Biology: Objectives 5.1-5.3 and Option G1-G5

5.3.2 Draw and label a graph showing a sigmoid (S-shaped) population growth curve.

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G.5.1 Distinguish between r-strategies and k-strategies

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

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

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5.1.12 Explain reasons for the shape of pyramids of energy.

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5.2.2 Analyse the changes in concentration of atmospheric carbon dioxide using historical records.

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G.2.2 Calculate values for gross production and net production using the equation: gross production - respiration = net production

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

A food chain shows the direction of energy flow from one species to another. For example, an arrow from A to B means that A is being eaten by B and therefore indicates the direction of the energy flow. Example: Carrot Plant (Daucus Carota) --> Eastern Cottontail Rabbit (Sylvilagus floridanus) --> Red Fox (Vulpes vulpes) --> Golden Eagle (Aquila chrysaetos)

5.1.5 Describe what is meant by a food web.

A food web is a diagram that shows all the feeding relationships in a community with arrows which show the direction of the energy flow.

G.1.8 Distinguish between fundamental and realised niches

A fundamental niche is the potential mode of existence of a species (what can theoretically occupy based on adaptations) The realised niche is the actual mode of existence of a species (what the species actually occupies based on limiting factors) The realised niche is often smaller than the fundamental niche and the difference is due to competition and predation

G.2.5 Construct a pyramid of energy, given appropriate information

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

G.1.3 Describe one method of random sampling, based on quadrat method, that is used to compare population size of two plant or animal species

A quadrat is a rectangular or circular frame of known area that is used to establish population densities An area is defined and the quadrat is randomly placed inside (creating random number tables based on grids can reduce human bias) The number of individuals of a given species within the quadrat is counted and then the process is repeated for different areas Smaller quadrats must be placed more times than larger quadrate, but enough samples must be collected to make it representative The population density is the number of individuals counted for a given species divided by the area used Plants may be difficult to individually count, but an estimation of percentage ground coverage can be used as an alternative Care must be taken when counting animal species to ensure their movements do not result in the repeated sampling of the same animal

G.3.5 Discuss the impacts of alien species on ecosystems

Alien species (such as the cane toad) may impact a local ecosystems (i.e. Australia) in a number of ways: Interspecific Competition - cane toads competed with native toads and frogs and displaced them Predation - cane toads produce a toxin that poisons local predators, disrupting the food chain Species Extinction - the Northern quoll has become endangered due to cane toads Biological Control - cane toads were supposed to limit sugar cane invertebrate pests (they didn't!)

G.3.4 List three examples of the introduction of alien species that have had significant impacts on ecosystems

Alien species are those that have been transferred from their natural habitat to a new environment where conditions are still suitable for their survival The transfer of alien species can be either accidental or deliberate (i.e. as a means of biological control) If the alien species should have a detrimental effect on the pre-existing food chains it is classed as an invasive species Alien species that have had a significant impact on their new ecosystem include: Biological Control: Myxoma virus (causes myxomatosis) was introduced into Australia from South America to cull rabbit numbers Deliberate Release: Monterey pine trees were introduced to Australia (from California) as a commercial timber crop Accidental Release: Rats were introduced to New Zealand by early settlers, who unintentionally transported them on their ships

G.1.5 Explain what is meant by the niche concept, including an organism's spatial habitat, its feeding activities and its interactions with other species

An ecological niche describes the role of an organism within its ecosystem, including the precise conditions the organism needs to survive: Spatial habitat - including the abiotic factors of the environment and the set of all ranges of limiting factors an organism tolerates Feeding activities - including what the species eats and how it obtains its food Interactions with other species - including predator-prey and mutualistic relationships

5.1.2 Distinguish between autotroph and heterotroph.

Autotrophs are organisms that synthesize their organic molecules from simple inorganic substances whereas heterotrophs are organisms that obtain organic molecules from other organisms.

