Instructions:  This review is worth 75 points (12.5% of your course grade) and will be due in class Wednesday, 4/21/04.  No exceptions and late reviews will result in at least a 5% deduction.  You may not consult any references or any other person while working on this review.  Your signature at the bottom of the last page signifies that the work is yours alone and is pledged under the Honor Code.  When you break the seal on the envelope you will have three hours to complete the review!  Please print legibly; I can only grade what I can read!  For each question or part to a question, limit your answers to the space below each question, unless otherwise specified.  Any part of your answer outside of the space provided will not be graded.

1.      Describe one feedback loop associated with hormonal control of mammalian digestion, and how at least one other system (besides digestive and endocrine) is involved in this feedback loop (6 points).

Secretion of HCl in the stomach lowers pH, which decreases release of gastrin.  This, in turn, causes a decrease in release of HCl.  Gastrin circulates in the blood and returns to the stomach to exert its effect.

Delivery of acid chyme to small intestine that contains undigested fats and proteins causes release of cholecystokinin.  This has a negative feedback on secretion of gastrin, which ultimately decreases stomach motility and delivery of chyme.  The circulatory system carries cholecystokinin to the stomach.

2.      Describe the major differences between absorptive and postabsorptive metabolism, specifically identifying the major organs and hormones involved in directing nutrient traffic, and what nutrients are used when and by what organ systems (7 points).

During the absorptive period, nutrients, such as amino acids, simple sugars, triglycerides, and fatty acids are absorbed by the small intestine.  They are then transported by the circulatory system to the liver, adipose tissue (fats), nervous system (sugars), or directly to muscle (fats, amino acids).  In response to the increase in amino acids and glucose in the blood, insulin is secreted by the pancreas.  In general, this causes buildup of macromolecules (proteins, glycogen, and triglycerides).  Insulin also allows all cells in the body to take up glucose.

As blood glucose decreases, insulin secretion ceases, and, in general, all above processes are reversed.  Glucagon is secreted by the pancreas, and proteins, triglycerides, and glycogen are broken down for use muscle cells and other non-nervous system cells.  The nervous system still uses glucose from the blood, but other cells cannot take it up.

3.      What are the major problems of fat metabolism in diabetics?  Include in your answer the systems that are affected and the potential problems that may arise because of abnormal fat metabolism (6 points).

Because insulin decreases utilization of fat and promotes fatty acid synthesis in liver and glycerol production in adipose tissues, inhibits release of fatty acids into blood, lack of insulin can have major effects.  Excess fatty acids in blood plasma promotes liver conversion of fatty acids into phospholipids and cholesterol, which are released into blood as lipoproteins (increased up to 3x in blood in absence of insulin).  High lipid concentration of cholesterol (in LDL) leads to rapid development of atherosclerosis, arteriosclerosis, and severe coronary heart disease.  As fatty acid metabolism increases in liver, oxidation of fatty acids produces acetyl-CoA, which is converted to acetoacetic acid and released to blood.  This can cause loss of sodium and lowered pH in the blood.  Acidosis can lead to coma and death.

4.      LIST two specific problems associated with excretory systems of animals living in terrestrial habitats?  What about those living in marine habitats (again LIST only) (6 points)?

Loss of water and salts, energetic cost to maintain water and salt balance

Loss of water, maintenance of proper salt composition

5.      Describe how the integration of the circulatory, endocrine, and excretory systems regulate and control blood supply to mammalian kidneys (5 points)?

Maintaining blood supply to kidneys is critical for filtering blood and maintaining proper salt balance.  Renin is secreted by the kidneys in response to low blood pressure.  Rennin activates angiotensin in the blood.  Angiotensin causes peripheral arterioles and efferent renal arterioles to constrict.  It also causes release of aldosterone, which stimulates sodium reabsorption.  The more sodium reabsorbed, the more water will follow, increasing blood volume. 

ADH also plays a role.  ADH is secreted by the hypothalamus, and it has a variety of effects that help the kidney function.  It also causes peripheral vessels to constrict and it increases permeability of collecting duct cells to water (through insertion and up-regulation of aquaporins).

6.      Briefly describe the function of Malpighian tubules (4 points).

Malpighian tubules are found in Uniramia (insects, centipedes, and millipedes) & Chelicerata (scorpions, spiders, ticks, mites, etc.).  The tubes are fingerlike projections found at the midgut/hindgut transition.  They actively transport uric acid, K+, Na+ in, and water follows passively.  There’s no filtration.  Everything empties into the hindgut, where the solutes are reabsorbed and water follows back out into the hemolymph.  Uric acid then precipitates in the hindgut and is eliminated with the feces.

7.      What is atherosclerosis and what are two risk factors (LIST) that could increase incidence of atherosclerosis (4 points)?

