Biology 112 – Third Hour Exam                                                 Name_____________________


MULTIPLE CHOICE. (49 points total) Circle the one alternative that best completes the statement or answers the question.


1) (2 points) Lobsters can navigate back home at night using Earth's magnetic field. Does this statement describe a proximate cause or an ultimate cause?  

A) proximate cause                                       B)  ultimate cause 


2) (2 points) How would you classify the genetic basis for most behavioral traits in the animal kingdom?  

A) One gene codes for one behavior.                  B)  Many genes code for one behavior. 

C) Behaviors are learned, not coded by genes.      D) One gene codes for many behaviors. 


3) (2 points) You see young spiders hatch from eggs and within 5 hours, they are dispersing far from their parents and forming webs. What can you hypothesize about their behavior?  

A) Web building is learned by observation. 

B) Web building is a random behavior. 

C) Web building is an inflexible behavior. 

D) Web building is innate because there is no parental involvement. 


4) (2 points) It is rather easy to understand why relatives help each other in the animal kingdom-they share some of the same genes, and some self-sacrificing behavior will help the greater sum of their genes. What would be a reason for self-sacrificing behavior to have evolved in animals that are unrelated?  

A) This behavior might elicit a benefit at some future point in time. 

B) This behavior might have aided groups of unrelated animals. 

C) This behavior might have arisen due to genetic drift. 

D) Both A and B apply. 

E) Both B and C apply. 


5) (2 points) In a population, if the immigration rate is greater than the emigration rate, the population will ________ over time.  

A) decrease               B)  stay the same                         C) increase 


6) (2 points) A model that estimates the likelihood that a population will avoid extinction for a given period of time is termed? 

A) life table                                      B)  population viability analysis 

C) age pyramid                      D) metapopulation 


Use the figure below when answering question 7 and 7a.



7) (2 points) In the diagram above, which of the arrows represents the carrying capacity?  

A) arrow A               B)  arrow B                      C) arrow C 


7a) (2 points) In the diagram above, at which point is the fastest rate of increase in this population?  

A) arrow A               B)  arrow B                    C) arrow C 


Use the figure below when answering question 8.



8) (2 points) In the diagram above, which of the lines represents exponential growth?  

A) line A 

B) line B 

C) line C 

D) line D 

E) all of the above 


9) (2 points) A huge population of animals consisting of smaller isolated populations is termed a  

A) megapopulation   

B)  metapopulation             

C) cohort    

D) metropolis 


10) (2 points) What is niche differentiation?  

A) interactions that allow species to occupy their fundamental niche 

B) the claim that species with the same niche cannot coexist 

C) the degree to which the niches of two species overlap 

D) the evolution of traits that reduce niche overlap and competition


11) (2 points) Which of the following is not an example of a mutualism?  

A) fungi residing in plant roots, such as endomycorrhizae 

B) birds eating insects jumping out of the path of army ants 

C) bacteria fixing nitrogen in plants 

D) rancher ants that protect aphids in exchange for sugar-rich honeydew 


12) (2 points) Which hypothesis regarding what limits food-chain length has the most support?  

A) environmental complexity hypothesis        B)  energy transfer hypothesis 

C) stability hypothesis                                   D) all of the above 


13) (2 points) Perturbation of which of the following cycles contributes most to global warming?  

A) the global water cycle                                 B) the global nitrogen cycle 

C) the global carbon cycle                             D) all of the above cycles contribute equally 



14) (2 points) Which of the following is NOT a consequence of increased nitrogen fixation?

A) Eutophication of water bodies

B) Loss of biodiversity in terrestrial ecosystems

C) Decrease in the atmospheric store of N

D) Increased terrestrial productivity


15) (2 points) Plants are essentially helpless when it comes to predation by herbivores

TRUE                        FALSE 


16) (3 points) Bouchard and Brooks studied the effect of insect flight on dispersal and speciation in rain-forest insects. They sampled all of the insects in the study area and found that 60 insect species are flightless and 19 are macropterous (able to fly). What can you conclude so far about this study? (Bouchard and Brooks, Journal of Evolutionary Biology 17 [2004]: 994-1006.)

A) Flightless insects have a greater dispersal potential from this study area. 

B) This data does not lead to a conclusion. 

C) Flightless insects are better suited for the tropics. 

D) Flightless insects are more numerous in the study area. 

E) Flightless insects have a higher diversity in the study area. 


17) (2 points) Resource partitioning is best described by which of the following statements?

A) Competitive exclusion results in the success of the superior species

B) Slight variations in niche allow closely related species to coexist

C) Two species can coevolve and share the same niche

D) Species diversity is maintained by switching between prey species


18) (2 points) All of the following statements about community interactions are correct EXCEPT

A) closely related species may be able to coexist if there is at least one significant difference in their niches

B) plants can defend themselves against herbivores by the production of compounds that are irritating or toxic

C) keystone predators reduce diversity in a community by holding down or wiping out prey populations

D) mutualism is an important biotic interaction that occurs in communities

E) some prey species have evolved resemblances to other species, allowing them to avoid attack by predators


19) (2 points) Why are inducible defenses advantageous?  

A) They result from a coevolutionary arms race. 

B) They are always present-thus, an individual is always able to defend itself. 

C) They make efficient use of resources, because they are produced only when needed. 

