* 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)
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* 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