CHAPTER 22 Test Your Knowledge
DRIVING QUESTION 1
What are keystone species in a community, and why are pollinators considered keystone species?
By answering the questions below and studying Infographics 22.1, 22.2, and 22.3, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
How does a community differ from a population?
A community is a collection of interacting populations of different species in a given geographic area. A population is a group in interbreeding organisms of the same species in a given geographic area.
What are keystone species?
Keystone species are species that have a strong influence on the community, without necessarily having a high abundance.
A rocky shoreline that is covered at high tide but exposed at low tide supports a community of mussels, algae, barnacles, and starfish. An ecologist systematically removes species from different areas of the beach. Removing the mussels doesn’t substantially change the community, but removing the starfish dramatically changes the mix of species in the area. Which is the keystone species?
a. mussels
b. barnacles
c. algae
d. starfish
e. all of the above
d
Bees transfer pollen from the________to the
a. anther; stigma
b. stigma; style
c. filament; ovary
d. anther; ovary
e. stigma; anther
a
USE IT
Think about a community of organisms that you are familiar with. From what you know about this community, choose what you think might be a keystone species and defend your choice.
Answers will vary.
If you have pollen allergies, are you more likely to be suffering from the effects of bee-carried pollen or wind-carried pollen? Explain your answer.
You are more likely to be suffering from the effects of wind-carried pollen that is released in large amounts into the air to enable reaching suitable stigmas.
DRIVING QUESTION 2
What are food chains and food webs, and how does energy flow through them?
By answering the questions below and studying Infographics 22.4 and 22.5, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
In relation to a food chain, what do plants and photosynthetic algae have in common?
a. nothing.
b. They are both producers.
c. They are both first level consumers.
d. They are both top level consumers.
e. Their numbers are limited by the energy they take in from heterotrophic food sources.
b
A bear that eats both blueberries and fish from a river can be referred to as
a. an omnivore.
b. a heterotroph.
c. a consumer.
d. a producer.
e. all of the above.
f. a, b, and c
g. a and c
f
USE IT
Describe a natural food web that includes a terrestrial food chain (including honeybees) and at least one aquatic organism from an aquatic food chain.
Question 8 provides an example. The bear is a part of the terrestrial food chain, acting as a consumer by eating blueberries. The blueberry plants are pollinated by insect pollinators, which eat the nectar. The blueberry plants themselves are photosynthetic producers. The bear can also eat fish, which depend on algal producers in the aquatic environment.
Explain how a cow can eat so many kilograms of grass but not produce the equivalent amount of energy in the form of meat. What happens to the energy stored in the grass once it is ingested by the cow?
As the cow ingests grain, much of the energy stored in the grain is used to maintain the existing tissues in the cow. As the cow carries out cellular respiration, some of the energy stored in the grain is lost as heat. Some of the grain is not completely digestible, so some portion of it will be eliminated with the cow’s feces. Overall, only 10% of the energy stored in the grain is converted to stored cow protein (e.g., muscle protein and meat).
Compare the diet of a human who is an herbivore with that of a human who is a top consumer. Consider what each might actually eat; how much energy from a producer is captured in the herbivore human; and how much energy from a producer is captured in the top consumer human.
The true herbivore human is a vegan, eating only plant (that is, producer) products. When the human eats producers, 10% of the energy stored in the producer will end up stored in the human’s tissues. A human who is strictly a top carnivore will eat only other consumers (e.g., cows and predatory fish). In this case, the consumer has stored 10% of the energy of the producer, and the human will store only 10% of that.
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DRIVING QUESTION 3
What positive and negative interactions occur between members of a community?
By answering the questions below and studying Infographics 22.6, 22.7, 22.8, and 22.9, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
What are some important features of a honey bee niche? How is it that other nectar-feeding organisms can coexist with bees as part of a community?
The honey bee niche includes flowers that have a particular shape or color that attracts bees and facilitates the transfer of pollen. The niche will have a variety of flowering plants that will flower at different times during the seasons in which the bees are active. Ideally, the flowers will not have been treated with insecticides or pesticides that could have a negative impact on the honey bees. Because of different flowering times and different flower shapes and other attributes, different organisms can specialize on different sources of nectar
Competition is most likely to occur
a. when one species eats another.
b. when two species occupy different niches.
c. when one species helps another.
d. when two species occupy overlapping niches.
e. when two species help each other.
d
Which of the following characterizations best describes a symbiotic relationship?
a. Both organisms benefit.
b. The organisms live in close association.
c. Only one organism benefits.
d. The relationship is mutually harmful.
e. Neither organism benefits.
