Energy and Animals: Evolution and Organismal Biology

Energy Requirements of Animals and Organisms
  • Life and Energy
    • Energy is essential for life functions.
    • Original energy source is the Sun, which provides heat and light energy.
    • Different organisms harness energy differently:
    • Plants, fungi, and some microorganisms utilize photosynthesis.
    • Animals obtain energy from the consumption of organic material.
    • Energy takes the form of:
    • Heat energy
    • Chemical energy
    • Kinetic energy
ATP and Cellular Respiration

  • Adenosine Triphosphate (ATP):

    • ATP is the primary energy carrier in cells.
    • Conversion Process:
    • ATP is converted to ADP + Pi, releasing energy.
    • Chemical equation of Cellular Respiration:
    • extGlucose+extOxygen<br/>ightarrowextCarbonDioxide+extWater+extATPext{Glucose } + ext{Oxygen} <br /> ightarrow ext{Carbon Dioxide } + ext{Water} + ext{ATP}
    • All living organisms perform cellular respiration to generate energy.

  • Cellular Respiration Breakdown:

    • Glycolysis:
    • Occurs in the cytoplasm.
    • Cost energy initially; yields 2 Pyruvate, 2 ATP, and 2 NADH.
    • Krebs Cycle:
    • Takes place in mitochondria.
    • Requires Acetyl-CoA derived from Pyruvate.
    • Produces CO₂, ATP, NADH, and FADH₂.
    • Electron Transport Chain:
    • Final stage of cellular respiration.
    • Generates large amounts of ATP using electrons from NADH and FADH₂, with oxygen as the final electron acceptor.
    • Cyanide can block this step.
Aerobic vs. Anaerobic Processes

  • Aerobic Respiration:

    • Requires oxygen and produces more ATP.
    • Efficient energy release in cellular respiration.

  • Anaerobic Respiration:

    • Occurs in the absence of oxygen.
    • Produces far less ATP compared to aerobic respiration.
    • Byproducts may include lactic acid (in animals) and ethanol (in yeast).
Metabolism

  • Concept of Metabolism:

    • Collective biochemical reactions supporting life.
    • Anabolism: Building complex molecules (endergonic reactions).
    • Catabolism: Breaking down molecules to release energy (exergonic reactions).

  • Metabolic Rate:

    • Measures energy used per unit of time.
    • 1 Calorie = 1000 calories = 1 kilocalorie, equivalent to 4.18 joules to raise the temperature of 1 gram of water by 1°C.
Basal Metabolic Rate (BMR)
  • Represents the chemical energy consumed to maintain basic life processes.
  • Trends in BMR:
    • Smaller organisms generally have higher BMR than larger ones.
    • Endotherms (warm-blooded) have higher BMR than ectotherms (cold-blooded).
    • Young organisms have higher BMR than older ones due to growth demands.
Thermoregulation

  • Process to maintain internal temperature:

    • Important for metabolic reaction rates.

  • Types of Organisms:

    • Endotherms: Generate their own heat, maintain constant body temperature.
    • Ectotherms: Rely on environmental heat sources, body temperature varies with environment.
    • Homeotherms: Maintain constant temperature.
    • Poikilotherms: Allow body temperature to fluctuate.
Changes in Metabolism
  • Adaptations for energy conservation:
    • Torpor: Short-term decrease in body temperature and metabolism.
    • Hibernation and Aestivation: Long-term adaptations to extreme conditions.
Osmoregulation
  • Control of water and solute concentrations within the body.
  • Osmoconformers (e.g., sponges, jellyfish) have a body fluid composition closely matching their environment.
  • Osmoregulators (e.g., freshwater fishes, terrestrial animals)
    • Actively manage osmolarity to maintain homeostasis, necessary due to water loss through evaporation in terrestrial environments.