One common definition of ecology is the analysis of the abundance and distribution of organism. Another common definition is the study of the relationships between organisms and the physical/biological environments they inhabit. In either definition, the researcher is examining relationships in a "natural" world, i.e., a theoretical framework that exists in nature. Environmental science includes some of the same elements of ecology, but does not always involve living creatures as the focus, but may examine the interplay of environmental features, ie., their synergistic or combinational effects on other aspects of the environment. Environmental science is often thought of as an applied science with particular emphasis on human interactions with the environment.
One doesn't have to study science methodology or philosophy in order to do ecology, but one could perhaps do better science if those aspects were fully understood. One of the problems in any size is researcher imposed bias. If these biases are fully understood before doing science, the researcher can perhaps compensate in the research design for con-commitent problems. If they are not fully understood, then the researcher may come away with spurious results or incomplete outcomes.
2. Birds living on oceanic islands tend to have smaller clutch sizes than the same species (or close relatives) breeding on the mainland. Explain this observation in terms of evolutionary theory. (avearge 3.9)
In terms of evolutionary theory one would expect as large a clutch sizes as that would pass on to succeeding generations the greatest number of genes of the parents. Implicit in this assumption is that many of the offspring do not survive to breed, and thus the more offspring produced, the greater the chance of survival of at least one individual. Therefore one has to assume that on oceanic islands, the factors that decrease the number of viable offspring (or the numbers reaching maturity) have less of an effect. This allows the birds to produce fewer eggs in a clutch. Evolutionary theory says that those aspects of an organism's behavior, physiology, etc., that provide the individual with an advantage will be selected for and those that are negative will be selected against. Since large clutch size may have a positive advantage in continental birds, it must be selected for, whereas on oceanic islands, the same feature may be neutral or perhaps even negative.
3. In many ungulate species, males have horns or antlers that they can use in combat with other males during the breeding season. How can natural selection limit the "arms race" in species where combat is part of the reproductive cycle? (average 3.7)
Although the antlers or horns may be selected for during breeding season, there may be a negative selection during non-breeding season. For example, to produce horns or antlers may require a great deal of energy on the part of the bearer. During times of the year when food materials are unavailable or few in number, the demands of supplying regular metabolic needs and those of antler formation may be in conflict with each other and thus antler production may be detrimental to the creature. The "arms race" may also be self-limiting in that if the combatents both destroy each other, they may never breed and thus not pass on their genes. The organism with a smaller set of horns might surreptiously breed, but not get into combat and thus may have a greater chance of passing along his genes than the "fighters".
4. Discuss the application of general methods for studying distributions to the problems of what limits the geographic range of human beings both at the present time and early in our evolutionary history. (average 3.8)
The factors associated with distribution include: dissemination, choice of habitat, interaction with other species, and interaction with physical environments. I will discuss each. We know today that the human species can get anywhere on the globe and even to the moon. It is evident that even in previous times, the species was able to gain access to almost all portions of the globe except for Antarctica. Arrival at many of these locations was via walking and/or swimming, but with the development of culture, included boats, etc. Therefore, in contrast to many organisms, dissemination is not a problem for our species. In terms of choice of habitat, again because of culture, we can live/survive in any environment today. In the past we were somewhat limited to equatorial or temperate environments. With respect to interactions with other species, today we control the environment and almost at will determine the outcomes when interacting with other species. In the past, that was not true. It depended upon the development of weapons. Because of culture and technology today, there is no physical feature that limits our presence, but in early times, extremes were limiting, eg. temperature, moisture. Even at that we find that less complex cultures lived in pretty extreme environments, the Shoshones in Nevada, Tierro del Fueggians in southern S. America.
5. At one time there was a proposal to construct a sea-level Panama Canal. It was thought that such a canal would have possible effects on the distribution of poisonous sea snakes, creatures which are absent from the Atlantic. Discuss what effect this could have on the distribution of poisonous sea snakes. (average 3.8)
There are a number of factors at work here. The first question that might be asked is whether the snake is absent from the Atlantic because they were never able to get there, or because they could not survive there. If their absence is because of in ability to survive due to competition with other organisms or the wrong suite of environmental features, then although the sea level would provide access, they might have limited success upon arrival. It the problem was not any of the above, but one of dissemination, then the Atlantic basin, partiularly the Carribean is in for real problems.
6. Morse states:
This is a very good time to study the mechanisms of habitat selection, in that many natural habitats are undergoing changes as a result of human activities. These changes provide animals with potential opportunities and challenges, ones that in many instances may never have previously experienced.