As they are both filter feeders, it may be that each species is specializing on a different size of food (e.g., different bacteria or algae). In this way, they would not be in direct competition with each other.
Would you characterize the relationship between the bacteria that live symbiotically within bees and their bee hosts as a type of competition, parasitism, mutualism, or commensalism? Explain your answer.
The number and diversity of bees would decrease. There were a number of different wildflower species in the field, each with a different flower shape, flower color, and time of blooming. This diversity can support a number of bee species. In a monoculture of corn, there is only one species, with individuals that are essentially identical. This results in a single food source that can support a very limited diversity of bees.
USE IT
On a rocky intertidal shoreline (the area between the highest and lowest tidelines, so the intertidal zone is alternately exposed and covered by seawater), mussels and barnacles live together attached to rocks where they obtain food by filtering it from ocean water. Since these two species coexist in the same habitat, we predict that they do not have identical niches. What might be separating their niches enough to allow them to occupy the same rocky intertidal zone?
b
If a meadow of wildflowers were converted to a field of corn, would you predict the number and diversity of bees in the community to increase or decrease? Explain your answer.
This relationship is a mutualism: the bacteria get nutrients and a safe place to live and the bees get protection from infectious diseases
What is the evidence for and against each of the following being responsible for colony collapse disorder (CCD)?
a. varroa mites
b. IAPV
c. neonicotinoids
a: Evidence for varroa mites: they are known to feed on the blood of bees, to weaken the immune system, and to transmit viruses. Evidence against varroa mites: mite infestations are not more severe in collapsing colonies compared to infestation levels in the same colonies in previous years, and mite infestations don’t explain the disappearance of bees from collapsing colonies. b: Evidence for IPAV: IAPV is present in 96% of hives with CCD. Evidence against IAPV: not every colony with IAPV collapses, so IAPV can’t be the sole cause. c: Evidence for neonicotinoids: They are known to be toxic to bees and they appear to disorient bees, making it hard for them to return to the hive. Evidence against neonicotinoids: There is no strong evidence against, but there is a lack of determinative information.
It is likely that CCD results from a combination of factors.
We all have E. coli bacteria living in our intestinal tracts. Occasionally these E. coli can cause urinary tract infections. From this information, which of the following terms would you say describe(s) the relationship between us and our intestinal E. coli? Why did you choose the term(s) you did?
a. competition
b. mutualism
c. parasitism
d. symbiosis
e. predator-prey
choices b, c and d. As the bacteria live in close association with humans, the relationship is a symbiosis. As the bacteria benefit from the nutrients in the digestive tract and outcompete potential pathogens, the relationship is a mutualism. As the bacteria can occasionally cause disease, the relationship is a parasitism.
BRING IT HOME
Many people consider bees a stinging nuisance. What could you say to such people to dissuade them from killing all the bees in their backyards?
Bees are critical in helping many plants—including many of the plants that we humans rely on for food—to reproduce.
MINI CASE
Farmers often plant large acreage of a single crop in order to maximize yield and simplify harvesting. This is true of almonds in the central valley of California.
a. From what you have read in this chapter, what are some of the pros and cons associated with monoculture?
b. Do some online research to develop a specific model for an alternative to monoculture that addresses at least one of the issues you have identified.
a: Some of the pros include more efficient growing and harvesting, resulting in a higher yield. Some of the cons include reducing the diversity and availability of plants available for a variety of pollinators (including bees). This adverse impact on bees will have a spin-off effect on other bee-pollinated crops. b: There are a variety of alternative models that rely on planting different crops that flower at different times in the same fields.
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INTERPRETING DATA
Scientists carried out an experiment to test the hypothesis that a neonicotinoid pesticide called imidacloprid could cause colony collapse disorder (CCD). They had a total of 20 hives (colonies) that were broken into 5 groups (with 4 hives per group). Four groups received imidacloprid at different dosages (400µg/kg; 200µg/kg; 40µg/kg and 20µg/kg). One group did not receive imidacloprid. Hives were monitored for 23 weeks after the initial dose. The data are summarized in the table below.
a. Graph these data.
b. What patterns do you observe?
c. Do you think that the data support the hypothesis? Why or why not?
a: Graph is not included in answer key. b: In general, the higher the dose of imidacloprid, the earlier the hive mortality, and the greater the number of hives that experience mortality. c: The data are consistent with the hypothesis. Only 1 of the untreated hives died, compared to 4 hives at the highest dose. The single untreated hive that died did not die until 21 weeks into the study, whereas dead hives were present at 14 weeks in the treated groups. This is consistent with a delayed effect of imidacloprid on hive mortality. More research will be necessary to continue to elucidate the effect of imidacloprid on honey bee hive mortality.