Unit 5 – Ecology

Topic 4 – Ecology

4.1 – SPECIES, COMMUNITIES, ECOSYSTEMS

Define species, habitat, population, community, ecosystem and ecology

• Species: A group of organisms that can interbreed and produce fertile, viable offspring

• Habitat: The environment in which a species normally lives or the location of a living organism

• 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

• Ecosystem: A community and its abiotic environment• Ecology: The study of relationships between living

organisms and between organisms and their environment

Distinguish between autotroph and heterotroph

• Autotroph: An organism that synthesizes its organic molecules from simple inorganc substances (e.g. CO2 and nitrates) - autotrophs are producers

• Heterotroph: An organism that obtains organic molecules from other organisms - heterotrophs are consumers

Distinguish between consumers, detritivores and saprotrophs

• Consumer: An organism that ingests other organic matter that is living or recently killed (Ex. Lion, sea turtle)

• Detritivore: A heterotroph that obtains organic nutrients from detritus by internal digestion (Ex. Earthworm, pillbug)

• Saprotroph: A heterotroph that obtains organic nutrients from dead organisms by external digestion (secreting digestive enzymes into it and absorbing the products of digestion) (Ex. Mushrooms, other fungi)

APPLICATION AND SKILLS

• SKILL 1: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition

• SKILL 2: Setting up sealed mesocosms to try to establish sustainability (Practical 5)

• SKILL 3: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling

• SKILL 4: Recognizing and interpreting statistical significance

4.2 – ENERGY FLOW

Decribe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms)

• A food chain shows the linear feeding relationships between species in a community

• The arrows represent the transfer of energy and matter as one organism is eaten by another (arrows point in the direction of energy flow)

• The first organism in the sequence is the producer, followed by consumers (1°, 2°, 3°, etc.)

Examples of food chains

Describe what is meant by a food web

• A food web is a diagram that shows how food chains are linked together into more complex feeding relationships within a community

• There can be more than one producer in a food web, and consumers can occupy multiple positions (trophic levels)

Define trophic level

• An organism's trophic level refers to the position it occupies in a food chain

• Producers always occupy the first trophic level, while saprotrophs would generally occupy the ultimate trophic level of a given food chain or food web

• The trophic levels in a community are:

Deduce the trophic levels of organisms in a food web and food chain

• The trophic level of an organism can be determined by counting the number of feeding relationships preceding it and adding one (producer always first)

• Trophic Level = Number of arrows (in sequence) before organism + 1

• In food webs, a single organism may occupy multiple trophic levels

Construct a food web containing up to 10 organisms, using appropriate information

• Hint: When constructing a food web, always try to position an organism relative to its highest trophic level (to keep all arrows pointing in same direction)

Food web (trophic levels in red)

State that light is the initial energy source for almost all communities

• All green plants, and some bacteria, are photo-autotrophic - they use light as a source of energy for synthesizing organic molecules

• This makes light the initial source of energy for almost all communities

• Some bacteria are chemo-autotrophic and use energy derived from chemical processes (e.g. nitrogen-fixating bacteria)

Explain the energy flow in a food chain

• Energy enters most communities as light, where it is absorbed by autotrophs (e.g. plants) and converted into chemical energy via photosynthesis

• Energy then gets passed to the primary consumer (herbivore) when they eat the plant, and then gets passed to successive consumers (carnivores) as they are eaten in turn

• Only ~10% of energy is passed from one trophic level to the next, the rest is lost

• Because ~90% of energy is lost between trophic levels, the number of trophic levels are limited as energy flow is reduced at higher levels

Summary of Energy Flow in a Food Chain

State that energy transformations are never 100% efficient

• When energy transformations take place in living organisms the process is never 100% efficient

• Typically, energy transformations in living things are ~10% efficient, with about 90% of the energy lost between trophic levels

• This energy may be lost as heat, be used up during cellular respiration, be excreted in feces or remain unconsumed as the uneaten part of food

Explain the reason for the shape of pyramids of energy

• A pyramid of energy is a graphical representation of the amount of energy of each tropic level in a food chain

• They are expressed in units of energy per area per time (e.g. kJ m2 year -1)

• Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost when transferred to the next source

• This is an application of the second law of thermodynamics• Each level of the pyramid of energy should be

approximately one tenth the size of the level preceding it, as energy transformations are ~10% efficient

Pyramid of energy

Explain that energy enters and leaves ecosystems, but nutrients must be recycled

• The movement of energy and matter through ecosystems are related because both occur by the transfer of substances through feeding relationships

