ecology practice questionsmidterm -...

www.njctl.org PSI AP Biology Ecology

Ecology

Population Ecology Classwork

1. Ecologists often study both abiotic and biotic characteristics in an ecosystem. If you were assigned to study a swamp in the Florida everglades, list and describe 3 abiotic and 3 biotic characteristics that you would find.

2. Weather apps can be downloaded on computers or other smart devices to view local, regional, or world weather maps. Describe what microclimate means and how it might differ in the ground level, shrub layer, and canopy in a forest.

3. Explain what an ecosystem is, and what interactions are of primary interest in ecosystem ecology. Describe how ecosystems are different from communities. Describe ecosphere.

4. Describe several examples of density dependent and density independent controls over population growth.

5. As you learned in earlier units there are many obstacles and challenges a species must overcome throughout their life. Describe the types of density-dependent factors that regulate population growth.

6. Describe exponential population growth. Plot a graph that shows population growth using the following information: Houseflies lay 120 egg. Assume with each egg lay half will become females and they lay eggs at the same rate. If the initial population contains 100 males and 100 females. Plot the population growth for 3 generations.

7. A human population of 500,000 individuals has a birth rate of 70 per every 1000 persons and the death rate is 10 per every 1000 individuals. Using the equations (b-d)N, calculate the yearly increase for the population growth.

8. The human population will grow even if the birth rate is reduced to the replacement level of 2.5 births per couple. Explain why.

9. Selection is often described as either being K or r. Describe the strategies that populations develop in response to K and r selection.

Homework

10. Limnologist study aquatic bodies of water, both abiotic and biotic conditions can affect the health of the lake. Describe the cause of fall turnover in deep lakes. Explain how the conditions before and after the turnover affect population growth.

11. Soil is an important abiotic factor that can have a direct impact on populations living in a ecosystem. Describe how the parent rock produces soils. Explain what soil horizons are and how they are produced.

12. Describe what silts, clays, and sands are. Describe the effect of soil types on population growth.

13. Most humans what the news strictly for the daily weather forecast. Weather has been shown to affect our mood. Describe the ways that climate affects population growth and if it has density-dependent effects.

14. Describe logistic population growth. Explain how density- dependent controls can convert population growth from exponential to a logistic curve.

15. Male lions have been known to defend their pride across a territory that spans 100 square miles. Describe territoriality and how it limits population growth.

16. Describe the factors, acting singly or together, could produce a crash in the human population. Explain what birth control versus death control in reference to human population growth means.

17. If our population doubles in size, describe whether or not future agricultural production or food from the sea will feed the human population sufficiently enough.


18. It is important for scientist to track a population's life expectancy, this can be a direct indication as to whether an ecosystem is balanced or not. Explain what survivorship curves are and how they are related to K and r selection. Draw an example showing survivorship curve for K and r selection.

Community Ecology Classwork

19. Describe an ecological community. Explain what characteristics of communities are studied in ecology.

20. Describe predation and the types of predation that may occur. Explain how predation effects population growth.

21. Describe the effects that defensive measures evolved by prey species have on their population growth.

22. Mistletoe is a plant that is able to carry out photosynthesis but is unable to obtain water and nutrients on its own. To do so, it grows haustorium, which penetrate the branches of trees or shrubs, through which it absorbs water and nutrients. Describe this type of symbiosis and the effect it has on both the mistletoe and the tree/shrub. For the mistletoe, is this obligate or facultative symbiosis?

23. Describe what competition means and the four types of competition that occur between populations. Explain how competition affects population growth.

24. Describe the principle of competitive exclusion. Explain how natural populations inhabiting the same geographic region avoid extinction by competitive exclusion.

25. Describe ecological niche and niche overlap. Explain how niche overlap is related to competition.

26. Explain what biogeochemical cycles are. Describe which natural reserves serve as sources for the nutrients that cycle within ecosystems.

27. Describe primary producers. Explain the difference between gross and net primary production.

28. Describe what happens to the energy “lost” at each trophic level of a community. Explain how much energy is lost on the average at each trophic level.

29. Explain how entropy is related to the one-way flow of energy through ecosystems. 30. Describe the process of sunlight entering the Earth’s atmosphere and striking the

surface of the Earth. 31. Describe the major forms of toxic wastes are released by the human population to the

community. Provide your opinion about whether or not present needs justify the accumulation and storage of radioactive wastes from nuclear power plants.

Homework 32. Describe community structure, and patchy and continuous distributions of populations in

communities. Explain how a forest community is structured vertically. 33. Describe whether or not predators ever have beneficial effects on their prey populations,

and if so, how. 34. A symbiotic relationship is sometimes beneficial to an organism and sometimes harmful

to an organism. Describe an example of each. 35. Describe how natural selection reduces competition. Explain what niche specialization

is. 36. Describe niche refuge, fundamental niche, and realized niche. Explain how niche

overlap relates to population survival. 37. Describe the features that nitrogen, carbon, and phosphorous cycles have in common.

Explain how they differ. 38. Explain the important roles that detritus feeders have in biochemical cycles.


39. Describe primary consumers, secondary consumers, and detritus feeders. Explain biomass.

40. Describe a food chain and a food web. Explain why food chains rarely extend beyond three or four trophic levels.

41. Explain how heat is an unusable of energy in an ecosystem. Describe how the first and second laws of thermodynamics apply to ecosystems.

