Biodiversity – Nov. 21/12
- What is the range of a taxon?: It is the area of the earth where a species/genus/family
occurs/lives/occupies. It is usually tied to habitat type. Most species and often higher taxa are
adapted to particular environmental conditions and ecosystems. Most taxa have restricted ranges
that correspond to only a part of a biome, or a small part of a biome/ecosystem. Some taxa have very
broad ranges that include more than one biome/ecosystem (ex. giant swallowtail butterfly, white-
- Present day range of the seven species in the genus Apis: Apis mellifera occurs in North America and
worldwide. But it is not present in the sahara desert in northern Africa because the sahara is devoid
of plants and bees depend on plants and flowers.
- Biogeography: Is the study of the past and present distribution of the earth’s biodiversity – species
and higher taxa and ecosystems. Some questions biogeographers ask – What is the present
range/distribution of a particular species, genus, or family? Why are species (and higher taxa)
distributed in the way that they are today? What was the range/distribution of a species 100 years
ago? Is the present activity of human beings affecting the distribution of species (and if so, what
can/should be done about it)?
- Endemism: Is the state of being unique to a particular geographic location. Found only in that part of
the world and nowhere else. For example, a fish can be endemic to only one lake, an insect species
can be endemic to one mountain range, a plant family or insect genus or species can be endemic to
- The world’s zoogeographic regions: There are six regions or zones based on the observed
distribution of birds and mammals, and they are Nearctic, Neotropical, Australian, Oriental,
Ethiopian, and Palearctic. The Nearctic and Palearctic zones can be combined to form the Holarctic
zone. The range of many (but not all) animal species and higher taxa is restricted to one
zoogeographic zone. As was catalogued by Wallace, as one travels from continent to continent, there
are often large shifts in the presence and/or abundance of taxa. Some groups show substantial
endemism (they are restricted to certain continental regions). The zones almost correspond to the
- Floristic regions: Plants have a slightly different system of organization than animals. The six floristic
regions or zones are Holarctic, Neotropical, Paleotropical (Africa and Asia), South African, Australian,
and Antarctic. These are the largest natural geographic units of flowering plants (angiosperms).
These regions have a high degree of family endemism. For example, many families are restricted to
one region (the Neotropical region, or the Paleotropical region).
- How do we explain the distributions we observe today?: Climate changes that took place during the
Cenozoic era – ice ages/glaciation. Plate tectonics. Evolution – speciation and extinction. Human
- Cenozoic ice ages: There have been multiple ice ages in earth’s recent past in the Cenozoic era. An ice
age/glacial age is when there is a long-term reduction in earth’s temperature (surface and
temperature). This resulted in the presence of expansion of ice on earth’s surface. Ice took up huge
volumes of water resulting in sea level drops (+100m). Eventually temperatures rose again, some ice
melted, and sea levels rose. Over geologic time, there have been temperature changes, the presence
or absence of ice, and rising and falling of sea levels, and these have affected distributions of taxa
- Plate tectonics: Is the scientific theory which describes large scale motions of the earth’s lithosphere.
The lithosphere is the strong outermost shell and consists of the crust and uppermost part of the
mantle. The lithosphere exists as separate and distinct tectonic plates which float on the asthenosphere. The asthenosphere is the fluid, hotter, and deeper part of