G.4.3 Outline the biogeographical features of nature reserves that promote the conservation of diversity

Biological conservation involves setting aside land for restricted access and controlled use to allow for the maintenance of local biodiversity Nature reserves will typically show certain biogeographical features that help to promote the conservation of diversity: Size Larger nature reserves usually promote conservation better than smaller nature reserves Larger reserves allow for the mobility of far-ranging animals (e.g. grizzly bears) and have proportionally smaller perimeters (less affected by 'edge') Edge Effect Ecology at the edges of ecosystems is different from central areas due to edge effects (e.g. more sunlight, more wind, external predators, etc.) As organisms living near the edge of an ecosystem have more competition from other species, certain species will flourish where there are less edges However certain species will favour edge environments (e.g. the brown-headed cowbird) Fragmentation of forests will increase egde effect by reducing the central areas of fragmented reserves Habitat Corridors Habitat corridors (e.g. tunnels under roads, narrow belts of bushland) allow the movement of wildlife between different parts of a fragmented habitat Habitat corridors connect otherwise isolated habitats, increasing total size of the reserve and improving genetic diversity

G.4.4 Discuss the role of active management techniques in conservation

Biological conservation requires constant and continual management of the environment, including: Maintenance of effective boundaries (protection from poachers and invasive species) Restoration of degraded areas (maintaining habitat conditions in their original state) Measures to facilitate the successful completion of species' life cycles (e.g. nesting boxes for birds) Promotion of recovery of endangered species (restocking / reintroducing species whose populations are low)

G.3.7 Define biomagnification

Biomagnification is the process in which chemical substances become more concentrated at each trophic level

G.1.9 Define biomass

Biomass is the total dry organic matter of living organisms or ecosystems

G.2.9 Distinguish between biome and biosphere

Biome: A geographical area that has a particular climate and sustains a specific community of plants and animals (i.e. a type of ecosystem) Biosphere: The total of all areas where living things are found (i.e. the totality of biomes)

G.1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism

Competition is the interaction between two organisms striving for the same resource in the same place due to overlapping niches Competition can be either interspecific (between two different species) or intraspecific (within a single species) Example 1: Red foxes and coyotes compete for food (e.g. rabbits) within the grasslands of the United States Example 2: In the UK, the natterjack toad and the common toad compete for the same habitat (coastal dunes) Herbivory involves a primary consumer (herbivore) feeding on a producer (plant) Example 1: Rabbits eat marram grass in a sand dune ecosystem Example 2: Leaf monkeys (langurs) feeding on fig trees A predator is a consumer feeding on another consumer (prey) The number of predators will affect the number of prey, to create a cyclic interaction Example 1: The Canadian lynx feeds on the arctic hare Example 2: Tigers feed on wild pigs in the Thai rainforests A parasite is an organism which lives on or in a host and depends on the host for at least part of its survival to the harm of the host Example 1: Plasmodium is a parasite which spends part of its life cycle in a human host and causes malaria (endoparasite) Example 2: Leeches will puncture the skin of a host and feed on its blood, releasing an enzyme to prevent blood clotting (ectoparasite) A mutualistic relationship involves two species living together in an arrangement where both species benefit Example 1: Clownfish are covered in mucus which protects them from sea anemone tentacles - they draw food to anemones and feed on remains Example 2: Lichen is a mutualistic relationship between algae and fungi - algae photosynthesise and make sugars, fungi absorb minerals

5.1.3 Distinguish between consumers, detritivores and saprotrophs.

Consumer: an organism that ingests other organic matter that is living or recently killed. Detritivore: an organism that ingests non-living organic matter. Saprotroph: an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

G.3.1 Calculate the Simpson diversity index for two local communities

D=(N(N-1))/(n(n-1)) Location 1: Total for n = 1745; Total for n(n-1) = 659848 Location 2: Total for n = 1560; Total for n(n-1) = 1565840 (Source is the packet provided.)

G.3.8 Explain the cause and consequences of biomagnification, using a named example

DDT (dichlorodiphenyltrichloroethane) is a chemical pesticide that has been used to target insects (most notably mosquitos) It is fat soluble and is selectively retained within the tissues of an organism instead of being excreted Because organisms at higher trophic levels must consume more biomass to meet energy requirements, they experience increased contamination DDT sprayed on water to eliminate mosquito larvae will be taken up by algae and then passed on to the primary consumers (e.g. small fish) At each subsequent trophic level the concentrations of DDT stored in the body will increase due to the increased food intake Very high levels of DDT were discovered in birds that preyed on fish, and the chemical was found to interfere with formation of hard egg shells

G.2.6 Distinguish between primary and secondary succession, using an example of each

