not green, and have pigments that are adapted to
absorbing the blue wavelengths as red wavelengths do not easily penetrate water
Detail on how the factors affecting the distribution of Plant species:
n.b. Although it is unlikely you will need to learn all of these details understanding the concepts will enable
you to better communicate your examples.

Most plants only tolerate a narrow Soil pH range
•pH affects the availability of mineral nutrients, e.g. minerals can either be bound more
strongly in the soil or leeched from the soil more easily at different pHs.
•pH may affect the decomposition of organic matter, and hence the rate at which nutrients
are (re-)cycled and made available to plants
Most plants have a low Soil salinity tolerance or can only tolerate a narrow range of salinity
•High salinity either makes uptake of water (osmosis) by plants more difficult, or in extremes
causes water loss
•Halophytes, e.g. Mangrove trees, are adapted to high salinity soils
Minerals nutrient availability affects plant fertility, different plants need minerals (e.g.
Nitrogen, Phosphorus and Potassium) in different quantities.
•Waterlogged soils encourage denitrifying bacteria and lower the nitrogen availability to
plants
•Weathering of rocks often increases the availability of nutrients in the soil
Detail on how the factors affecting the distribution of Plant species:

Temperature must be within a viable range (based on adaptations) for survival – few
animals can survive extreme temperature conditions
•Body size (specifically SA:Vol ratio) will determine an animal's ability to conserve heat – a
large SA:Vol ratio means that heat is easily lost to /gained from the environment
•Homeotherms (organisms that maintain a stable internal body temperature) can colonize a
wider range of habitats than poikilotherms (internal temperature varies considerably)
Water must be available in quantities sufficient for the particular species concerned.
•Apart from drinking to maintain cells’ osmotic balance water can be required as a habitat,
transport medium, a place to lay eggs, a source of dissolved oxygen, food maybe filtered
from water (e.g. corals), and as a coolant. [See 2.2 Water for details]
Breeding sites are required for the maintenance of the species.
•Breeding sites need to provide protection for eggs, juveniles, and nesting adults.
•Sites are often rich in food or other resources necessary for juveniles, and breeding adults
•Juveniles may have specialized environmental requirements different from the adults, e.g.
dragonfly nymphs live underwater.
Detail on how the factors affecting the distribution of animal species:

Food availability is critical in determining the maximum population size.
•Animals maybe specialized so that they will only consume a particular species of animal or
plant, e.g. the caterpillars of the Small Tortoiseshell butterfly eat only nettle plants.
•Seasonal or geographical variation in food directly affects abundance of the population.
Territory – not all animals are territorial, but those that may do so to attracting mates,
rearing young, forage for food or to avoid predators.
•Animals may mark territories, e.g. by urinating or marking trees
•Territories can be established by individuals, breeding pairs or groups
•Territories maybe temporary (e.g. just for the duration of breeding cycle) or permanent
•Establishment of territories can lead to intra-specific (within species) or inter-specific
(between species) competition
Detail on how the factors affecting the distribution of animal species:

C.1 A.1 Distribution of one animal and one plant species to illustrate
limits of tolerance and zones of stress.
Black mangrove (Avicennia germinans) is a very widespread
mangrove tree. It can survive and grow in a wide range of
salinity levels from 0 to 96 part per thousand (ppt).
Greatest growth rates occur at salinity levels of 24 and 48
ppt, the optimal zone, outside of this range the Black
Mangrove trees experience the zones of stress.
http://commons.wikimedia.org/wiki/File:Avicennia_germinans.jpg

Interactions Between SpeciesInteractions Between Species
• CompetitionCompetition is when two species need the same resource
such as a breeding site or food. It will result in the removal of
one of the species. There are two major types of competition

I. Intraspecific competition
• A form of competition in which individuals of the same species compete
for the same resource in an ecosystem. This tends to have a stabilizing
influence on population size. If the population gets too big, intraspecific
population increases, so the population falls again.

II. Interspecific competition
• A form of competition in which individuals of different
species compete for the same resource in an ecosystem.

Types of Species Interactions
• An ecological community is a group of actually or
potentially interacting species, living in the same
place
• A community is bound together by the network of
influences that species have on one another.
• There are four main classes of two-way
interactions, and many possible pathways of
indirect interaction.

