04_Animals_Environment_20260223_student - Tagged

Unit 2: Animals

Animals in Their Environment

Date: February 23, 2026
Instructor: Dr. Ana Longo
Course: BSC2011 - Spring 2026

Chapter Outline

  • 29.1 Animals Prosper in Diverse Thermal Environments
  • 29.2 Animals Live in the Ocean, Fresh Water, and Intermediate Salinities
  • 29.3 The Phenotypes of Individual Animals Can Change in Response to Environmental Change
  • 29.4 Animals Have Biological Clocks Tuned to Cycles in Their Environment

Learning Objectives

  • Provide examples of behavioral and physiological adaptations to thermal environments.
  • Explain the principal mechanisms by which an aquatic animal maintains its body fluids at a consistent salinity that differs from the salinity of its environment.
  • Discuss the role of molecular evolution in animal diversification.
  • Define phenotypic plasticity and provide examples in biochemistry and organ function.
  • Differentiate between exogenous and endogenous timing.
  • Explain why circadian clocks do not keep exact time and require resetting.

Adaptations to Thermal Environments

Differences Between Small and Large Bodies

  • Small-bodied animals often cope with environmental stresses using behavioral adaptations.
  • Large-bodied animals usually exhibit fewer behavioral options and depend more on physiological adaptations.
Example: Reindeer (Rangifer tarandus)
  • This species illustrates adaptations to extreme cold environments.

Challenges in Thermal Environments

Challenge #1: Cold Extremes

Physiological Responses to Cold
  • Commonly, reindeer maintain an average core body temperature of 37ºC.
  • They exhibit a much lower metabolic rate during winter than humans.
  • Phenotypic Plasticity is observed as reindeers adapt from summer to winter conditions.
  • They have effective insulation and exhibit localized hypothermia—allowing appendage tissues to remain cooler than core tissues, preventing freezing.
Visual Representation
  • Refer to Fig. 29.1 and Fig. 29.3 for illustrations of temperature gradients in snow and the anatomy of reindeer hair.

Challenge #1b: Preventing Heat Loss

Countercurrent Heat Exchange System
  • Arteries and veins in the limbs utilize a countercurrent heat exchange system to conserve heat.

Hibernation

  • Defined as a state of low body temperature and thermal conformity that persists over an extended period, primarily during winter.
  • Core body temperature matches external temperatures, utilizing stored body fat or food from the previous summer.
  • Utilizes metabolic depression, a biochemically induced reduction in metabolic rate.
Visual Representation
  • See Fig. 29.9 for details on hibernation physiology.

Challenge #2: Heat Extremes

Adaptations in Hot Deserts
  • Two primary challenges include lack of water and high temperatures.
Example: Kangaroo Rats
  • Behavioral Adaptations: Mostly nocturnal, stay in burrows during the day.
Example: Grant’s Gazelle
  • Can tolerate an increase in core body temperature up to 46ºC, reducing water needs and avoiding sweating.
  • Possesses a countercurrent cooling system in the brain.
Visual Representation
  • Illustrated in Fig. 29.6 and Fig. 29.7.

Adaptations of Other Species

  • Lizards (e.g., Desert Spiny Lizard - Sceloporus serrifer) utilize burrows and shade and stay close to the ground surface to manage heat.
Visual Representation
  • Depicted in Fig. 29.8.

Challenge #3: Water and Salt Balance

Osmotic Problems

  • Different challenges faced by various aquatic organisms:
    • Freshwater fish: Hyperosmotic to freshwater environment, leading to water influx.
    • Marine fish: Hyposmotic to seawater, losing water and gaining ions by diffusion.
    • Mussels/Crabs: Face fluctuations in salinity due to salt-loaded diets.
Mechanisms of Water Regulation
  • Freshwater Fish:
    • Actively transport Na+ and Cl- back into their bodies, producing large volumes of dilute urine.
Example of Osmotic Regulation
  • Bony Fish in Marine Environments:
    • Drink seawater to compensate for water loss, use intestinal ion pumps to excrete excess ions.

Adaptations in Marine Organisms

  • Seabirds, ocean lizards, and sea turtles have specialized salt glands that excrete excess salt using energy from ATP.
Marine Invertebrates
  • Most function as osmotic conformers, with body fluid osmotic pressure matching that of the surrounding water.
    • Some (e.g., blue crab) have adaptations for osmotic regulation, maintaining constant internal osmotic pressure despite varying external salinities.
Visual Representation
  • See Fig. 29.14 and Fig. 29.18 for further analysis of these adaptations.

Challenge #4: Environmental Variability

Phenotypic Plasticity

  • Described as an individual's ability to display different phenotypes at different phases of life, where one genotype expresses multiple phenotypes.
  • Acclimation (or acclimatization): Occurs after long-term exposure to particular environments.
  • Example: Daphnia (water fleas) can show significant phenotypic plasticity based on environmental conditions.
Visual Representation
  • Refer to Fig. 29.20 for illustrative evidence.

Molecular Adaptation

Temperature Adaptation in Fishes
  • Fishes develop multiple forms of enzymes for various metabolic pathways, including enzymes for the citric acid cycle and anaerobic glycolysis.
    • Polar species possess enzyme forms optimized for cold temperatures.
  • Example: Barracudas can experience a temperature variance of 3-4ºC within aquatic environments, affecting enzyme functionality.

Impact of Pollution

  • Cytochrome P450 enzymes: Vital for detoxifying environmental toxins, levels are elevated in fishes from polluted waters compared to those from pristine contexts, enhancing their detoxification abilities.
Visual Representation
  • Illustrated in Fig. 29