Ecological succession describes the process by which a sequence of increasingly complex communities develop over time The climax community is reached when succession has ended and the community has all of its characteristics Primary Succession - Occurs when succession starts on entirely new land without any established soil - this may occur at river deltas, sand dunes or on exposed rock As the organisms which first colonise a region (pioneer community) die and decompose, they establish a layer of soil for future organisms to utilise On exposed rock, lichen and moss may initally colonise the area and provide a layer of soil for seeds to germinate, increasing species diversity Secondary Succession - Occurs when succession starts on existing soil following a natural or artificial upheaval of the primary succession Secondary succession occurs when the existing biota is removed from soil that is already formed - such as following a bushfire or earthquake During secondary succession, dominance is usually achieved by the fastest growing plants

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

Energy is not recycled. It is constantly being supplied to ecosystems through light energy and then flows through the trophic levels. As it flows through the trophic levels energy is lost in feces, tissue loss and death. This energy from these losses is passed on to detritivores and saprotrophs. However the energy is then lost from the ecosystem as the remaining energy in the trophic levels and the energy in the saprotrophs and detritivores is lost through cell respiration in the form of heat. As a result, energy needs to be constantly supplied to the ecosystems. Nutrients on the other hand are different as they constantly have to be recycled. Carbon, nitrogen and phosphorus are all examples of nutrients. There is only a limited supply of these as they are not resupplied to the ecosystems like energy. Therefor they have to be recycled over and over. They are absorbed from the environment, used by living organisms and then returned to the environment.

G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels

Energy transfer along a food chain is less that 100% efficient (~10% of energy is transferred between trophic levels) The remainder is lost as heat, used up in respiration, excreted (as faeces or urine) or simply not consumed Nutrient transfer is also less than 100% efficient between trophic levels Consequently, there is a reduced total amount of biomass available to higher order consumers (resulting in small biomass at these levels) Higher order consumers need to hunt prey to survive, adding an extra energy cost to the feeding process Because predators need to consumer larger quantities of prey to derive sufficient energy, more competition exists - resulting in lower numbers

5.1.11 State that energy transformations are never 100% efficient.

Energy transformations are never 100% efficient.

G.4.6 Outline the use of ex situ conservation measures, including captive breeding of animals, botanic gardens and seed banks

Ex situ conservation describes the preservation of an endangered species away from its natural habitat Such conservation may involve captive breeding of animals (e.g. zoos), botanical gardens and seed banks (stored supplies of seeds) Advantages: Ex situ conservation allows for greater control of necessary conditions (e.g. climate control, dietary intake, veterinary care, etc.) Such methods can improve the chances of successful breeding by allowing the use of artificial methods (e.g. embryo transfer, IVF, etc.) Disadvantages: Species raised in captivity are less likely to be successfully reintroduced into the wild and does not prevent the destruction of their natural habitat Ex situ conservation increases inbreeding by restricting the gene pool and reduces evolution as species are not in their natural habitat

G.4.2 Outline the factors that contributed to the extinction of one named animal species

Extinction is the cessation of a species or higher taxon level, reducing biodiversity The Tasmanian tiger (Thylacinus cynocephalus) became extinct after the arrival of European settlers to Australia and the introduction of sheep Tasmanian tigers would feed on the introduced sheep and were subsequently hunted by man, causing numbers to rapidly decline The loss of habitat to human development and the lack of successful breeding programs in zoos saw population numbers dwindle The last Tasmanian tiger died in captivity in 1936 and they were declared extinct by international standards in 1986 Aboriginal rock paintings suggest the Tasmanian tiger once lived on mainland Australia but died out from predation and competition from dingoes

5.2.6 Outline the consequences of a global temperature rise on arctic ecosystems.

Global warming could have a number of disastrous consequences largely affecting the arctic ecosystems: The arctic ice cap may disappear as glaciers start to melt and break up into icebergs. Permafrost will melt during the summer season which will increase the rate of decomposition of trapped organic matter, including peat and detritus. This in turn will increase the release of carbon dioxide which will increase the green house effect even further. Species adapted to temperature conditions will migrate north which will alter food chains and have consequences on the animals in the higher trophic levels. Marine species in the arctic water may become extinct as these are very sensitive to temperature changes within the sea water. Polar bears may face extinction as they loose their ice habitat and therefore can no longer feed or breed as they normally would. Pests and diseases may become quite common with rises in temperature. As the ice melts, sea levels will rise and flood low lying areas of land. Extreme weather events such as storms might become common and have disastrous effects on certain species.