Type of
interaction Sign Effects
mutualism +/+ both species benefit
commensalism +/0 one species benefits,
one is unaffected
competition-/- each is neg. affected
predation +/- each is pos. affected
(includes herbivory,
parasitism)
Types of Species Interactions

• A. Predation is the relation between the predator, which is usually bigger,
and the prey, which is usually smaller. An example would be a fox and a
rabbit
Anteater Ant

• B. Parasitism is the relation between the host and the parasite. The
parasite causes harm to the host to get food and other resources. Examples
of parasites are some viruses, fungi, worms, bacteria, and protazoa.
Bass Lamprey

C. MutualismMutualism is where two members of different
species benefit and neither suffers. Examples include
rumen termite/protazoa that digest cellulose

D. Herbivory
• Primary Consumers that feed only on plant
material. Considered predators of plants. Ladybug
and a caterpillar are examples of herbivories

Niche ConceptNiche Concept
• A population’s niche refers to its role in its ecosystem.
• This usually means its feeding role in the food chain.
• A description of a niche should really include many
different aspects such as its food, its habitat, its
reproduction method and the organisms it interacts
with.
• Identifying the different niches in an ecosystem helps us
to understand the interactions between populations.
Members of the same population always have the same
niche, and will be well-adapted to that niche.

Competitive Exclusion
• No two species in a community can occupy the
same niche
Species A niche
Species B niche

Principle of Competitive ExclusionPrinciple of Competitive Exclusion
• Where two species need the same resources and
will compete until one species is removed.
• One would be more capable of gathering more
resources or reproducing more rapidly until the
other was run out of existence.
• Experiments with paramecium populations in the
lab of Ecologist G.F. Gause demonstrated this
concept scientifically.

The niche concept was investigated in some classic experiments in
the 1930s by Gause. He used flasks of different species of the
protozoan Paramecium, which eats bacteria and yeast.
• Conclusion: These two species of Paramecium share the same niche, so they
compete. P. aurelia is faster-growing, so it out-competes P. caudatum.
Experiment 1

P. aureliaP. aurelia
P. caudatumP. caudatum

• In the second experiment he took P. caudatum and had it
compete with a second type of Paramecia. It is important to
understand the distribution in experiment 2.
• P. caudatum lives in the upper part of the flask because only
it is adapted to that niche and it has no competition. In the
lower part of the flask both species could survive, but only P.
bursaria is found because it out-competes P. caudatum.
Experiment 2Experiment 2

Experiment 2
• Conclusion: These two species of Paramecium have slightly different
niches, so they don't compete and can coexist.

Fundamental vs. Realized Niche
• Fundamental Niche: the potential mode of
existence, given the adaptation of the species
• Realized Niche: the actual mode of existence,
which results from its adaptations and
competition with other species
Competition II
Competition
I
Com
petiti
on III
Realized Niche

Keystone Species Concept
•In ecological communities there are little
players and big players. The biggest players of
all are referred to as keystone species.
•A keystone species may be defined as one
whose presence/ absence, or
increase/decrease in abundance, strongly
affects other species in the community.
•Evidence usually comes from addition or
removal experiments.
Example: Kelp forests
• Can grow two feet per day
• Require cool water
• Host many species – high biodiversity
• Fight beach erosion
Kelp forests threatened by
• Sea urchins
• Pollution
• Rising ocean temperatures
Removal of the keystone in the arch
will cause the structure to collapse.

Southern Sea Otter
Keystone Species

Endangered Southern Sea Otter
Keystone species: plays a role affecting many
other organisms in ecosystem
specifically sea otters eat sea urchins that would
otherwise destroy kelp forests
• Kelp forests provide essential
habitat for entire ecosystem
•~16,000 around 1900
•Hunted for fur and because considered
competition for abalone and shellfish
•1938-2008: increase from 50 to ~2760
•1977: declared an endangered species

Sea star (Pisaster orchraceus) is a keystone
species in the rocky intertidal habitat along the California.
They have a profound impact on mussel bed population,
thereby reducing the health of the intertidal environment https://sfmsi.files.wordpress.com/2014/03/2010-040.jpg

Keystone modifier species, such as the North
American beaver (Casor candensis), determine the
prevalence and activities of many other species by
dramatically altering the environment. http://www.joshnagel.com/wp-content/uploads/2012/11/beaver-.jpg

C.1 U.2 Community structure can be strongly affected by keystone
species.
Species like the Saguaro cactus (Carnegiea gigantea) in desert
environments and palm and fig trees in tropical forests are called
keystone host species because they provide habitat for a variety of
other species. Keystone prey are species that can maintain their
numbers despite being preyed upon, therefore controlling the
density of a predator.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
http://commons.wikimedia.org/wiki/File:Carnegiea_gigantea_Saguaro_NP_1.jpg

C.5 Population ecology (AHL)
Essential idea: Dynamic biological
processes impact population
density and population growth.
Fish populations, such as the schooling Anchovies
(right) being hunted by the Dolphin (left) are an
excellent example of how dynamic populations are.
http://i.dailymail.co.uk/i/pix/2015/03/28/15/2711793A00000578-0-image-m-103_1427557828184.jpg

Statement Guidance
C.5 U.1 Sampling techniques are used to estimate population size.
C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited
environment.

