Oxygen

Nutrition

* Chemoheterotrophs(animals): cannot make organic molecules from inorganic carbon; need to ingest organic molecules

* Cellular respiration breaks down organic molecules to co2 and h20 , releases energy

  * Usually cannot be aerobic for extended periods: need

  * If proteins are broken down: creates N-Waste

* Animals need food, gas exchange, excretion

  * How? Influenced by size, environment, metabolism

Evolution

* Originated and diversified in the water

  * Most aquatic animals breathe ( exchange gases with water)

  *   Diffusion is sufficient for smaller animals (whose surface area is large compared to its volume)

  *

* Became larger and more complex

  * If shape is maintained, volume increases faster than surface area.   Volume determines complexity, surface area determines supply

  * Diffusion was no longer sufficient, need bulk flow, large scale movement of materials.

  * Organ systems (with increased surface area ) transport materials within the body the body and to exchange materials with materials with the environment

  * More tissue dedicated to support and movement.

* Some lineages colonized the land : molluscs, arthropods, tetrapod vertebrates

  * Breathe air (more O2 than h20)

  * Greater risk of h20 loss

  * Greater temperature variation; H2O has a high specific heat capacity, so it maintains a fairly constant temperature.

* Tetrapod evolution

  *   endothermy in birds and mammals: high metabolic rates and activity

    * Require more food produce more waste

    * Most other animals are ectotherms : lower metabolic rates and activity levels

  * Some tetrapods returned to the water : they still breathe air

* Animals exist because they respond to their environment; responses can be:

  * Over evolutionary time: natural selection favors adaptations

  *   within an organism’s lifetime

    * Seasonal...