G.2.1 Define gross production, net production and biomass

Gross Production: The amount of organic matter (biomass) produced by plants Net Production: The amount of organic matter produced by plants minus what is needed for plant respiration Biomass: The total dry organic matter of living organisms or ecosystems

G.4.5 Discuss the advantages of in situ conservation of endangered species (terrestrial and aquatic nature reserves)

In situ conservation describes the preservation of an endangered species 'on site' (i.e. in its natural habitat or nature reserve) Such conservation allows species to live in the environment to which they are adapted and to occupy their natural position in the food chain In situ conservation maintains the animal's normal behaviour (offspring usually aquire skills from parents and peers around them) Retaining the natural habitat prevents its eventual loss and ensures it remains available for other endangered species Such reserves provide a place to return animals from breeding programs as they provide more realistic conditions for reintegration Reserves in different regions of the world can share information and provide a place for scientific study and developing public awareness

G.4.1 Explain the use of biotic indices and indicator species in monitoring environmental change

Indicator species are sensitive to specific environmental conditions and consequently have a limited range of tolerance Their population growth, reduction or disappearance indicates specific changes in the environment, making them a useful means of monitoring change Indicator species may be sensitive to a number of different environmental conditions: Lichen, along with mosses, are susceptible to air-borne pollutants dissolved in water (e.g. sulphur dioxide) Tubifex worms are sensitive to concentrations of heavy metals Mayfly larvae and certain aquatic invertebrates are sensitive to dissolved oxygen levels in water Biotic indices compare the relative frequency of indicator species and is calculated to provide an overall environmental assessment of an ecosystem Calculating biotic indices involves multiplying the population size of each indicator species by its pollution tolerance rating A high biotic index indicates an abundance of pollution sensitive organisms and hence denotes an unpolluted environment A low biotic index indicates the absence of indicator species and an abundance of pollution tolerant organisms (hence a polluted environment) A change in the biotic index over time marks a change in the environmental conditions within the ecosystem

G.5.6 Discuss international measures that would promote the conservation of fish

Large areas of the ocean are not under any specific government's control and thus require international cooperation and legislation Fish stocks are a renewable resource if managed carefully - international measures that promote the conservation of fish include: Limiting total allowable catch size Regulating allowable gear (e.g. mesh sizes, banning drift nets, etc.) Limiting number of allowable fishing days for fishermen Registering and regulating the number of fishing vessels allowed to operate Close fishing during fish breeding seasons Cordon off certain waters for biological conservation Encourage the use of fish farms

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

Light is the initial energy source for almost all communities.

5.3.1 Outline how population size is affected by natality, immigration, mortality and emigration.

Natality: increases population size as offspring are added to the population. Immigration: increases population size as individuals have moved into the area from somewhere else and so this adds to the population. Mortality: decreases the population as some individuals get eaten, die of old age or get sick. Emigration: decreases the population as individuals have moved out of the area to go live somewhere else.

G.3.11 State that ozone in the stratosphere absorbs UV radiation

Ozone in the stratosphere absorbs UV radiation, however there is a limit to how much can be absorbed Regions where the ozone layer is thinner (e.g. due to CFCs) will experience higher terrestrial UV levels and increased risks of cancer

5.1.7 Deduce the trophic level of organisms in a food chain and a food web.

Plants or any other photosynthetic organisms are the producers. Primary consumers are the species that eat the producers. Secondary consumers are the species that eat the primary consumers and tertiary consumers in turn eat the secondary consumers.

G.2.8 Explain the effects of living organisms on the abiotic environment, with reference to the changes occurring during primary succession

Primary succession begins on new land, with pioneer species breaking down substrate to create organic soil As plant species colonise the area, the litter produced by their growth and their decomposing remains will cause the following changes: Will increase soil depth (adds humus to soil) Will increase soil mineral content (and break down rock through root growth) Will aerate soil and alter the soil pH Will improve soil water retention and reduce draining This will allow for the growth of larger plants, which will provide shade and reduce erosion through the binding action of their roots

5.1.10 Explain the energy flow in a food chain.

Producers receive their energy from light energy (the sun) by means of photosynthesis. After this, the energy in organic matter flows from producers to primary consumers to secondary consumers to tertiary consumers. This is because producers will be eaten by primary consumers which in turn will be eaten by secondary consumers and so on. However, between these trophic levels, energy is always lost. All of the trophic levels lose energy as heat through cell respiration. Also, as the organic matter passes from one trophic level to the next, not all of it is digested and so we have loss of energy in organic matter through feces. This energy then passes on to the detritivores and saprotrophs. Another energy loss occurs through tissue loss and death which can happen at any trophic level. Once again, this energy would be passed on to detritivores and saprotrophs as they digest these. Detritivores and saprotrophs in turn lose energy as heat through cell respiration.