C.5 U.3 Population growth slows as a population reaches the carrying
capacity of the environment.

C.5 U.4 The phases shown in the sigmoid curve can be explained by
relative rates of natality, mortality, immigration and emigration.

C.5 U.5 Limiting factors can be top down or bottom up.
C.5 A.1 Evaluating the methods used to estimate the size of commercial
stock of marine resources.

C.5 A.2 Use of the capture-mark-release-recapture method to estimate the
population size of an animal species.

C.5 A.3 Discussion of the effect of natality, mortality, immigration and
emigration on population size.

C.5 A.4 Analysis of the effect of population size, age and reproductive
status on sustainable fishing practices.

C.5 A.5 Bottom-up control of algal blooms by shortage of nutrients and
top-down control by herbivory.

C.5 S.1 Modelling the growth curve using a simple organism such as yeast
or species of Lemna.

Populations
• The total number of individuals of a species in a
given area.
Populations are affected by four main factors

Four Factors Influence the Size of a
Population:
Natality: Birth Rate (offspring
produced and added to population)

Mortality: Death Rate (individuals that die)

Immigration:Immigration: Movement of membersMovement of members
of the species into the areaof the species into the area

Emigration:Emigration: Movement of members of the species outMovement of members of the species out
of area to live elsewhere.of area to live elsewhere.

3 Phases:
1. Exponential growth Phase
2. Transitional Phase
3. Plateau Phase
Limited Growth Sigmoid (S-Shaped)Sigmoid (S-Shaped)

1. Exponential Growth Phase
• Population increases
exponentially.
• Resources are abundant.
• Predators and disease are
rare.

2. Transitional Phase
• As a result of intra-specific
competition
for food, shelter, nesting
space, etc.,
and the build up of
waste.
• The growth rate slows down.
Birth rates decline and
death rate increases

3. Plateau Phase
• Natality and mortality are equal so population size is
constant.
• When the number of individuals in the population have
reached the maximum which can be supported by the
environment.
The number is called the
CARRYING CAPACITY

Population size oscillates around the
carrying capacity (K)
Time
N
K
overshoot
oscillations

• Density Dependent Limits
 Food
 Water
 Shelter
 Disease
• Density Independent Limits
 Natural Disasters
 Humans (logging, mining, farming)
Water and shelter are
critical limiting factors in
the desert.
Fire is an example of a
Density independent
Limiting factor.
Limits on
Population Growth

C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited
environment.
This graph shows the explosion of human population over the
last 10,000 years along with some relevant historical events.

How has the human population
grown so quickly?
• When I graduated high school
in 1975 there were 4 billion
people.
• Today there are almost 7
billion people

If we look back, to about 5 million years ago.
We were hunter-gathers, with about 1 million humans

Neolithic Period (6000 B.C.)
No longer living in a natural settingNo longer living in a natural setting.
We moved to an agrarian society, increased food availability.
100 million people

Common area 2000 years ago
300 million
people

1800-2000?
• From 1 billion to 6 billion? How???

Steam engineSteam engine
1800’s the population increases to 1 billion people
Humans take over the carbon cycle (burning fossil fuel),
leading to an increase in population

London between 1800 to 1880
• 1800 pop. 1 million
• 1880 pop. 4.5 million
• Improvements in medicine and public health

Life Expectance
• Neolithic it was 20
• 1900 it was 30
• 1950 it was 47
• Current world
average is 70

1908 News flash!
Humans have taken control of the
Nitrogen Cycle
• Up until 1908 farms were dependent
on organic sources for nitrogen
(manure)
• Haber figured out how to convert N2
into NH3 and then into NH4
+
of NO3
-
Commercial
fertilizers are
Born!
Human population grows!
Fritz Haber

1944 Plant Breeding
• Improves yields
• Disease resistance
improvements
• Less day-length sensitive
• Improve sharing of ideas on
plant breeding
Human population grows!

