Download Topic 4: Ecology

Topic 4: Ecology
This section includes all or parts of Campbell Chapters 3,9,10,24,29,31,33,37,52,54,55, and 56
*It is strongly recommended that you read and take column notes on the page numbers listed below. In addition, you should
answer the “Understandings” and “Sample Questions and Assessment Statements” below. You should also check out the
presentations listed online.
Species, Communities and Ecology—Chapters 55 and 56
Essential Idea: The continued survival of living organisms including humans depends on sustainable
communities.
Nature of Science:
•
Looking for patterns, trends and discrepancies—plants and algae are mostly autotrophic but some
are not.
Understandings:
1. Species are groups of organisms that can potentially interbreed to produce fertile offspring. 488
2. Members of a species may be reproductively isolated in separate populations. 488; 1149
3. Species have either an autotrophic or heterotrophic method of nutrition (a few species have both
methods). 185
4. Consumers are heterotrophs that feed on living organism by ingestion. 185; 1224; Online
5. Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
185; 1224; Online
6. Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external
digestion. 185; 1224; Online
7. A community is formed by populations of different species living together and interacting with
each other. 1149
8. A community forms an ecosystem by its interactions with the abiotic environment. 1149
9. Autotrophs obtain inorganic nutrients from the abiotic environment. 185
10. The supply of inorganic nutrients is maintained by nutrient cycling. 1231-1236;
11. Ecosystems have the potential to be sustainable over long periods of time. 787-789; 1264-1265
Applications and Skills:
•
Skill: Classifying species as autotrophs (185), consumers (185; 1228-1230), detritivores
(online), or saprotorphs (online) from a knowledge of their mode of nutrition.
•
Skill: Setting sealed mesocosms to try to establish sustainability. (Practical 5) Online.
•
Skill: Testing for association between two species using the chi-squared test with data obtained
by quadrat sampling. Pervasive in course.
•
Skill: Recognizing and interpreting statistical significance. Pervasive in course.
Sample Questions and Assessment Statements:
•
Define species (488), habitat (Online), population (1149), community (1149), ecosystem (1149)
and ecology (1148).
•
Distinguish between autotroph and heterotroph. 185
•
Distinguish between consumers, detritivores and saprotrophs. 185; 1224; Online
•
Draw and label a diagram of the carbon cycle to show the processes involved. 1231-1236
Guidance:
•
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.
•
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 absences of the
chosen species should be recorded.
International-Mindedness:
•
The need for sustainability in human activities could be discussed and the methods needed to
promote this.
AIMS:
•
Aim 6: It would be best for students to obtain data for the chi-squared test themselves, to give
first-hand experience of field work techniques.
Energy Flow—Chapters 54 and 55
Essential Idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace
energy lost as heat.
Nature of Science:
•
Use theories to explain natural phenomena—the concept of energy flow explains the limited
length of food chains.
Understandings:
1. Most ecosystems rely on a supply of energy from sunlight. Chapter 10; 1224-1228
2. Light energy is converted to chemical energy in carbon compounds by photosynthesis. Chapter
10
3. Chemical energy in carbon compounds flows through food chains by means of feeding. 12241230;
4. Energy released from carbon compounds by respiration is used in living organisms and converted
to heat. 1223-1224; Online
5. Living organisms cannot convert heat to other forms of energy. 1223-1224; Online
6. Heat is lost from ecosystems. 1223-1224
7. Energy losses between trophic levels restrict the length of food chains and the biomass of higher
trophic levels. 1205-1210; 1228-1230; Online
Application and Skills:
•
Skill: Quantitative representations of energy flow using pyramids of energy. 1228-1230
Guidance:
•
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. 1228-1230
•
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. 1228-1230
•
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. 12311235; Online.
Sample Questions and Assessment Statements:
•
State that light is the initial energy source for almost all communities. Chapter 10; 1224-1228
•
Describe what is meant by a food chain, and give an example with at least three linkages (four
organisms). 1205-1207
•
State that energy transformations are never 100% efficient. 1228-1230
•
Explain reasons for the shape of pyramids of energy. 1228-1230
•
Explain that energy enters and leaves ecosystems, but nutrients must be recycled. 1231-1235
•
State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. 648-652; Online
•
Define trophic level. 1223-1224
•
Describe what is meant by a food web. 1205-1206
•
Deduce the trophic level of organisms in a food chain and a food web. 1205-1210; 1223-1229
International Mindedness:
•
The energetics of food chains is a factor in the efficiency of food production for the alleviation of
world hunger.
