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Study of the interactions of organisms with other Study of the interactions of organisms with other organisms and with the physical environmentorganisms and with the physical environment
Figure 42.1 The Hierarchy of Ecological Systems
Concept 42.1 Ecological Systems Vary in Space and over Time
• At any given time, an ecological system is potentially unique.
• In the human gut, the microbial species vary from person to person and with diet.
• The host’s genotype and diet affect the gut environment from the bacterial point of view; and the bacteria influence their environment, which includes the host.
• Some health disorders may be treatable by manipulating the gut bacterial community.
Populations
• Groups of organisms of the same species that live within a given area
• Key characteristics:– Dispersion patterns– Population density – Growth rate
Ostriches are nomadic, wandering
in small groups.
Aspen trees are quick to pioneer areas that have been disturbed
by fire.
Dispersion Patterns Within Populations
Three common patterns of population distribution are:
Population Density• Population density is total population size per unit of
area.• Population densities depend on:
– Interactions within the environment
– Quality of habitat
– Density dependent factors
– Density independent factors
• Carrying capacity is the maximum number of organisms that can be supported in a given habitat.
• Population size can be measured by several sampling techniques.
Population Growth
Exponential vs. Logistical Growth
Survivorship in Populations
Reproductive Strategies• r- Selected (maximum
growth rate, below carrying capacity)– Early reproduction– Short life span– High mortality rate– Little or no parental care– Large investment in producing
large numbers of offspring– Below carrying capacity– Examples:
• Bony fish• Grasshoppers
• K-Selected (maximizes population size near carrying capacity)– Late reproduction– Long life span– Low mortality rate– Extensive parental care– Greater investment in
maintenance and survival of adults
– At or near carrying capacity– Examples:
• Sharks• Elephants
Limits on Population Growth
• Density Dependent Limits– Food– Water– Shelter– Disease
• Density Independent Limits– Weather – Climate
Water and shelter are critical limiting factors in
the desert.
Fire is an example of a
Density independent
Limiting factor.
Figure I shows the growth of an algal species in a flask of sterilized pond water. If phosphate is added as indicated, the growth curve changes as shown in Figure II.Which of the following is the best prediction of the algal growth if nitrate is added instead of phosphate?
a.
b.
c.
d.
Use the graph above to calculate the mean rate of population growth (individuals per day) between day 3 and day 5. Give your answer to the nearest whole number.
A population of microscopic eukaryotic organisms growing in a large flask had the growth pattern shown.
In one paragraph, explain the biological factors that determine the shape of the growth pattern shown above in both period 1 and period 2.
Use the graph above to calculate the lag time in months between the change in the densities of the prey and the predator populations. Give your answer to the nearest tenth of a month.
(Camouflage)
The diagram above shows the progression of ecological events after a fire in a particular ecosystem. Based on the diagram, which of the following best explains why the oak trees are later replaced by other trees?(A) Eventually the other trees grow taller than the oak trees and form a dense canopy that shades the understory.(B) Oak trees alter the pH of the soil, making the forest better suited for shrubs and other trees.(C) Roots of shrubs proliferate in the soil of the forest and prevent the oak trees from obtaining water.(D) Oak trees succumb to environmental pollutants more readily than do either the shrubs or the other trees.
Assume there are 50,000 joules (J) of energy available in trophic level II in the figure. According to the conventional model of energy flow in ecosystems, which of the following statements correctly describes the flow of energy in the system?
(A) Trophic level I generates a maximum of 50,000 J of energy. (B) Trophic level I has approximately 5,000 J of available energy. (C) Trophic level III has approximately 50 J of available energy. (D) Trophic level IV has approximately 500 J of available energy.
What percent of the biomass in the forest community represented above is tied up in the shrub layer? Give your answer to the nearest whole number.
The following is a food web for a meadow habitat that occupies 25.6 km2. The primary producers’ biomass is uniformly distributed throughout the habitat and totals 1,500 kg/km2.
Developers have approved a project that will permanently reduce the primary producers’ biomass by 50 percent and remove all rabbits and deer.Which of the following is the most likely result at the completion of the project?(A) The biomass of coyotes will be 6 kg, and the biomass of hawks will be 0.5 kg.(B) The biomass of coyotes will be dramatically reduced.(C) The coyotes will switch prey preferences and outcompete the hawks.(D) There will be 50 percent fewer voles and 90 percent fewer hawks.
The food web above represents feeding relationships in a biological community near a deep-sea hydrothermal vent. Hydrothermal vents are geysers on the seafloor that gush super-heated, mineral-rich water. The seawater surrounding hydrothermal vents typically contains carbon dioxide , molecular hydrogen, hydrogen sulfide, and methane. Sunlight, however, fails to reach the seafloor where deep-sea hydrothermal vents are located. As part of an investigation, researchers collected living specimens from an area near a deep-sea hydrothermal vent. Mussels in the collection were found to be dependent on molecular hydrogen in seawater. Also, the researchers discovered multiple species of bacteria living in the gills of the mussels. Mussels use gills for filter-feeding and gas exchange with the surrounding seawater. On the basis of their experimental results, the researchers hypothesized that some bacteria living in the gills of the mussels are capable of chemosynthesis.
Which of the following best explains how biological communities near deep-sea hydrothermal vents can exist in a habitat lacking sunlight? (A) Environmental conditions on some distant planets resemble those experienced by organisms living near hydrothermal vents. (B) Heterotrophs metabolize carbon-containing compounds produced by the photosynthetic organisms that live on the seafloor. (C) Some organisms rely on energy captured from inorganic compounds to drive basic biological processes. (D) Some organisms that can tolerate high temperatures are single celled, whereas others are multicellular.