C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
Examples of exponential population growth
http://www.nature.com/scitable/knowledge/library/an-introduction-to-population-growth-84225544
Throughout the 1800's, hunters
decimated the American
Plains bison populations, and
by 1889, only about one
thousand bison remained.
The US government, along with private
landowners, established protected herds
in the late 1800's and early 1900's. The
herds started small, but with plentiful
resources and few predators, they grew
quickly. The bison population in
northern Yellowstone National Park
increased from 21 bison in 1902 to 250
in only 13 years.

C.5 U.4 The phases shown in the sigmoid curve can be explained by
relative rates of natality, mortality, immigration and emigration.
Limiting factors are environmental factors that controls
the maximum rate at which a process, e.g. population
growth, can occur.
• build-up of toxic by products
of metabolism
• Injury
• Senescence (death from age
related illness)

All examples of competition
for resources
• Injury
related illness)
of metabolism

of metabolism
The effect of these limiting
factors increases as the
population increases. These
factors are described as
being density dependent
limiting factors.
• Injury
related illness)

of metabolism
The this limiting factor does
not increases as the
population increases. This
factor is described as being a
density independent limiting
factor.
• Injury
related illness)
Examples include:
•Climate / weather
•Availability of light (for plants)
•Natural disasters such as volcanic eruptions and fire

C.5 U.5 Limiting factors can be top down or bottom up.
A limiting factor is an environmental selection pressure that limits
population growth. There are two categories of limiting factor:
Top-down factors are pressures
applied by other organisms at higher
trophic levels.
Bottom-up factors are those that
involve resources or lower tropic
levels.
A keystone species exerts top-down influence
on its community by preventing species at
lower trophic levels from monopolizing critical
resources, such as competition for space or
food sources. http://commons.wikimedia.org/wiki/File:Tierpark_Sababurg_Wolf.jpg
http://commons.wikimedia.org/wiki/File:Green_Sea_Turtle_grazing_seagrass.jpg

An algal bloom is a rapid increase or
accumulation in the population of
algae (typically microscopic) in a water
system. http://commons.wikimedia.org/wiki/File:Mar%C3%A9_vermelha.JPG

•The water around coral-reef ecosystems is generally
nutrient-poor.
•Essential nutrients in these areas are e.g.
magnesium is needed to make chlorophyll are in
short supply
•Algae depend on photosynthesis for nutrition and
photosynthesis depends on proteins. Proteins such
as chlorophyll in short supply the rate of
photosynthesis is limited. Nutrients are therefore a
bottom-up limiting factor to growth.
•Free-living algae blooms can disrupt coral reef
communities by blocking sunlight and preventing
photosynthesis in the symbiotic zooxanthellae. With
Nutrient enrichment through human activity (fish
farming, fertilizer or sewage outflows directly or
from nearby rivers) can cause known as
eutrophication – algal populations increase rapidly
(blooms) due to the removal of nutrients as a
limiting factor.
https://pointreyesscience.files.wordpres
s.com/2011/09/thumbnail-for-web.jpg

• Parrotfish are herbivores that graze on free-living algae at a lower trophic level. This is an
example of top-down control of algae.
• Fishing practices which remove herbivorous fish from coral reefs can lessen the predation of
algae.
• If herbivorous fish numbers decline this can lead to algal blooms
http://upload.wikimedia.org/wikipedia/commons/f/f3/Stoplight-parrotfish.jpg

C.5 S.1 Modelling the growth curve using a simple organism such as
yeast or species of Lemna.
http://commons.wikimedia.org/wiki/File:Lemna_minor_Prague_2012_1.jpg
Duckweed (Lemna sp.) is a good model
organism for measuring sigmoidal population growth

• Place a small number of plants in a container, e.g. a plastic cup
• Count the number of fronds (leaves) every day until the surface
of the container is covered, i.e. the population has ceased to
increase.
• Plot your results – you should obtain a sigmoidal curve
• Your investigation can be extended by considering different
independent variables e.g. nutrient availability and the surface
area of the container.
In the absent of equipment using one or more of the following resources to model
population growth:
• Yeast Population Growth lab and simulation by i-Biology (
http://www.slideshare.net/gurustip/population-growth-9457952)
• Bunny population growth by PhET (
http://phet.colorado.edu/files/activities/3896/04.02 - CW - bunny simulation - 2014-07-30 -
)
C.5 S.1 Modelling the growth curve using a simple organism such as
yeast or species of Lemna.

Why monitor populationsWhy monitor populations??
• Determine current status of a population
• Determine habitat requirements of a species
• Evaluate effects of management
*Complete “census” of natural populations is often
very difficult!
Population Sampling
C.5 U.1 Sampling techniques are used to estimate population size.