42. Describe the ozone layer. Explain the effect this has on the light passing through the atmosphere.

43. It is more efficient for humans to act as primary rather than secondary consumers in the food chains of our communities. Explain why.

44. Describe the conservation methods that could be used to reduce the per capita energy consumption in the U.S. Explain whether or not you believe that conservation methods are needed now and why/why not.

45. Describe community diversity. Explain what regular patterns are observed in community diversity in relation to latitude, topography, temperature and moisture, and island area?

46. Describe the historical and equilibrium hypotheses for community diversity, and give evidence that supports the equilibrium hypothesis.

47. Describe community succession, and make a list of the processes frequently observed as common elements in successions in different regions.

48. Explain what the difference is between primary and secondary succession. Describe which one usually proceeds more rapidly and why.

49. Using a small lake as an example, trace the overall pattern of succession you would expect. Using an abandoned field surrounded by deciduous forest, as an example, trace the succession you would expect.

50. Describe climax community and community stability. Explain what factors are believed to underlie community stability.

Free Response

Bacterial Vesicles in the Ocean

David Scanlan

Science 10 January 2014: 343 (6167), 143-144.

1. Many heterotrophic bacteria are known to release extracellular vesicles, facilitating interactions between cells and their environment from a distance. Vesicle production has not been described in photoautotrophs, however, and the prevalence and characteristics of vesicles in natural ecosystems is unknown. Cultures of Prochlorococcus, a numerically dominant marine cyanobacterium, continuously release lipid vesicles containing proteins, DNA, and RNA. Also, vesicles carrying DNA from diverse bacteria are abundant in coastal and open-ocean seawater samples. Prochlorococcus vesicles can support the growth of heterotrophic bacterial cultures,


which implicates these structures in the marine carbon cycle. The ability of vesicles to deliver diverse compounds in discrete packages adds another layer of complexity to the flow of information, energy, and biomolecules in marine microbial communities. (A) Scanning electron micrograph of Prochlorococcus strain MIT9313 shows the presence of numerous small spherical features (vesicles, indicated by arrows) near the cells. Scale bar, 1 μm. (B) Purified Prochlorococcus vesicles as seen by negative-stain TEM. Scale bar, 100 nm. (C) Thin-section electron micrographs confirm that Prochlorococcus vesicles are circular, membrane-enclosed features lacking notable internal structure. Scale bar, 100 nm. (D) Possible functions of the secreted vesicles.

Bacterial Vesicles in Marine Ecosystems

Steven J. Biller, Florence Schubotz, Sara E. Roggensack, Anne W. Thompson, Roger E. Summons, and Sallie W. Chisholm

Science 10 January 2014: 343 (6167), 183-186.

a) Pose at least 2 questions about what mechanisms and structural features allow organisms to capture, store and use free energy questions that can be answered by studying Prochlorococcus and the excretion of vesicles.

b) Prochlorococcus continuously release lipid vesicles containing proteins, DNA, and RNA. With the help of diagram C, why are the molecules in vesicles, and why would a cell release molecules that it usually needs?

c) Using diagram C, where do you see an exchange of materials between organisms or the environment? Write one or more equations that can represent the exchange of materials between organisms and their environment.

d) The following diagram shows the relative abundance of the Prochlorococcus vesicles and cells. Identify the approximate average size of the cells and vesicles. Predict whether the cells or the vesicles would be more able to efficiently exchange materials with the environment, and state your rationale for your prediction.

D


2. Desiccation of the Sahara since the middle Holocene has eradicated all but a few natural archives recording its transition from a “green Sahara” to the present hyperarid desert. Our continuous 6000-year paleoenvironmental reconstruction from northern Chad shows progressive drying of the regional terrestrial ecosystem in response to weakening insolation forcing of the African monsoon and abrupt hydrological change in the local aquatic ecosystem controlled by site-specific thresholds. Strong reductions in tropical trees and then Sahelian grassland cover allowed large-scale dust mobilization from 4300 calendar years before the present (cal yr B.P.). Today's desert ecosystem and regional wind regime were established around 2700 cal yr B.P. This gradual rather than abrupt termination of the African Humid Period in the eastern Sahara suggests a relatively weak biogeophysical feedback on climate. The above figure shows the evolution of aquatic and terrestrial ecosystem components over the past 6000 years, with episodes of marked change highlighted with stippled vertical lines. The aquatic ecosystem of Lake Yoa is described by paleosalinity reconstructions based on fossil chironomids and diatoms (A); and diatom silica in weight percent of SiO2 (B) and bulk organic matter (C) as indicators of primary productivity. Core lithology is illustrated by sections of laminated sediment representative for lower, middle, and upper portions of the cored sequence (D). The terrestrial ecosystem of the Ounianga region is described by the magnetic susceptibility record of eolian dust input (E), the dry-weight fraction of fine sand (F), and the influx rate (G, right axes) and percentage (G, left axis, Poaceae only) of pollen or spores from principal plant taxa. (H) shows local summer insolation over the past 6000 years. The age-depth model is constrained by the sediment-water interface (2003 AD), the 137Cs marker of peak nuclear bomb testing (1964 AD, purple) and 17 14C dates on bulk organic matter (green; open triangles are outliers), with a lake-carbon reservoir correction based on paired 14C dating of bulk organic matter and either charred grass (brown) or 1918 AD in varve years (black).

Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years

S. Kröpelin, D. Verschuren, A.-M. Lézine, H. Eggermont, C. Cocquyt, P. Francus, J.-P. Cazet, M. Fagot, B. Rumes, J. M. Russell, F. Darius, D. J. Conley, M. Schuster, H. von Suchodoletz, and D. R. Engstrom

Science 9 May 2008: 320 (5877), 765-768

a) Pose a scientific model of climate change in northern Africa that the analysis of the above data supports. Describe how the data supports your model.

b) Design a plan for collecting data to reconstruct the climate history of a particular area, for example, North America.

c) Use the data in the above diagram to describe the effects the climate had on the biological systems in the Saharan region.


3. Flight of the honeybee.

The round and waggle dances are performed by foraging bees on an area of vertical comb close to the entrance of the hive to signal the availability of food. When food is close to the hive, foragers perform a round dance, which gives no indication of the direction in which the food is located. For sites more distant than about 50 m, the direction of food with respect to the sun's azimuth is signaled by the angle of the waggle component (S) relative to gravity, and the distance of the food from the hive is signaled by the duration of the waggle component. Duration increases nonlinearly with distance.

Measuring Beelines to Food

Thomas Collett

Science 4 February 2000: 287 (5454), 817-818.

a) How does the bee dance differ depending on the location of flowers?

b) How does the bee adjust its dance to signal a change in distance the food is from the beehive?

c) Draw two representations of the bee dance with the size of the drawing being proportional to the time the bee spends doing the dance for food that is 1 and 3 km away from the hive.

Faster Decomposition Under Increased Atmospheric CO2 Limits Soil Carbon Storage

Kees Jan van Groenigen, Xuan Qi, Craig W. Osenberg, Yiqi Luo, and Bruce A. Hungate


Science 1249534Published online 24 April 2014

4. Soils contain the largest pool of terrestrial organic carbon (C) and are a major source of atmospheric carbon dioxide (CO2). Thus, they may play a key role in modulating climate change. Rising atmospheric CO2 is expected to stimulate plant growth and soil C input but may also alter microbial decomposition. The combined effect of these responses on long-term C storage is unclear. Combining meta-analysis with data assimilation, we show that atmospheric CO2 enrichment stimulates both the input (+19.8%) and the turnover of C in soil (+16.5%). The increase in soil C turnover with rising CO2 leads to lower equilibrium soil C stocks than expected from the rise in soil C input alone, indicating that it is a general mechanism limiting C accumulation in soil.

C t = C 0 [ e xp ( – k t ) ] + I / k [ 1 – e xp ( –k t ) ] ( 1 ) where Ct is the soil C content (g C m−2) at time t (year), C0 is the soil C content at the start of a CO2 enrichment experiment (g C m−2), k is the decomposition rate constant (year−1, the rate at which C leaves the soil system), and I is the annual input of C to soil (g C m−2 year−1). The model was constrained by multiple independent data streams from 53 CO2 enrichment experiments (see table S1 and databases S1 to S4). We then used meta-analysis to synthesize the results (13).

Thus, we took a slightly different approach and applied a model that distinguished the k of soil C initially present at each experimental site (kold) from the k of soil C added after CO2 enrichment started (knew):C t = C 0 [ e xp ( – k o l d × t ) ] + I / k n e w [ 1 – e xp (– k n e w × t ) ] ( 2 ) Based on this approach, we found that CO2 enrichment increased both kold and knew (Fig. 1B and table S4) to similar degrees. These findings corroborate recent studies suggesting that increased CO2 stimulates the decomposition of old soil C (10, 11) as well as new soil C pools (23).

a) Given the equation C t = C 0 [ e xp ( – k o l d × t ) ] + I / k n e w [ 1 – e xp (– k n e w × t ) ] , e va lua t e f o r t ime = 0 ( t= 0 ) .

b) How does the increase in carbon dioxide affect the carbon in the soil (equilibrium C)? c) How does model A differ from model B? d) Once the equilibrium C is reached, how would the concentration of CO2 in the air be

affected?

http://www.sciencemag.org/content/early/2014/04/23/science.1249534.full#ref-13

http://www.sciencemag.org/content/early/2014/04/23/science.1249534.full#F1





5. Substances that accumulate to hazardous levels in living organisms pose environmental and human-health risks, which governments seek to reduce or eliminate. Regulatory authorities identify bioaccumulative substances as hydrophobic, fat-soluble chemicals having high octanol-water partition coefficients (KOW)(≥100,000). Here we show that poorly metabolizable, moderately hydrophobic substances with a KOW between 100 and 100,000, which do not biomagnify (that is, increase in chemical concentration in organisms with increasing trophic level) in aquatic food webs, can biomagnify to a high degree in food webs containing air-breathing animals (including

humans) because of their high octanol-air partition coefficient (KOA) and corresponding low rate of respiratory elimination to air. These low KOW–high KOA chemicals, representing a third of organic chemicals in commercial use, constitute an unidentified class of potentially bioaccumulative substances that require regulatory assessment to prevent possible ecosystem and human-health consequences. Fig. 1.

