OPTION G ECOLOGY AND CONSERVATION G1 Community ecology
G.1.1  Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, sa...
G.1.1  Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, sa...
G.1.1  Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, sa...
G.1.2  Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, f...
G.1.2  Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, f...
G.1.3  Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of tw...
G.1.3  Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of tw...
G.1.4  Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable. (2...
G.1.4  Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable. (2)
G.1.5  Explain what is meant by the niche concept, including an organism’s spatial habitat, its feeding activities and its...
G.1.6  Outline the following interactions between species, giving two examples of each: competition, herbivory, predation,...
G.1.6  Outline the following interactions between species, giving two examples of each: competition, herbivory, predation,...
G.1.6  Outline the following interactions between species, giving two examples of each: competition, herbivory, predation,...
G.1.7  Explain the principle of competitive exclusion. (3) <ul><li>The principle of competitive exclusion states that no t...
G.1.7  Explain the principle of competitive exclusion. (3)
G.1.8  Distinguish between  fundamental  and  realized  niches. (2) <ul><li>An organism’s niche is affected by both abioti...
G.1.9  Define  biomass . (1) <ul><li>Biomass is the dry weight of organic matter of a group of organisms found in a habita...
G.1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem. (2) <ul><li>There a...
G.1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem. (2) <ul><li>A more ...
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  1. 1. OPTION G ECOLOGY AND CONSERVATION G1 Community ecology
  2. 2. G.1.1 Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, salinity and mineral nutrients. (2) <ul><li>The climate of a region, especially temperature and water , determines whether a particular organism or group of organisms live in a certain area. </li></ul><ul><li>These two factors are partially determined by global climate patterns. </li></ul><ul><li>Terrestrial biomes named in G.2.10 and G.2.11 are defined by the predominant type of vegetation, which in turn relies on the factors of temperature and rainfall. </li></ul><ul><li>The curvature and tilt of the Earth result in an uneven distribution of light , creating tropical, temperate, and arctic areas. </li></ul>
  3. 3. G.1.1 Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, salinity and mineral nutrients. (2) <ul><li>Among the many soil properties, soil pH is one of the most important. Soil pH provides a good indication of the chemical status of the soil and can be used in part to determine potential plant growth. </li></ul><ul><li>Soil pH influences nutrient uptake and tree growth. Many soil nutrients change form because of reactions in the soil that are largely controlled by soil pH. </li></ul><ul><li>Soil pH values at the extremes (<4.0 and > 8.5) can make some nutrients toxic and others unavailable to plants. At lower pH levels (<4.5), aluminum, iron, and manganese are readily available for plant uptake. At high pH levels (>5.5), calcium and potassium are overabundant. </li></ul>
  4. 4. G.1.1 Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, salinity and mineral nutrients. (2) <ul><li>Salinity is the presence of salt in the land surface, in soil or rocks, or dissolved in water in rivers or groundwater. Salinity can develop naturally, but where human intervention has disturbed natural ecosystems, the movement of salt into rivers and onto land has been accelerated. </li></ul><ul><li>Some species of plants are more salt tolerant than others. We can see evidence of this in Florida, by observing the vegetation differences near salt water environments. </li></ul><ul><li>Plant health depends on essential nutrients . </li></ul><ul><ul><li>Macronutrients—carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus (together 98% of plant dry weight) and potassium, calcium, magnesium (1.5% of plant dry weight) </li></ul></ul><ul><ul><li>Micronutrients—chlorine, iron, manganese, boron, zinc, copper, nickel, molybdenum </li></ul></ul>
  5. 5. G.1.2 Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory. (3) <ul><li>Terrestrial biomes named in G.2.10 and G.2.11 are defined by the predominant type of vegetation, which in turn relies on the factors of temperature and rainfall . </li></ul><ul><li>The predominant vegetation will in part determine the animal species found in the ecosystem. </li></ul><ul><li>Several limiting factors regulate growth in natural populations, the most obvious being competition among members of the population for limited resources, such as a food supply . </li></ul>
  6. 6. G.1.2 Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory. (3) <ul><li>A limited resource may be something other than food or nutrients. In many vertebrates that defend a territory , the availability of space may limit reproduction. The space needed for breeding and finding sufficient food is included in this territory. </li></ul><ul><li>Even when space is sufficient, suitable breeding sites may not be available. </li></ul><ul><li>As a population’s density increases, factors such as limited food supply and increased disease or predation may increase the death rate, decrease the birth rate, or both. </li></ul><ul><li>Most populations are regulated by a mixture of factors and fluctuations in numbers are common. </li></ul>
  7. 7. G.1.3 Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of two plant or animal species. (2) <ul><li>To determine what kind of plants and animals are in a particular habitat, and how many there are of each species, it is usually impossible to count each and every organism present. </li></ul><ul><li>This problem is usually solved by taking a number of samples from around the habitat, making the necessary assumption that these samples are representative of the habitat in general. </li></ul><ul><li>Samples are usually taken using a standard sampling unit of some kind. This ensures that all of the samples represent the same area or volume (water) of the habitat each time. </li></ul><ul><li>The usual sampling unit is a quadrat. </li></ul>