Discuss why you agree or disagree with this statement. (average 3.8)
I guess I would have to disagree with this statement. If anything, the natural habitat is become less diverse rather than more diverse. Through filling, cutting, etc. we have taken very three dimensional environments and changed into more two dimensional environments. At the same time we have substituted artifical physical/chemical factors for existing natural factors. For example, pH changes have always been part of the natural world, but with air pollution, acid rain has become a transforming agent that is human caused rather than volcanic caused. It would seem that with our manipulation of the environment, we have increased the likelyhood that generalist species succeed whereas the specialist go extinct.
7. One criterion of interspecies competition is this: Closely related species having mutually exclusive ranges are in competition at their zones of contact. Discuss this criterion in relation to the factors that limit distribution. (average 4.0)
If for example, we take the two species of barnacles, Chthalmus and Balanus, we can determine how their distributional ranges are affected by predation, dessication, and/or competition for space. Dessication is more of a factor for Balanus and thus it occurs deeper in the zone, predation limits Chthalmus from occurring deeper. Competition for space affect both species. As a results, when both species are present the former occurs in the higher portion of the zone and the latter lower, with not much overlap. When one or the other is absent, the one that is present extends it distribution up or down to a position where the other factors; dessication or predation take over as a controlling agents.
8. "To become widespread, a species must develop many ecological races". Is this true in both animals and plants? Discuss with reference to colonizing species such as the starling. (average = 3.7)
Since the environment is never uniform over a large area, it does pay for a species to occur in a number of ecotypes, that is subgroups that have special attributes related to the particular location they can be found in. Because animals are mobile and plants are sedentary, this would seem to be more important in plants. Animals should be able to pick sub-locations within any envionment that provide the requirements necessary for success. If we examine the starling, therefore, we should probably not expect to see any particular ecotypes, but we might expect to see a great deal of variability in species attributes.
9. Bartholomew states:
"Although the distribution of many marine and aquatic organisms and many tererstrial invertebrates may be explicable in terms of physiological tolerances, no such general statement can at present be made for terrestrial vertebrates."
Is this generalization valid? Discuss why or why not. (average 3.5)
This for the most part relates to size. Terrestrial vertebrates are very large sized and at the same time rather mobile. The terrestrial environment likewise at the scale of the organism is rather heterogenous. As a consequence, organisms can move to find habitats that fulfill their needs. In contrast terrestrial invertebrates are small. Therefore, they live in a micro-habitats that exists within the macro-environment. Thus they are limited by their physiological tolerance to the set of conditions that characterize that micro-habitat.
10. There is only one known C4 tree species. Why should this be? (average 3.1)
Forest environments are characterized by low light intensities, particularly at mid-temperate latitudes and during mid-summer. C4 plants, grasses, bamboos, etc., are plants that survive and do well in high intensity light environments. Therefore, it seems unlikely that a tree would evolve to be a C4 plant, but would utilize the more common mode of C3 photosynthesis due to the limitations of light availability in the environment.
a. red-wing black birds
habitat selection
sexual competition for mates
territoriality
b. the plant speies from from San Francisco to the ridge of the Sierras and thence to Reno.
ecological races
edaphic factors
c. Chthalamus and Balanus
competition
physical factors versus biologic factors
d. the Chestnut blight
dispersal
e. tree snails in Hawaii
competition with introduced species
evolution -- polymorphic characters
f. Australian mammals
convergent evolution
evolutionary divergence
Gleason believes whether a plant is present at any location is dependent upon two factors, was it able to reach that location through "gemmules" and if so, were condition such, that the gemmule was able to grow and reach maturity. He provides a large number of instances where "fixed and definite vegetational structures" do not exist. These include new dunes at the south end of lake Michigan, new ponds on a farms. In each of these cases he shows how common environments may have different suites of organisms. In another situtation he shows where there are no sharp lines between two different associations, eg., between the oaks and the grasslands of California. Although he acknowledges that similar areas may contain some of the same species, he argues that the association as a superorganism or the association as a natural entity does not trully exist. He velieves that there is too much heterogeneity in physical environments and to much randomness in terms of the arrival of gemmules in any particular location for plant associations to act as organic wholes. What does believe is that similar environments may encourage plants with similar requirements to be present in those environments and thus from a "distantance" make those communities look alike. In the end though, he claims that if the botanist examines each association in detail, there are no associations, on collections of individual species, which may have common requirements.