... The biodiversity of planet Earth is the total variability of life
forms. Currently about 1.9 million species are known, but this
is thought to be a significant underestimate of the total
number of species. The actual number may be as high as 50
million or more.
Latitudinal Gradients in Richness
... Temporal variation in the environment causes
higher extinction and lower speciation
A. Low latitudes, stability results in finer niche
division and lower extinction
B. High latitudes, environmental variation results
in biota that are speciation and extinction
Example Thesis Statements Remember, one useful approach to
... 1) Topic/Title: Understanding the Latitudinal Species Richness Gradient
“Divergence in species richness is attributed to a combination of seven
explanations. Together these hypotheses provide the most thorough and
complete explanation to the existence of a richness gradient for all ...
... Orbitally forced species range dynamics (Dynesius and Jansson 2000)
• Mean duration of species 1-30 my, so species have endured many
• Oscillations more severe at higher latitudes than around
equator, selecting in temperate, boreal and arctic species for
– More vagility
Chapter 10: The Geography of Diversity
... ► The Peninsula Gradient – Decreasing
diversity away form the mainland
► The Elevation Gradient – Species diversity
decreases with elevation
► The Aridity Gradient – Species diversity
decreases with diminishing water availability
► Aquatic Environments – Similar patterns
Biodiversity - Alexander College
... • A community is a group of organisms living in the same habitat
that are connected to each other by interactions, such as
feeding or energy flow.
... Ideas about how to incorporate new
technology into botanical collections
A bit of plant ecology but will also
allow you to practice identifying trees
that you will see on a daily basis.
... • Currently in a time of high biodiversity
• Estimated by 2030, 20% of species will be
• Rainforest biome contains 1/5 of the world’s
species but is quickly disappearing
Chapter 48 - Community Ecology
... commensalism and given an example of a pair of species that illustrates each.
2. Search for information on the internet on the relationship between Monarch and Viceroy
butterflies. Is this a case of Batesian or Müllerian mimicry? Explain your reasoning.
3. Explain the Competitive Exclusion Principle ...
biodiversity - Association of American Geographers
... The term biodiversity refers to the extraordinary variety of the world’s organisms, the complex patterns of their interdependence, and
the understanding that this diversity is absolutely essential to the viability of all life on the
planet. The Convention on Biological Diversity describes the concep ...
Species Diversity in Continental and Marine Habitats Questions: 1
... Animals that depend on plants will probably show comparable patterns of diversity
shown for plants in Table 15.1.
Similar latitudinal gradients demonstrated for continents are also found in the
oceans. Tropical coral reefs support the most diversity.
Ditto for freshwater systems.
What processes expl ...
... WHAT IS THE LOGISTIC GROWTH
• N/t rmaxN((K – N)/K)
• What kind of curve do we see with this?
• S curve
Divergence and constraint in the origin of new species The origin of
... The origin of new species creates biological diversity and understanding species formation is thus a
key goal in biology. In this talk, I will tackle the issue of why some populations that begin the
speciation process diverge further than others, a phenomenon central to understanding
... In addition to biodiversity hotspots, we can see some
global trends in biodiversity:
Diversity tends to be higher in the tropics than at
higher latitudes. Why?
In terrestrial habitats, diversity tends to be higher in
mountainous regions. Why?
In marine habitats, diversity tends to be higher in
Week 5a - Evergreen State College Archives
... supported by the global-scale correlation between productivity and diversity,
experimental studies refute it. Productivity alone is not a sufficient explanation for higher
diversity in the tropics, although it probably plays some role. The second hypothesis
states that the tropics contain more dive ...
The latitudinal diversity gradient
... diversification rates, measured in various taxonomic groups, is equivocal but certainly exhibited in some groups including New World birds
(Fig. 5, Cardillo et al. 2005). However it is less clear that these species
richness patterns over broad spatial scales are necessarily linked to
population size ...
CH 41 Reading Guide Communities
... 26. There are probably two key factors in latitudinal gradients. List and explain both here, and put a star next
to the one that is probably the primary cause of the latitudinal difference in biodiversity.
Latitudinal gradients in species diversity
The increase in species richness or biodiversity that occurs from the poles to the tropics, often referred to as the latitudinal diversity gradient (LDG), is one of the most widely recognized patterns in ecology. Put another way, in the present day localities at lower latitudes generally have more species than localities at higher latitudes. The LDG has been observed to varying degrees in Earth's past.Explaining the latitudinal diversity gradient is one of the great contemporary challenges of biogeography and macroecology (Willig et al. 2003, Pimm and Brown 2004, Cardillo et al. 2005). The question “What determines patterns of species diversity?” was among the 25 key research themes for the future identified in 125th Anniversary issue of Science (July 2005). There is a lack of consensus among ecologists about the mechanisms underlying the pattern, and many hypotheses have been proposed and debated. A recent review noted that among the many conundrums associated with the LDG (or LBG, Latitudinal Biodiversity Gradient) the causal relationship between rates of molecular evolution and speciation has yet to be demonstrated.Understanding the global distribution of biodiversity is one of the most significant objectives for ecologists and biogeographers. Beyond purely scientific goals and satisfying curiosity, this understanding is essential for applied issues of major concern to humankind, such as the spread of invasive species, the control of diseases and their vectors, and the likely effects of global climate change on the maintenance of biodiversity (Gaston 2000). Tropical areas play a prominent role in the understanding of the distribution of biodiversity, as their rates of habitat degradation and biodiversity loss are exceptionally high.