IB SL ESS Environmental Systems and Societies Test 4 PDF

**ENVIRONMENTAL SYSTEMS AND SOCIETIES/ENVIRONMENTAL SCIENCE** STUDY GUIDE **TEST 04** **Subtopic 2.1. Individuals, populations, communities, and ecosystems** **YOU WILL NEED A CALCULATOR FOR THIS TEST** **IB SL ESS** - **State limitations of using a dichotomous key.** 1. Examine physical c...

**ENVIRONMENTAL SYSTEMS AND SOCIETIES/ENVIRONMENTAL SCIENCE** STUDY GUIDE **TEST 04** **Subtopic 2.1. Individuals, populations, communities, and ecosystems** **YOU WILL NEED A CALCULATOR FOR THIS TEST** **IB SL ESS** - **State limitations of using a dichotomous key.** 1. Examine physical characteristics rather than behavior. 2. Use of technical terms. 3. May not be a key available for the type of organisms. 4. Some features cannot be easily established in field. 5. Some organisms significantly change their body shape during their lifetime. - **Outline methods, other than a dichotomous key, that may be used to classify a species.** - [Three main methods:] a. *Dichotomous key* = allows users to identify an organism by answering a series of questions, each representing 2 choices, where the user must choose the option that best describes the organism they're trying to identify. Based on the answers, the key leads to the correct identification. b. *Comparisons with specimens in reference collections* = by expert taxonomists, which compare an unknown specimen to similar ones in a reference collection (zoos, botanic gardens, museums, etc.), which then helps them identify the unknown specimen by comparing it to known ones. c. *DNA surveys* = involve sequencing a small piece of DNA from an organism and comparing it to known sequences in a data base, helping to identify unknown organisms, especially if it's difficult to distinguish by physical characteristics alone, making it more accurate than by just using physical characteristics (key). - **Define species.** - [Species] = group of organisms that share a common characteristic and are able to successfully interbreed and produce fertile offspring. - **Identify limitations of the biological species concept.** - [Biological species concept] = species' integrity is maintained through interbreeding within a species, and reproductive barriers between organisms in different species. BUT: a. Doesn't identify whether geographically isolated populations belong to the same species. b. Doesn't classify species in extinct populations. c. Doesn't account for asexually reproducing organisms. d. Doesn't clearly define species when barriers to reproduction are incomplete (ring-species). - **Outline different types of population interactions (predation, herbivory, parasitism, mutualism, competition, saprotrophism, and disease).** - [Predation] = when one animal (predator) kills and eats another animal (prey) -- one benefits, other suffers. Lions eating zebras. - [Herbivory] = when one animal (herbivore) eats green plants -- one benefits, one suffers. Cattle feeding on grass. - [Parasitism] = where one species (parasite) lives in or on another (the host) and is able to feed itself from the host -- one benefits, other suffers. vampire bats and fleas. - [Mutualism] = relationship between 2 species in which both benefit from it. leguminous plants and nitrogen-fixing bacteria. - [Competition] = 2 species competing and fight over resources -- both suffer. Lions and hyenas. - [Saprotrophism] = organisms that feed on dead organic material -- one benefits. Earthworms. - [Disease] = where one species (pathogen) harms another (host), affecting its function -- one benefits, other suffers. bacteria causing tuberculosis in animals. - **Explain why predation may be beneficial for both predator and prey species (check the practice exercises below).** - The [predator] benefits by gaining food from prey, allowing them to stabilize in population size, keeping their population limited, by the amount of prey available. - The [prey] benefits as the predators limit their population growth, which stabilizes their population. They also hunt on weaker and diseased individuals, which maintains a healthy gene pool for the prey species. Lastly, it reduces competition in prey for available food and other resources. - **Define and provide examples of density-dependent and density-independent factors.** - [Density-dependent factors] = limiting factors that cause population growth rate to decrease with increasing density/size (FACTORS DEPEND ON THIS), biotic factors that cause negative feedback, regulating population size around K. disease, predation, competition for food/space. - [Density-independent factors] = limiting factors that cause population growth rate to decrease regardless of density/size (FACTORS DO NOT DEPEND ON THIS), abiotic factors. extreme temperatures, forest fires, floods, pollution, earthquakes. - **Compare and contract predation and parasitism.** - [Both]: a. One of the species (predator and parasite) benefits, while the other is harmed (prey and host). b. One of the organisms (predator and parasite) are able to obtain food. c. Predators/parasites may eliminate weaker individuals in a population. - [Difference]: a. Parasite doesn't kill its host on purpose, but only weakens it. b. Predator does kill and eat the prey. - **Distinguish between intraspecific and interspecific competition.