GRADE 12A: Biology 6
UNIT 12AB.6
13 hours
Ecological relationships
About this unit
Previous learning
Resources
This unit is the sixth of seven units on biology for
Grade 12 advanced.
To meet the expectations of this unit, students should already understand
that ecosystems are dynamic and subject to change, and that human
activities can have an impact on the environment.
The main resources needed for this unit are:
The unit is designed to guide your planning and
teaching of biology lessons. It provides a link
between the standards for science and your
lesson plans.
The teaching and learning activities should help
you to plan the content and pace of lessons.
Adapt the ideas to meet your students’ needs.
For consolidation activities, look at the scheme of
work for Grade 11A.
You can also supplement the activities with
appropriate tasks and exercises from your
school’s textbooks and other resources.
Introduce the unit to students by summarising
what they will learn and how this builds on earlier
work. Review the unit at the end, drawing out the
main learning points, links to other work and real
world applications.
Expectations
By the end of the unit, students know how some organisms are
structurally and physiologically adapted to their environment and distinguish
between acclimatisation and adaptation. They understand the carrying
capacity of a habitat and can use population curves. They understand
ecological colonisation and succession. They know examples of biological
control of unwanted organisms. They distinguish between environmental
preservation and conservation and understand the conflicts between nature
conservation and production.
Students who progress further will be able to follow and take part in future
debates on environmental issues such as nature conservation and food
production.
• overhead projector(OHP) or whiteboard
• various sets of cards on the environment
• datalogger/computer with sensors
• haemocytometer
• colorimeter
• fermenter, yeast culture
• microscopes, video camera, still camera, monitor
• video that illustrates biological control
• Internet access
Key vocabulary and technical terms
Students should understand, use and spell correctly:
• environmental resistance, biotic factors, abiotic factors
• biotic potential, carrying capacity
• ecological succession, primary colonisation, climax community
• pioneer species, xerophyte, hydrophyte, mesophyte
• sere, xerosere, hydrosere, zonation
• biological control
• environmental preservation, environmental conservation
441 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Objectives for the unit
13 hours
SUPPORTING STANDARDS
12A.13.2 Distinguish between the permanent adaptation of an organism to its normal
adaptations and
acclimatisation
environment and the temporary acclimatisation of a visitor.
11A.16.1 Explain examples of a predator–prey
population
growth
2 hours
Ecological
succession
2 hours
Biological
control
2 hours
Comparing
preservation and
conservation
2 hours
Food production
and conservation
EXTENSION STANDARDS
their environment.
Animal
Dynamics of
CORE STANDARDS
Grade 12 standards
12A.13.1 Explain examples of structural and physiological adaptations of animals to
3 hours
2 hours
Unit 12AB.6
relationship and the possible effects
on the population size of both the
predator and the prey.
12A.14.1 Explain and give examples to illustrate the carrying capacity of an
environment.
11A.16.2 Explain examples of inter- and intra-
specific competition for food and
space and the effects on the
distribution and size of the
populations of organisms.
11A.16.3 Explain how disease affects the size
of population of organisms and the
significance of limiting factors in
determining the ultimate size of a
population.
12A.14.2 Know how to construct and interpret population curves for different
organisms; identify the stages in population growth and decline.
11A.16.4 Explain how the diversity and
numbers of organisms and the
environmental factors in an
ecosystem form a dynamic
relationship that is open to disruption.
11A.16.5 Explain examples of short- and long-
term human impact on a variety of
environments.
12A.14.3 Describe the progression of the development of an ecological community
from primary colonisation to climax community.
12A.15.1 Explain examples of biological control of population growth in natural and
commercial settings.
12A.15.2 Assess the advantages and disadvantages of biological pest control.
12A.16.1 Explain the similarities and differences between environmental
preservation and conservation; understand that conservation is a dynamic
process involving management and reclamation.
12A.16.2 Explain how a wish to use an environment for food production can conflict
with a wish for its conservation.
442 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Activities
Unit 12AB.6
Objectives
Possible teaching activities
3 hours
Get students to do some card-matching activities. First provide a set of cards (set A) naming
specific environments (e.g. ocean, polar, mountain, temperate, tropical savannah, desert,
steppe), and another set of cards (set B) describing the characteristics of the environments
(e.g. large expanse of grassland, large numbers of deciduous trees). Arrange students in pairs,
mix up the cards and ask students to organise the cards into their matched groups.
Animal adaptations and
acclimatisation
Explain examples of
structural and physiological
adaptations of animals to
their environment.
Distinguish between the
permanent adaptation of an
organism to its normal
environment and the
temporary acclimatisation of
a visitor.
