2.C.2

Feedback mechanisms

2.C.1 – Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes.

·      Discuss how negative feedback works. Discuss the following two examples – Thermoregulation in animals and plant responses to water limitations.

Negative feedback is a mechanism that maintains dynamic homeostasis by returning a changed condition set to its target set point. ­­­­­­An example of negative feedback is thermoregulation in animals. The central thermo receptors in your body respond to a change in your body temperature by either releasing sweat to reduces heat in your body, or shiver and your skin will get goose bumps to contain heat and produce heat to bring your body temp to its set point. Another example in plants is its responses to water limitation. If a plant has a low supply of H20 in in its system it can create a acid that will close the stomata so little water is lost.

·      Discuss how positive feedback works. Discuss the following three examples – lactation in mammals, onset of labor in childbirth, and ripening of fruit.

Positive feedback is a mechanism that amplifies  responses. Three examples of positive feedbacks are lactation in mammals, onset of labor in childbirth, and ripening of fruit. In lactation, sucking stimulates cause nerves to tell the hypothalamus to create Oxytocin which in term creates milk. In childbirth, the head of the baby is presses against the cervix and causes nerve impulses to stimulate a pituitary glad to secrete oxytocin and causes the uterine to contact to push the baby out towards the cervix. When fruit is ripe. A chemical called ethylene is produced by the fruit, which acts as a chain reaction towards other fruit and makes them produce ethylene

·      Discuss how an alteration in the mechanism of feedback can result in dire consequences by using the following three examples: diabetes mellitus in response to decreased insulin, dehydration in response to decreased antidiuretic hormone and Grave’s disease.

Diabetes mellitus is a example of an alteration in a feedback mechanism because in type 1 diabetes, the pancreas is unable to create insulin and results in high blood sugar if not monitored due to a autoimmune disease to insulin. Type 2 diabetes is a alteration in a feedback caused by an unhealthy diet and also results in cells not producing insulin because the cell producing insulin stop production. Some people are unable to produce the hormone, antidiuretic and one of the side effects is grave disease. Grave disease is the result of no antidiuretic hormone and causes a persons eyes to hyperthyroid.

2.C.2 – Organisms respond to changes in their external environments.

·      Discuss how organism respond to changes in their environment by using the following examples:

o   Photoperiodism and phototropism

Photoperiodism is a physical response in plants that results in flowering. The photoperiod of the plant, which is the length of night and day so the plant knows what time of year it is. Is regulated by a phytochrome. A phytochrome is ultimately that makes a plant flower. 

o   Hibernation and migration in animals

Hibernation and migration are both results of a change in conditions. Hibernation is a state of inactivity endotherms go through to slow down metabolic rate and to survive cold and harsh winters. Animals that do not hibernate go on migration, which is a long distance movement of individuals on a seasonal basis.

o   Taxis and kinesis in animals

A taxi is a automatic movement towards or away from a stimulus. A animal will move closer or away from a stimulus . Kinesis is a simple nondirection change in activity or turning rate in response to a stimulus. This cause animal to run in a frenzy in response to something in its environment.

o   Chemotaxis in bacteria, sexual reproduction in fungi

Chemotaxis is a process in bacteria where they can detect food or poison and will move away or to the stimulus. For fungi to reproduce, pheromones are released as a social response to members of the same species to produces gametes.

o   Nocturnal and diurnal activity: circadian rhythms

Circadian rhythm is the biological clock that both plants and animals activity. Bats are nocturnal because they are inactive during the day and their circadian rhythm allows them to wake up for the night. In humans, the average person is designed to sleep during the night and be active during the day, people also can feel tired right after they wake up and they are in the middle of their circadian rhythm.

o   Shivering and sweating in humans

Your body respond to a change in your body temperature by either releasing sweat to reduces heat in your body, or shiver and your skin will get goose bumps to contain heat and produce heat to bring your body temp to its set point