Limnology Fall 2006 -- Practice Questions For Second Exam

The format of the second exam will be similar to the first exam, with the addition of a matching (choose the correct taxonomic group) section in the short answer portion (Part 2)

Part 1 -- Definitions – Define the following and explain their limnological significance

1. Resource spiraling

- A conceptual framework for describing resource use in streams -- looks at downstream transport of nutrients -- the spiral length is a function of the distance an atom is transported before it is captured by organisms and the distance moved while in the organisms.
-Some possible significances:

2. Vertical migration

-Movement of zooplankton up and down in the water column (most common pattern is to move up at night and down during the day)
-Significance: Is an adaptation of some zooplankton to avoid predation by visual (e.g., fish) predators

Part 2
Find the organism in the list below that best corresponds to the characteristic, and put its letter in the blank (List only ONE organism per question and use each answer only ONCE; there will be extra organism names left over – don’t panic!)

a. Chlamydomonas              d. Rotifers               g. Myriophyllum
b. Anabaena                        e. Chara                  h. Porifera
c. Calanoida                        f. Typha                   i. Ephemeroptera

1.           Sex determination is based on ploidy level (i.e., haploid, diploid) in these animals.
2.           This algae can perform nitrogen fixation.
3.           A type of macrophyte that can live in water deeper than 10 meters (given sufficient light).
4.           Often found in stream ‘drift.’

Answers:
    1-d
    2-b
    3-e
    4-i

Part 3 – Short Essays

1. Describe one reason why an invasive unrooted floating macrophyte (such as Eichornia, the water hyacinth), might have more detrimental effects on the lake or wetland it invades than would an exotic rooted submerged macrophyte (3 points)

Possible answers:
An invasive unrooted floating macrophyte has several potential effects that wouldn't be seen for an exotic rooted submerged macrophyte.  While both types might displace native species or be poor food for native organisms, some effects that would be unique to a floating plant include:

(1) Proliferation of the floating plant would cover the surface of the lake or wetland and decrease the light available to both phytoplankton and submerged macrophytes.  Thus the primary production of native phytoplankton and macrophytes would be decreased.

(2) Because the floating macrophytes are at the surface of the lake, they are a major sink of water from the lake due to evapotranspiration -- thus they might result in a decrease in overall water level decrease that could have potentially major effects on other organisms in the lake or wetland.

(3) Floating macrophytes can easily be blown to one end of a wetland or lake if winds are strong.  This proliferation of plants might cause dramatic declines in oxygen as the plants decay, decreasing habitat for oxygen-sensitive invertebrates and fish

2. Give three examples of morphological adaptations in stream insects that may help them survive in stream environments (6 points)

Possible answers:

(1) Insects may be flattened or streamlined (this may decrease their resistance to flow and the possibility that they are swept away by currents, but it can also be an adaptation for living under rocks)
(2) Some insects have suckers or hooks for grasping rocks (tarsal claws)
(3) Some insects, such as chironomid larvae, make tubes out of sticky substances or silk-like substances that keep them attached to rocks.
(4) Some insects, such as caddis flies, make heavy cases (for example out of stone or wood) that provide ballast (weight) and allow them to remain on the bottom

(Hint:  There’s sure to be at least one graph on the exam as well)