Relationship between observed tissue residue concentrations (ng·g–1 lipid equivalent) and trophic level for PCB 153 (a high KOW–high KOA compound) and β-HCH (a low KOW–high KOA compound) in Arctic organisms of the piscivorous (A), terrestrial (B), and marine mammalian (C) food webs. Data represent geometric means ± 1 SD.

Food Web–Specific Biomagnification of Persistent Organic Pollutants

Barry C. Kelly, Michael G. Ikonomou, Joel D. Blair, Anne E. Morin, and Frank A. P. C. Gobas

Science 13 July 2007: 317 (5835), 236-239.

a) Compare and contrast the accumulation PCB 153 (a high KOW–high KOA compound) and β-HCH (a low KOW–high KOA compound) of the piscivorous food web.

b) Why do pollutants such as PCBs accumulate at higher concentrations at each trophic level?


c) Approximate the slopes of the piscivorous food web and the mammalian food web for β-HCH. Compare the two rates and their possible consequences.

d) Predict both the local and global consequences on ecosystems if uncontrolled use of PCB 153 (a high KOW–high KOA compound) and β-HCH (a low KOW–high KOA compound) are continued.

Answer Key

1. Examples but not limited to: A- soil, water, climate. Biotic – alligator, insects, birds. 2. Microclimate is the climate of a very small or restricted area especially when this differs

from the climate of the surrounding area. The three layers of the forest differ in their microclimate: ground level is cooler and moister than other parts, the shrub level differs in wind speed, humidity, and temperature, the canopy differs in humidity, wind speed, and light intensity.

3. An ecosystem is a biological community of interacting organisms and their physical environment. The interactions of primary interest in ecosystem ecology are emphasized on energy flow and cycling of chemicals among various biotic and abiotic components. The difference because community and ecosystem is that a community is just the assemblage of population vs. an ecosystem which interacts with each other and their physical environment and are just one population in itself. An ecosphere is a biosphere of the earth or another planet when the interaction between living and nonliving is emphasized.

4. Density dependent controls: competition for food, shelter, mates raw materials. Density independent controls: climate conditions, or natural catastrophes such as floods, earthquakes, fires or volcanic eruptions to name a few.

5. Density dependent factors include natural catastrophes, climate, soil types, available water.

6. 1st = 120 x100 = 12000, 2nd = 6000 x 120 = 720,000, 3rd = 360,000 x 120 = 43,200,000. Graph should have population size on Y axis and time on X axis and should show J shape.

7. Birth rate is 70/1000 = 0.07 Death rate is 10/1000 = 0.01, therefore (0.07 – 0.01 = 0.06)N. 0.06 x 500,000 = 30,000 per year increase.

8. The human population will inevitably grow because the equation for human population growth is exponential. Thus, even when the birth rate is decreased, the births that occur will still exceed the death rates each year. Especially because the more humans become advanced in technology and medication the human life span is drawn out longer. Longer lives mean less annual deaths rates. This ultimately results in the human population increasing, despite lower birth rates.

9. R selection is a strategy in response to environmental conditions that are unstable and fluctuate enough to cause a constant threat. They invest their resources into reproductive capacity rather than adult survival. K strategists invest their resources in adaptations making adults competitive.

10. The events that lead to a fall turnover include cooling of surface waters, density change in surface waters, producing convection currents from top to bottom, and circulation of total water volume by wind action. Basically, the cool air causes a decrease in temperature of the top layer of water, causing it to become more dense, therefore sinking to the bottom. The sinking process pushes the warmer water up towards the surface causing an even mixture in temperature and distributes oxygen throughout the body of water. Fish tend to thrive in cooler water which tends to carry more oxygen. Because the fall turnover causes a distribution of cool water and oxygen throughout, the


fish can thrive in their environment. 11. Soil horizons are the layers in the soil profile. The soil horizon is mostly split into the O

horizon, A horizon, E horizon, B horizon, C horizon and R horizon (bedrock), they are described by different physical features. They are produced through along process weathering. Weathering is caused by air, water, solar radiation and plant material.

12. Silts are fine sand, clay or other material carried by running water and deposited as a sediment. Clays are stiff, sticky fine-grained earth and often forming an impermeable layer in the soil. Sands are loose granular substances resulting from the erosion of siliceous and other rocks. The soils affect the competition of plant population at low and high nutrient supply. Plants thrive in moist areas that are full of nutrients for their roots to grow whereas dry soils lack in life since there is no sustainable supply for anything to live in.

13. The growth of populations depends directly on the conditions of light, moisture and temperature produced by climates. A species survival depends on its ability to adapt to regional climate conditions.

14. A population’s growth will begin exponentially but will level off as the number of predators and competition for food increases. This will control the overall population growth.

15. Territoriality is when an organism has an area or territory and will fight and or kill any animal of the same species who enters their territory. This limits the population growth by affecting how many organisms can live in one area or territory. Maintaining the territory essentially monopolizing the area of prey and how many organisms survive within that area.

16. Factors that contribute to a crash in the human population are: disease, natural disaster, geographical complications or famine/ loss of resources. Diseases that are incurable may strike and diminish our population, natural disasters like tsunamis, hurricanes, earthquakes and tornados or geographical dis embodiments or famine of food and vital resources due inclement circumstances would have a detrimental effect on the human population. Human population growth is determined by birth and death control. Based on the exponential population growth equation, birth rate exceeds death rates. The more experienced we become with medication and technology to preserve life, the more we have over death control. Despite the contraception factors that people utilize, the birth control tends to be less efficient than that of death control medications and technologies.