Atherosclerosis is a buildup of fatty deposits in the smooth lining of arteries.  Atherosclerosis invades superficial and deep layers of vessel walls, which narrows the lumen and decreases elasticity. 

Risk factors include smoking, high blood pressure, stress, gender, age, high LDL and low HDL, diabetes, obesity, a diet with saturated fats, too much meat and too little fiber, a sedentary lifestyle, and genetic predisposition

8.      LIST two costs and two benefits of sexual reproduction in animals (4 points).

Benefits include increased genetic variation, ability to adapt to changing environment

Costs include time and energy spent mating/searching for a mate, increased risk of predation, damage, it detracts from feeding and/or caring for other offspring

9.      Describe how hormones are involved in the human ovarian/uterine cycles (5 points).

From puberty to menopause, interactions of GnRH, gonadotropins, and sex steroids control the ovarian and uterine cycles.  Menstruation marks the start of the cycle.  FSH and LH levels increase and follicles begin maturing to produce estrogen.  All but one of the follicles withers away, and it continues to secrete estrogen causing the endometrium to grow.  Estrogen exerts negative feedback control on gonadotropin release during the first 12 days of the ovarian cycle, and then exerts a positive surge of LH and some FSH, triggering the follicle to rupture and release the egg.  The follicle cells develop into the corpus luteum and secrete estrogen and progesterone to continue endometrial growth.  These same two hormones provide negative feedback to the pituitary, inhibiting gonadotropin release to prevent maturation of new follicles. 

If fertilization fails, the corpus luteum degenerates on about day 26 of the cycle, the endometrium sloughs off, and menstruation occurs.  Lowered levels of steroids in the blood cancel the negative feedback on the hypothalamus and pituitary, allowing GnRH, LH, and FSH to increase again. 

10.  The Theory of Island Biogeography has been applied to fragmented terrestrial habitats.  Explain one pro and one con associated with this application (6 points).

Pros: for most areas studied, there is a relationship between the number of species found and the area of the habitat.  The TIB could be applied to conservation of species by simply conserving more habitat – that should preserve more species. 

Cons: uncritical application of TIB could lead to problems – not all species will react the same way when habitats are fragmented and separated by other types of terrestrial habitats, in comparison to islands separated by water.  In addition, many animals and plants can live in more than one type of habitat, so fragmentation doesn’t always reduce usable habitat for those species.

11.  Consider one grass-dominated and one tree-dominated biome that occur at the same latitude (6 points).

a.      What are the two biomes you chose, and where do they occur? 

Grass-dominated biomes include grasslands, prairies, savannahs, steppe.

Tree-dominated biomes include temperate deciduous forest, tropical rainforest (evergreen and deciduous), boreal forest, temperate rainforest.

b.      Which biome is likely to have higher:

i)        annual temperature?  At the same latitude, average annual temperatures are often similar, although grasslands may have more variance in temperatures.

ii)       annual precipitation?  Forests generally receive more annual precipitation.

iii)     animal diversity?  Forests generally have more animal diversity, although it may depend on the taxa of animal.

iv)     annual primary productivity? This is a tough one – it’s often similar, although there are seasonal variations.  It depends on the latitudes you chose.

12.  LIST two factors that determine ocean productivity and, at the same time, help explain variation in productivity in different regions of the ocean (4 points)?

Light, depth, temperature, nutrients, and currents are the main factors that affect and determine ocean productivity.  Variation in productivity can be explained by light penetration (which is the same as depth effects) – shallow waters are more productive.  These shallow waters are also coastal waters, and generally receive higher nutrient levels from river systems.  Currents may also cause upwelling near coastal zones, and temperatures may be higher, too.  All these factors favor higher productivity near the coast, in shallow waters.

13.  Describe how the carbon cycle is being disrupted by humans.  Specifically, what are two activities of humans that are causing disruption, and how exactly are they disrupting the cycle (6 points)?

Burning of fossil fuels and deforestation are two major activities that are disrupting the carbon cycle.  The former adds carbon dioxide to the atmosphere and removes a stable reservoir where carbon has been stored for millions of years.  The latter removes potential carbon sinks, so the two activities are synergistic.  In addition, decomposition of degraded forests can also add carbon dioxide to the atmosphere.

14.  Describe, in one sentence each, one impact in the atmosphere and one in aquatic habitats that are occurring as a result of the disruption by human activities on the nitrogen cycle (6 points).

Burning fossil fuels and other activities produces nitrous oxides, which are greenhouse gases, and involved in smog and acid precipitation.

Deforestation and overuse of N fertilizer return N to soils, where it is converted to nitrate and leaches from soil to streams.  The input of nitrate to waters can cause algal blooms, which later can lead to anoxic zones as dead algae sink to the depths and are decomposed by aerobic bacteria.  Loss of oxygen can lead to fish kills and other adverse environmental effects.

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