Biodiversity and Conservation 1 Flashcards
What is biodiversity or heterogeneity
Biodiversity is the term given by sociobiologist Edward Wilson, to describe the combined diversity at all levels of biological organisation.
types of diversity: genetic diversity
A single species might show high diversity at
the genetic level over its distributional range. The genetic variation
shown by the medicinal plant Rauwolfia vomitoria growing in
different Himalayan ranges might be in terms of the potency and
concentration of the active chemical (reserpine) that the plant
produces. India has more than 50,000 genetically different strains
of rice, and 1,000 varieties of mango.
types of diversity: species diversity
The diversity at the species level, for example,
the Western Ghats have a greater amphibian species diversity than
the Eastern Ghats.
types of diversity: ecological diversity
At the ecosystem level, India, for instance,
with its deserts, rain forests, mangroves, coral reefs, wetlands,
estuaries, and alpine meadows has a greater ecosystem diversity
than a Scandinavian country like Norway.
it refers to difference in entire ecosystems in terms of topography, sunlight,soil etc.
how many species have we discovered currently
According to the International Union for Conservation of Nature and
Natural Resources (IUCN) (2004), the total number of plant and animal
species described so far is slightly more than 1.5 million, but we have no
clear idea of how many species are yet to be discovered and described.
what is an estimate of the no of species in the world?
Some extreme estimates
range from 20 to 50 million, but a more conservative and scientifically
sound estimate made by Robert May places the global species diversity
at about 7 million.
For
many taxonomic groups, species inventories are more complete in
temperate than in tropical countries. Considering that an overwhelmingly
large proportion of the species waiting to be discovered are in the tropics,
biologists make a statistical comparison of the temperate-tropical species
richness of an exhaustively studied group of insects and extrapolate this
ratio to other groups of animals and plants to come up with a gross
estimate of the total number of species on earth.
explain species classification
More than 70 per cent of
all the species recorded are animals, while plants (including algae, fungi,
bryophytes, gymnosperms and angiosperms) comprise no more than 22
per cent of the total. Among animals, insects are the most species-rich
taxonomic group, making up more than 70 per cent of the total.
The number of
fungi species in the world is more than the combined total of the species
of fishes, amphibians, reptiles and mammals.
are there any figures given for the amt of bacteria?
It should be noted that these estimates do not give any figures for
prokaryotes. Biologists are not sure about how many prokaryotic species
there might be.
The problem is that conventional taxonomic methods are
not suitable for identifying microbial species and many species are simply
not culturable under laboratory conditions.
If we accept biochemical or
molecular criteria for delineating species for this group, then their diversity
alone might run into millions.
population diversity in india
Although India has only 2.4 per cent of the world’s land area, its share
of the global species diversity is an impressive 8.1 per cent. That is what
makes our country one of the 12 mega diversity countries of the world.
Nearly 45,000 species of plants and twice as many of animals have been
recorded from India.
Patterns of Biodiversity: Latitudinal gradients
- The diversity of plants and animals is
not uniform throughout the world but shows a rather uneven
distribution. For many group of animals or plants, there are
interesting patterns in diversity, the most well- known being the
latitudinal gradient in diversity. In general, species diversity
decreases as we move away from the equator towards the poles.
-With very few exceptions, tropics (latitudinal range of 23.5° N to
23.5° S) harbour more species than temperate or polar areas.
Colombia located near the equator has nearly 1,400 species of birds
while New York at 41° N has 105 species and Greenland at 71° N
only 56 species. India, with much of its land area in the tropical
latitudes, has more than 1,200 species of birds.
-A forest in a tropical region like Equador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest
of the USA.
-The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth- Scientists estimate that in these rain forests
there might be at least two million insect species waiting to be
discovered and named.
What is so special about tropics that might account for their greater biological diversity?
Ecologists and evolutionary biologists have
proposed various hypotheses; some important ones are
(a) Speciation
is generally a function of time, unlike temperate regions subjected
to frequent glaciations in the past, tropical latitudes have remained
relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification,
(b) Tropical environments,
unlike temperate ones, are less seasonal, relatively more constant
and predictable. Such constant environments promote niche
specialisation and lead to a greater species diversity and
(c) There
is more solar energy available in the tropics, which contributes to
higher productivity; this in turn might contribute indirectly to greater
diversity.
what is species area relationship
Alexander von Humboldt
observed that within a region species
richness increased with increasing
explored area, but only up to a limit.
In
fact, the relation between species richness
and area for a wide variety of taxa
(angiosperm plants, birds, bats,
freshwater fishes) turns out to be a
rectangular hyperbola (Figure13.2). On
a logarithmic scale, the relationship is a
straight line described by the equation
log S = log C + Z log A
where
S= Species richness A= Area
Z = slope of the line (regression
coefficient)
C = Y-intercept
Ecologists have discovered that the
value of Z lies in the range of 0.1 to 0.2,
regardless of the taxonomic group or the
region (whether it is the plants in Britain,
birds in California or molluscs in New York state, the slopes of the regression
line are amazingly similar). But, if you analyse the species-area
relationships among very large areas like the entire continents, you will
find that the slope of the line to be much steeper (Z values in the range
of 0.6 to 1.2). For example, for frugivorous (fruit-eating) birds and
mammals in the tropical forests of different continents, the slope is found
to be 1.15.
What do steeper slopes mean in this context?
- In graphical forms, steeper slopes means slopes which are closer to vertical
axis, or in other words they make larger angle with horizontal axis. - Steeper slopes signifies that number of species found increases faster than
the area explored in very large areas like the entire continents.
What exactly is stability for a biological community?
A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to
occasional disturbances (natural or man-made), and it must also be
resistant to invasions by alien species.