17. No, because if the population doubles (primary and secondary consumers) so does the need for primary producers because the trophic levels need to be in equivalent ratios .

18. Survivorship curves provide a visual of the percentage of total life span vs. the number of survivors at a given time. R strategists typically have a high mortality rate for the offspring and only a few that survive the total lifespan. Another curve shows that there is an equal chance of survival during the organism's life span. The 3rd type of curve represents the K strategists. It shows low death after birth, with most of them surviving their lifespan.

19. An ecological community is a group of populations of different species in an area. Community ecology examines how interactions between species, such as predation and competition, affect community structure and organization.

20. Predation is where an organism (predator) kills another organism (prey) for food and nutrition. There is carnivorous predation, eating other animals for food, herbivory is eating plants for food, and parasitism is feeding off the alive host. Predation effects population growth by keeping the prey population in check and keeps the food chain, ecosystem, balanced.

21. Prey species have adaptations that help them avoid being eaten. Common behavioral


defenses include hiding, fleeing, and formation of herds. These forms of protection enable prey to survive and reproduce. Consequently, the populations of these prey species are able to increase more quickly as the prey thrives in its environment.

22. This is an example of parasitism. The mistletoe is benefitted because it receives water and nutrients from the host plant. The host plant is harmed because water and nutrients are taken away from it. For the mistletoe, this is an obligate relationship because the mistletoe cannot survive without the host plant.

23. Competition between organisms may be for a number of different factors, including food, light, territory or reproductive partners. Competition can control population density or growth because it decrease resources for other organisms in the area, allowing some to survive and some to die out more commonly known as survival of the fittest. There are four types of competition: Intraspecific competition is competition for a resource between individuals from the same population. It causes the population growth rate to slow down, and has a greater effect the less plentiful the resource is; Scramble competition occurs when many members of a population compete for a scarce resource, and each member gains a portion of that resource. This is often seen when populations compete for a food source and each member of the population gains some of that food source; Contest competition occurs when two or more members of a population compete for a resource but only one member of the population gains that resource. This can be seen when competing for mates or territory; Interspecific competition is competition for a resource between members of different populations in the same community. It will result in the competing populations increasing in size more slowly than normal. This type of competition may result in the extinction of one of the competing populations.

24. The concept of competitive exclusion is that when populations of two similar species compete for the same limited resources and one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population. Natural populations inhabiting the same geographic region avoid extinction by competitive exclusion by changing their pattern of resources because they are not efficient enough with their original resources they must avoid extinction by changing those resources and coexist successfully.

25. An ecological niche is all species use of biotic and abiotic resources in the environment. Niche overlap is when an environment shares its resources. A greater niche overlap will be able to support more species. Niche overlap will decide the competition between the species. A greater niche overlap will create less competition while a smaller niche overlap creates more competition.

26. The flow of chemical elements and compounds between living organisms and their physical environment which involve biotic and abiotic of ecosystems. Nature reserves are biodiversity islands in a sea of habitat. They are degraded by human activity therefore they must be protected, in order to maintain the nutrients that are needed for the cycles within their ecosystem.

27. Primary producers are autotrophs, meaning they convert non usable forms of energy (like light energy) into chemical energy. They are the source of food energy for other organisms in a trophic structure. They are often photosynthetic. Gross primary production measures the amount of light energy converted to chemical energy by photosynthetic organisms per unit of time. Net primary production measures the GPP, but subtracts the amount of energy used by producers in cellular respiration.

28. At each trophic level 90% of the energy is lost and only 10% is transferred onto the next level. The 90% of energy is lost through metabolic processes such as maintaining heat for body temperature in endotherms and growth and development of biomass, while some is released as waste.

29. Entropy is related to the one way flow of energy through ecosystems because certain


organisms are assigned different trophic levels. Energy flows through these different levels starting with the sun, then the primary producers, primary consumers, secondary consumers, and finally the decomposers.

30. The process of sunlight entering the earth’s atmosphere is reduced in the clouds, atmosphere, and some radiates back into space. Some UV radiation is blocked by the thermosphere, mesosphere, and stratosphere. Then striking the surface of earth by incoming of some solar energy into the land and absorbed into oceans.

31. A community is when organisms in a particular area are interacting. Humans are affecting it by channeling, littering, recreating, invading species, etc. affecting the food chain. Therefore, humans need to invest in engineering to find eco-friendly solutions to radioactive wastes to not damage our community

32. Community structure is composed of three major elements, species diversity, species richness, and relative abundance. Species diversity is the variety of different kinds of organisms that make up a community. One component of this is species richness, the number of different species in the community. The other component is relative abundance, the proportion each species represents of all individuals in the community. Patchy distributions of populations are characterized by minimized distance between neighboring individuals. Continuous distribution of populations is characterized by maximized distance between neighboring individuals (evenly spaced). A forest community is structured vertically by layers. Each layer is a height group, depending on sunlight demand. The sunlight demand generally separates the forest into three layers, the tree layer, the bush layer, and the underwood.

