Physiology and Homeostasis

How Organisms Maintain Internal Stability

Physiology and homeostasis are processes by which organisms maintain constant internal conditions despite the changing outer environment. They are essential to survival because they allow organisms to regulate temperature, water balance, hormones, and cellular activities.

1. Temperature Regulation

• Ectotherms: Rely on ambient heat (e.g., reptiles, amphibians).
  • Behavioral adaptations: Basking to warm up.
• Endotherms: Generate heat internally (e.g., mammals, birds).
  • Structural adaptations: Fur, feathers, blubber for insulation.
• Hibernation: Metabolic slowdown to conserve energy in harsh conditions.

Sun is giving external heat to the lizard which is Ectotherm Thermoregulation

The digestion of the fruits in the deer is providing heat which is endotherm thermoregulation.

2. Water Balance & Excretion

Organism	Excretory Structure	Function
Vertebrates	Kidneys	Filter blood, produce urine
Insects	Malpighian tubules	Remove nitrogenous waste
Annelids (worms)	Nephridia	Regulate water/salt balance

- Critical for preventing dehydration and toxic buildup.

3. Endocrine Control

• Reproductive Hormones:
  • Regulate mating behaviors, growth, and fertility cycles.
• Stress Response (e.g., cortisol):
  • Adjusts metabolism and immunity under threat.

STRESS RESPONSE SYSTEM

Hypothalamus
CRH
Pituitary gland
ACTH
Adrenal gland
CRH - Corticotropin-releasing hormone
ACTH - Adrenocorticotropic hormone

4. Cellular & Molecular Adaptations

• Ion Channels: Maintain electrical/chemical gradients.
• Aquaporins: Facilitate water movement (critical for osmotic balance).
• Heat Shock Proteins: Stabilize other proteins during extreme temperatures.

Conclusion

These molecular and physiological mechanisms work together to sustain life's delicate equilibrium, enabling organisms to thrive in diverse environments.

Sources

1. "Temperature Regulation in Animals." Khan Academy, https://www.khanacademy.org/science/biology/ecology/animal-structure-and-function/a/temperature-regulation.
2. "Hibernation." National Geographic Education, https://education.nationalgeographic.org/resource/hibernation.
3. "Kidneys and Excretion." National Institute of Diabetes and Digestive and Kidney Diseases, https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work.
4. "Malpighian Tubules." Encyclopedia Britannica, https://www.britannica.com/science/Malpighian-tubule.
5. "Nephridia." Britannica Kids, https://kids.britannica.com/kids/article/nephridia/629870.
6. "Hormones and the Endocrine System." Khan Academy, https://www.khanacademy.org/science/biology/human-biology/human-body-systems/a/hormones-and-the-endocrine-system.
7. "Ion Channels." National Institutes of Health, https://www.ncbi.nlm.nih.gov/books/NBK26836/.
8. "Aquaporins." Nature Education, https://www.nature.com/scitable/topiepage/aquaporins-water-channel-proteins-14053998.
9. "Heat Shock Proteins." ScienceDirect, https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/heat-shock-protein.
10. "Cortisol: What It Is, Functions, and Associated Conditions." Verywell Health, Dotdash Meredith, 15 Mar. 2023, www.verywellhealth.com/cortisol-what-it-is-its-functions-associated-conditions-5208916.