Biology Homework Chapter 25: Internal Regulation and Homeostasis

Homework

• Reading Preparation
• WebLecture
• Study Activity
• Preparation work for chat
• Online Quiz
• Lab Instructions

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Textbook assignment: Chapter 25: Control of the Internal Environment, all.

Study Notes

This chapter focusses on ways that animals minimize change within their bodies. Most metabolic functions take place within narrow limits of temperature, acidity, and concentrations of salts or other molecules like CO₂ or nitrogenous wastes. Large deviations from these "norms" waste energy, and can lead to systemic problems, sickness, and death if they are not corrected.

• 25.1 Thermoregulation covers the ways animals control their internal body temperature. Ectotherms are dependent on their environment for their body temperature, while endotherms maintain their own body temperature within a set range.
• 25.2 Heat only moves in three ways really: convection, conduction, and radiation. Evaporation is really a form of convection, with particles of liquid carrying energy away as they change phase to vapor particles.

  Thermoregulation includes the metabolic and behavioral activities used by warm-blooded animals to keep their body temperature within certain limits.

  • Metabolic activities include sweating evaporation (evaporative cooling), radiation (changes in blood flow), gaining or losing fat layers seasonally, and adjusting skin and hair position to maximize insulation from external changes (goose bumps). Animals may also change blood flow rates to increase or decrease internal temperatures.
  • Behavioral activities include things like seeking warmer/cooler environments, reducing activity (hibernation, aestivation, torpor), or increasing activity.
• 25.3 "Drop-keeping" in mosquitoes provides clues to how species develop different methods of controlling internal temperatures.
• 25.4 Osmoregulation is the control of both water and solute concentrations.
  • Water is obtained from food and drink; water levels trigger sensations of thirst.
  • Sweating, digestion, and elimination control the rate at which water is returned to the environment.
  • Marine animals have special problems with water regulation, since they have to fight osmosis and diffusion flows that depend on the solutes dissolved in their bodies and in their wet environment.
  • Osmoconformers keep their internal concentrations the same as the environment.
  • Osmoregulators keep their internal concentrations higher than their environment by absorbing ions more efficiently in their food, and by flushing water constantly.
• 25.5 Nitrogen wastes pose special problems, since they change the blood's acid (pH) levels. Nitrogen-bearing ammonia diffuses easily through cells.
  • Marine animals can excrete ammonia (NH₃ directly to their environment through their skin.
  • Birds and some reptiles excrete nitrogen wastes in uric acid.
  • Other land animals secrete nitrogen wastes in urea CO(NH₂)₂.
• 25.6 Excretory system All animals have a need to dispose of useless materials (such as cellulose) and materials which in high concentrations can be harmful (nitrogen compounds, mostly). The parts of the human excretory system include the kidney, ureter, urinary bladder, and uretha.
  • The kidney is divided into the renal cortex outer layer and medula inner layer.
  • The renal medulla contains many nephrons, each with its own filtration unit. As blood flows through the filtration path, water, salts, and other molecules may first be excreted, then reabsorbed until the ideal balance is achieved.
• 25.7 The processes of filtration, reabsorption, secretion, and excretion depend on concentration gradients to drive diffusion and osmosis exchanges across the membranes of the blood vessels and waste-carrying tubes in the nephron. The excretory system filters filters solutes out of water and reabsorbes them into the blood; any components not needed are secreted back into the waste fluids, which are excreted from the body. Lymph and blood flow through each nephron, exchanging excess concentrations.
• 25.8 The body controls concentrations of salts in the blood, stimulating or restricting urine flow by dispensing antidiuretic hormone (ADH) into the blood. Some foods and drinks (alcohol and caffeine among them) increase water loss.
• 25.9 Dialysis machines provide a mechanical way to filter blood and remove toxic wastes when kidneys have failed.

Web Lecture

Read the following weblecture before chat: Osmoregulation

Take notes on any questions you have, and be prepared to discuss the lecture in chat.

Study Activity

Perform the study activity below:

Chapter Quiz

• Required: Complete the Mastery Exercise with a score of 85% or better.
• Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
• Go to the Moodle and take the quiz for this chapter.

Lab Work

Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.

• Lab Instructions: If you have elected to do Scholars Online Biology Investigation #1, complete that lab at this time. Alternatively, you may do Field Lab #5.

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