AP Bio 3.4

Organisms use free energy to…

Maintain organization, Grow, and Reproduce

Animals harvest chemical energy from

the food they eat

On the other hand, plants

make their own chemical energy

Once food has been digested the… are usually used to…

 energy-containing molecules are usually used to make ATP, which powers cellular work

Metabolic Rate

the amount of energy an animal uses in a unit of time  

Organisms use various strategies to… such as…

regulate body temperature and metabolism

EX: Endothermy and Ectothermy

Endothermy

bodies are warmed mostly by heat generated by metabolism; temperature does not fluctuate with environment

• Higher metabolic rates

• EX: Birds and mammals

Ectothermy

bodies gain heat mostly from external sources; temperature fluctuates with the environment

• Lower metabolic rates

• EX: fish, reptiles, and amphibians

Ectotherms tolerate

greater variation in internal temperature than endotherms

Endothermy is more… but… This enables…

more energetically expensive than ectothermy, but buffers animals’ internal temps again external fluctuations

• Enables animals to maintain a high level of aerobic respiration

Metabolic rates are affected by many factors including

body mass

Body mass

Inverse relationship between metabolic rate per unit body mass and size of multicellular organisms

Smaller animals…because…

Smaller animals lose heat more quickly because of their high surface area-to-volume ratio

**The smaller the organism, the higher the metabolic rate

Homeostasis

balance between external changes and the animal’s internal environment.  Maintaining an ideally constant internal environment

Homeostasis is controlled by

negative feedback

Negative Feedback purpose

Maintains homeostasis by reversing(reducing) a change

Negative Feedback effect

Decreases the original stimulus

Negative feedback is

stabilization (of internal environment)

Negative Feedback outcome

returns the system back to its target set point

EX of Negative feedback

• Buildup of end product 

  • Example is feedback inhibition in cellular respiration

• Hormone regulation of blood sugar (insulin/glucagon), temperature regulation in endotherms

Positive Feedback Purpose

Accelerates a change to drive a process forward

Positive Feedback effect

increases the original stimulus

Positive Feedback is…

amplification

Variable initiating the response is

moved farther away from the initial set point

Positive Feedback outcome

Leads to a rapid, often temporary, change

Positive Feedback EX

childbirth, blood clotting, and fruit ripening.

Organisms respond to change in their environment through

behavior and physiological mechanisms

Thermoregulation

the process by which animals maintain an internal temperature with tolerable range

Thermoregulation EX

• EXAMPLES (warm and cool)

  • Shivering and goosebumps

  • Sweating

  • Panting

  • Torpor (hibernation and estivation)