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Syllabus Details - Topic 4: Ecology and Evolution and OPTION G

4.1 Communities and Ecosystems (5h)
This reference is adapted from a Syllabus of the IB. In no way is it intended to replace parts of that syllabus, it is intended only to enhance your links with racerocks.com references to such syllabus objectives . Only the Ecology -related topics are presented here.

The brown text
and the
blue hyperlinks
..take you to a file that presents Race Rocks data or reference material relating to the objective stated.
4.1.1   Define ecology, ecosystem, population, community, species and habitat. 1
    • Ecology—the study of relationships between living organisms and between organisms and their environment.
    • Ecosystem—a community and its abiotic environment.
    • Population—a group of organisms of the same species who live in the same area at the same time.
    • Community—a group of populations living and interacting with each other in an area.
    • Species—a group of organisms which can interbreed and produce fertile offspring.
    • Habitat—the environment in which a species normally lives or the location of a living organism.
Ecosystems on different scales are represented at Race Rocks. Structure and function can be studied using the assignments presented in the OceanQuest assignments Abiotic factors are available in the environmental data and sensors section.
4.1.2   Explain how the biosphere consists of interdependent and interrelated ecosystems.
.Internal Link:
Campbell Biology Images ( Internal link) Introduction to Ecology chapter 50
4.1.3   Define autotroph (producer), heterotroph (consumer), detritivore and saprotroph (decomposer). 1
4.1.4   Describe what is meant by a food chain giving three examples, each with at least three linkages (four organisms).

note: In my opinion, the term food chain should never be used as it is misleading! (GF)

    Food chains are best determined using real examples and information based on natural ecosytems. A -> B indicates that A is being "eaten" by B (ie the arrow indicates the direction of energy flow). Each food chain should include a producer and consumers, but not decomposers. Named organisms at either species or genus level should be used. Common species names can be used instead of binomial names.
4.1.5   Describe what is meant by a food web

Internal Link:Campbell Biology Images ( Internal link) Ecosystems chapter 54

4.1.6   Define trophic level. 1
4.1.7   Deduce the trophic level of organisms in a food chain and a food web. 3
    The student should be able to place an organism at the level of producer, primary consumer, secondary consumer etc, as the terms herbivore and carnivore are not always applicable.
4.1.8   Construct a food web containing up to 10 organisms, given appropriate information. See 4.1.4.
This reference is on the Energy Flow involving organisms at Race Rocks note that several organisms feed at more than one trophic level.

Further information and Case Studies may be found by "Googling" "Odum,energy flow diagram"

4.1.9   State that light is the initial energy source for almost all communities.
    Reference to communities that start with chemical energy is not required.
4.1.10   Explain the energy flow in a food chain.
This reference on the Black Oyster Catcher contains information on the food web of this sea bird which nests at Race Rocks.
    Energy losses between trophic levels include material not consumed or material not assimilated, and heat loss through cell respiration.
4.1.11   State that when energy transformations take place, including those in living organisms, the process is never 90% efficient, commonly being 10–20%.
This reference on Solar Radiation at Race Rocks provides useful reference on the effect of this factor on the environment.
    Reference to the second law of thermodynamics is not expected.
4.1.12   Explain what is meant by a pyramid of energy and the reasons for its shape. 3
    A pyramid of energy shows the flow of energy from one trophic level to the next in a community. The units of pyramids of energy are therefore energy per unit area per unit time, eg J m -2 yr-1.
4.1.13   Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled. 3
4.1.14   Draw the carbon cycle to show the processes involved. 1
This reference on Biogeochemical Cycles includes an exercise in building the Carbon Cycle at Race Rocks.
4.1.15   Explain the role of saprotrophic bacteria and fungi (decomposers) in recycling nutrients.

See the link to LBPC FUNGI FILE

    Specific names of decomposer organisms are not required.

