FRESHWATER BIOLOGY (207) Name:

Exam 3 (Dec 11, 1995)

1) In aquatic systems, light energy is absorbed by water. (A) Given this, which group of macrophytes -- emergents, floating-leaved, free-floating, or submerged -- shows more adaptations for light absorption and why? (B) The above plants receive ultraviolet (UV) radiation (a type of light energy), which is harmful to organisms. As our atmospheric ozone layer thins, and more UV radiation reaches the earth, which plant group(s) will need to make the most adjustment to higher levels of UV? (C) If you were an aquatic invertebrate associated with macrophytes, which macrophyte group mentioned in (A) would you want to associate with under the UV scenario mentioned in (B)? (8 points)

2) Many exotic species introductions have occurred in our Great Lakes region. Name 2 harmful and 1 beneficial species that have been introduced and briefly explain (a) how the species was introduced and (b) how it exerts its effect. (10 points)

How Intro'd Effect

1)

2)

3)

3) What is a beneficial and a detrimental role that macrophytes like cattails, rushes, and sedges play in a lake or pond? (4 points)

4) How can bacteria, which are merely microscopic, have a large role in aquatic ecosystems?

(5 points)

5) Zebra mussels tend to increase water clarity in lakes that they invade. (a) How do they do this? (b) How would this (the process you describe in "a") affect populations of (i) phytoplankton, (ii) submerged macrophytes, (iii) epifaunal (i.e., substrate-dwelling) invertebrates, (iv) and piscivorous fish? (10 points)

a)

b) i) phytoplankton -

ii) submerged macrophytes -

iii) epifaunal invertebrates -

iv) piscivorous fish -

6) You have conducted a winter survey of littoral zone invertebrates along a 5 mile stretch of river and found an abrupt shift in the assemblage, as well as a greater activity level, of invertebrates immediately downstream of a shore-based power plant (large facility that burns coals to generate electricity). You also noticed that submerged macrophytes in this area were still lush and green (there was winter die-back in the other areas). What might explain these 3 observations?

(10 points)

7) In general, which group of macrophytes -- emergents, floating-leaved, or submerged -- has evolved farthest from terrestrial plants and why? Consider what plant characters might help illustrate your answer. (3 points)

8) You are once again an aquatic food web scientist and this time you have found the following organisms and compounds (simplified listed shown below) present in a lake. After performing laboratory feeding experiments with these organisms and compounds (to decide who eats or grows on what) you have a good idea of the probable food web structure in the lake. Draw (very clearly) your food web. Use arrows to show the direction of transfer (for example, of energy, substance) between these organisms and compounds. (10 points)

·planktonic heterotrophic bacteria (suggested abbreviation = Hbact)

·planktonic algae (diatoms)

·planktonic zooflagellates (zflag)

·planktonic ciliates (cil)

·planktonic copepods (copes)

·planktonic fish larvae (flarvae)

·alewife

·dissolved organic matter (DOM)

·large salmonid

·sea lamprey

·zebra mussel

·dissolved inorganic nutrients (DIN) like nitrogen

·benthic blackfly larvae

·catfish

9) What are 2 responses that a floating-leaved plant like a pondweed (Potamogeton) might make to deal with increased water clarity? Why would these changes occur? (6 points)

10) How are cyanobacteria (a.k.a. blue-green algae) different from and similar to true algae (diatoms, for example)? (4 points)

11) All photoautotrophs need fertilizing nutrients (nitrogen (N), phosphorous (P)) for growth and reproduction. Diatoms, a type of algae, also require silica (S) to build their cell walls. Many aquatic systems that drain agricultural areas receive large inputs of nutrients which lead to algal blooms; however, few of these algae are diatoms. Why might this be? (4 points)

12) Sphagnum mosses were used as a diapering material by some early cultures of people. What characteristic of these mosses made them useful in this way? Why do these mosses naturally have such a quality about them? (4 points)

13) How are these 4 pieces of data related? (10 points)

14) What is the importance of air spaces in the roots/rhizomes of emergent vegetation? (2 points)

15) Definitions (choose only 10) (10 points)

·Kingdom Monera

·Kingdom Protista

·algae

·diatom

·prokaryote

·eukaryote

·photoautotrophs

·decomposer

·heterotroph

·aerobe

·phytoplankton

·Division Bryophyta

·macrophyte

·biological disturbance

·pollution

·eutrophication