• However, energy cannot be recycled and an ecosystem must be powered by a continuous influx of new energy from an external source (e.g the sun)

• Nutrients refer to material required by an organism, and are constantly being recycled within an ecosystem as food (either living or dead)

• The autotrophic activities of the producers (e.g. plants) produce organic materials from inorganic sources, which are then fed on by the consumers

• When heterotrophic organisms die, these inorganic nutrients are returned to the soil to be reused by the plants (as fertilizer)

• Thus energy flows through ecosystems, while nutrients cycle within them

5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients

• In order for organisms to grow and reproduce, they need a supply of the elements of which they are made

• The saprotrophic activity of decomposers (certain bacteria and fungi), free inorganic materials from the dead bodies and waste products of organisms, ensuring a continual supply of raw materials for the producers (which can then be ingested by consumers)

• Thus saprotrophic bacteria and fungi play a vital role in recycling nutrients within an ecosystem

APPLICATION AND SKILLS

• SKILL 1: Quantitative representations of energy flow using pyramids of energy

4.3 – CARBON CYCLING

Draw and label a diagram of the carbon cycle to show the processes involved

• Here are four main 'pools' of carbon in the environment:– • Atmosphere– • Biosphere – • Sediments – • Ocean

• There are a number of processes by which carbon can be cycled between these pools:

• Photosynthesis: Atmospheric carbon dioxide is removed and fixed as organic compounds (e.g. sugars). In aquatic ecosystems, carbon is present as dissolved carbon dioxide and hydrogen carbonate ions.

• Feeding: In which organic carbon is moved from one trophic level to the next in a food chain

• Respiration: All organisms (including plants) metabolize organic compounds for energy, releasing carbon dioxide as a by-product

• Fossilization: In which carbon from partially decomposed dead organisms from past geological eras becomes trapped in sediment as coal, oil and gas that accumulates in porous rocks (fossil fuels) – In oceans, Reef building corals and Mollusca have hard parts that

are composed of calcium carbonate and can become fossilized in limestone

• Combustion: During the burning of fossil fuels and biomass• Other processes

– In oceans, carbon can be reversibly trapped and stored as limestone (storage happens more readily at low temperatures).

– Methane is produced from organic material in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground

– Methane is oxidized to carbon dioxide and water in the atmosphere– Peat forms when organic matter is not fully decomposed because of

acidic and/or anaerobic conditions in waterlogged soils.

APPLICATION AND SKILLS

APPLICATION 1: Estimation of carbon fluxes due to processes in the carbon cycleAPPLICATION 2: Analysis of data from air monitoring stations to explain annual fluctuationsSKILL 1: Construct a diagram of the carbon cycle

Carbon cycle game (lab grade)

1) After 15 times of rolling the dice, create a BAR graph using the data you collected to represent the number of times you were at each station

2) Where was the most/least amount of carbon in the cycle?

3) Write a story about your carbon atom as it moved through the carbon cycle.

4) Construct a labeled diagram of the carbon cycle

4.4 – CLIMATE CHANGE

Explain the relationship between the rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen

and the enhanced greenhouse effect

• The greenhouse effect is a natural process whereby the earth's atmosphere behaves like a greenhouse to create the moderate temperatures to which life on earth has adapted (without the greenhouse effect, temperatures would drop significantly every night)

• The incoming radiation from the sun is short-wave ultraviolet and visible radiation

• Some of this radiation is reflected by the earth's surface back into space as long-wave infrared radiation (heat)

• Greenhouse gases absorb this long-wave infrared radiation and re-reflect it back to the earth as heat, resulting in increased temperatures (the greenhouse effect)– Greenhouse gases include carbon dioxide and

water vapor, methane and nitrous oxides

The Greenhouse Effect

Analyze the changes in concentration of atmospheric carbon dioxide using historical records

• Recent Trends:• Atmospheric carbon dioxide concentrations have

been measured at the Mauna Loa atmospheric observatory in Hawaii from 1958 and has since been measured at a number of different locations globally

• The data shows that there is an annual cycle in CO2 concentrations which may be attributable to seasonal factors, but when data from the two hemispheres is incorporated, it suggests that atmospheric CO2 levels have risen steadily in the past 30 years

• Long Term Estimates:• Carbon dioxide concentration changes over a long

period of time have been determined by a variety of sources, including analyzing the gases trapped in ice (and thus providing a historical snapshot of atmospheric concentrations)

