2. Biological systems utilize free energy
and molecular building blocks to grow,
to reproduce and to maintain dynamic
homeostasis.
A.
Growth Reproduction and maintenance of the organization of
living systems require free energy and matter.
B. Growth, reproduction and dynamic homeostasis require that cells
create and maintain internal environments that are different from
their external environments.
C. Organisms use feedback mechanisms to regulate growth and
reproduction, and to maintain dynamic homeostasis.
D. Growth and dynamic homeostasis of a biological system are
influenced by changes in the system’s environment.
E. Many biological processes involved in growth, reproduction and
dynamic homeostasis include temporal regulation and
coordination.
2.C. Organisms use feedback mechanisms
to regulate growth and reproduction, and
to maintain dynamic homeostasis.
1. Organisms use feedback mechanisms to
maintain their internal environments and
respond to external environmental changes.
2. Organisms respond to changes in their
external environments.
2.C.1. Organisms use feedback
mechanisms to maintain their internal
environments and respond to external
environmental changes.
a. Negative feedback mechanisms maintain dynamic
homeostasis for a particular condition (variable) by
regulation physiological processes, returning the changing
condition back to its target set point.
b. Positive feedback mechanisms amplify responses and
processes in biological organisms. The variable initiating
the response is moved farther away from the initial setpoint. Amplification occurs when the stimulus is further
activated which, in turn, initiates an additional response
that produces system change.
c. Alteration in the mechanisms of feedback often results in
deleterious consequences.
2.C.1.a. Negative feedback mechanisms
maintain dynamic homeostasis for a particular
condition (variable) by regulation physiological
processes, returning the changing condition
back to its target set point.
• Operons
– trp Operon
– lac Operon
• Temperature Regulation
• Plant Response to Water Limitations
trp Operon
• “On” by default – repressible
lac Operon
• “Off” by default - inducible
Lac Operon (continued)
• This operon is further enhanced when glucose
is in short supply.
2.C.1.a. Negative feedback mechanisms
maintain dynamic homeostasis for a particular
condition (variable) by regulation physiological
processes, returning the changing condition
back to its target set point.
• Operons
– trp Operon
– lac Operon
• Temperature Regulation
• Plant Response to Water Limitations
Temperature Regulation in Mammals
2.C.1.a. Negative feedback mechanisms
maintain dynamic homeostasis for a particular
condition (variable) by regulation physiological
processes, returning the changing condition
back to its target set point.
• Operons
– trp Operon
– lac Operon
• Temperature Regulation
• Plant Response to Water Limitations
2.C.1. Organisms use feedback
mechanisms to maintain their internal
environments and respond to external
environmental changes.
a. Negative feedback mechanisms maintain dynamic
homeostasis for a particular condition (variable) by
regulation physiological processes, returning the changing
condition back to its target set point.
b. Positive feedback mechanisms amplify responses and
processes in biological organisms. The variable initiating
the response is moved farther away from the initial setpoint. Amplification occurs when the stimulus is further
activated which, in turn, initiates an additional response
that produces system change.
c. Alteration in the mechanisms of feedback often results in
deleterious consequences.
2.C.1.b. Positive feedback mechanisms amplify
responses and processes in biological organisms. The
variable initiating the response is moved farther away
from the initial set-point. Amplification occurs when
the stimulus is further activated which, in turn,
initiates an additional response that produces system
change.
• Lactation in mammals
• Onset of labor in childbirth
• Ripening of fruit
Onset of Labor in Childbirth
2.C.1. Organisms use feedback
mechanisms to maintain their internal
environments and respond to external
environmental changes.
a. Negative feedback mechanisms maintain dynamic
homeostasis for a particular condition (variable) by
regulation physiological processes, returning the changing
condition back to its target set point.
b. Positive feedback mechanisms amplify responses and
processes in biological organisms. The variable initiating
the response is moved farther away from the initial setpoint. Amplification occurs when the stimulus is further
activated which, in turn, initiates an additional response
that produces system change.
c. Alteration in the mechanisms of feedback often results in
deleterious consequences.
2.C.1.c. Alteration in the
mechanisms of feedback
often results in deleterious
consequences.
• Diabetes Mellitus
– Type 1 – lack of insulin
production
– Type 2 – decreased response
to insulin
2.C.1.c. Alteration in the mechanisms of feedback
often results in deleterious consequences.
• Graves Disease
– Antibodies bind to TSH receptors
– Overproduction of T3 and T4
– Exophthalmos, Hyperactivity, Nervousness,
Irritibality, Insomnia
2.C. Organisms use feedback mechanisms
to regulate growth and reproduction, and
to maintain dynamic homeostasis.
1. Organisms use feedback mechanisms to
maintain their internal environments and
respond to external environmental changes.
2. Organisms respond to changes in their
external environments.
2.C.2. Organisms respond to changes
in their external environments.
a.
b.
c.
d.
Photoperiodism and phototropism in plants
Hibernation and migration in animals
Taxis and kinesis in animals
Chemotaxis in bacteria, sexual reproduction
in fungi
e. Nocturnal and diurnal activity: circadian
rhythms
f. Shivering and sweating in humans
2.C.2.a. Photoperiodism
Organisms respond to changes in their
external environments.
a.
b.
c.
d.
Photoperiodism and phototropism in plants
Hibernation and migration in animals
Taxis and kinesis in animals
Chemotaxis in bacteria, sexual reproduction
in fungi
e. Nocturnal and diurnal activity: circadian
rhythms
f. Shivering and sweating in humans