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

Saprotrophic bacteria and fungi (decomposers) recycle nutrients.

G.5.4 Describe the methods used to estimate the size of commercial fish stock

Scientists can estimate the size of commercial fish stocks by a number of methods: Gathering information from fishermen to determine abundance from quantities caught Studying catches to identify fish ages (too few young indicates lack of spawning, while too few old suggests overfishing) Using echo sounders to monitor fish populations for density and locations Using research vessels and coded wire tag detectors to mark and release fish

5.3.4 List three factors that set limits to population increase.

Shortage of resources (e.g. food) Increase in predators Increase in diseases and parasites

G.3.3 Discuss reasons for the conservation of biodiversity using rainforests as an example

Sources of pharmaceuticals may become lost if plant species become extinct Certain crops may be improved with alleles from wild plants found in rainforests Loss of biodiversity will affect ecotourism, diminishing a potential source of local income Interdependent species may be lost, while other organisms may also expand to fill unoccupied niches (negative effects on food chains) Loss of plant species may lead to environmental effects such as erosion, flooding, silting of rivers and global warming (trees act as carbon sinks) The ability of indigenous human populations to live sustainably within ecosystem might be affected (rainforests preserves human cultural diversity) Loss of beauty of the system, depriving future generations of the aesthetic benefits of the rainforest

G.2.7 Outline the changes in species diversity and production during primary succession

Species diversity will increase as primary succession proceeds Only a few species (lichen and moss) are capable of living in environments that have never sustained life before (pioneer species) As these species alter the environment, it becomes more habitable, leading to a larger diversity of species colonising the region Production - an increase in biomass or available energy - will also increase as primary succession proceeds In early succession, there are few plants, so gross production and net production are low As the number and density of plant species increases with more soil, productivity also becomes greater

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

Species: a group of organisms that can interbreed and produce fertile 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.

G.3.2 Analyse the biodiversity of the two local communities using the Simpson index

The Simpson diversity index determines the species richness of an ecosystem - a higher index indicates a greater level of diversity Changes in the index indicates environmental change - as selective pressures become greater, biodiversity diminishes with extinctions

G.5.3 Describe one technique used to estimate the population size of an animal species based on a capture-mark-release-recapture method

The capture-mark-release-recapture method is a means of estimating the population size of a given species in a given environment (like what we did for the population lab) Method: An area is defined and marked off Within this area, a selection of individuals are captured, counted, marked and released (n1) Markings may include a spot of paint or an ear tag Sufficient time is then allowed to pass to enable released individuals to mix with the population A second capture is then made from the same area (n2), with both unmarked and marked (n3) individuals counted The Lincoln index is applied to estimate population size: (n1 × n2) ÷ n3 The Lincoln index assumes that all individuals have an equal chance of selection, marked individuals will be randomly distributed after release and marking will not affect mortality or natality

G.3.6 Outline one example of biological control of invasive species

The cottony cushion scale is an insect pest from Australia that was accidentally released in California It spread and fed on citrus plants (e.g. orange trees) to such an extent that it devastated the Californian citrus industry The vedalia beetle is a predatory insect from Australia that was released as a means of biological control It worked to limit the numbers of the cottony cushion scale and minimise the economic impact to the Californian citrus industry

5.2.3 Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect.

The earths mean average temperature is regulated by a steady equilibrium which exists between the energy reaching the earth from the sun and the energy reflected by the earth back into space. The incoming radiation is short wave ultraviolet and visible radiation. Some of the radiation will be absorbed by the atmosphere and some of it will be reflected back from the earths surface into space. The radiation that is reflected back into space is infrared radiation which has a longer wavelength. Green house gases such as carbon dioxide, methane, and oxides of nitrogen tend to absorb some of the reflected infrared radiation and re-reflect it back towards the earth. This is what causes the greenhouse effect and it results in an increase in average mean temperature on earth. It is a natural phenomenon. However, since there has been an increase in the green house gases in the past century, this has resulted in an increase of the green house effect leading to higher than normal average temperatures which could lead to disastrous consequences in the future.