• Data taken from the Vostok ice core in Antarctica shows that fluctuating cycles of CO2 concentrations over thousands of years appear to correlate with global warm ages and ice ages

• It is compelling to note that CO2 levels appear to be currently higher than at any time in the last 400,000 years (especially since the start of the industrial revolution 200 years ago)

Recent and Long-term Changes in Carbon Dioxide Concentration

Mauna Loa CO2 Data (last 50 years)

Vostok Ice Core Data - CO2 vs Temperature (last 400,000 years)

• The enhanced greenhouse effect refers to the suggested link between the increase in greenhouse gas emissions by man (combustion of fossilized organic matter) and changes in global temperatures and climate conditions

• The main greenhouse gases are water vapor, carbon dioxide (CO2), methane (CH4) and oxides of nitrogen (e.g. NO2)

• While these gases occur naturally, man is increasing greenhouse gas emissions via a number of processes, including:– • Deforestation (less trees) – • Industrialization (more combustion) – • Increased farming / agriculture (more methane)

• With increases in greenhouse gas emission, it is thought that the atmospheric temperature may increase and threaten the viability of certain ecosystems, although this link is still being debated

Outline the precautionary principle

• The precautionary principle states that when a human-induced activity raises a significant threat of harm to the environment or human health, then precautionary measures should be taken even if there is no scientific consensus regarding cause and effect

• Because the global climate is a complex phenomena with many emergent properties, and is based on time frames well beyond human lifespans, it is arguably impossible to provide appropriate scientific evidence for enhanced global warming before consequences escalate to potentially dire levels

• According to the precautionary principle, the onus falls on those contributing to the enhanced greenhouse effect to either reduce their input or demonstrate their actions do not cause harm - this makes it the responsibility of governments, industries, communities and even the individual

• The precautionary principle is the reverse of previous historical practices whereby the burden of proof was on the individual advocating action

Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced

greenhouse effect

• Arguments for Action• Risks of inaction are potentially severe, including increased frequency of severe

weather conditions (e.g. droughts, floods) and rising sea levels• Higher temperatures will increase the spread of vector-borne diseases• Loss of habitat will result in the extinction of some species, resulting in a loss of

biodiversity• Changes in global temperature may affect food production, resulting in famine in

certain regions• The effects of increased temperatures (e.g. rising sea levels) could destroy

certain industries which countries rely on, leading to poverty• All of these consequences could place a far greater economic burden on

countries than if action were taken now

• These factors would increase competition for available resources, potentially leading to increased international tensions

• Arguments for Inaction• Cutting greenhouse emissions may delay economic growth in

developing countries, increasing poverty in these regions• Very difficult to police - what level of action would be considered

sufficient on a global scale in the current absence of scientific consensus?

• Boycotting trade with non-compliant countries could negatively effect economies and create international tensions

• No guarantee that human intervention will be sufficient to alter global climate patterns

• Money and industrial practices that may be used to develop future technologies may be lost due to restrictions imposed by carbon reduction schemes

• Carbon reduction schemes will likely result in significant job losses from key industries, retraining workers will require significant time and money

Outline the consequences of a global temperature rise on arctic ecosystems

• Increases in global temperature pose a credible threat to arctic ecosystems, including:

• Changes in arctic conditions (reduced permafrost, diminished sea ice cover, loss of tundra to coniferous forests)

• Rising sea levels • Expansion of temperate species increasing competition with native species

(e.g. red fox vs arctic fox)• Decomposition of detritus previously trapped in ice will significantly increase

greenhouse gas levels (potentially exacerbating temperature changes)• Increased spread of pest species and pathogens (threatening local wildlife)• Behavioural changes in native species (e.g. hibernation patterns of polar

bears, migration of birds and fish, seasonal blooms of oceanic algae)• Loss of habitat (e.g. early spring rains may wash away seal dens)• Extinction and resultant loss of biodiversity as food chains are disrupted

‘Inconvenient Truth’ and opposing viewpoints articles

1) What is the position the author/Gore is taking?

2) How do they support their position? What are their specific arguments?

3) What are the weaknesses of their arguments?

4) How could they strengthen their arguments?

APPLICATION AND SKILLS

APPLICATION 1: Threats to coral reefs from increasing concentrations of dissolved carbon dioxideAPPLICATION 2: Correlations between global temperatures and carbon dioxide concentrations on EarthAPPLICATION 3: Evaluating claims that human activities are not causing climate change