Notes
Prepare sets of appropriate cards.
School resources
Use this column to note
your own school’s
resources, e.g.
textbooks, worksheets.
Next introduce a set of cards naming specific animals (set C), and another set of cards (set D)
describing the adaptations of the animals (e.g. has layer of thick blubber, has extremely welldeveloped sense of smell / hearing / eyesight). Arrange students in pairs, mix up the cards and
ask students to organise the cards into their matched groups.
Alternatively, use these sets of cards for a class interactive activity. For example, issue each of
students several cards from set D and then ask another student to select an unseen card from set
C. Ask the class to indicate who has got the specific animal adaptations on any of their cards.
Enquiry skill 12A.1.4
Get students to work as a team to produce a booklet on the animals of Qatar.
Give students lettered / numbered lists of animals, environments and adaptations in three columns
and ask them to match the animal to the most appropriate components in the other columns.
Prepare suitable lists.
Give each student the name of a different animal, or ask them to name a species of their own
choice, and then ask them to use the library or the Internet to find out how that animal is
adapted to its environment.
ICT opportunity: Use of the Internet.
Enquiry skills 12A.1.6, 12A.1.8
Ask them each to write a short report on their animal and then make a brief presentation to the
other students.
Alternatively, ask each student to make a poster on the animal’s adaptations to its environment.
Then hold a class poster conference in which students view each other’s work and ask each
other questions.
Take students on a field trip to a local ecosystem for study. For example, go to a local pond, a
rocky shore or an area of desert, and make observations of the plants and animals found there.
Ask students to make notes about how the organisms are adapted to the specific environment.
Visit opportunity: Visit a local ecosystem.
Enquiry skills 12A.1.4, 12A.1.7
Ensure students take appropriate measures to limit disturbance to wildlife and habitats when
engaged in field work.
Ask students to make a photographic record of the xerophytic adaptations of plants.
ICT opportunity: Use of a digital camera.
Distinguish between the permanent adaptation of an organism to its normal environment and
the temporary acclimatisation of a visitor. Use the example of people who live permanently at
altitude, such as the natives of Peru, compared with temporary visitors to the Andes. Show
students graphs of the red blood cell counts of the two categories of people: those living
permanently at altitude compared with visitors before, during and after their visit. Ask students
to interpret the graphs using their textbook or the library.
Ask students to find out from the library or the Internet the difficulties experienced by athletes at
the Olympic Games and the football World Cup when they were held in Mexico.
443 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
ICT opportunity: Use of the Internet.
Enquiry skill 12A.1.8
© Education Institute 2005
Objectives
Possible teaching activities
2 hours
Reinforce previous knowledge of populations by quizzing students on inter- and intra-specific
competition, disease and predator–prey relationships.
Dynamics of population
growth
Explain and give examples to
illustrate the carrying capacity
of an environment.
Know how to construct and
interpret population curves for
different organisms; identify
the stages in population
growth and decline.
Get students to use computer models to explore population growth and decline. For example,
show how a change in an environmental factor, such as the introduction of a new predator,
changes the carrying capacity of the population.
Notes
School resources
ICT opportunity: Use of computer models.
Introduce the rapid growth rates of micro-organisms. Ask students to work out the potential
numbers of micro-organisms produced from a bacteria with a doubling time of 20 minutes over
a period of 6, 12, 18 and 24 hours. Discuss the figures with the class.
Provide students with a table of data for producing a growth curve for bacteria. Get them to plot
a graph and to examine and explain shape obtained. Use this example to ask students to
explain what the limits to growth are, and what an organism’s carrying capacity is.
Provide a suitable table of data.
Ensure students appreciate that an organism growing in a limited environment experiences
environmental resistance due to one or more limiting factors during growth. This means that
biotic potential is not realised because of environmental changes (resistance), and the organism
reaches its carrying capacity for a particular set of environmental factors.
Either carry out the following activity as a demonstration or get students to work in pairs and
carry out these investigations, record the data and analyse it, and write a report.
Determine the growth pattern of a population of yeast cells by inoculating a liquid media, a
broth, in a laboratory fermenter, and follow the progress of growth. Use a datalogger and sensors
to monitor the temperature, pH and oxygen level during the growth period. Remove unit samples
at regular intervals. Several different methods can be used to follow the growth, including:
• use a haemocytometer – the haemocytometer was originally used for counting blood cells,
but can be equally useful in counting yeast, bacteria or algae cells in liquid medium;
• use a colorimeter – a colorimeter can be used in a photometric method for estimating density
by recording the optical density of the sample.