The food web above represents feeding relationships in a biological community near a deep-sea hydrothermal vent. Hydrothermal vents are geysers on the seafloor that gush super-heated, mineral-rich water. The seawater surrounding hydrothermal vents typically contains carbon dioxide , molecular hydrogen, hydrogen sulfide, and methane. Sunlight, however, fails to reach the seafloor where deep-sea hydrothermal vents are located. As part of an investigation, researchers collected living specimens from an area near a deep-sea hydrothermal vent. Mussels in the collection were found to be dependent on molecular hydrogen in seawater. Also, the researchers discovered multiple species of bacteria living in the gills of the mussels. Mussels use gills for filter-feeding and gas exchange with the surrounding seawater. On the basis of their experimental results, the researchers hypothesized that some bacteria living in the gills of the mussels are capable of chemosynthesis.
On the basis of the food web, which of the following members of a deep-sea biological community is most likely to also have a symbiotic relationship with chemosynthetic organisms? (A) Octopuses (B) Blind crabs (C) Zoarcid fish (D) Shrimp
On the evening of Saturday December 6th 2008 a number of Irish news sources reported that testing had revealed "extremely high" levels of PCBs in pork products, ranging from 80 to 200 times the EU's upper safe limit of 1.5 pg/g i.e. 0.12 to 0.3 parts per billion. The PCB levels involved are small in comparison to other contamination incidents, indeed in 1986 the breast milk of healthy nursing mothers in the US contained between 1020 to 1770 ppb of PCBs and the PCB contaminated rice-bran oil that caused mass poisoning (Yu-Cheng) in Taiwan in 1979 contained between 53,000 to 99,000 ppb of PCBs.Brendan Smith, the Minister for Agriculture, Fisheries & Food, stated that pork contamination was caused by PCB contaminated feed that was used on 9 out 400 of Ireland's pig farms and only one feed supplier was involved. Smith added that 38 beef farms also used the same contaminated feed, but those farms were quickly isolated and no contaminated beef entered the food chain. While the contamination was limited to just 9 pig farms, the Irish government requested the immediate withdrawal and disposal of all pork-containing products produced in Ireland and purchased since September 1st 2008.
A researcher is investigating the relationship between the existing species diversity in a community and the ability of an introduced nonnative species to destabilize the community.Which of the following graphs is most consistent with the claim that communities with high diversity are more resistant to change than are communities with low diversity?
a.
b.
c.
d.
The lionfish is a venomous fish found primarily in the Red Sea and the Indian Ocean. In the 1990s, lionfish were accidentally released into the Atlantic Ocean, where they found abundant resources and favorable environmental conditions. Which of the following scenarios is most likely to result in the lionfish having a major impact on the communities into which they were introduced?
(A) With no natural predators, the lionfish population will become very large. (B) Some native species of invertebrates will develop a resistance to lionfish venom. (C) Random mating will allow the lionfish population to reach
Hardy-Weinberg equilibrium. (D) A virus that specifically infects lionfish will become more prevalent.
In a certain prairie community, a dominant prairie grass species has recently been infected with a virus thatdisrupts one of the electron transport proteins in the chloroplasts of infected cells.
(a)Describe the most likely effects on cellular processes (be specific as to which processes and moleculesare most likely to be directly affected).(b) Describe and explain the most likely effects on individual infected plants.(c) Predict the short-term effects (within a year of infection) on the infected plant populations and their communities. Justify your prediction.(d) Predict the long-term effects (years to decades after infection) on the infected plant populations and their communities. Justify your prediction.
How much carbon (in g/m2) is released into the atmosphere as a result of the metabolic activity of herbivores?Give your answer to the nearest whole number.
Figure I shows the growth of an algal species in a flask of sterilized pond water. If phosphate is added as indicated, the growth curve changes as shown in Figure II.Which of the following is the best prediction of the algal growth if nitrate is added instead of phosphate?
a.
b.
c.
d.
• Prevailing winds drive the major ocean surface currents.
• Example: northeast trade winds drive water to the west; when it reaches a continent it is deflected northward until the westerlies drive the water back to the east.
• Deep ocean currents are driven by water density differences.
• Colder, saltier water is more dense and sinks to form deep currents.
• Deep currents regain the surface in areas of upwelling, completing a vertical ocean circulation.
• Oceans and large lakes moderate climate because water has a high heat capacity.
• Water temperature changes slowly as it exchanges heat with the air.
• Poleward-flowing ocean currents carry heat from the tropics toward the poles, moderating climate at higher latitudes.
Example: the Gulf Stream warms northern Europe.
Topography produces additional environmentalheterogeneity
Biomes
The area covered by tropical rain forest is reducedby millions of hectares per year due to agricultureand logging. Which of the following best describes a likely result of tropical rain forest deforestation?
(A) Populations of plants and animals will decrease as more rain forest disappears, leading to a decrease in biodiversity.(B) An increase of soil moisture will lead to a rapid increase in new vegetation coverage.(C) An increase in atmospheric carbon dioxide will lead to higher levels of ultraviolet radiation reaching the surface of Earth.(D) More oxygen will be available to other organisms as plant numbers decrease.
In the Arctic Ocean, the predominant primaryproducers are phytoplankton. Phytoplanktonare consumed by zooplankton, which in turn areeaten by codfish. In years when there is moreopen water (less ice coverage), there are morezooplankton and fish than in years with less openwater (more ice coverage). Based on the graphabove, the difference is most likely because
(A) when there is less open water, light is blockedfrom the zooplankton, so they cannot produce as much food for the fish(B) when there is more open water, the temperature is warmer, so the zooplankton and fish populations increase in size(C) the ice blocks the light, so in years with more ice coverage, there is less photosynthesis by the phytoplankton(D) the ice increases the light available for photosynthesis, so primary production increases and zooplankton populations increase in size
