Kind of

Morphological species A morphological species is a group of people that are different in appearance biont For example, we can tell chicken and duck Because they have different shaped beaks, and ducks have webbed feet. Species have been defined this way since before recorded history. Despite criticism, the concept of morphological species remains the most commonly used species concept in everyday life, and continues to play an important role in biology, especially botany.

Biological species or Isolated species The concept defines a species as a group of organisms capable or potentially capable of nurturing each other. For the study of existing higher organisms, such as mammalia , fish and Birds That's a neat way of saying it for scientists; But for those who do not reproduce sexually biont For starters, this definition is meaningless. It distinguishes between the theoretical possibility of mating and the possibility of gene flow between populations. Such as The horse and The donkey Hybridization is possible and can produce offspring, however they still belong to both species. There are two reasons for this: First, because in the wild, horses and donkeys don't usually interbreed. Second, because their combined offspring are rarely fertile. The key to defining biological species is that there is no significant relationship between two populations Genetic material Communicate. It is worth noting that some species differentiated early, but still did not produce complete reproductive isolation; Some species differentiate later, but have developed complete reproductive isolation.

Mate recognition species Defines a group of organisms capable of identifying other individuals in the population as potential mates. As with the concept of isolated species above, it applies only to organisms that reproduce sexually.

Phylogenetic species perhaps Evolutionary species perhaps The Darwen Is a group of organisms that share a common ancestor; In time and space, this lineage remains separate from other lineages. At some point in such a group of organisms, its members may diverge. As their differences become more pronounced, the two populations are considered to be separate species.

See also parthenogenesis Hit the mark microspecies And covers those that have not gone through meiosis or mitosis Resulting in each generation being genetically identical to the previous one.

Belong to... prokaryote the bacteria and archaea Speaking, because it doesn't exist Sexual reproduction , one species removed form and biochemistry The characteristics can not be greatly different, but also must be satisfied rRNA The sequence similarity is greater than 97%.

It is the basis for ordinary people to distinguish between different creatures - dogs are one, cats are another.

Scientists usually use standard Binary nomenclature (or Three-name nomenclature ) to refer to living things.

This is the only level of classification that has an empirical component, for example asserting that two animals are two species is more than just categorizing them.

The first two species Areal overlap - They occupy the same habitat. After many years of observation, it was not possible to distinguish more than two populations in the overlapping area, and these populations may have merged into one large population at a later time. Without reproductive isolation, populations cannot differentiate, and with reproductive isolation, genes cannot communicate between populations and differences cannot be erased. That's not to say that interbreeding doesn't happen at all, just that it's negligible. Usually, hybrid individuals do not reproduce as successfully as their parent purebred individuals.

The first two species Geographical isolation - They occupy different geographical areas. It is clear that reproductive isolation cannot be directly observed between two populations that are separated from each other. Nor is it usually possible to do this by experiment: even if two initial species can reproduce in captivity, it does not mean that they will mate freely in the wild, and it does not always provide much information about the evolutionary fitness of the hybrid offspring. Other experiments may yield more information: populations, for example A Whether the individuals are on the population B Is there a correct response to a recorded mating call? Sometimes, experiment Be able to Provide exact answers. For example, Isthmus of Panama The two sides are inhabited by seven groups of virtually identical shrimps ( Altheus They emerged about 3 million years ago. Until recently, they were thought to be the same seven species. But when males and females from both sides of the channel were put together, instead of mating, they fought. Even if the strait were to sink again, these populations would remain genetically isolated: so, they were divided into different species. But more often than not, observation and experimentation fail to provide definitive answers, and it is up to the experience of neighboring species to guess their relationships.

The first two species Geographical proximity - Their breeding areas are adjacent but do not overlap. This is rare, especially in temperate regions. Boundaries are usually places where habitat changes suddenly ( ecotone Such as the edge of a forest or the snow line on a mountain, but sometimes it is not obvious. Geographical proximity indicates that the two populations occupy very similar populations Ecological niche As a result, they cannot coexist in the same area. And because they do not interbreed, it is safe to say that there is a mechanism (usually behavioral) to prevent gene exchange between populations, so they should belong to different species.

There are two mixed population areas Hybridization region . Typically, there will be representatives of one or both of the 'purebred' populations, plus the offspring of the first hybrids and the opposites. The extent of resistance to gene exchange between two 'purebred' populations can be assessed by comparing the breadth of the hybridization area with the breadth of the typical dispersal area of the two populations in question. Such as Oak The distribution distance is the distance a bird or squirrel carries an acorn; Marsupial anteater The dispersal distance is about 15 km, as this is the distance that marsupial anteaters usually travel when they leave the nest in search of free territory. The narrower the hybridization area relative to the dispersal area, the less gene exchange between the two populations, and the more likely they are to continue to diverge along the evolutionary path. However, it is difficult to predict the changes of hybridization areas in the future. Whether a population with hybridization is classified as two species or one species is potentially controversial.

The population change is tapered At the poles of a population's geographic distribution, differences between typical individuals are evident, but the transition between them is gradual. For example, Northern Australia Koala bear They are smaller and lighter than their southern relatives, but there is no stark dividing line between them: koalas are larger and darker the farther south they go; Individuals in the middle are of medium size and color. Conversely, within the same geographic range, black-backed (north) and white-backed (south) Bell magpie Not transitioning from one form to another; The northern population has black back and the southern population has white back, and "pure" and hybrid types are equally common in hybrid areas. Changes in koalas are gradual (a gradual transition from north to south, with a uniform appearance in small populations), but changes in bell magpies are not gradual. In both cases, there is some uncertainty about the classification, but the majority view is that neither north nor south is sufficient to constitute a species. It is believed that the genetic exchange between the northern and southern magpies is limited enough to call them subspecies (not species); But there is a substantial north-south genetic exchange between koalas, so experts refuse to even identify them as two subspecies.