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POSSIBLE ANSWERS FOR ASSIGNMENT # 1 INVERT. ZOOLOGY FALL 1999 DR. W. CRONE

Topics: Introduction to Zoology and Classification; Ecology; Cells

distributed Monday 8/30, due Tuesday 9/14 at lecture time

What I have looked while grading are answers that address the question(s) asked, include documentation of sources, and are free of grammatical and spelling errors. Below are possible answers to these rather open-ended questions.

  1. Would you expect to find radially symmetrical animals on land? Why or why not?

    2. Radial symmetry applies to those organisms that can be divided into two parts by multiple planes running through their main axis. Such organisms as jellyfish (Phylum Cnidaria), comb jellies (Phylum Ctenophora), and sea stars (Phylum Echinodermata) come to mind. Most animals are bilaterally symmetrical, or have only one mirror plane down their midline. Radially symmetrical animals do well when conditions are the same in any direction, such as in the ocean. They do not have a clustering of sensory information at any one end. In contrast, bilaterally symmetrical animals will move along their one axis, which will lead to a clustering of sensory information at one end, or what we call a head. Moving along in one direction works better for the varying challenges of finding food/avoiding being food on land.

    (Sources: week 1 lecture notes and handout; text (7th ed.), Ch. 15, pp. 353-355)

     

  2. The human population of the world has quadrupled during this century (from 1.5 to 6 billion). What effect(s) might this have on the population sizes (increase, decrease, no or little effect) of the following invertebrates? Why? Be sure to support your answers:

    3. a) cockroach b) American lobster c) deep-sea tube worm (check Ch. 5, p. 125 and Ch. 24, p. 533 to see what these are)

    Human populations may interact with other animal populations directly, as in hunting, or indirectly, as in habitat modification. I tried to use organisms with three distinctive possibilities of these types of interactions. Cockroaches are ancient organisms that have coexisted well with humans, making homes in kitchens and other dark, damp spots with waste products to eat. Even though pesticides (new improved Raid!) may be used to fight them, it is likely that cockroach populations have increased as human populations have increased, given the probable expansion of niche and habitat. In contrast, lobsters are desired sea food and are fished at high rates. Furthermore, their favored living grounds off of coast lines may make them vulnerable to human pollution runoff from shores. This combination of human hunting and habitat destruction have probably combined to lower lobster numbers this century. Finally, the recently-discovered deep-sea tube worms living near hot vents live in specialized ecosystems that are very self-contained and isolated from other ecosystems. As a result, the populations of these worms have probably remained little affected by human activity, except for pollution that might have migrated to that part of the deep ocean floor.

    (Sources: week 1 lecture notes and handout; text (7th ed.), Ch. 5, pp. 112, 114, 117, 118, 125, 132, 133, Ch. 10, p. 237, Ch. 23, pp. 506, 521)

     

  3. What are the functions of cilia and flagella? Primary ciliary dyskinesia is a rare (human) disease where cilia and flagella do not function well--predict one problem such a patient would exhibit and explain why.

Cilia and flagella are structurally-similar hair-like processes made up of microtubules that"slide" past another. Cilia are shorter and more hair-like, and flagella tend to be fewer and longer. In addition, they have slightly different"beating" patterns. Both can either be used to move cells or to move materials past cells (we will see flagella moving water in sponges next week in lecture). In human beings, cilia are present in major respiratory pathways to move mucus that is produced to trap particles. Cilia are also present in the fallopian tubes to move eggs. Flagella are prominent in sperm. In those (fortunately rare) individuals where cilia and flagella do not function, repeated lung infections from uncleared airways and infertility are therefore typical consequences.

(Sources: week 2 lecture notes and handout; text (7th ed.), Ch. 2, pp. 30, 31, Ch. 6, pp. 156-157, Ch. 8, p. 202; Ch. 14, pp. 314, 315, 318, Ch. 17, pp. 384-386)

 

|main page| |background| |03028: Physiology| |03048: Anatomy|

|03050: Invertebrate Zoology| |03051: Vertebrate Zoology| |03074: Economic Botany|

 

Please send comments and questions to: cronewil@hvcc.edu

 

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This page updated on September 16, 1999