D) They make it impossible for a consumer to launch surprise attacks. 


20) (2 points) All of the following are possible explanations for why herbivores eat so little of the food available to them EXCEPT:

A) that plants could defend themselves effectively against attack.

B) that plant tissues could offer poor or incomplete nutrition.

C) that herbivores could be kept in check by predation and disease.

D) that herbivores prefer a variety of plants and thus do not overstress a species.


21) (2 points) Devegetation has what effect on ecosystem dynamics?  

A) It increases belowground biomass. 

B) It increases nutrient export. 

C) It increases the pool of soil organic matter. 

D) It increases rates of groundwater recharge (penetration of precipitation to the water table). 


22) (2 points) What is the main reason for using food webs instead of food chains in analyzing ecosystems?  

A) Most organisms eat more than one type of food. 

B) Most organisms feed at several trophic levels. 

C) The decomposition cycle needs to be shown. 

D) A and B 

E) A, B, and C 


23) (2 points) Which of the following is normally the longest-lived reservoir for carbon?  

A) atmosphere (CO2)                          B) petroleum

C) marine plankton                            D) wood  

SHORT ANSWER (51 points total).


24) (5 points) Draw type I, II, and III survivorship curves on a graph with labeled axes.



See page 1194, figure 52.2 in your text





25) (6 points) What is a keystone predator and how does a keystone predator control the structure of a community?


A keystone predator is one whose influence on the community is far more important / extensive than the size of its population would suggest. Keystone predators maintain species diversity in a community by reducing populations of species that would otherwise outcompete all others and dominate a community. Without the keystone predator, diversity would be reduced. 




26) (6 points) What does it mean when we say a niche is an Ōn-dimensional hypervolumeĶ?


Hutchinson coined the phrase to describe a speciesÕ fundamental niche. It refers to the fact that for every abiotic and biotic factor, there is a range of values under which the species can survive. The number of factors is very large, thus the term ŌnĶ.

You can think of any particular factor as an axis on chart. If you only had two factors, it would be easy to see on an X-Y chart (2-dimensional) how a species can only exist within a range of values for those two factors. However, a niche is defined by an almost unlimited set of factors, so instead of having a 2 dimensional description of just 2 factors, you have n-dimensions in your description of the conditions under which the species can survive.




27) (8 points) What is a life table and what are its main components (i.e., what information does it contain)?


A life table is a formal description of a populationÕs demographic characterisitics. Briefly, it summarizes and individualÕs probability of surviving and producing offspring at any particular point in its lifespan. For details of what is in the life table, look at Table 52.1 in your book.




28) (6 points) Why do we say that energy flow through an ecosystem is linear whereas nutrient flow is cyclical?


Energy is derived from the sun and is transferred through trophic levels. At every trophic level most of the energy is lost due to entropy. Energy lost cannot be re-used. Eventually, energy is lost to heat and escapes our atmosphere. It cannot be recycled. Nutrients, however, are not lost to the world. Nutrients move from one form of storage to another and can be resued. Healthy ecosystems usually retain most nutrients and cycle them within the ecosystem. When nutrients are lost to the ecosystem, they are moved to another ecosystem where they are reused. They are not lost to the earth as a whole as energy is.






29) (8 points) Why does population growth decline as population size approaches carrying capacity?  Explain your answer in terms of this equation: . Be sure to explain what each variable represents.



Carrying capacity (K in the equation) describes a maximum population size that a habitat can sustain. Carrying capacity is what keeps a population from endless exponential growth. Population growth rate (R) can be defined in terms of the intrinsic rate of growth (r) for the species, the current population size (N), and carrying capacity (K). without the effect of K, there would be exponential growth (r*K). Growth slows as a population approaches carrying capacity because it is modified by the expression (1-N/K). When N is very small, there is little effect of population size on growth (N/K is almost 0; 1-0=1). When N is very large, N/K approaches 1 and 1-1=0; no growth occurs. When N is greater than K, the population has exceeded the carrying capacity and growth rate is negative, which happens when N>K, at which point the expression becomes negative.



31) (8 points) Some species of ground squirrels live in colonies. When on watch for predators, the individual calling the alarm is sometimes killed, but this allows other members of the colony to seek shelter. In these species, males leave the burrow in which they were born and reestablish at some distance, while females stay close to home. Based on this, what sex is doing the calling and what does this have to do with HamiltonÕs Rule (which you should explain)?



HamiltonÕs rule describes when individuals should sacrifice for other individuals who are related to them. It is the foundation of kin selection. It is based on the equation r*B > C, which says that the cost (C) to the sacrificing individual (donor) must be less than the benefit (B) given to the recipient individual modified by the coefficient of relatedness (r) of the donor to the recipient. In other words, if enough of your genes are in a relative, the best way to get your genes into the future is to sacrifice for that relative. In the case of the squirrels, the females call because most of the females in the colony are related to each other (they donÕt leave the colony). So taking a chance like an alert call can help close relatives. Males arenÕt related to any of the colony members except their offspring.




32) (4 points) Explain the difference between gross primary productivity and net primary productivity.


GPP is the total amount of solar energy converted by producers into usable energy. NPP is GPP minus maintenance costs, respiration, etc. NPP is the amount of new tissue grown and it is the amount of energy available to consumers.