A. People: For each of the following individuals, briefly describe as specifically as possible a contribution the individual has made to our ecological understanding.
1. Raymond Lindeman--1.5
Raymond Lindeman was one of the first ecologists to propose that energy flow through and ecosystem could be analyzed from a trophic dynamica aspect. He sorted the organisms into trophic levels and then determined the energy flows between trophic levels. He then determined what we call today, the Lindeman efficiency coefficient.
2. John Tyler Bonner--1.1
Bonner's contribution to ecology relates to photosynthesis. His idea is called the light absorption theory. That theory indicates that are lots of sites for absorption of light, but overall productivity is low. Bonner therefore felt that plants were designed for dim light situations.
3. Charles Elton (not Elton John)--1.4
Elton was an Oxford University professor who is reponsible for the concept of pyramids of number and pyramids of biomass. These concepts came out of his work in arctic environments. By sorting the organisms into categories associated with feeding modes, he determined that both numbers and biomass decreased as you went from autotrophs to carnivores.
B. Places: Answer each question as fully as possible.
1. Describe briefly the meteorological features that make the Sonoran desert of northern Mexico and southern Arizona a hot, arid location.2.8
The specific features associated with the Sonoran desert are:
a. latitude-the desert is at a latitude where low levels of rainfall are expected
b. rain shadow effect-the flow of moisture from the Pacific Ocean is block by a north-south mountain chain
c. interior rather than coastal location
d. current systems off the coast take surface water away and bring up cooler deep water. This has an effect on the total rainfall.
2. The forests of the western side of the Olympic peninsula have been described as temperate rain forests. What meteorological features associated with the area allow such dense coniferous forests to grow in that location.2.9
a. The Olympics are a fairly high mountain range. Adiabatic cooling of the air masses as they flow over the mtns dump a lot of moisture.
b. The trees grow in a moderate climate where there are no extreme differences between summer and winter temperatures.
c. The prevailing directions of air currents are from a cool ocean to a warmer continent
d. Moisture is not a limiting factor, but sunlight is. The amount of sunlight favors coniferous vegetation, particularly Douglas fir
C. Organisms: Answer each question as fully as possible.
1. The marine iguanids of the Galapagos are unusual in a number of features. Firstly, they consume seaweed as the food source. Secondly they bask on the rocks when not feeding. Lastly, they seem to be unafraid of humans. Describe the ecological features that allow them to have this kind of life style.8.6
a. Basking in the sun aids and abets the digestive processes in the iguanids by facilitating the digestion of a relatively non-nutritive material.
b. If organisms were basking in another location, they most-likely would be eaten, but since the Galapagos lack an "iguanid" predator, this is not a problem.
c. Island species typically lack fear of humans and this is related to item b, the lack of predators on most island systems.
2. The cacti of Arizona are often tall, but lack leaves, are cylindrical in shape and have very sharp spines. Relate these features to how the organism behaves photosynthetically and ecologically.8.8
a. The cacti use a CAM mode of photosynthesis, that is, they are able to grab CO2 during the day, but only fix it at night.
b. The lack of leaves and cylindrical shape reduces transpiratory losses of water, yet provides a photosynthetic surface area.
c. The spines prevent consumption of soft, palatable tissues.
d. The thickened cuticle prevent water loss and the tissues serve for water storage.
3. Describe how the relationship between wolves and moose on Isle Royale have enabled us to better understand the nature of energy flow in the ecosystem.7.3
a. Because the wolves only consume moose, we can determine rather easilty what their caloric intake is. This then along with other studies enable us to determine the ecological efficiencies associated with both the moose and the wolves.
These values (ecological efficiency values) show us that the 10% rule is not always a valid rule. The efficiencies in the wild are often much lower.
D. Concepts: Answer each question as fully as possible
1. What does Colinvaux see as Lindeman's major contribution to ecology? Why does he say that there was an error in Lindeman's approach?5.8
Colinvaux shows how Lindeman's work refocused the work of ecologists from autecology to synecology, that is, instead of studying individual species, the ecologists began grouping species by their trophic levels. He believes that Lindeman made an error in calculating ecological efficiencies because he double-counted in compiling his budgets. He determined not only turnover rates, but respiration and mortality rates, both of which are associated with turnover rates.
2. In some ways, one would assume that the area around the equator would be extremely hot and that at the poles extremely cold and that both conditions would preclude the presence of life forms. Yet, we find that there are organisms that live in each of those environments. What aspects associated with the distribution of heat energy on the earth explain this paradox?6.9
The earth gains energy through radiation from the sun and looses energy through re-radiation. The amount of the first is determined by latitude, the latter is always at right angles to the earth's surface. Thus there is an imbalance in the distribution of heat energy between the poles and the equatorial regions. The earth acts to redistribute the heat energy received at the equator towards the poles. It does this through two media, the atmospher and the ocean. Transfer of heat via the atmospher is rapid, but the toals conducted are low. Transfer via ocean currents are slow, but because of the high heat capacity of water for thermal energy, the amounts transported are large. The actual movements of the heated masses are modified by the rotation of the earth and by the rising and sinking of the heated masses because of density features.