G.1 The Ecology of Species (3h)

G.1.1   Outline the factors that affect the distribution of plant species including temperature, water, light, soil pH, salinity and mineral nutrients.
ALGAE references See the extended essay and other information relating the combined factors of exposure and season to algal distribution.
G.1.2   Explain the factors that affect the distribution of animal species including temperature, water, breeding sites, food supply and territory.
Two resources may be useful : The Abiotic factors assignment , and the links found by clicking on each of the abiotic factors on the Ecodata page Currently real time data are provided for many of the abiotic factors at Race Rocks. More are being added.
G.1.3   Deduce the significance of the difference between two sets of data using calculated values for t and the appropriate tables. 3
    The t-test can be used to compare two sets of data and measure the amount of overlap. Students will not be expected to calculate values of t.
    ( The t-test should only be used on normally distributed data, ideally with large samples (>30 measurements per set of data) and the value of t should be compared with the critical value at # degrees of freedom. For sample sizes <30 the value of t is only approximate and the degrees of freedom is n1+ n2 - 2. If t > critical value then it is possible to reject the null hypothesis)
G.1.4   Explain what is meant by the niche concept, including an organism's spatial habitat, its feeding activities and its interactions with other organisms.
Modeling ecological niches
at Race Rocks
This exercise will enable one to use photographic transects from Race Rocks.
G.1.5   Explain the principle of competitive exclusion.


G.2 The Ecology of Communities (5h)

G.2.1   Explain the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism. 3
    Mutualism is where two members of different species benefit and neither suffers. Examples include rumen bacteria/protozoa, lichens and Chlorella/Chlorohydra.
    Biotic Associations a file of some of the biotic associations at Race Rocks
G.2.2   Define gross production, net production and biomass. 1
G.2.3   Calculate values for gross production, net production and biomass from given data.

Productivity lab Using single celled green algae in productivity determinations
    Gross production - respiration = net production
G.2.4   Discuss the difficulties of classifying organisms into trophic levels. 3
G.2.5   Explain the small biomass and low numbers of organisms in higher trophic levels. 3
G.2.6   Construct a pyramid of energy given appropriate information. 3
    The lowest bar of the pyramid of energy represents gross primary productivity, the next bar represents the energy ingested as food by primary consumers, and so on. The units are energy per unit area per unit time.
G.2.7   Describe ecological succession using one example. 2
G.2.8   Explain the effects of living organisms on the abiotic environment with reference to the changes occurring during ecological succession to climax communities.Include soil development, accumulation of minerals and reduced erosion.
This exercise on the abiotic environment provides a number of exercises designed to familiarize you with the wide range of abiotic factors in the Race Rocks ecosystem.

(G4 ) Extension Material—HL only


G.4 The Nitrogen Cycle (4h)

G.4.1   State that all chemical elements occuring in organisms are part of biogeochemical cycles and that these cycles involve water, land and the atmosphere. 1
G.4.2   Explain that all biogeochemical cycles summarize the movement of elements through the biological components of ecosystems (food chains) to form complex organic molecules, and subsequently simpler inorganic forms which can be used again. 3
G.4.3   Explain that chemoautotrophs can oxidize inorganic substances as a direct energy source to synthesize ATP. 3
G.4.4   State that chemoautotrophy is found only among bacteria.

reference on Marine Chemoautotrophy

a quiz on chemoautotrophy:

G.4.5   Draw a diagram of a nitrogen cycle.
This reference on Biogeochemical Cycles includes an exercise in building the Nitrogen Cycle at Race Rocks.
G.4.6   Outline the roles of Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter and Pseudomonas denitrificans in the nitrogen cycle.

(The Rhizobium group is studying the bacterial and legume genes involved in establishing and maintaining the symbiosis.)http://www.jic.bbsrc.ac.uk/SCIENCE/molmicro/Rhizo.html (advanced reference)

G.4.7   Describe the conditions that favour denitrification and nitrification. 2
G.4.8   Discuss the actions taken by farmers/gardeners to increase the nitrogen fertility of the soil including fertilizers, plowing/digging and crop rotation (use of legumes).


4.2 Populations (3h)

4.2.1   Outline how population size can be affected by natality, immigration, mortality and emigration.
The abalone population This study presents some useful raw data for some statistical exercises
4.2.2   Draw a graph showing the sigmoid (S-shaped) population growth curve.
Link to Population Internet References
4.2.3   Explain reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases.
Demography- a BioQuest Simulation-
Internal Link
4.2.4   Define carrying capacity. 1
4.2.5   List three factors which set limits to population increase. 1
4.2.6   Define random sample.
For a very good reference on Ecological Sampling and Statistics , you can start by reviewing the information presented on the following website:
4.2.7   Describe one technique used to estimate the population size of an animal species based on a capture-mark-release-recapture method. 2
    Various mark and recapture methods exist. Knowledge of the Lincoln index (which involves one mark, release and recapture cycle) is required.

      population size =

      n1= number of individuals initially caught, marked and released
      n2 = total number of individuals caught in the second sample
      n3 = number of marked individuals in the second sample

    Although simulations can be carried out (eg sampling beans in sawdust), it is much more valuable if this is accompanied by a real exercise on a population of animals. The limitations and difficulties of the method can be fully appreciated and some notion of the importance of sample size can be explained.

