According to the theory of evolution, all living things on Earth evolved from simplest to more complex forms. But if everything moved in one straight line, then where did such a variety of species and populations come from? Divergence and convergence can explain this phenomenon. In biology, these concepts denote the features and patterns of species development.
Features of evolutionary theory
The basic theory about the development of life on our planet that science supports is the theory of evolution. Its first provisions and laws were formulated in the XVII century. It implies a long natural process of changes in living organisms to a qualitatively new level.
The theory involves the development of organisms from the simplest to the most complex forms, which was accompanied by genetic mutations, adaptations, extinction, and the formation of species. The modern theory is based on the assumptions of Charles Darwin on natural selection and population genetics data on mutations, genetic drifts, changes in the frequency of alleles.
Evolution implies the presence in living organisms of a common root from which their development began. Moreover, the assumption of one or a pair of ancestors is optional. Scientists say that there could be more ancestral organisms, but they all belonged to related groups.
The main patterns along which evolution proceeded are convergence and divergence. In biology, examples and features of these processes were described by Charles Darwin. We will tell you more about what they are below.
Divergence in biology
From the Latin language the term is translated as “discrepancy” and can be used not only in relation to wildlife. Divergence in biology means the occurrence of differences in traits in organisms. At its core, this is multidirectional variability that arises from the adaptation of living beings to different conditions.
It manifests itself in a change in parts of the body or some organs and the acquisition by them of partially new functions and capabilities. Divergence in biology is a common occurrence. It appears as a result of natural selection, that is, the struggle for existence. Acquisition of traits reduces competition - each new population can occupy its ecological niche without affecting other individuals. It also occurs as a result of isolation.
Divergence can occur at the level of species, genus, family and order. With its help, for example, the class of mammals was divided into rodents, carnivores, proboscis, cetaceans, primates and other orders. They, in turn, split into smaller groups that differ in their external and internal structure.
Divergences in Biology: Examples
Divergence leads to the appearance of organisms of various structures that belong to the same systematic group. However, they still have a common foundation, the mutated parts of the body perform the same functions. For example, the ears remain ears, only in some they have become more elongated, in others rounded, the wings of some birds are short, while others are long.
A good example is the appearance of limbs in mammals. In different species, they differ depending on the mode of life and habitat. So, cats have soft pads on their paws, and primates have long and mobile fingers to grab branches, the sea lion has flippers, and the cows have hooves. Understand what divergence in biology is, using the example of whites. Butterflies of this family eat different foods at the caterpillar stage: some eat cabbage, others eat turnips, others eat beets, etc.
In plants, the divergence of characters appears in the form of leaves. In cacti, they became thorns; in barberry, needles developed. Divergence is also traced at the level of the root system. Some plants have sucker roots, for potatoes they are tubers, for beets and carrots they have added thickness and turned into root crops.
Convergence
If divergence is characteristic of related organisms, then convergence, on the contrary, is observed in distant groups. It manifests itself in the similarity of characters in systematically different organisms. Like divergence, it appeared as a result of natural selection, but in this case it is directed identically in different species, orders, etc.
Animals or plants that belong to completely different classes acquire organs of the same structure and function. This is due to the general habitat or the similarity of lifestyle. But their similarity does not apply to the whole body, convergence affects only those organs that are necessary for adaptation to certain conditions.
So, animals that move through the air have wings. But some may relate to insects, while others - to vertebrates. Organisms living in water have a streamlined body shape, although they are not necessarily related to each other.
Convergence Examples
The body shape of dolphins, whales and fish is a typical convergence. Due to their outward resemblance to sharks, whales and dolphins were initially classified as fish. It was later proved that they are mammals, since they breathe lightly, are born by live birth and have a number of other signs.
An example of convergence is the wings of bats, birds, and insects. The presence of these organs is associated with the way of life of animals that move through flight. In this case, the type and structure of the wings in them are significantly different.
Another example is the presence of gills in fish and mollusks. Sometimes convergence is manifested in the absence of any organs. For example, wingless butterflies, flies and other insects live on some volcanic islands.