3. At times bees act as though they are ectothermic, homeotherms. Explain what is meant by these terms and describe what physiological and behavioral features enable them to maintain very active lives.7.3
Bees are poikilotherms in that some of the sources of heat are generated externally and their body temperatures are normally controlled by external factors. They can act as endotherms because they can increase their metabolic rates through muscular contractions (mainly wing movements). They can do this efficiently because they use a tracheolar system to deliver O2 to the tissues involved in metabolism. The are also social and can as a group elevate the hive temperature by individually elevating their own temperatures via increased metabolic activity. The material they eat, nectar and pollen, are very rich energy sources and can fuel this sort of activity, particulary since they can store the materials in the hive.
4. Grasses are found in grasslands and deciduous trees in forests. Briefly describe morphological and physiological features that differ between the two groups.7.1
Trees are typically C3 plants and grasses are C4 plants. Trees maximize leaf surface area to act as solar collectors. This comes at the same time as losses of H2O to maintain core temperatures. They can do this as long as water is readily available. In winter time, they rid themselves of leaves so as to minimize water balance problems. Grass plants minimize surface area and respiratory losses by design factors that put leaves in a vertical position so as to minimize heat gain and stomates on leaf surfaes where relative humidities are high so as to minimize water losses.
5. Studies of optimal foraging strategy are often done using birds as a resource group. What is meant by the phrase "optimal foraging strategy and what aspects of bird biology make them an ideal experimental group.7.0
In optimal foraging strategy, an organism will attempt to maximize the gain (food energy obtained, the benefit) by minimizing the expense (the cost) of obtaining the food. When the item that brings the best return begis to cost more than what is received, the organism should switch. Because birds are large and active diurnally, the are readily observable i terms of their food choices. Biologists can also readily determine the calric values of the items eaten and at the same time ascertain the cost of obtaining those items.
6. When one researches the concept of tree-line, you immediately realize that the trees you are viewing are coniferous and not deciduous. Briefly explain why there is a tree line (in the mountains) and what aspects of conifer biology explain their presence below the tree line, but not above the tree line.5.7
Temperatures and moisture availability change as one proceeds up a mountain. Problems that plants living at the higher altitudes experience are related to water stress, freezing temperatures and wind. Also light intensity is greater to lesser thicknesses of atmosphere. Conifers succeed in this environment to the point of the tree line, because due to needle shape and construction, they loose less water than a deciduous tree would and they can maintain a more constant leaf temperature because of a boundary layer effect that prevents overheating/cooling. As long as they are able to get water from the ground to their leaves, they can even photosynthesize on winter days when temperatures and light intensities allow this to happen. At tree line, water availability and wind caused desication become important and above treeline, environmental conditions are so cantankerous so as to preclude conifer growth except in very protected areas or areas where snow drifts occur.
E. Terminology: Explain each of the following terms, noting in each explanation things that are of ecological importance.
1. Kin selection1.7
The rule of thumb for evolution is selectio at the level of the individual. Kin selection indicates a mode of group selection and supports why certain aspects of social behavior have evolved, particularly altruistic acts in social organisms.
2. poikilothermy1.5
Body temperature is dependent upon external temperatures. This allows poikilotherms to allocate their energy in other aspects of their life histories, particularly growth and reproduction. It also means that they are inactive most of the time and especially during times when temperatures are low.
3. counter current system1.3
A counter current system is a system that allows organism such as ducks and marine mammals to retain heat in their body cores, yet circulate blood to appendages. This is accomplished by blood flow in two adjacent vessels that have flows in opposite directions. Similar systems occur in some desert animals.
4. low-energy systems1.3
Low-energy system are systems where organism are able to put a large percentage of their energy budget into reproductive activities. These animals are periodically active rather than continually active. They may wait for their food to pass by rather than to pursue/stalk their prey.
5. heat budget (animal)1.0
Animals receive heat energy through radiant energy, conduction and internal production. They loose energy via conduction, radiation, convection, and evaporative heat loss. Homeotherms are constantly adjusting one of the values, particularly internal production and have at the same time evolved body configurations that minimize gains or losses (fur, feathers, fat, etc.) Poikilotherms spend less time worrying about their budgets and under go torpor when conditions are unfavorable.
6. turnover time0.8
Turnover time is the generation time for the members of a particular trophic level. Rule of thumb is that the short the turnover time, the smaller the biomass appears in a pyramid of numbers and biomass diagram.
7. ten percent rule1.4
The rule says that 10% of the energy is passed on to the next trophic level (ie., the ecological or Lindeman efficiency of the system is 10%). This means that food chains are usually pretty short and big predators are rare.
8. plant as a solar panel1.5
Plants for the most part use the sunlight that falls on them to fix carbon. Therefore it behooves them to array their leaves in a pattern that maximizes the amount of area exposed to the sun. They can do this in a monolayer or a multilayer. If the latter, leaf overlap is maxed.
9. PEP-Carboxylase1.6
This is the enzyme that facilitates the production of 4-C chains (oxalacetic acid or malic acid) in C4 plants. This process increases CO2 uptake in plants that live in water stressed environments or environments where heat gain is a factor.
10. efficiency of photosynthesis1.3
The ecological efficiency of photosynthesis is 1-3%. The biochemical efficiency is about 30-35%. The difference between the two values is explained by ecological and physiological aspects.