    It is important that students appreciate the need for choosing an appropriate method for marking organisms.

4.2.8   Describe one method of random sampling used to compare the population numbers of two plant species, based on quadrat methods. 2
4.2.9   Calculate the mean of a set of values. 2
    Candidates will be expected to know the formula for calculating the mean.
4.2.10   State that the term standard deviation is used to summarize the spread of values around the mean and that 68% of the values fall within ±1 standard deviation of the mean. 1
    For normally distributed data about 68% of all values lie within ±1 standard deviation (s.d. or s or s) of the mean. This rises to about 95% for ±2 standard deviations.
4.2.11   Explain how the standard deviation is useful for comparing the means and the spread of ecological data between two or more populations. 3
    A small standard deviation indicates that the data is clustered closely around the mean value. Conversely a large standard deviation indicates a wider spread around the mean. Details of statistical tests to quantify variations between populations, such as standard error, or details about confidence limits are not required.
See this field lab on STANDARD DEVIATION AND T- TEST

See this data to do statistical exercises. Christmas Bird Counts at Race Rocks
See this reference on doing a transect field lab transects for a quantification technique.

G.3 Biodiversity and Conservation (7h)
See the Assignment on Biodiversity Issues at
Campbell link ( Internal network) Conservation Biology

G.3.1   Discuss reasons for the conservation of biodiversity using rainforests as an example. Reasons should include ethical, ecological, economic and aesthetic arguments.
Link to PC Student File on Biodiversity

Link to Biodiversity InTools File for useful internet links

G.3.2   Outline the factors that caused the extinction of one named animal and one named plant species. 2
    Choose examples from recent historical time.
G.3.3   Outline the use of the Simpson diversity index.

This is probably one of the best references available on this index- note the use of the reciprocal form.

D= diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species

    The Simpson diversity index is a measure of species richness. A high value of D suggests a stable and ancient site and a low D value could suggest pollution, recent colonization or agricultural management. The index is normally used in studies of vegetation but can also be applied to comparisons of animal (or even all species) diversity.


4.5 Human Impact (2h)

4.5.1   Outline two local or global examples of human impact causing damage to an ecosystem or the biosphere. One example must be the increased greenhouse effect.

Link to PC Student Files on Ozone depletion
Link to PC Student Files on Greenhouse effect
Considering Ecosytem Services provides a way of looking at the environment to show the value of undisturbed ecoystems Perhaps if we looked at the value that Ecosystems can provide for us we would have more concern with limiting human impact.
    In studying the greenhouse effect students should be made aware that it is a natural phenomenon and that without it organisms may have evolved differently. The problem lies in its enhancement by certain human activities. Knowledge that gases other than carbon dioxide exert a greenhouse effect is required (eg methane and CFCs).
4.5.2   Explain the causes and effects of the two examples in 4.5.1, supported by data.
4.5.3   Discuss measures which could be taken to contain or reduce the impact of the two examples, with reference to the functioning of the ecosystem.
Refer to this section on Ecosystem Services
Link to PC Student File on Alternate Energy
Refer to this section on Alternate Energy for Race Rocks
G.3.4   Explain the use of biotic indices and indicator species in monitoring environmental change.
G.3.5   Outline the damage caused to marine ecosystems by the overexploitation of fish.

G.3.6   Discuss international measures that would promote the conservation of fish. 3
G.3.7   Discuss the advantages of in situ conservation of endangered species (terrestrial and aquatic nature reserves).
G.3.8   Outline the management of nature reserves.
Adopt an Ecosystem if you really want to start to do something about the problems of human impact! This file provides an outline of some of the things you can do to be part of the solution!
G.3.9   Outline the use of ex situ conservation measures including captive breeding of animals, botanic gardens and seed banks.
G.3.10   Discuss the role of international agencies and conservation measures including CITES and WWF.


    CITES—Convention on International Trade in Endangered Species

    WWF—World Wildlife Fund



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