33. Predators have beneficial effects on prey populations by acting as a limiting factor keeping the prey population in check so the prey have enough resources to survive. Also, prey that survive predation have evolved traits that enhance their ability to escape the predators, which leads into natural selection of the survivors with more suited traits. Prey that survive are more fit than the others so they will pass on their traits.

34. Mutualism is a symbiotic relationship in which both organisms benefit. For example, clownfish live in sea anemones. The fecal matter from the clownfish provides nutrients to the sea anemone and the sea anemone’s tentacles provide protection from predators to the clownfish. Parasitism is a symbiotic relationship in which one organism benefits and another organism is harmed. A tick is an arachnid that drinks the blood of other animals. The host animal is harmed via disease and decreased blood volume. The tick benefits by receiving nutrition from the host animal.

35. Natural selection reduces competition as the species that are more fit to the environment survive making competition more difficult because the prey that survives has better traits that will allow it to escape predation. Niche specialization is the process in which a species becomes better adapted by natural selection to the specific characteristics of a particular habitat.

36. The niche refuge or ecological niche is the sum of a species use of the biotic and abiotic resources in its environment. The fundamental niche is a niche that is potentially occupied by that species. The realized niche is the portion of its fundamental niche that is actually occupied in a particular environment. Two species cannot coexist if their niches are identical therefore niche overlap relates to population survival by competition causing evolution by natural selection in which one species niche must be modified by using a different set of resources. Describe the features that nitrogen, carbon, and phosphorous cycles have in common. Explain how they differ.

37. The degradation of dead animal and plant materials in soil is a fundamental biological process because carbon is recirculated to the atmosphere as carbon dioxide, nitrogen as ammonium and nitrate and other associated elements such as phosphorus appear in inorganic forms required by higher plants. They differ in that organisms use nitrogen


less than they do carbon or water, it could also be said that a lack of nitrogen would eradicate life on Earth. As with carbon, most of the nitrogen in the world is found in the atmosphere. One major difference between carbon and nitrogen gases, however, is that most organisms on Earth are completely unable to use atmospheric nitrogen directly. In order for nitrogen to enter a community, it must first be converted into a usable form by special nitrogen "fixing" bacteria in the soil.

38. Detritus is the dead organic material at the very bottom of the food chain. In the forms of leaf litter, feces, bacteria, and fungi, detritus is consumed and holds a large factor in the nutrients distribution among living matter. Linking all levels of consumption and releasing the last source of heat, detritivores take in the left over material and break its components down even further. Detritivores break down organic material and recycle the chemical elements in inorganic forms to abiotic reservoirs such as soil, water, and air, via cellular respiration. Being the decomposers, detritus feeders secrete enzymes that digest organic material, to then absorb the products. With such a large role, life would simply be cease without decomposers.

39. Primary consumers are herbivores and get their energy from consuming primary producers. Secondary consumers are carnivores and get their energy from consuming primary consumers. Detritus feeders, also called detritivores or decomposers, consume nonliving organic material, such as dead organisms, feces, fallen leaves, and wood. Detritus feeders contribute to the cycling of energy within a community. Biomass can refer to two ecological aspects. First, biomass can describe the total mass of all individuals in a population. Additionally, biomass can mean dry weight of organic material in an ecosystem.

40. A food web is a series of interrelated parts which link organisms together by way of obtaining energy from one another. Each link describes a transfer of energy from one of the organisms to another. For example: rabbits and mice both eat grass, and are both consumed by falcons. Mice and rabbits are also eaten by foxes and owls. A food chain, similarly, links organisms together, but it follows a single path - grass is eaten by rabbits which are eaten by falcons. Furthermore, it is rare that a food chain will contain more than three or four trophic levels. This is due to the fact that the chains become less stable, and the energy transfer between the levels becomes inefficient, which is called the dynamic stability hypothesis. For instance, the grass gives rabbits energy. When the falcon eats the rabbit, much of the energy that was contained in the grass has become lost.

41. Plants can’t photosynthesize heat; they use sunlight to start their process of being primary producers of this light to the rest of the ecosystem. This light energy is dissipated in the form of heat. The first law of thermodynamics applys to ecosystems because all ecosystems we can potentially trace energy exactly from its input as solar radiation to its release as heat from organisms. The second law tells us that energy conversions cannot be completely efficient; some energy will always be lost as heat.

42. The ozone layer is a deep layer in the stratosphere, which shields the entire earth from much of the harmful ultraviolet radiation that comes from the sun. The ultraviolet radiation is absorbed and filtered out, which creates the ozone layer when trying to pass through the atmosphere.

43. It is more efficient for humans to act as primary consumers because plants obtain 100% of solar energy. 90% of the energy is lost when transferring trophic levels. Therefore a direct consumption will give us the absolute max of energy to be obtained.

44. Conservation methods that could be used to reduce the per capita energy consumption in the some examples might be: U.S are carpooling, recycling, reusable water bottles, restriction on food consumptions, and restrictions of water/ electricity usage. Conservations methods are needed throughout the world today because of a quickly


increasing population that is stripping away earths primary producers, which supply all of Earth’s energy. As primary producers are quickly deteriorating, the less energy is being created for the necessities of our human race.

