Gas Exchange

Aerobic Respiration

• all life is driven by energy

• the most powerful mechanism for energy is aerobic respiration

  • the Krebs cycle requires O₂

• animals distribute O₂ VIA diffusion or circulatory system

• there are 8 types

Modes of Respiration

Integumentary Exchange (Diffusion)

• Sea Anemone 

• Planarian 

• Sea Star

• Clam Worm

Invertebrate Gills

• Mayfly Nymph 

• Horseshoe Crab

Tracheal Systems

• No cell is >3 (0.0003 cm) from a tracheole

• flight muscles help compress and expand tracheal trunks

• Beetles

• Grasshopper

Book Lungs

• paired invaginations

• folded into lamellae 

• air enters through spiracle

• gases diffuse into hemolymph

• spiders

Gills

• respiratory organs

• thin, moist vascularized layer of epidermis

• can be internal or external

• often “countercurrent”

Bimodal Breathing

• ability to exchange gases through 2 different media (water/air)

• salamanders, crabs, bivalves, lungfish

• arose?

  • due to one mode of breathing not working all the time

    • tide pools

  • significance?

    • transition to land life

Cutaneous Respiration (Integumentary)

• some frogs get 25% of oxygen from skin

• plethodontid (lungless) salamanders carry out all exchange through skin buccal region

Lungs

• internal, sac-shaped organ

• lined with vascularized epithelium

• lungs likely originated as supplemental source of oxygen in stagnate conditions

• amphibians and some reptiles ventilate lungs using positive pressure (push air)

  • “buccal pumping”

• mammals/birds ventilate using negative pressure

  • PV=nRT

• blind pouch in mammals/reptiles

  • supply of oxygen is interrupted

  • only a portion of the lung contents are exchanged 

  • removes ~25% of O₂ in air

• birds are much more efficient

  • it is continuous, therefore there’s never any “dead” air or down time

  • remove ~90% of O₂ in air