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, NH3

• Toxic byproduct of protein degradation• In dilute concentrations is no big deal, so

aquatic orgs can excrete it into water

Urea• Mammals convert NH3 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 H2O loss and buildup of H2O waste in 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 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)