45. A community is an assembly of different populations in a habit or area. Diversity is created by the relative abundance, the number of organism of specific species, and species richness, the number of species a community contains. For example, in island areas, species richness is dependent upon distance from the mainland as well the climate. Tropical islands in particular have a larger species richness because the warm climate and high water availability attract a wider diversity of plant and animal species. Additionally, higher altitudes have shorter growing periods because there is less water availability for plants and subsequently less animals.

46. The equilibrium hypothesis states that, when a community is left to its own accord, it will regulate itself. For instance, say that a grassy area has a population of rabbits and foxes. If the foxes were to over-consume the rabbits, then there would be less resources - though the rabbit population would decline, so would the fox population. Similarly, if the rabbits were to overgraze, the rabbit population would decrease, and so would the fox. Conversely, the historical hypothesis states that natural disasters or occurrences - such as hurricanes, fires, droughts, floods, overgrazing, human activity etc. - can be the cause of population decline, thus, keeping communities in a state of non-equilibrium.

47. Community succession is the process of an ecosystem renewing itself after a disturbance and returning to a stable, climax community. The steps of succession are as follows: First the habitat is disturbed, by a volcanic eruption for example. The species are destroyed along with the structure of the soil which supported them. At first, few species can thrive, but as new plants take root, they alter the habitat, like the amount of shade present or the mineral composition of the soil. The modifications those plants create allow new plants to replace old ones, and the cycle continues until complex organisms once again inhabit the region.

48. Primary succession begins in a virtually lifeless area where soil has not yet formed. Secondary succession occurs where an existing community has been cleared by a disturbance leaving soil intact. Since secondary succession depends on the existing conditions of the habitat, the rate at which it proceeds also depends on the previous inhabitants of the habitat. For example, if the earlier species make the habitat favorable for later species, then secondary succession can occur at a faster rate.

49. In a lake environment, the first species to grow after a disturbance would be algae. As the environment stabilized newer aquatic plants grow, and animals would begin returning to the habitat, until the lake ecosystem is back to the way it was. In an abandoned field, the first species to grow would be grasses. Then shrubs and small plants would grow, while animals would return to the environment. Then taller plants would take root with the more stable soil, and more diverse animals would come to the habitat too, until the field became a complex community again.

50. Climax community is a biological community of plants and animal which have reached the final stage of succession. Community stability is where stability is in the context of a community to reach and maintain an equilibrium or relatively constant composition of species in the face of disturbances. Factors that are believed to underlie community stability are disturbances, which include storms, fire, floods, droughts, overgrazing or human activities that will damage these communities.

1. Bacteria in the Ocean a. Prochlorococcus are photoautotrophic cyanobacterium. Two questions that can be

answered are: how do they capture the energy from light? Are there any mutant strains that do not produce vesicles? What are genetics components responsible for the vesicle production and secretions? Does vesicle production affect photosynthetic


rate? b. Vesicles are the means that cells use to export or import substances that are too

large or amenable charge for diffusion or facilitated diffusion. Cells choose to export certain molecules because the molecules function extracellularly. A seen in the diagram, the vesicles may function as forms of communication with heterotrophic bacteria, immune responses to viruses, and as vehicle of generating genetic diversity by transporting portions of DNA and RNA from Prochlorococcus to other cells.

c. The exchange of material between cells is shown on the lower left with the bidirectional arrows between the autotrophic and heterotrophic cells. One possible equation would be photosynthesis-respiration equation: 6CO2 + 6H20 ←→C6H12O6 + 6O2. Also, the exchange could be amino acids from the autotroph with nitrogen-containing waste products from the heterotrophy.

d. The approximate size of the vesicles is between 125-200 nanometers, while cells are ~750 nm in diameter. The vesicles would be more efficient at exchanging materials with the environment, because they have a larger surface area to volume ratio than cells due to their smaller surface area, which the gives internal volume more areas of direct contact with the cell membrane or shorter distances to diffuse out of the cell.

Learning Objectives:

LO 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store and use free energy. [See SP 1.4, 3.1]

LO 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store or use free energy. [See SP 6.2]

LO 2.6 The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion. [See SP 2.2]

LO 2.7 Students will be able to explain how cell size and shape affect the overall rate of nutrient intake and the rate of waste elimination. [See SP 6.2]

LO 2.8 The student is able to justify the selection of data regarding the types of molecules that an animal, plant or bacterium will take up as necessary building blocks and excrete as waste products. [See SP 4.1]

LO 2.9 The student is able to represent graphically or model quantitatively the exchange of molecules between an organism and its environment, and the subsequent use of these molecules to build new molecules that facilitate dynamic homeostasis, growth and reproduction. [See SP 1.1, 1.4]

2. Desertification a. The past 3000 years has seen a gradual change in climate and the changes in the

ecosystem that the climate change entails. A study of the lake Yao core that corresponds to the last 3000 years shows that the water has increase salinity compare to the next 4000 years (more conductance, more salinity). Diatoms that are the producers in an aquatic ecosystem were more abundant in the past 4000 or more years; There is more organic matter present 4000 years or more than last 3000 years, suggesting a robust ecosystem existed in the past 4000 or more years ago. The lithology of rock shows different depositions and erosions forces were at play; the magnetic susceptibility differences support different climate scenarios. The pollen and spores of tropical plants are found in cores 4000 years or older, while Mediterranean plants took about 1000 years to take hold after the transition in


climate. In all, the data supports a change from a tropical, warm, wet climate to a drier, windy climate in the Saharan region.

b. For reconstructing the climate history of a particular area you would want to find an area where there is a constant settling material or build up of material over time, such as the bottom of bodies of water , glaciers, living organisms (bone, teeth, hair). With the found data you can correlate the findings with plants or animals that are found in one type of climate or another.

c. There was a gradual change in climate about 4000 years that change the Saharan region from a forest to a desert; The bodies freshwater became more saline, and Mediterranean plants that were in low abundance supplant the tropical plants that were dominant before the climate change.


LO 2.22 The student is able to refine scientific models and questions about the effect of complex biotic and abiotic interactions on all biological systems, from cells and organisms to populations, communities and ecosystems. [See SP 1.3, 3.2]

LO 2.23 The student is able to design a plan for collecting data to show that all biological systems (cells, organisms, populations, communities and ecosystems) are affected by complex biotic and abiotic interactions. [See SP 4.2, 7.2]

LO 2.24 The student is able to analyze data to identify possible patterns and relationships between a biotic or abiotic factor and a biological system (cells, organisms, populations, communities or ecosystems). [See SP 5.1]

3. Flight of the Honeybee a. For distances less than 50 meters, the bee does an S shaped, top down maneuver

to signal that the food is nearby. For distances of more than 50 m, the flies perform a bottom up, repeated turning at angles that signal the direction of the food, and the length of the turns signals the distance to the food.

b. How long the bee performs the waggle dance is correlated to the distance to the food.

c. One of the diagrams (3 km) should be about 3 times as big as the other diagram for 1 km.



LO 3.40 The student is able to analyze data that indicate how organisms exchange information in response to internal changes and external cues, and which can change behavior. [See SP 5.1]

LO 3.41 The student is able to create a representation that describes how organisms exchange information in response to internal changes and external cues, and which can result in changes in behavior. [See SP 1.1]

LO 3.42 The student is able to describe how organisms exchange information in response to internal changes or environmental cues. [See SP 7.1]

4. Soil Carbon a. C t = C 0 [ e xp ( – k o l d × 0 ) ] + I / k n e w [ 1 – e xp (– k n e w × 0 ) ] , f o r t =0 ;

C t = C 0 [ e xp ( 0 ) ] + I / k n e w [ 1 – e xp (0 ) ] ; C t = C 0 [ 1 ] + I / k n e w [ 1 – 1 ] ; C t = C 0 + 0 ; C t = C 0 , f o r t =0

b. I nc reas ed CO 2 s l i gh t l y inc r eases t he am oun t o f Car bon in t he s o i l be f o re r each ing an equ i l i b r ium po in t where i t does no t dec r ease o r i nc r eas e .

c. Once an equ i l i b r i um i s r eac hed , t he so i l w i l l no t absor b exc ess CO 2 i n t he a tmosphe re , lead ing po t en t i a l l y t o a n inc r ease in t he r a te o f CO 2 a ccumu la t ing i n t he a tm os phere t ha t exacerba te g l oba l warm ing .


LO 4.14 The student is able to apply mathematical routines to quantities that describe interactions among living systems and their environment, which result in the movement of matter and energy. [See SP 2.2]

LO 4.15 The student is able to use visual representations to analyze situations or solve problems qualitatively to illustrate how interactions among living systems and with their environment result in the movement of matter and energy. [See SP 1.4]

LO 4.16 The student is able to predict the effects of a change of matter or energy availability on communities.[See SP 6.4]

5. Biomagnification a. PCB accumulates increasingly in higher trophic levels, but β-HCH does not

accumulate in the tissues of aquatic organisms. The concentration per body weight of β-HCH actually decreases for larger organism.

b. The producers accumulate the chemical pollutants and the primary consumers eat the producers with pollutants concentrating within the consumer. The primary consumer is eaten by the secondary consumer, with pollutants concentrating within the secondary consumer at higher concentrations than the primary. The secondary consumer is eaten by the tertiary consumer and so on.

c. . Get 2 approximate data points for each of the regression lines, say (1, 0.8) and (5, 0.5) for the aquatic food chain and (1, 0.1) and (5, 50). 0.5-0.8 / 5-1 = ~-0.08 and 50-0.1 / 5-1= ~13. The rates of pollutant accumulation are much larger for terrestrial, air breathing animals.

d. If continued use of these chemicals is persistent, local ecosystems will get the initial accumulation of pollutants increasingly over trophic levels and those accumulation will increase as well due to the increasing accumulation of the chemicals over time in


the environment. Eventually, the accumulation of the chemical in the food chain will go global. The effects of these chemicals are yet to be seen, with the exception of PCB that has health consequences to almost every organ system in the living organisms.


LO 4.21 The student is able to predict consequences of human actions on both local and global ecosystems. [See SP 6.4]

LO 4.14 The student is able to apply mathematical routines to quantities that describe interactions among living systems and their environment, which result in the movement of matter and energy. [See SP 2.2]

LO 4.15 The student is able to use visual representations to analyze situations or solve problems qualitatively to illustrate how interactions among living systems and with their environment result in the movement of matter and energy. [See SP 1.4]

LO 4.16 The student is able to predict the effects of a change of matter or energy availability on communities.[See SP 6.4]


6.

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