Lab Topic 27
Investigating Excretory and Reproductive Systems

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STUDENT OBJECTIVE

Students observe the structure and function of flame cells in live planarians and nephridia in live earthworms. They dissect the excretory and reproductive systems in the fetal pig and look at prepared slides of the kidney and gonads.

EQUIPMENT AMOUNT
  (Class of 24 with 8 groups)
Compound microscope
Dissecting microscope 		1/student
1/student
MATERIALS  
Fetal pigs from previous exercise
Dissecting pans
Dissecting instruments
Slides and coverslips
Petri dishes with clean paraffin
Live animals

Planaria (CBS#13-2950)
Earthworms

Prepared slides (can be shared to reduce costs)

Mammalian kidney cortex (CBS#31-5770)*
Mammalian ovary with graafian follicles (CBS#31-5982)*
Mammalian testis, cross section (CBS#31-6386)*

1/student
1/student
set/student
1 box/lab
1/student


1/student
1/group

 

1/student
1/student
1/student

*Please refer to the Appendix for name and address of supplier.

SOLUTIONS

10% ethanol
0.8% saline

PREPARATION

Week before Lab

  1. Planaria should be ordered to arrive at this time. Upon arrival, check to be certain cultures are alive. Store at room temperature with loosened lids.
  2. Saline preparation:

      0.8 g NaCl/100 ml water

    Dissolve the salt in water and store in dropper bottles.

  3. All dissecting equipment should be inspected and any missing or dull instruments replaced. Fetal pigs used in previous exercise should be checked for usability.
  4. Alcohol preparation:

10% ethanol 50 ml 95% ethanol/425 ml water

Mix and store in two or three dispensing bottles.

NOTES

Glassware for live cultures may need to be acid washed and rinsed well before using to remove polymerized organic material such as paraformaldehyde.

classroom suggestions

  1. Check out the links for this lab topic at http://auth.mhhe.com/biosci/genbio/dolphin/ You will find useful materials for developing your lab introduction or summary, and in some cases, you may want to tell students to connect to a particular site for further information.

ANSWERS TO CRITICAL THINKING QUESTIONS

  1. Sperm production is temperature sensitive. Viable sperm production requires temperature lower than body temperature. By being outside of the abdominal cavity, the testes are cooled by about 3oC (below body temperature of 37oC). Other adaptive mechanisms for maintaining proper temperature involve cremaster muscles which elevate the testes when cold, dartos muscle which wrinkles the scrotal skin, also to conserve heat, and a fine network of veins that surrounds the testicular artery and absorbs heat from arterial blood before it arrives at the testes.
  2. Consider the following:

Bears :

— possible adaptations

— decrease protein metabolism, which decreases nitrogenous wastes

— switch to fat metabolism

— absorb and "recycle" urine

Woodchucks:

— possible adaptations — "Hibernation"

— metabolic activity greatly reduced (body temperature drops)

— minimal metabolic wastes produced

— minimal water loss through respiration

SUPPLEMENTAL MATERIALS

Bio Sci II, videodisc—contains pictures of dissected fetal pig and histology photographs. Dubuque, IA: WCB/McGraw-Hill Publishers.

Introduction to Excretion, slide set. West Los Angeles, CA: Science Software Systems. #480-0170

Liquid Waste and the Kidney, videocassette. Rochester, NY: Ward’s. #193W1097

Urinary System CD-ROM in Interactive Physiology Series. Menlo Park, CA: Benjamin Cummings Publishing Company.