G.2.10 Explain how rainfall and temperature affect the distribution 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

G.5.5 Outline the concept of maximum sustainable yield in the conservation of fish stocks

The maximum sustainable yield (MSY) is the highest proportion of fish that can be removed from the total population without jeopardising this maximum yield in the future The MSY will reflect the optimum balance between the reproductive and growth rate of the stock versus the rate of death due to harvesting and natural mortality The MSY should be half the carrying capacity of the species, as this is the stage at which population growth will be highest Calculating the MSY requires the collection of data over many years (~20 years) - harvesting above the MSY will soon reduce the size future yields

G.3.10 Outline the effects of chlorofluorocarbons (CFCs) on the ozone layer

The ozone layer is a stratospheric region composed of ozone (triatomic oxygen - O3) CFCs are broken down by ultraviolet radiation to release chloride ions which react with ozone, breaking it down into oxygen (O2) One chlorine atom can destroy 100,000 ozone molecules - small amounts of CFC can break down large amounts of ozone The thinning of the ozone layer by CFCs reduces the absorption of UV light in the stratosphere

5.2.4 Outline the precautionary principle.

The precautionary principle holds that, if the effects of a human-induced change would be very large, perhaps catastrophic, those responsible for the change must prove that it will not do harm before proceeding. This is the reverse of the normal situation, where those who are concerned about the change would have to prove that it will do harm in order to prevent such changes going ahead.

G.1.7 Explain the principle of competitive exclusion

The principle of competitive exclusion is based on the idea that ecological separation of species in competition is an inevitable outcome All species occupy a niche, which describes the roles of the organism within an ecosystem No two species can occupy the same niche in a community, as there will be competition for the same resources Species either segregate within a habitat (resource partitioning), or one species numbers will increase and the other die off (competitive exclusion) The principle of competitive exclusion can be summarised by Gause's Law - complete competitors cannot coexist

G.1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem

The process of measuring the dry organic mass kills the organisms, making it a costly and ethically questionable activity Step 1: Collect a representative sample and sort into trophic levels Step 2: Organisms in sample is cleaned of excess material (e.g. plants pulled free of soil and roots washed) Step 3: Measure the wet mass of the sample Step 4: Dry sample in an incubator (~80ºC) - sample considered completely dry when there is no further change in mass Step 5: Measure the mass of each sample to determine biomass of trophic level

5.3.3 Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases.

The sigmoid graph showing the population growth of a species has three phases which are; the exponential phase, the transitional phase and the plateau phase. At the start of the sigmoid curve we can see the exponential phase. This is where there is a rapid increase in population growth as natality rate exceeds mortality rate. The reason for this is because there are abundant resources available such as food for all members of the population and diseases as well as predators are rare. As time passes, the population reaches the transitional phase. This is where the natality rate starts to fall and/or the mortality rate starts to rise. It is the result of a decrease in the abundance of resources, and an increase in the number of predators and diseases. However, even though population growth has decreased compared to the exponential phase, it is still increasing as natality rate still exceeds mortality rate. Finally, the population reaches the plateau phase. Here, the population size is constant so no more growth is occurring. This is the result of natality rate being equal to mortality rate and is caused by resources becoming scarce as well as an increase in predators, diseases and parasites. These are the limiting factors to the population growth. If natality rate starts to drop then mortality rate will drop too as more resources become available. As natality rate starts to increase again so does mortality rate as resources become scarce. This keeps the population number relatively stable. If a population is limited by a shortage of resources then we say that it has reached the carrying capacity of the environment.

G.2.3 Discuss the difficulties of classifying organisms in higher trophic levels

There are a number of reasons why it may be difficult to classify organisms in higher trophic levels: Organisms may fit into more than one trophic level (as seen in food webs) Omnivores consume organisms from all levels of the food chain (plants and animals) There may be seasonal changes in trophic level depending on availability of food supplies Some organisms may alter their diet over the course of their life cycle (e.g. some amphibians)

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

There is strong evidence that shows that green house gases are causing global warming. This is very worrying as global warming has so many consequences on ecosystems. If nothing is done, and the green house gases are in fact causing the enhanced green house effect, by the time we realize it, it will probably be too late and result in catastrophic consequences. So even though there is no proof for global warming, the strong evidence suggesting that it is linked with an increase in green house gases is something we can not ignore. Global warming is a global problem. It affects everyone. For these reasons, the precautionary principle should be followed. Anyone supporting the notion that we can continue to emit same amounts or more of the green house gases should have to provide evidence that it will not cause a damaging increase in the green house effect.

