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

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)

Biotic vs. Abiotic Factors

Biotic = Living

• Animals• Plants• Fungi• Bacteria/

Archaeans

Abiotic = Non-living

• Sunlight• Water• Vitamins/

Minerals/ Nutrients• Temperature

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)

Organisms Interact with Biotic/Abiotic Factors

• Organisms access to nutrients is affected by other factors• i.e. symbiosis,

predator-prey, nutrient availability etc

Symbiosis-Two species living together

• Mutualism-both benefit

• Commensalism- one benefits, other unaffected

• Parasitism- one benefits at other’s expense

"live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance".

Abiotic Effects on Growth

• Better nutrition Taller individuals

• More sunlight More plant growth

Evolution of Homeostatic Mechanisms

• Some mechanisms are conserved- showing common ancestry

• Others have changed, demonstrating divergent evolution

i.e. nitrogenous waste removal

• All animals produce nitrogen byproducts

• Animals in different environments have evolved different mechanisms for excreting these wastes

Ammonia

• Toxic byproduct of protein degradation• In dilute

concentrations is no big deal, so aquatic organisms can excrete it into water

Urea

• Mammals convert ammonia into urea

• Urea travels through the blood to the kidneys and is excreted with water and other substances as urine

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

Evolution of Circulatory System Shows Common Ancestry and Divergence

Evolution of Circulatory System Shows Common Ancestry and Divergence

Disruptions at the Molecular/Cellular Level Affect Organisms

• I.e. viral infection of a cell• Allergies• Dehydration

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

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!)

Invasive Species

• Usually have no natural predators and grow uncontrollably

• Disrupt the food chain and outcompete native species