Global Biodiversity
Encyclopedia
The biodiversity
of planet Earth is the total variability of life forms forms. Currently about 1.9 million species are known, but this is thought to be a significant underestimate of the total number of species.
Biodiversity has grown and shrunk in earth's past due to changes abiotic factors such as mass extinction, change in oxygen levels and sea levels. Climate change 300 million years ago was one such event. A cooling and drying resulted in catastrophic rainforest collapse and subsequently a great loss of diversity, especially of amphibians.
Current threats to global biodiversity include natural extinction
, an event that occurs to species
yearly, as well as human
actions such as pollution
. Invasion of non-native species can also have a negative affect on global biodiversity.
Taxonomic diversity, that is the number of species, genera, family is the most commonly assessed diversity type. A few studies have attempted to quantitatively clarify the relationship between different types of diversity. For example, Sarda Sahney a researcher at the University of Bristol has found a close link between vertebrate taxonomic and ecological diversity.
The numbers of identified modern species as of 2010 can be broken down as follows:
One early estimate by Terry Erwin
put global species richness at 30 million, following extrapolations from the numbers of beetles found in a species of tropical tree. In one species of tree, Erwin identified 1200 species of beetle, of which he estimated 163 were found only in that tree. Based on the 50,000 species of tropical tree, this would suggest that there are almost 10 million species of beetle in the tropics.
It is interesting to mention that according to the school of Indian philosophy known as(Vedanta
) there are 8.4 million types of living beings on earth. This statement was made more than 1000 years ago.
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
of planet Earth is the total variability of life forms forms. Currently about 1.9 million species are known, but this is thought to be a significant underestimate of the total number of species.
Biodiversity has grown and shrunk in earth's past due to changes abiotic factors such as mass extinction, change in oxygen levels and sea levels. Climate change 300 million years ago was one such event. A cooling and drying resulted in catastrophic rainforest collapse and subsequently a great loss of diversity, especially of amphibians.
Current threats to global biodiversity include natural extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
, an event that occurs to species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
yearly, as well as human
Human
Humans are the only living species in the Homo genus...
actions such as pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
. Invasion of non-native species can also have a negative affect on global biodiversity.
Measuring Diversity
Biodiversity is usually plotted as the richness of a geographic area, with some reference to a temporal scale. Types of biodiversity include:- taxonomic diversity
- species diversitySpecies diversitySpecies diversity is an index that incorporates the number of species in an area and also their relative abundance. It is a more comprehensive value than species richness....
- ecological diversity
- morphological diversity
- genetic diversityGenetic diversityGenetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
Taxonomic diversity, that is the number of species, genera, family is the most commonly assessed diversity type. A few studies have attempted to quantitatively clarify the relationship between different types of diversity. For example, Sarda Sahney a researcher at the University of Bristol has found a close link between vertebrate taxonomic and ecological diversity.
Known species
- 3,067 brown algae
- 321,212 plantPlantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, including:- 10,134 red & greenChlorophytaChlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...
algae - 16,236 mossMossMosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es, - 12,000 fernFernA fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s & horsetailHorsetailEquisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...
s, - 1,021 gymnospermGymnospermThe gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...
s, - 281,821 angiosperms;
- 10,134 red & green
- 74,000-120,000 fungi;
- 17,000 lichenLichenLichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s; - 1,367,555 animalAnimalAnimals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s, including:- 1,305,250 invertebrates
- 2,175 corals
- 85,000 mollusks
- 102,248 arachnids
- 47,000 crustaceans
- 1,000,000 insects
- 62,305 vertebrates
- 31,300 fishFishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, - 6,433 amphibianAmphibianAmphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s, - 9,084 reptileReptileReptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s, - 9,998 birdBirdBirds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, - 5,490 mammalMammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s.
- 31,300 fish
- 68,827 other animal species;
- 1,305,250 invertebrates
Estimates of total number of species
However the total number of species for some taxa may be much higher.- 10-30 million insectInsectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s; - 5-10 million bacteriaBacteriaBacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
; - 1.5 million fungi;
- ~1 million miteMiteMites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s
One early estimate by Terry Erwin
Terry Erwin
Terry L. Erwin is an entomologist with the Smithsonian Institution.Erwin is notable for his controversial estimate of 30 million as the total number of species....
put global species richness at 30 million, following extrapolations from the numbers of beetles found in a species of tropical tree. In one species of tree, Erwin identified 1200 species of beetle, of which he estimated 163 were found only in that tree. Based on the 50,000 species of tropical tree, this would suggest that there are almost 10 million species of beetle in the tropics.
It is interesting to mention that according to the school of Indian philosophy known as(Vedanta
Vedanta
Vedānta was originally a word used in Hindu philosophy as a synonym for that part of the Veda texts known also as the Upanishads. The name is a morphophonological form of Veda-anta = "Veda-end" = "the appendix to the Vedic hymns." It is also speculated that "Vedānta" means "the purpose or goal...
) there are 8.4 million types of living beings on earth. This statement was made more than 1000 years ago.