5.1.6 Define trophic level.

Trophic level: the trophic level of an organism is its position in the food chain. Producers, primary consumers, secondary consumers and tertiary consumers are examples of trophic levels.

G.3.9 Outline the effects of ultraviolet (UV) radiation on living tissue and biological productivity

Ultraviolet (UV) light penetrates tissues and damages DNA, causing gene mutation that can lead to uncontrollable cell division (skin cancer) It can damage the ability of plants to carry out photosynthesis and can kill phytoplankton, reducing primary production and total productivity

G.1.4 Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable

When there is a gradient in an abiotic factor (e.g. salinity, elevation, etc.), communities will show variation in response to this trend A transect is a path along which the distribution of a plant or animal species can be observed and recorded The transect is placed at right angles to the impact of the abiotic gradient so as to display the change in distribution in response to the factor Line transects involve laying out a length of string and counting individuals at certain intervals along the line Belt transects involve placing quadrats at various intervals and counting the density of the population at each interval

G.5.2 Discuss the environmental conditions that favour either r-strategies or k-strategies

r-strategies - Occur in unstable environments where there are ecological disruptions and resources are used for maximising reproduction (once) An environment which would favour r-strategists would be coastal rock pools and an example of an r-strategist is a pathogen or other pest species k-strategies - Predominates in stable or predictable environments where resources are invested in maximising long-term survival An environment which would favour k-strategists would be a rainforest an examples of k-strategists include humans, elephants and whales It can be difficult to determine if a species is following an r-strategy or a k-strategy as they represent two extremes of a spectrum In actuality, most organisms demonstrate an intermediate strategy and some species may even change strategies depending on the environment

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

• Temperature: must be within a viable range for survival; few animals can survive extreme temperature conditions; homeotherms can colonize a wider range of habitats than poikilotherms (for which habitat is determined by external temperatures); body size (specifically surface area to volume ratio) will determine an animal's ability to conserve heat • Water: must be available in species-specific quantities (larger animals will have greater water requirements); dissolved oxygen levels and salinity will determine the survival of aquatic organisms. • Breeding Sites: required for the maintenance of the species - sites where infants are reared may have specialized environmental requirements; food resources and protection from predators will play a significant role in the viability of a species. • Food Supply: availability of food is a critical determinant of the carrying capacity of a population (example is maximum population size); must be of the right kind for the species (e.g. nuts for squirrels and leaves for rabbits) or else habitation is limited. • Territory: some animals establish and defend an area for the purposes of attracting mates, rearing young and avoiding predator; if this is limited, it can lead to either intra-specific (within species) or inter-specific (between species) competition.

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

• Temperature: rate of biochemical reactions and rate of evaporation are reliant on it; plants can only survive temperature ranges to which they are adapted to. • Water: imperative to photosynthesis, respiration, and the ability to maintain cell turgor (prevents wilting); limiting factor in most terrestrial ecosystems; plants that adapt to desert environments are called xerophytes. • Light: its intensity and duration are vital to photosynthesis; shaded plants typically have darker leaves due to a greater amount of chlorophyll; plants that prefer light normally are found in early succession. • Soil pH: narrow soil pH range is what most plants can tolerate; affects the availability of essential minerals and nutrients which affects decomposition of organic matter by soil bacteria; also affects attachment of minerals to soil particles. • Salinity: if this is high than it increases water loss from plants through osmosis; most plants cannot tolerate large fluctuations in salinity; plants adapted to salty environments are called halophytes. • Mineral Nutrients: affect plant fertility and water retention; weathering of rocks and soil pH will affect mineral nutrient levels.

G.2.11 Outline the characteristics of six major biomes

• Tropical rainforests have a large amount of biodiversity. • Temperate rainforests have a moderate amount of biodiversity. • Deserts have a low amount of biodiversity. • Tundra's have the lowest amount of biodiversity.