The true alligators are today represented to two species, A. mississippiensis in the southeastern United States, which can grow to 4. 24 m ( 14 ft ) and weigh 1000 lbs ( 454. 5 kg ) and the small A. sinensis in the Yangtze River, People's Republic of China, which grows to an average of 1. 5 m ( 5 ft ).

The species we see today are but the smallest part of what blind destiny has produced ...

In contrast, the multiregional hypothesis proposed that Homo genus contained only a single interconnected population like it does today ( not separate species ), and that its evolution took place worldwide continuously over the last couple million years.

Early naturalists well understood the similarities and differences of living species leading Linnaeus to develop a hierarchical classification system still in use today.

There are 41 known species of felids in the world today, all of which descended from the same ancestor.

* Plesiorycteropus, a genus containing two species of digging mammal unlike anything alive today

The group was once much larger, and, in addition to the thirteen species living today, also contains eleven extinct species in six genera.

Although the word jackal has been historically used to refer to many small-to medium-sized species of the wolf genus of mammals, Canis, today it most properly and commonly refers to three species: the black-backed jackal and the side-striped jackal of sub-Saharan Africa, and the golden jackal of northern Africa and south-central Eurasia.

Though it is often called a whale today, the Hebrew, as throughout scripture, refers to no species in particular, simply sufficing with " great fish " or " big fish " ( whales are today classified as mammals and not fish, but no such distinction was made in antiquity ).

One particular plant species, the ginkgo biloba, is perceived to have evolved at this time and still exists today as the only surviving species from its phylum.

A species of Neoceratodus lungfish existed in Lake Bungunia ( McKay & Eastburn, 1990 ); today Neoceratodus lungfish are only found in several Queensland rivers.

The Pleistocene epoch was a time of gigantism, in which most species were much larger than their descendants of today, including exceptionally large lions, hippopotamuses, mammoths, and deer.

As more accurate historic and botanical evidence comes to light, some scholars today propose that only the ' five grain species ' native to the Land of Israel can become chametz.

However, due to release of aquarium specimens and the widespread use of species of the genera Poecilia and Gambusia for mosquito control, poeciliids can today be found in all tropical and subtropical areas of the world.

There are two species: the northern ( M. angustirostris ) and southern elephant seal ( M. leonina )-the largest carnivore living today.

But perhaps the feathers served as the kinds of sexual ornaments still common in most bird species, and especially in birds such as Peacocks and Birds-of-paradise today.

Furthermore, they noted that quill knobs are almost never found in flightless bird species today, and that their presence in Velociraptor ( presumed to have been flightless due to its relatively large size and short forelimbs ) is evidence that the ancestors of dromaeosaurids could fly, making Velociraptor and other large members of this family secondarily flightless, though it is possible the large wing feathers inferred in the ancestors of Velociraptor had a purpose other than flight.

Of the many species alive today, some are highly endangered.

In a simple genus, containing only two species, it was easy to distinguish them apart with a one-word genus and a one-word specific name ; but as more species were discovered the names necessarily became longer and unwieldy, for instance Plantago foliis ovato-lanceolatus pubescen tibus, spica cylindrica, scapo tereti ( Plantain with pubescent ovate-lanceolate leaves, a cylindric spike and a terete scape ), which we know today as Plantago media.

While early ornithology was principally concerned with descriptions and distributions of species, ornithologists today seek answers to very specific questions, often using birds as models to test hypotheses or predictions based on theories.

The broadly defined family is large, with some 153 genera and 2480 species, and occurs worldwide.

Hypnozoites are found in Karyolysus lacerate and most species of Plasmodium ; transovarial transmission of parasites occurs in life cycles of Karyolysus and Babesia.

In both zones, Chagas occurs almost exclusively in rural areas, where triatomines breed and feed on the over 150 species from 24 families of domestic and wild mammals, as well as humans, that are the natural reservoirs of T. cruzi.

Its distribution within the Americas, however, is most likely restricted to the United States and Mexico, where the highest species diversity occurs.

Over 98 % of documented species are now extinct, but extinction occurs at an uneven rate.

Colour morphism occurs in the species.

This species occurs over a large range.

* The Southern Brown Kiwi, Apteryx australis, relatively common species of kiwi known from south and west parts of the South Island that occurs at most elevations.

Hybridization between some of the species occurs naturally.

Mitosis occurs only in eukaryotic cells and the process varies in different species.

Macroevolutionary studies focus on change that occurs at or above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes ( typically described as changes in allele frequencies ) within a species or population.

* Nucellar embryony ( Nu +), a form of seed reproduction that occurs in certain plant species

Vertical gene transfer is the passage of genes from parent to offspring, and horizontal ( also called lateral ) gene transfer occurs when genes jump between unrelated organisms, a common phenomenon especially in prokaryotes ; a good example of this is the acquired antibiotic resistance as a result of gene exchange between various bacteria leading to multi-drug-resistant bacterial species.

Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus ' Antechinus and bandicoots, around 1 % of all bird species, such as jacanas, insects such as honeybees, and fish such as pipefish.

Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea.

While some evolutionary biologists claim that speciation events have remained relatively constant over time, some palaeontologists such as Niles Eldredge and Stephen Jay Gould have argued that species usually remain unchanged over long stretches of time, and that speciation occurs only over relatively brief intervals, a view known as punctuated equilibrium.

Wild type ( or wildtype abbreviated wt ) refers to the phenotype of the typical form of a species as it occurs in nature.

The absence of such a division in living amphibian species may be at least partly due to the amount of respiration that occurs through the skin in such species ; thus, the blood returned to the heart through the vena cavae is, in fact, already partially oxygenated.

This is a common mode of oviposition, and most species of Culex are known for the habit, which also occurs in some other genera, such as Culiseta and Uranotaenia.

When a female reproduces without such parasitic meals, she is said to practise autogenous reproduction, as in Toxorhynchites ; otherwise, the reproduction may be termed anautogenous, as occurs in mosquito species that serve as disease vectors, particularly Anopheles and some of the most important disease vectors in the genus Aedes.

It occurs on a regular basis at a very young age, maturation, in females of certain mammal species, until menopause.

It remains controversial whether sufficient morphological and genetic divergence occurs within the genus as a result of geographical or ecological isolation to justify recognition of more than one species.

The highest concentration of large deer species in temperate Asia occurs in the mixed deciduous forests, mountain coniferous forests, and taiga bordering North Korea, Manchuria ( Northeastern China ), and the Ussuri Region ( Russia ).