Download Growth, Reproduction, and Homeostasis 2 HW.

Growth, Reproduction, and Homeostasis Homework 2
Part One: IDENTIFICATIONS (IDs). Use the book to help you identify the following. Be as specific as possible, and include
names, dates, and relevant facts as appropriate. Be sure to explain the significance of the term.There should be a minimum
of three (3) sentences for each ID. Use of the internet is okay if you are stuck, as long as you do not plagiarize.
Chapter 40: Basic Principles of Animal Form and Function Reading Guide, Page 820, 7th edition
A) Body Size and Exchange with Environment
B) Size and Metabolic Rate Relationship
C) Regulators vs Conformers
D) Negative Feedback
E) Positive Feedback
F) Torpor
G) Hibernation
H) Estivation
Part Two: Feedback Loops. Identify if the statements below are examples of positive or negative feedback loops. Explain
why please.
1) An example of feedback is body temperature regulation. If blood temperature rises too high, this is sensed by specialized
neurons in the hypothalamus of the brain. They signal other nerve centers, which in turn send signals to the blood vessels
of the skin. As these blood vessels dilate, more blood flows close to the body surface and excess heat radiates from the
body. If this is not enough to cool the body back to its set point, the brain activates sweating. Evaporation of sweat from the
skin has a strong cooling effect, as we feel when we are sweaty and stand in front of a fan.
2) If the blood temperature falls too low, this is also sensed by the hypothalamus and signals are sent to the cutaneous
arteries (those supplying the skin) to constrict them. Warm blood is then retained deeper in the body and less heat is lost
from the surface. If this is inadequate, then the brain activates shivering. Each muscle tremor in shivering releases heat
energy and helps warm the body back toward its 37 degrees Celsius set point.
3) Feedback is seen in protein digestion, where the presence of partially digested protein in the stomach triggers the
secretion of hydrochloric acid and pepsin, the enzyme that digests protein. Pepsin digests proteins, casing more HCl and
pepsin to be released.
4. The kidneys sense that the oxygen levels in the blood are low. The kidney sends a hormone signal to the bone marrow to
make more red blood cells. The number of red blood cells increases, so more oxygen is carried in the blood.
Part Three: Phototropism. Darwin and Darwin and Boysen-Jensen both experimented with phototropism. They performed
a series of tests on a germinating seeds to determine how plants are affected by the movement of the sun. Their results are
shown in the diagram below. For each germinating seedling, describe what occurred with the experiment and why the plant
either moved or did not move toward the sunlight. You may also mention the siginficance of the findings. Please refer to
Page 792 if you are stuck.
Control:
Tip Removed:
Tip covered by Opaque cap:
Tip covered by transparent cap:
Base covered by opaque shield:
Tip separated by gelatin block:
Tip separated by mica: