The Science of Biogeography

1) What is the science of biogeography?

Biogeography is that study of geographical distribution of flora and fauna considering the different taxonomic levels, present and past, the habitats in which they are found together with the involved ecological relationships. Today, there are two theories in biogeography that have been developed to discuss more on the distribution of biological species in the world. The two of them are Distance-decay and Island biogeography theories. The distance-decay theory asserts that the correlation and similarity between species in any two geographical locations will continue decreasing as the distance between the two increases. The second biogeographical theory, island biogeography asserts that those pockets of life (islands) that are closely spaced will support more biological life/species. It is still this second theory that explains that these closely spaced islands are rarely threatened by extinction if compared to the tiny isolated islands of the world. The Geographic Information Systems Scientists say that the above two theories were developed in order for us to be able to fully understand the distribution of species but not the distribution or even movement of human beings.

As it was developed, the science of biogeography was meant to answer so many questions that are varied. It was developed so that it can answer some of the questions like why are there so many kinds of animals and plants in the world. It seeks to answer why some of these animals and plants are rare while others are common. Some animals and plants are widely dispersed while others are confined to a limited place. The science of biogeography seeks to explain the reason as to why this is so. There are some parts of this world that are richer in terms of species compared to others. It’s only by use of the study of biogeography that we can be in a position to understand this.

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There are several major types of biogeography distributions. They include; Endemic (restricted to specific locations), cosmopolitan (e.g.Caenorhabdities elegans and Drosophila melanogaster), and Disjunct (separated). The disjunct biogeographic distributions are believed to have been caused by Vicariance and dispersal. In biogeography, evidence that can be based on its history can be classified in terms of Paleontology and systematics.

2) Describe the 5 observations upon which the science of biogeography is founded. Give TWO examples for each observation

a) Each and every species and other higher group animals are said to have a discrete and a non random distribution in time and space. A good example of this is the gorilla that is only found in two African forests.
b) In different geographical regions of the world there is an assemblage of animals that are distinct and they coexist. A good example to explain this is the fauna that is found south of the desert of Sahara together with its monkeys, antelopes, pigs and this is totally different from the Australian fauna and its duck billed platypus, wombats and kangaroos.
c) The differences and the similarities in these regions cannot be in any way be described in terms of the distance between them or even the area of origin. A good example is that the fauna of eastern Asia and Europe is to large extent similar although they are both separated by 11,500km of land. Also the fauna of New Guinea and Borneo are different though are separated by a small piece of land compared to the ones above which is across water and land.
d) All those faunas that look different from those of today once previously occurred in all other geographical regions. An example is the dinosaurs which existed in most parts of the geographic locations in Cretaceous.
e) The faunas which resemble the ones found today and their antecedents once occurred, but its sometimes at far distances from the current range. A good example is the subtropical-warm temperature fauna which is found in Eocene Wyoming. This includes fishes which are fresh-water, turtle groups and salamander which are restricted to southeastern parts of the United States.

3) Discuss this statement: “The history of biogeography is essentially a continuing conflict between creation myth and empirical science.”

Empirical science describes that the distribution of organisms in the whole world was as a result of continuous evolution of the past existing species. Science asserts that the present fauna and flora are as a result of evolution from past organisms which were not developed as they are today. On the other side of the creation myth, people and especially the Christians believe that the current population of plants and animals are a product of what God created long time ago. Some of the things that are explained in the bible are in total conflict with what science has provided a detailed account on. A good example is the Global Flood during the time of Noah. The Bible says that God instructed Noah who by then was 600 years old to construct an ark. Noah was then supposed to take two of every unclean animal and seven of every clean animal. All food and fresh water was then supposed to be in the ark. Noah and his family were to remain in the ark for six months until the flood waters subsided. This creation story in the book of genesis continues to explain that after the flood waters subsided, Noah, his family and the animals that were released then were the ones who later repopulated the earth. This is in total conflict with the empirical scientists who argue that today there is too much of genetic diversity in the world for us to be consistent that every animal that is land based descended from the few breeding pairs and this is just some few thousands years ago. According to empirical science, some of the species we have today in the planet will evolve locally. This thus means that they are immobile geographically according to scientists. The scientists will ask today how comes the Duckbill platypus ended up only in Australia and not anywhere else in the planet.

Scientists still argue that Noah did not take any fish or coral in the ark. During the flood thus, all the fish would have become extinct and all the corals would have been swept away. Some of the corals according to the scientists even appear older than the given history of the floods. For scientists they believe that there is no way the short lived species could have survived the time they were in the ark. They say that the adult mayflies would have died in just a few days while the larvae of many mayflies will require shallow fresh and running water. Other similar insects and many of them would actually face the same problems. There is no way the scientists would believe that the human population could rebound in such a short period. Other controversies apart from the field of evolutionary biology can also be seen in cosmology, thermodynamics, paleontology, geology and nuclear physics.

4) Describe the main contributions to biogeography of the people listed below. Alexander von Humbolt, Liebig, MacArthur and William.

Alexander Von Humbolt:

He was German naturalist who is normally referred to as the father of phytogeography. He was the one who felt that study on geographical distribution was an important scientific inquiry that could lead to the discovery of laws of nature that are fundamental. He was the one who did the explorations of South and Central America together with Aime Bonpland who was a French naturalist. These two travelled along the Orinoco and Amazon rivers as they explored the Andes and the present day parts of Ecuador, Venezuela and Colombia. He managed to study vegetation and climatic conditions of Urals Mountains, Siberia and Caspian Sea. He was the one who invented the isobar and isotherm which are used today in description of climatic associations of plant communities. He had a passion for the beauty of nature. He had a good description of the physical environment together with the plant distribution that are widely used in biogeography.

Liebig:

He was born in Darmstadt, Germany. He went to Paris where was working in the laboratory of Joseph Gay-Lussac. His main interest was in chemistry. He did much in order to establish chemistry as a discipline. He started the first chemical periodical for scholars. He was the one who showed that studies like physiology, agriculture, and psychology are only intelligible if based on sound chemical principles. He was one of the contributors in discovery of isomerism (a condition where two different compounds may have the same chemical formula). He showed that organic compounds can actually be dealt with in a rational way. He once rejected the current humus theory. He showed his contrasting idea by describing that some plants will leave the soil richer in terms of carbon that they really found it. He visited England once and was not happy with the way they were setting out their sewage to the sea. He was of the opinion that they should use their sewage as a fertilizer.

William:

He collected vertebrates in many remote regions of Hispaniola between the years 1916 and 1923. He also did collections in other regions of the world like the famous Himalayas. To date, most his collections are still in Smithsonian. He is landscape ecologist and a biogeographer. He has made tremendous contributions in the understanding of landscapes and disturbances. His research in these fields has made tremendous influence on the field of biogeography and also the academic biogeographers.

MacArthur:

He came up with the MacArthur and Wilson equilibrium model on insular biogeography. This is a model that is used to provide a good foundation on the distribution of species on islands. Its also useful in explanation of the composition of insular biotas. It’s because of his model that many analyses have been made on the distributions of mammals on insular habitats.

5) Describe the relationships among the following physical factors: pressure, physiography, ocean currents, latitude, temperature, light, precipitation, and wind

Physiography is a description of the features and even phenomena of nature. Most of the physical features of the world cannot be well described unless we use other factors like temperature. Physiography stands for physical geography. What is in physical geography is all the physical features like the mountains, forests/vegetations among others. When we attempt to describer any climatic condition of a place or of a certain region, we use temperature, the level of rainfall/precipitation and the effects that winds may have on it. It therefore translates that we cannot describe most of the physical phenomena without using the other factors mentioned. They interdepend on each other for description of physical phenomena.

Ocean currents depend on pressure. They usually move from where the pressure is low to where it’s high. Wind is said to be air in motion. Air can only be in mo0tion if one region has a high pressure compared to another. Air moves from high pressure centers to low pressure centers. This is wind. It therefore means that wind can only be thee if there is difference in pressure amounts in two regions. Ocean currents are usually associated with the precipitation. They usually make the nearby areas in the ocean to receive rainfall if they are usually accompanied by high temperatures. Areas of low latitude have high temperatures while high latitude areas are generally cool. Light intensity in certain ecosystems helps the growth of specific organisms. Physiography/physical geography cannot be fully described if light intensity is not going to be applied to describe some of the conditions in some places (physical phenomena).

6) Give the Holdridge Bioclimate Classification of climate for the following places: Honolulu, Hawaii; Adelaide, Australia; Timbuktu, Mali; La Paz, Bolivia.