You will need: fermenter, nutrient broth, yeast
culture, datalogger, sensors, haemocytometer,
colorimeter, video camera attached to a
microscope and monitor.
ICT opportunity: Use of datalogger and
sensors.
Details of the procedures can be found in
P. Freeland, Micro-organisms in Action, Hodder &
Stoughton, 1991 (ISBN 0-340-53268-8).
Demonstrate the use of the haemocytometer as a counting chamber for yeast cells by using a
video camera attached to the microscope and displayed on a monitor.
Get students to draw a diagram of the biotic factors (e.g. high reproductive rate, adequate food
supply) and abiotic factors (e.g. light, temperature, oxygen supply) that influence a population’s
carrying capacity.
Ask students to suggest an example in the wild where the organism itself causes a reduction in
its carrying capacity. Discuss their answers in class. One example is the African elephant, which
has to be culled occasionally in game parks when its numbers exceed the carrying capacity,
which causes the elephants to overgraze and destroy many of their food trees.
Show students a graph of the change in the human population over time (or get them to
construct their own graph from census data) and some graphs showing how carrying capacity
varies; debate which model may apply to the human population.
Enquiry skill 12A.1.8
Show students a growth curve of bacteria, yeast or a unicellular algae on an OHT. Ask them to
explain the growth stages: the lag phase, the exponential or logarithmic phase, the stationary or
plateau phase and the final decline or death phase.
444 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Objectives
Possible teaching activities
2 hours
Discuss with students whether ecosystems are stable systems or whether they are changing
dynamic systems.
Ecological succession
Describe the progression of
the development of an
ecological community from
primary colonisation to climax
community.
Notes
School resources
Introduce the concept of succession. Ensure students appreciate that populations of plants and
animals change over time through a succession of changes, or seres, to reach a relatively
stable climax community.
Take students to a suitable site displaying succession to carry out a field work investigation. For
example, visit an area that shows succession from open water to reed swamp to marsh land
and finally to dry land. Use a transect to follow the hydrosere from water to land.
Visit opportunity: Visit a local site displaying
succession.
Alternatively, take students to follow a xerosere from the sand dunes at the shore back to
woodland, if possible.
A rocky shore tends to show zonation of seaweeds in the inter-tidal region rather than
succession. However, small-scale succession can be seen by comparing different sites at
different stages of development. In particular, when pieces of rock flake off, or boulders fall from
cliffs or become overturned by stormy seas, these sites can be colonised by a succession of
organisms and are suitable for study. Alternatively, a small area of rock can be scraped clear to
investigate succession.
Get students to use the library or the Internet to find information that helps them to draw a
diagram of a primary succession. Ensure they include references to the following: pioneer
species, xerophytes, hydrophytes, xerosere, hydrosere, mesophytes, climax community.
ICT opportunity: Use of the Internet.
Enquiry skill 12A.1.8
Ask students to explain the process of primary succession:
• for a xerosere;
• for a hydrosere.
Ask students to trace the development of a biological community through a photographic
record.
2 hours
Discuss biological control with students. What is it? What is its aim?
Biological control
Ensure students appreciate that it involves humans exploiting a natural predator–prey
relationship that exists between other species. A beneficial organism (the predator) is deployed
against an undesirable one (the pest). The aim is not to eradicate the pest, but to reduce it to a
level where it has little detrimental effect.
Explain examples of
biological control of
population growth in natural
and commercial settings.
Assess the advantages and
disadvantages of biological
pest control.
ICT opportunity: Use of a digital camera.
Enquiry skill 12A.3.4
Show students a video that illustrates biological control.
Ask students to use the library or the Internet to find examples of biological control in the natural
environment and in the greenhouse. Examples they discover might include the following:
ICT opportunity: Use of the Internet.
• In the natural environment. There are two pests that lay their eggs on cattle dung in Australia:
the bush fly and the buffalo fly. In addition, the dung carries the eggs of worms that parasitise
the cattle. The indigenous dung beetles cannot deal with the soft cattle dung. The
introduction of an African species of dung beetle, which buries the dung within 48 hours, has
resulted in the control of the population of these pests.
• In the greenhouse environment. Greenhouse whitefly are controlled by introducing a parasitic
wasp into the greenhouse.
445 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Objectives
Possible teaching activities
Notes
School resources
Get students to match lists of examples of organisms involved in biological control. For
example, have one list of the target organisms (the pests) and another list of the control agents
(the predators). Additional lists could include harmful effects of the pest and method of action for
the controlling agent.