** - [Intraspecific] = between members of the same species. high reproductive success from stronger individuals. - [Interspecific] = between different species. balance or one outcompetes other. - **Define ecological niche.** - [Ecological niche] = describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends. - It includes type of food consumed, temperature/humidity ranges tolerated, and type of environment the species inhabits. - **Explain why species cannot occupy the same niche and what happens if they do.** - Species can survive together if they have different needs, and not be the exact same in the same place: ecological niche. If both species occupy the same niche, then the one with the fastest growth rate and higher efficiency in energy use will outcompete the other, leading to an imbalance of population size in the ecosystem.   - **Outline the differences between the J and S population growth curves, and to what type of species can they be applied.** - [J-population growth curve] = *no limiting factors* slowing growth, so the number of organisms will increase geometrically/exponentially. show "boom and bust" IN microbes, invertebrates, fish, small mammals. - [S-population growth curve] = *limiting factors* slowing growth until K. IN large mammals (deer, etc.). - **Define carrying capacity.** - [Carrying capacity (K)] = maximum population number that an ecosystem can support based on its available resources. - **Define limiting factors.** - [Limiting factors] = factors that slow down growth of a population as it reaches its carrying capacity, which can be biotic (predation, lack of food, difficulty in mating, etc.) or abiotic (oxygen, light, water, temperature). - **Explain the role of limiting factors in S and J population growth curves.** - The initial gradient of both curves is low due to low numbers of reproduction and unmodified habitats. Then, as biotic potential exceeds environment resistance, there is an exponential increase and positive feedback in both. - *S-curves* = limiting factors (limited food, increased disease/predation, accumulation of waste and competition) slow the population growth, maintaining equilibrium and a balanced ecosystem. - *J-curves* = limiting factors (seasonal climate change, disease, overexploited food resources) lead to rapid decline/population crash. - *Both* curves may be influenced by density independent factors, but density dependent factors bring equilibrium in S-curves. - **Use the Lincoln Index to estimate population size (formula will be provided).** - [Formula] (estimates population size of small animals that are mobile/motile in a study area) [\$\\frac{M\*N}{R}\$]{.math.inline} - *M* = number caught in 1^st^ sample and marked. - *N* = number caught in 2^nd^ sample. - *R* = number caught in 2^nd^ sample which were previously marked. - **Name the method used to gather the data for the Lincoln Index.** - [Capture, mark, release, recapture] = collect a sample, mark organisms in some way, release them back into the wild, resample some time later and count how many marked ones you can find in this 2^nd^ capture. - **Evaluate the methods used to mark organisms (strengths and weaknesses).** - They have to be [ethically acceptable] (cannot harm organism or weaken their quality of life or characteristics) AND [non-conspicuous] (animals cannot easily be seen by predators). - **Identify factors that might impact the accuracy of the method used to gather the data for the Lincoln Index.** - [Limiting factors (in accuracy)]: a. Number of trials carried out. b. Type of traps/bait used to identify captured organisms. c. Type of marking. d. Time for organisms to reintegrate after first capture. e. How easily organisms become trap happy or shy. f. Size of samples trapped. g. Animals may move in or out of sample area. h. Density of population in different habitats might vary. i. Assumption that they're equally spread all over, which may not be true. j. Seasonal variations in animals may affect population size. - **Identify abiotic factors that affect terrestrial and aquatic ecosystems.** - [Terrestrial] = temperature, light intensity, wind speed, soil texture, slope, soil moisture, drainage and mineral content. - [Aquatic] = salinity, pH, temperature, dissolved oxygen, and wave action. - **Explain how abiotic factors may affect species distribution.** - Abiotic factors influence species distribution by determining the environmental conditions in which species can survive and reproduce. They determine whether an area provides suitable conditions for survival, reproduction, and resource availability. If the environment does not meet a species\' needs, it limits their ability to thrive there, restricting their presence to areas where conditions are more favorable. - **Explain how you can measure a named abiotic factor (instrument + technique used to ensure a fair test).** - *Rainfall* = rain gauge. 