Timbuktu (Mali)

Class 35; according to Holdridge bioclimatic classification it is in a tropical dry forest. The climate is characterized by high temperatures all year. There is however a better developed dry season compared to the tropical rain forest. The soils are just like for the tropical rain forest. Most of the evergreen tree species become deciduous. Tree canopy is lower compared to tropical rain forest. Undergrowth is dense. There is lower species diversity. Trees have thicker back and small leaves. Roots are long and trees have thorns also. Larger mammals are more dominant

Honolulu (Hawaii)

Class 25; subtropical desert scrub with an annual climate of 24 degrees. Average temperature in a day is 29 degrees and the minimum is 21 degrees. Its humidity is moderated by its mid-ocean positioning. There is intense rainfall in the winter months though most of the winter days have warm bright sunshine. Rarely will temperatures go beyond 32 degrees.

Adelaide (Australia)

Class 30; subtropical rain forest
Generally, rainfall is more than 1300mm. there are fertile eutrophic rocks. A multi layered canopy of between 10 and 60 species of trees. Most of these trees will exhibit buttressing w2hich is a feature that is common in rain forest areas.

La Paz (Bolivia)

Class 27; subtropical dry forest

7) Define endemism. Give and explain five characteristics associated/correlated with areas of endemism

This is a situation where a plant or an animal taxon is said to be restricted in a geographical range or a particular region. Since the times of Darwin, it has been known that islands are the ones which are mostly rich in endemic species. Endemism will arise because of several mechanisms. The major one is the geographical isolation. In this geographic isolation, a small population that has a limited genetic diversity may be isolated. After several generations, the drift in genetics will lead to formation of a distinct species. A population that may arrive on a new island may fill different ecological niches. Other generations of natural selection may result in formation of distinct species. Again, a certain species that was widespread may suffer extinction. This island may now become a “refugia”. This describes the origin of the major species of Macaronesian endemic “laurels”. These are mostly found in the Mediterranean region.

Latitude:

species richness of most organisms in an endemic region increases form high temperature to low tropical latitudes. Lower latitudes have high levels of endemism.

Species richness:

The levels of species richness and those of endemism cannot be said to be infrequently correlated. Oceanic islands have high levels of endemism but will have low numbers of species.

Unusual environmental conditions:

Most endemic areas are known to have environmental conditions that are very different from other areas. There occurs independent evolution of the local adaptations. These will mostly enable the species to persist under the existing conditions.

Isolation:

Almost all areas of endemism are separated or isolated from others geographically. There are barriers to other areas such that even independent evolution is going to give rise to endemic taxa.

Historical:

In these areas there are usually changing abiotic and biotic environmental conditions. High levels of endemism may be associated with areas that have long-term ecoclimatic stability. This can even enable these populations to be able to survive global changes in climate conditions.

8) Describe the three possible tectonic plate boundaries, give an example of each and explain the possible consequences of a convergent boundary.

Divergent boundary:

It’s the soft boundary and it’s also called the spreading center. Two plates move away from each other and mid-ocean ridges will be formed. Magma from the mantle will move though a crack to the ocean and it then cols. This cooling causes the formation of oceanic crust on both sides of the vent. When the plates continue to move, more crust will be formed. The ocean basin then expands forming a ridge system. This crust formed causes the pushing of the plates on either side further. A good example of this kind of plate boundary is that of North America and Europe.

Convergent boundary:

It’s also called a subduction zone. This is a plate margin where one plate will override the other. This forces the other into beneath its mantle. They are boundaries which are in the form of trench. Old oceanic crust will go into these systems as there is new crust formed when the centers are spreading. They are usually locations of strong earthquakes as the action of the plate that is going down interacts with the overriding one. It can also be as a result of volcanic activity. A good place to be associated with it is Japan. The plate that is going down the other will continue to become even hotter. This is because of its proximity to the mantle. The plate will thus melt to form magma. This magma will move upwards through the crust and volcanoes are formed. A good example is the Aleutian Islands.

Conservative/transform boundary:

Its called conservative as there is neither creation nor destruction of plate materials at the boundaries. What usually happens here is that the plates will slide past each other. These are usually areas where there are many earthquakes. They are caused by the accumulation and release of strain when the plates slide past each other. Good examples of conservative boundaries are the San Andreas Fault in California and mid-ocean ridges, the Rockies in North America.

Possible consequences of convergent boundary:

These are areas that are earthquake prone. These earthquakes can cause a lot of deaths to human beings and animals. A good example is the 1883 eruption of Krakatau volcano of Indonesia that killed more than 37,000 people. The hot magma contains some chemical that may be harmful to the human beings and also the existing vegetation. Where these big mountains are formed after the plate boundary formation, climatic conditions may change which may not be conducive to the existing flora and fauna.