Carry out case studies of biological control, for example:
• The cane toad. Ask students to use the library or the Internet to find out about the cane toad,
which was introduced to Australia to control a sugar cane pest. The cane toad, a very large
amphibian, is now a cause of concern itself as it is eating its way through the local unique
fauna. In addition, its skin is poisonous, so it is a danger to pets and potential predators.
ICT opportunity: Use of the Internet.
• The rabbit. Ask students to use the library or the Internet to find out about the control of the
rabbit population in the UK. The controlling agent, a virus called myxomatosis, devastated the
rabbit population, which had reached pest levels.
Carry out a role-play exercise in which one student acts as an advocate for biological pest
control and another student acts as a protester against it.
2 hours
Comparing preservation
and conservation
Explain the similarities and
differences between
environmental preservation
and conservation; understand
that conservation is a
dynamic process involving
management and
reclamation.
Enquiry skill 12A.3.4
Get students to make two lists – conservation and preservation – and ask them to write
underneath the similarities and differences between these processes.
Alternatively, provide a list of statements referring to either conservation or preservation, or to
both, and get students to sort them into the appropriate categories.
Provide a suitable list.
Get students to contact environmental groups in Qatar and determine their policies regarding
conservation and preservation.
Ask students to find out about National Parks and how they are managed.
Carry out a simulation exercise. Divide the class into two and hold a debate. Get one side to
present the case for a development and get the other side to present the case opposing it. For
example:
Enquiry skill 12A.2.3
• the proposed development of a new marina on an important wildlife site;
• a proposed new highway development through an important nature reserve.
Get students, in pairs, to use the library or the Internet to examine and compare old and new
maps of an area of Qatar to see how land use has changed. Ask them what conclusions can be
drawn about the areas of nature reserves or wildlife sites over the last 30 years, for example.
ICT opportunity: Use of the Internet.
Enquiry skill 12A.2.3
Get students to find out which plant and animal species are in danger of extinction in the world
and what measures, if any, are being taken to halt their decline.
446 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Objectives
Possible teaching activities
2 hours
Debate the issue of growing genetically modified (GM) crops. Divide the class into two and ask
one group to present the case for GM crops and the other group to present the case against,
citing the argument for conservation. Get them to use the library or Internet to find their
information.
Food production and
conservation
Explain how a wish to use an
environment for food
production can conflict with a
wish for its conservation.
Notes
School resources
ICT opportunity: Use of the Internet.
Enquiry skill 12A.2.3
Ask students, individually, to review the evidence that science has provided the knowledge
needed to breed plants and animals that could feed the world, and to consider why people
starve.
Debate the issue of the deforestation that takes place to allow farmers to grow food crops.
Divide the class into two groups and ask one group to support the policy and the other group to
argue against the policy. Get them to use the library or Internet to find their information.
Make sure students refer to the forest community as being essential to conserve the biodiversity
of the planet and its genetic potential, and to the fact that it is an important potential source of
new drugs, medicines and unknown, undiscovered chemicals.
Debate the desirability of restricting fishing to conserve fish stocks. For example, use the case
study of the cod. The NW Atlantic cod stocks were over-fished off the coast of Newfoundland by
off-shore trawlers until the cod had virtually disappeared by 1992.They show little signs of any
recovery and the fishermen are out of work. Conversely, the Norwegian government controlled
fishing in the North Sea and the cod stocks are now recovering slowly. Introducing fishing
quotas is not the best answer either. Many EU nations have fish quotas, but the fishermen just
catch more fish than allowed in their quota, retain the higher value fish and throw back the rest
(around a third of their catch) dead.
447 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005
Assessment
Examples of assessment tasks and questions
Assessment
a. Draw a population curve from the data provided for the growth of the micro-organism.
Set up activities that allow
students to demonstrate what
they have learned in this unit.
The activities can be provided
informally or formally during
and at the end of the unit, or
for homework. They can be
selected from the teaching
activities or can be new
experiences. Choose tasks
and questions from the
examples to incorporate in
the activities.
b. Explain the four phases of growth identified.
Unit 12AB.6
Notes
School resources
Provide data for the growth of a micro-organism.
Explain, with examples, the relationship between an organism’s biotic potential, the
environment’s carrying capacity and the process of environmental resistance.
Describe the progression of the development of an ecological community from primary
colonisation to climax community.
Explain, with examples, the advantages and disadvantages of biological pest control.
Explain the similarities and differences between environmental preservation and conservation.
Explain the structural and physiological adaptations displayed by a named animal to its
environment.
448 | Qatar science scheme of work | Grade 12 advanced | Unit 12AB.6 | Biology 6
© Education Institute 2005