1. Position the rain gauge in an open area, free from obstructions. 2. Check it daily at the same time. 3. Pour the collected rain into a graduated cylinder and record the amount. - [Techniques:] 1. Repeated measurements to check validity. 2. Measurements at both sites at same time/same day. 3. Attempting to keep other abiotic factors constant, so that they don't influence results. 4. Always use the same device for all measurements for that factor, making sure it's calibrated properly. - **Distinguish between percentage frequency and percentage cover.** - [Percentage frequency] = when it's impossible to count or large sample -- measure of the number of organisms of a particular species in a given area. - [Percentage cover] = when you can identify individual plants or small sample area -- measure of the proportion of a given area covered by a particular species. - **Calculate percentage cover, percentage frequency, and population density (formulas will not be given).** - [Percentage cover] = estimate of an area in a quadrat covered by the organisms, which is based of ACFOR scale. 1. Find the area of all the quadrats ([*l* \* *W*]{.math.inline}). 2. Find the area of one quadrat in percentage ([\$\\frac{usually\\ 100}{\\text{answer\\ above}}\\ \$]{.math.inline}). 3. Multiply \#2 by the number of quadrats species occupy. - [Percentage frequency] = [\$\\frac{number\\ of\\ actual\\ occurences\\ (quadrat\\ species\\ actually\\ occupy)}{number\\ of\\ possible\\ occurences\\ (quadrat\\ species\\ could\\ occupy\\ in\\ total)}\*100\$]{.math.inline} *(as a %).* - [Population/species density] = number of individuals of each species per unit area (as individuals / m\^2) = [\$\\frac{\\text{number\\ of\\ individuals\\ in\\ sample\\ area}}{quadrat\\ number\*area\\ of\\ one\\ quadrat}\$]{.math.inline} - **Draw systems diagrams showing storages, flows, inputs and outputs (you may select the one you want to represent, revise the ones done in subtopic 1.2)** - A diagram consists of *storages and flows*: - *Storage* = box (living or non-living component, where matter or energy is kept in a system, looked at) - *Flows (inputs/outputs)* = arrows (directional movements of energy and matter) - *Processes* = transfer/transform energy/matter from one storage to another (labels on top of the arrows) - [Consumers and producers will always have the storages].  - **Discuss how different environmental value systems may see the concept of carrying capacity.** - [Ecocentrism] = emphasis on living within ecological limits, human population should adhere to carrying capacity to avoid damaging ecosystems, advocates for minimal resource use and increase in sustainable practices to ensure that there is balance in nature. - [Anthropocentrism] = emphasis on human needs over carrying capacity (would see it as something flexible), and would promote innovation, resource substitution and policies to expand the capacity to support human populations. Would see "K" as a benchmark, and create legislation to stay within the limits, possibly not realizing that they are the ones contributing to overuse of resources. - [Technocentrism] = emphasis on how technology could overcome environmental limits, viewing carrying capacity as something that could be expanded through advancements in agriculture/energy/waste management. - **Using a named example, explain the boom-and-bust pattern (hint: review the reindeer on St. Matthew Island, or the lemmings and stoats).** - [Boom-and-bust] = population grows exponentially at first and then quickly collapses. - *St. Matthew Island reindeer* - Reindeer were taken to this island by US coastguards, to be introduced to that region in order to benefit humans regarding food source. - The reindeers weren't native to that island, but the lichen that they ate was present there. Because of this, they had food sources, and their population numbers significantly increased over the years. - But after a while, the resource of lichen was all eaten, and many starved to death; because of this, the population numbers crashed to a very low amount. - Lichen also grows very slowly, so the rest of the reindeer weren't able to get food quick enough, and evenly, they all died off. - **Draw labeled diagrams, representing named examples, to explain the concept of negative feedback.** - [Negative feedback] = output of a process inhibits or reverses the operation of the same process in such a way as to reduce the change, stabilizing the system and counteracting deviation. DRAWN AS CYCLES - *Global temperatures* they rise, causing ice caps to melt, so more water and more evaporation in the atmosphere means more clouds, so more solar radiation is reflected by clouds so global temperatures fall again. - *Evaporation* as Earth warms, there is increased evaporation of water that produces more clouds, clouds increase albedo (so more light is reflected away from Earth), temperatures fall, rates of evaporation fall. - *Predator-prey* zebra population increases, lion population increases as there is more prey, zebra population decreases as there is more predation by lions, lion population decreases as there is less prey...