Population vs.Population vs.
SampleSample
SampleTrue Population

RANDOM SAMPLING
• A sampling procedure that assures that each
element in the population has an equal chance of
being selected
• Sampled population should be representative of
target population

Sample Methods
• Quadrat
• Mark-Recapture
• There are MANY more…

Quadrat Sampling
• A square frame is placed in a habitat
• All the individuals in the quadrat are counted
• The process is repeated until the sample size is large enough

• Useful for small organisms or for organisms that do not
move

Converting a population study
into a graph

MARK-RECAPTURE (Lincoln Index)
• Capture and mark known number of individuals
• 2nd
round of captures soon after
Time for mixing, but not mortality
• Fraction of marked individuals in recapture sample is
estimate of the proportion of population marked in
first capture

Marking methods
• Paint or dye
• Color band
 birds
• Unique markings
 Large mammals; keep
photo record
• Toe clipping
 Reptiles, amphibians,
rodents
• Radio Collars
• Micro chips
(NPS 2000)

Lincoln Index
• Using mark-recapture sampling to estimate
animal populations
Population Size P =(# initially marked) x (total 2nd
catch)
(# of marked recaptures)
Or
N1 x N2
N3

Mark
Recapture
Lincoln Index
N1 = 4
N2 = 5
N3 = 2
N1 = first capture
N2 = second capture
N3 = #’s of marked in
second capture

Survey 1:
N1= 12
Survey 2:
N2 = 15
N3 = 4

• You capture and mark 150 fish in a lake. (This must be a
random, representative sample.)
• You release them back into the lake, allowing enough time
for them to remix with the population.
• You trap another 220 fish, of which 25 are recaptures (i.e.,
marked from the initial trapping.
• What is your estimate of the total population of fish in the
lake?
Example:

• N1 = 150
• N2 = 220
• N3 = 25
• P = [(220)(150)] / 25
= 1320 FISH
Example:

Example:
• Use the Lincoln Index to monitor this mountain gorilla
population over time

Human Effect on the World Fish PopulationHuman Effect on the World Fish Population
• Overexploitation of species affects the loss of genetic
diversity and the loss in the relative species abundance
of both individual and/or groups of interacting species.
Overexploitation may include over fishing and over
harvesting
• Historically, humans have fished the oceans, which
never seemed to pose a problem due to their
abundant resources. Gear (fish trap, gill nets, electro-
fishing) and vessel efficiency modifications have
caused a significant decrease in fish populations.

A case study: The Peruvian Anchovy
(Engraulis ringens)
Universidad de La Serena

The Peruvian Anchovy
• This is a small (12-20cm), short-lived species
maturing in 1 year
• Anchovy live in the surface waters in large shoals
off the coast of Peru and northern Chile
• Here there are cold currents up-welling from the
sea bed bringing nutrients for phytoplankton
• Plankton is at the base of the food chain.

The Peruvian Anchovy
• The harvest of this fish doubled every year from 1955 to
1961
• Experts estimated the maximum harvestable yield (MSY) at
10 to 11 million tonnes per year
• Through the 1960s the harvest was about this level
• The biggest fishing harvest in the world
• Some of the anchovy were used for human food
• But a lot was ground into fishmeal for animal feed

The collapse of the anchovy fishery
• In 1972 there was an El Niño event that brought warm tropical water
into the area
• The up-welling stopped,
• the phytoplankton growth decreased
• the anchovy numbers fell and concentrated further south
• The concentrated shoals of anchovy were easy targets for fishing boat
eager to recuperate their harvest
• The political will was not there to impose reduced quotas
• Larger catches were made
• No young fish were entering the population (no recruitment)
• No reproduction was taking place
• The fish stocks collapsed and did not recover

Population dynamics of fisheries
• A fishery is an area with an associated fish population which is
harvested for its commercial or recreational value. Fisheries
can be wild or farmed.
• Population dynamics describes the ways in which a given
population grows and shrinks over time, as controlled by birth,
death, and emigration or immigration. It is the basis for
understanding changing fishery patterns and issues such as
habitat destruction, predation and optimal harvesting rates.
• The population dynamics of fisheries is used by fisheries
scientists to determine sustainable yields