Carbon Cycling—Chapters 9, 10 and 55
Essential Idea: Continued availability of carbon in ecosystems depends on carbon cycling.
Nature of Science:
•
Making accurate, quantitative measurements—it is important to obtain reliable data on the
concentration of carbon dioxide and methane in the atmosphere.
Understandings:
1. Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds. Chapter 10
2. In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions.
54-55
3. Carbon dioxide diffuses from the atmosphere or water into autotrophs. Chapter 10
4. Carbon dioxide is produced by respiration and diffuses out of organism into water or the
atmosphere. Chapter 9
5. Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and
some diffuses into the atmosphere or accumulates in the ground. Online
6. Methane is oxidized to carbon dioxide and water in the atmosphere. Online
7. Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic
conditions in waterlogged soils. 609-610; Online
8. Partially decomposed organic matter from past geological eras was converted either into coal or
into oil and gas that accumulate in porous rocks. 615; Online
9. Carbon dioxide is produced by the combustion of biomass and fossilized organic matter. 164;
615; Online
10. Animals such as reef-building corals and mollusca have hard parts that are composed of calcium
carbonate and can become fossilized in limestone. 54-55; 673; 1165; Online
Applications and Skills:
•
•
•
Application: Estimation of carbon fluxes due to processes in the carbon cycle. 1231-1241;
Online
Application: Analysis of data from air monitoring stations to explain annual fluctuations. 12391240
Skill: Construct a diagram of the carbon cycle. 1231-1236
Sample Questions and Assessment Statements:
•
Draw and label a diagram of the carbon cycle to show the processes involved. 1231-1236
•
Analyze the changes in concentration of atmospheric carbon dioxide using historical records.
1239-1242
Guidance:
•
Carbon fluxes should be measured in gigatonnes.
AIMS:
•
Aim 8: The ethical implications of diverting crops such as maize from a food to a fuel crop could
be considered.
Climate Change—Chapter 55
Essential Idea: Concentrations of gases in the atmosphere affect climates experienced at the Earth’s
surface.
Nature of Science:
•
Assessing claims—assessment of the claims that human activities are producing climate change.
Understandings:
1. Carbon dioxide and water vapor are the most significant greenhouse gases. 1239-1242
2. Other gases including methane and nitrogen oxides have less impact. 1239-1242
3. The impact of a gas depends on its ability to absorb long wave radiation as well as on its
concentration in the atmosphere. 1239-1242; Online
4. The warmed Earth emits longer wavelength radiation (heat). 1239-1240; Online
5. Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
1239-1240; Online
6. Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
1239-1240; Online
7. There is a correlation between rising atmospheric concentrations of carbon dioxide since the state
of the industrial revolution 200 years ago and average global temperatures. 1231-1234; 12391240; Online
8. Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of
fossilized organic matter. 1236; 1239-1240; Online
Applications and Skills:
•
Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
54-55; 1165; Online
•
Application: Correlations between global temperatures and carbon dioxide concentrations on
Earth. 1240-1241; Online
•
Application: Evaluating claims that human activities are not causing climate change. Online
Sample Questions and Assessment Statements:
•
•
•
Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane
and oxides of nitrogen and the enhanced greenhouse effect. 1239-1242; Online
Outline the precautionary principle. Online and handouts
Evaluate the precautionary principle as a justification for strong action in response to the threats
posed by the enhanced greenhouse effect. Online and handouts
Guidance:
•
Carbon dioxide, methane and water vapor should be included in discussions.
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.
International Mindedness:
•
Release of greenhouse gases occurs locally but has a global impact, so international cooperation to
reduce emissions is essential.
TOK:
•
The precautionary principle is meant to guide decision-making in conditions where a lack of
certainty exists. Is certainty ever possible in the natural sciences?
AIMS:
•
Aim 7: Databases can be used to analyze concentrations of greenhouse gases.
•
Aim 8: There are interesting parallels between humans that are unwilling to reduce their carbon
footprint and cheating in social animals. When the level of cheating rises above a certain level,
social behavior breaks down.