1. 2.D: Growth and dynamic homeostasis are influenced by changes in the environment

2. Organisms Respond to External Events
I.e. taxis or kinesis
Many animals change speed based on light (pillbugs run wild when exposed to light)
Many animals change direction in response to stimuli (sharks swim towards blood)
Plants grow towards light (phototropism)

3. Biotic vs. Abiotic Factors
Biotic = Living
Abiotic = Non-living
Animals
Plants
Fungi
Bacteria/ Archaeans
Sunlight
Water
Vitamins/ Minerals/ Nutrients
Temperature

4. Cells Are Affected by Both Biotic/Abiotic Factors
i.e. bacterial cells attach to each other to form biofilms
Cells shrink/grow depending on water availability
Cells stop growing after a certain density (except in the case of cancers)

5. Organisms Interact with Biotic/Abiotic Factors
Organisms access to nutrients is affected by other factors
i.e. symbiosis, predator-prey, nutrient availability etc

6. Symbiosis-Two species living together
Mutualism-both benefit
Commensalism- one benefits, other unaffected
Parasitism- one benefits at other’s expense

7. Abiotic Effects on Growth
Better nutrition Taller individuals
More sunlight  More plant growth

8. Evolution of Homeostatic Mechanisms
Some mechanisms are conserved- showing common ancestry
Others have changed, demonstrating divergent evolution

9. i.e. nitrogenous waste removal
All animals produce nitrogen byproducts
Animals in different environments have evolved different mechanisms for excreting these wastes

10. Ammonia Toxic byproduct of protein degradation
In dilute concentrations is no big deal, so aquatic organisms can excrete it into water

11. Urea Mammals convert ammonia into urea
Urea travels through the blood to the kidneys and is excreted with water and other substances as urine

12. Solid Uric Acid
In birds and reptiles (and some desert mammals) nitrogen waste is excreted as a solid
Prevents water loss and buildup of water wastes in the shell of an egg

13. Evolution of Circulatory System Shows Common Ancestry and Divergence

14. Evolution of Circulatory System Shows Common Ancestry and Divergence

15. Disruptions at the Molecular/Cellular Level Affect Organisms
I.e. viral infection of a cell
Allergies
Dehydration

16. Disruption of One Organisms Affects Others
I.e. disrupting the food chain
If you break one link of the chain, everyone is affected
Toxins in one organism get passed on

17. Biomagnification
Toxins get concentrated as they move up the food chain
So small amounts of mercury can become extremely toxic to polar bears (or humans!)

18. Invasive Species
Usually have no natural predators and grow uncontrollably
Disrupt the food chain and outcompete native species