Sampling
method
Situation in which
the method is used
Usage and limitations
Random sampling Not used. Ineffective as fish are too mobile.
Capture-mark-
release-recapture
Fish are temporarily
stunned with electric
shocks and then
counted
Used in lakes and rivers, but
recapture numbers are too small
to be useful in open waters such
as oceans.
Echo sounders Can be used to
estimate the size of
fish shoals
Only useful for schooling fish
species
Fish catches Age structure of
landed fish can be
used to estimate
population size.
Violators of fishing regulations
designed to control the age of fish
landed often do not report what
they land or they dump the
restricted fish causing a bias in
the estimates.
Estimating Fish populations

Sampling
method
Situation in which
the method is used
Usage and limitations
Random sampling Not used. Ineffective as fish are too mobile.
Capture-mark-
release-recapture
Fish are temporarily
stunned with electric
shocks and then
counted
Used in lakes and rivers, but
recapture numbers are too small
to be useful in open waters such
as oceans.
Echo sounders Can be used to
estimate the size of
fish shoals
Only useful for schooling fish
species
Fish catches Age structure of
landed fish can be
used to estimate
population size.
Violators of fishing regulations
designed to control the age of fish
landed often do not report what
they land or they dump the
restricted fish causing a bias in
the estimates.
Estimating Fish populations
C.5.A1 Evaluating the methods used to estimate the size of commercial stock of marine resources.
• Fish are very mobile – they pursue what is
frequently a mobile food supply.
• They often school so are unevenly distributed.
… so how can we count/estimate their numbers?
If we know how big fish population are we can
fish sustainably, but ….

Maximum Sustainable Yield (MSY)
Based upon:
1. the harvest rate
2. the recruitment rate of new (young) fish into the
population
• a population can be harvested at the point in their
population growth rate where it is highest (the
exponential phase)
• Harvesting (output) balances recruitment (input)
• Fixed fishing quotas will produce a constant
harvesting rate (i.e. a constant number of individuals
fished in a given period of time)
C.5 A.4 Analysis of the effect of population size, age and reproductive status on
sustainable fishing practices.

Maximum Sustainable Yield
(MSY)

Maximum Sustainable Yield
• The Largest possible catch without adversely affecting
the ability of the population to recover.

Problems with MSY
Age structure: If all the age groups are harvested recruitment
of young fish into the reproductive group will be reduced.
The answer is to use a net with a big enough mesh size that
lets the young fish escape
Age and sustainable fishing
• If a population is growing, then the relative number of
younger fish will be higher (there are many potential
breeding fish for the future).
• If a population is in decline, then the proportion of older fish
will be higher (older fish have a higher mortality and are
unlikely to be as productive in breeding).

Problems with MSY
Limiting factors: If the limiting factors in the environment
change so does the population growth rate
• Limiting factors set the carrying capacity (K) of an
environment
• Increasing limiting factors will cause K to drop
• Fixed quotas cannot cope with this
• Data: For MSY to work accurate data in fish
populations is needed (population size, age structure,
recruitment rates)
• Usually these are not well known

What is required?
• Nets with bigger mesh size
• Regulated fishing methods
• More data on fish populations (e.g. by fish tagging
investigations – mark and recapture)
• Constant monitoring to observe changes in environmental
factors (e.g.El Niño events
• Policing of fishing industry – respect of quotas
• International agreements
• Greater exploitation of fish farming
• But this is not without its own problems (space, diseases
and pollution are all associated with intensive fish culture)

C.1 A.1 Distribution of one animal and one plant species to illustrate
limits of tolerance and zones of stress.
Shelford's law of tolerance is a useful tool to understand the relative abundance of
a species and hence predict community structure. It plots the range of a biotic or
abiotic factor that is tolerated by a species,. Because their is variability but within a
population the limits of tolerance and where the zones of stress start is not always
easy to measure.
http://www.anselm.edu/homepage/bpenney/teaching/BI320/elements/Krohne_Shelfords.jpg

4.4 Climate change
Essential idea: Essential idea: Concentrations of gases in the atmosphere affect
climates experienced at the Earth’s surface.

Statement Guidance
4.4 U.1 Carbon dioxide and water vapour are the most significant
greenhouse gases.
4.4 U.2 Other gases including methane and nitrogen oxides have less
impact.
The harmful consequences of ozone
depletion do not need to be discussed
and it should be made clear that ozone
depletion is not the cause of the
enhanced greenhouse effect.
4.4 U.3 The impact of a gas depends on its ability to absorb long wave
radiation as well as on its concentration in the atmosphere.
Carbon dioxide, methane and water
vapour should be included in
discussions.
4.4 U.4 The warmed Earth emits longer wavelength radiation (heat).
4.4 U.5 Longer wave radiation is absorbed by greenhouse gases that retain
the heat in the atmosphere.
4.4 U.6 Global temperatures and climate patterns are influenced by
concentrations of greenhouse gases.
4.4 U.7 There is a correlation between rising atmospheric concentrations
of carbon dioxide since the start of the industrial revolution 200
years ago and average global temperatures.
4.4 U.8 Recent increases in atmospheric carbon dioxide are largely due to
increases in the combustion of fossilized organic matter.
4.4 A.1 Threats to coral reefs from increasing concentrations of dissolved
carbon dioxide.
4.4 A.2 Correlations between global temperatures and carbon dioxide
concentrations on Earth.
4.4 A.3 Evaluating claims that human activities are not causing climate
change.

