Big Idea 2.D: Growth and dynamic homeostasis are influenced by changes in the environment Homeostasis in a Changing Environment

Essential Knowledge 2D1: All biological systems from cells to organisms to populations, communities, and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy. 2D2: Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. 2D3: Biological systems are affected by disruptions to their dynamic homeostasis.

Organisms Respond to External Environments What was this called???

External Environment Made up of Biotic Things: Living

And Abiotic Things: Not Living External Environment

TPS: With your partner, make a list of 4 other biotic and 4 other abiotic factors that may affect organisms in an environment.

Case Study: Biofilms Bacterial cells attach to each other to form biofilms (a protective protein matrix cover) Communal group for protection and shared nutrients Grow with limited nutrients.

Cells Interact with Biotic/Abiotic Factors

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

Interactions Among Organisms Symbiosis: relationship b/t 2 species Mutualism (+,+) Commensalism (+,0) Parasitism (+,-)

Mutualism Both Species Benefit Rhinos and oxpeckers

Commensalism One member is helped, the other neither benefits or is harmed Cows and Cattle Egrets

Parasitism + and - relationship parasite benefits, host loses parasite usually smaller than host Leech Bite, Thailand Lamprey

Ecosystems’ Stability is based upon interactions w/ biotic or abiotic factors

Evolution of Homeostatic Mechanisms Some mechanisms are conserved- showing common ancestry Others have changed, demonstrating divergent evolution (due to changing envs)

Case Study: Nitrogenous Waste Removal All animals produce N byproducts Animals in diff. envs. have evolved different mechanisms for excreting these wastes

Ammonia, NH 3 Toxic byproduct of protein degradation In dilute concentrations is no big deal, so aquatic orgs can excrete it into water

Urea Mammals convert NH 3 into urea  travels through blood to kidneys and is excreted w/ water and other substances as urine

Solid Uric Acid In birds and reptiles (and some desert mammals) N waste is excreted as a solid Prevents H 2 O loss and buildup of H 2 O waste in shell of an egg

Evolution of Circulatory System Shows Common Ancestry and Divergence

Disruptions at the Molecular/Cellular Level Affect Organisms Homeostasis Exs: viral infection of a cell, allergies, or dehydration in Willis’s body ;)

Disruptions to Ecosystems Affect Homeostasis Exs: food chain disruptions, natural disasters, salination (adding salt)