  8. 8. G.1.3 Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of two plant or animal species. (2) <ul><li>Quadrats normally consist of a square frame, the most frequently used size being 1m 2 . </li></ul><ul><li>The purpose of using a quadrat is to enable comparable samples to be obtained from areas of consistent size and shape. </li></ul><ul><li>Random sampling is usually carried out. The quadrat frame is placed on the ground (or on whatever is being investigated) and the animals, and/ or plants inside it counted, measured, or collected, depending on what the survey is for. This is done many times at different points within the habitat to give a large number of different samples. </li></ul><ul><li>In the simplest form of random sampling, the quadrat is thrown to fall at ‘random’ within the site. A better method of random sampling is to map the area and then to lay a numbered grid over the map. A (computer generated) random number table is then used to select which squares to sample in. </li></ul>
  9. 9. G.1.4 Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable. (2) <ul><li>This is another way to assess distribution of organisms within a habitat. </li></ul><ul><li>A tape is laid along the ground between two poles. </li></ul><ul><li>In a line transect, sample is confined to describing all of the organisms that touch the line. </li></ul><ul><li>In a belt transect, sampling is confined to a strip of fixed width such as 0.5 or 1 meter. </li></ul><ul><li>The graph on the following slide shows how data from a transect can be plotted and compared to an abiotic factor. This graph was scanned from the Biology Course Companion . </li></ul>
  10. 10. G.1.4 Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable. (2)
  11. 11. 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. (3) <ul><li>A habitat is where an organism lives, and an ecological niche is the role an organism plays in its community, including its habitat and its interactions with other organisms. </li></ul><ul><li>The niche includes the resources an organism uses to meet its energy, nutrient, and survival demands. </li></ul>
  12. 12. G.1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism. (2) <ul><li>Competition ( - - ) </li></ul><ul><li>Herbivory ( + - ) </li></ul><ul><li>Predation ( + - ) </li></ul><ul><li>When members of different species try to use a resource that Is in limited supply </li></ul><ul><li>When one organism (herbivore) feeds on a plant </li></ul><ul><li>When one animal (predator) feeds on another living animal (prey) </li></ul><ul><li>Interactions between predator and prey and between prey and its won food source can produce complex population cycles. </li></ul>
  13. 13. G.1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism. (2) <ul><li>Parasitism ( + - ) </li></ul><ul><li>Commensalism ( + o ) </li></ul><ul><li>An organism (parasite) derives nutrition from another organism (host). The effects of parasites on hosts can range from slight weakening to actually killing the host. The parasite also uses the host as a habitat. </li></ul><ul><li>One species benefits, while the other neither benefits nor is harmed. When closely examined these may be instances of either parasitism or mutualism. </li></ul>
  14. 14. G.1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism. (2) <ul><li>Mutualism ( + + ) </li></ul><ul><li>Parasitism, commensalism, and mutualism are all types of symbiosis . </li></ul><ul><li>Both organisms in this relationship receive a benefit. Mutualistic relationships often help organisms obtain food or avoid predation. </li></ul>
  15. 15. G.1.7 Explain the principle of competitive exclusion. (3) <ul><li>The principle of competitive exclusion states that no two species can occupy the same niche at the same time. </li></ul><ul><li>Demonstrated by Gauss in cultures of Paramecium species. You could describe this experiment in answering this question on an IB test. </li></ul><ul><li>The definition of this principle in the Biology Course Companion states that two species cannot coexist in the same habitat if their niches overlap. Either one species will lead to the decline and extinction of the other, or one or both of the competitors will narrow their niches to avoid competition. (Their realized niche will be narrower than their fundamental niche.) </li></ul><ul><li>See the next slide for an illustration of this narrowing of competitive species’ niches. </li></ul>
  16. 16. G.1.7 Explain the principle of competitive exclusion. (3)
  17. 17. G.1.8 Distinguish between fundamental and realized niches. (2) <ul><li>An organism’s niche is affected by both abiotic factors (such as climate and habitat) and biotic factors (such as competitors, parasites, and predators in the habitat). Because of this, ecologists distinguish between the fundamental and realized niches. </li></ul><ul><li>An organism’s fundamental niche comprises all conditions under which the organism can potentially survive and reproduce. </li></ul><ul><li>The realized niche is the set of conditions under which it exists in nature. </li></ul><ul><li>Examples??? </li></ul>
  18. 18. G.1.9 Define biomass . (1) <ul><li>Biomass is the dry weight of organic matter of a group of organisms found in a habitat. ( Biology Course Companion ) </li></ul><ul><li>Biomass may refer to the entire community or to a single trophic level of even to a single individual. </li></ul>
  19. 19. G.1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem. (2) <ul><li>There are a number of ways to measure plant biomass with varying degrees of destructiveness. In the area set aside for biomass, randomly locate a quadrat. </li></ul><ul><li>Biomass can be assessed indirectly and completely nondestructively by </li></ul><ul><ul><li>Counting the number of individuals of the target species. </li></ul></ul><ul><ul><li>Randomly selecting a sample of individuals. </li></ul></ul><ul><ul><li>Determining mean height within the sample (height will be an indirect measure of biomass). </li></ul></ul><ul><ul><li>Multiply the mean height by the stem density (number of individuals). </li></ul></ul>
  20. 20. G.1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem. (2) <ul><li>A more destructive method involves taking a sample of individuals of the target species and cutting them at soil level. Tag each individual with a label, dry it to a stable weight and weigh it. Determine the mean mass of the plants in the area and multiply by the stem density in the area. </li></ul><ul><li>A third method is to completely harvest all the target species in the quadrat, dry them to a stable weight and then determine the total biomass. </li></ul><ul><li>Herbivorous insects can be collected from a plant to determine their mass and then the biomass of the plant they are consuming can be determined. </li></ul>

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