C.3 Impacts of humans on ecosystems
Essential idea: Human activities impact on ecosystem
function.
Rhododendrons are beautiful eye catching shrubs that grow
in many gardens throughout the world. Rhododendrons are
native to alpine regions in Asia. Since their introduction to
non-native regions they become an invasive species causing
major disruptions to ecosystems, e.g. in Western Europe
they have out-competed local woodland plants causing
major reductions in local biodiversity.
http://www.gardeningknowhow.com/wp-content/uploads/2012/07/rhododendron1.jpg
By Chris Paine
https://bioknowledgy.weebly.com/

Statement Guidance
C.3 U.1 Introduced alien species can escape into local ecosystems and
become invasive.
C.3 U.2 Competitive exclusion and the absence of predators can lead to
reduction in the numbers of endemic species when alien species
become invasive.
C.3 U.3 Pollutants become concentrated in the tissues of organisms at higher
trophic levels by biomagnification.
C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.
C.3 A.1 Study of the introduction of cane toads in Australia and one other
local example of the introduction of an alien species.
C.3 A.2 Discussion of the trade-off between control of the malarial parasite
and DDT pollution.
C.3 A.3 Case study of the impact of marine plastic debris on Laysan
albatrosses and one other named species.
C.3 S.1 Analysis of data illustrating the causes and consequences of
biomagnification.
C.3 S.2 Evaluation of eradication programs and biological control as
measures to reduce the impact of alien species.

C.4 Conservation of biodiversity
Essential idea: Entire communities need to be
conserved in order to preserve biodiversity.
The tremendous biodiversity of the amazon
rainforest can only be conserved in situ it is simply
too complex to recreate or conserve in part. Many
species rely on a complex web of interactions with
other species that they share the environment with,
if the balance is disturbed then species will be lost
and the community will become less diverse.
http://3.bp.blogspot.com/-p19vnPIw5WY/Tla1Xp07zQI/AAAAAAAAAkE/Ot-Lo1ZwKOQ/s1600/amazon.png
By Chris Paine
https://bioknowledgy.weebly.com/

Statement Guidance
C.4 U.1 An indicator species is an organism used to assess a
specific environmental condition.
C.4 U.2 Relative numbers of indicator species can be used to
calculate the value of a biotic index.
C.4 U.3 In situ conservation may require active management of
nature reserves or national parks.
C.4 U.4 Ex situ conservation is the preservation of species
outside their natural habitats.
C.4 U.5 Biogeographic factors affect species diversity.
C.4 U.6 Richness and evenness are components of biodiversity.
C.4 A.1 Case study of the captive breeding and reintroduction
of an endangered animal species.
C.4 A.2 Analysis of the impact of biogeographic factors on
diversity limited to island size and edge effects.
C.4 S.1 Analysis of the biodiversity of two local communities
using Simpson's reciprocal index of diversity.
The formula for Simpson’s reciprocal
index should be known by students.

4 Serious Environmental Issues
1. Reduction in Biodiversity
2. Biomagnification
3. Plastics
4. Climate Change

1. Reduction in Biodiversity1. Reduction in Biodiversity

Simpson diversity indexSimpson diversity index
The index of diversity is used as a measure of the range and
numbers of species in an area. It usually takes into account
the number of species present and the number of individuals
of each species. It can be calculated by the following
formulae:
D = N(N-1)
∑n(n-1)
D= Diversity index
n = number of individuals of a each species found in an area.
N = total # of organisms of all species found in an area.
The Simpson diversity index is a measure of species richness.
A high value of D suggests a stable and ancient site.

Example:
Crested newt 8
Stickleback 20
Leech 15
Great pond snail 20
Dragon fly larva 2
Stonefly larva 10
Water boatman 6
Caddisfly larva 30
N = 111
N(N-1) = 111(111-1) = 12,210
∑n(n-1) = (8x7) + (20x19) + (20x19) + (15x14) + (20x19) +
(2x1) + (10x9) + (6x5) + ( 30x29) = 2018
D = 12,210 =6.05

Example: In another pond there were:
Crested newt 45
Stickleback 4
Leech 18
Great pond snail 10
N=77
D = 2.6
Comparing both indices, 6.05 is an indicator of greater
diversity. The higher number indicates greater diversity

Abiotic factors for Biodiversity
In extreme environmentsIn extreme environments
the diversity of organisms is
usually low (has a low index
number). This may result in an
unstable ecosystem in which
populations are usually
dominated by abiotic factors.
The abiotic factor(s) are extreme
and few species have adaptations
allowing them to survive.
Therefore food webs are
relatively simple, with few food
chains, or connections between
them – because few producers
survive.

In less hostile environmentsIn less hostile environments
The diversity of organisms is
usually high (high index
number). This may result in a
stable ecosystem in are usually
dominated by biotic factors,
and abiotic factors are not
extreme. Many species have
adaptations that allow them to
survive, including many
plants/producers. Therefore
food webs are complex, with
many
inter-connected food chains.
Abiotic factors for Biodiversity

The use of biotic indicator for monitoring
environmental change
• Are a good indicator of change
• Highly sensitive to environmental changes
• Highly sensitive to population increases or
decreases.
• The numbers of organisms in the indicator
species populations, can be measured directly so
they are easy to keep track of larger changes
that maybe occurring.

American DipperAmerican Dipper
•Feeds on aquatic insects and their larvae, including dragonfly,
nymphs and caddisfly larvae. It may also take tiny fish.
•The presence of this indicator speciesindicator species shows good water quality; it
has vanished from some locations due to pollutionpollution or increased silt
load in streams

Lichens (Air pollution)
•Lichens are formed from a symbiotic relationship between a fungus and an alga.
•They often grow on exposed rocks and trees, and need to be efficient at absorbing
water.
•Air pollutants dissolved in rainwater, especially sulphur dioxide, can damage lichens
and prevent them from growing.
•By looking at the species present in a particular area, scientists can assess the level of
air pollution.

Humans Contribute to Declining
Biological Diversity
Introduction of exotic species
harms native species due to
competition, predation, or
interbreeding
• The zebra mussel native to
Russia, introduced into the
American Great Lakes by
tanker ships. These mussels
not only cause billions of
dollars of damage but have
displaced the native clams
and mussels
Invasive of Alien Species

REMEMBER GAUSE…
Competitive exclusion principle: Two species cannot occupy the same niche in a
community, as there will be competition for the same resources. When one species
has even the slightest advantage or edge over another then the one with the
advantage will dominate.
Advantages can come in different forms, 5 examples
of advantages between species occupying similar
niches are:
1.High reproductive rate
2.Larger size / more aggressive
3.Faster / more efficient forager
4.Absence of predator
Invasive species often lack a predator, due to
being in a foreign environment. In the case of
invasive plants this can mean an absence of
suitable herbivores.
C.3 U.2 Competitive exclusion and the absence of predators can lead to
reduction in the numbers of endemic species when alien species
become invasive.

Asian long-horned beetleAsian long-horned beetle
• Discovered in the US in 1996 on several hardwood trees (destroying the hardwood
tree) in Brooklyn, NY. The wood-boring beetle is believed to have been introduced
on wood pallets and wood packing material in cargo shipments from Asia. The
infestation quickly spread to Long Island, Manhattan and Queens

Phragmites
• A wetland plant species found in every U.S. state (crowding out the native
species).
• It can grow up to 6 meters high in dense stands and is long lived. The species is
invasive particularly in the eastern states along the Atlantic Coast and increasingly
across much of the Midwest and in parts of the Pacific Northwest.

Biological ControlBiological Control
• The use of an organism (introduced)
to control another organism
• Risks: introduced organism may not
behave as expected (Cane Toads)
• Benefits: introduced organism may
be the only control mechanism
flexible enough to be effective
against another invasive with no
predators
Examples
• Purple loosestrife (invasive in US
and Canada) – controlled by 2
species of beetles (Gallerucella)

IB Biology Ecology Optional Topic C 2015

IB Biology Ecology Optional Topic C 2015

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to IB Biology Ecology Optional Topic C 2015

Similar to IB Biology Ecology Optional Topic C 2015 (20)

More from Bob Smullen

More from Bob Smullen (20)

Recently uploaded

Recently uploaded (20)

IB Biology Ecology Optional Topic C 2015

Editor's Notes