Vestigial features are fully developed and functional in one group of organisms but reduced and function less in a similar group.
Explanation:
Vestigial structures are anatomical features such as cells, tissues or organs in an organism that are previously functional and performed some important functions in the organism but no longer serve any functions in the current form of the organism and become useless as a result of a large evolutionary change. Examples include the coccyx or the tailbone in humans, the pelvic bone of a snake, wisdom teeth in humans, nipples in human males, the wings of flightless birds such as kiwi, ostrich, etc.
Homologous features are the features that are similar in different organisms having similar embryonic origin and development and are inherited from a common ancestor that also had that feature. Also, they might have different functions. An example is the presence of four limbs in tetrapods such as crocodiles, birds, etc.
Analogous features are the features that are superficially similar in different organisms but had separate evolutionary origins i.e., different in origin, but similar in function. An example includes the wings on a fly, a moth, and a bird where the wings were developed independently as adaptations to perform the common function of flying.
Polygenic features are the traits or features that are controlled by multiple genes that are located on the same or different chromosomes and are also affected by the environment. These features do not follow Mendel’s pattern of inheritance and are represented as a range of continuous variation. Examples of polygenic traits or features include skin color, height, hair color, eye color, etc. For example, there is wide variation in the human skin color (from light to dark) and height (short or tall or somewhere in between).
Sympatry describes a species or a population that inhabit the same geographic region at the same time. In sympatric speciation, new species are evolved from a surviving ancestral species while both the species inhabit the same place at the same time i.e., in a single population, reproductive isolation occurs without geographic isolation.
An action potential is an excitatory presynaptic nerve. An EPSP (Excitatory postsynaptic potential) takes place in the dendrites of the postsynaptic nerve. This spreads passively to the axon hillock. Depolarization of this region opens voltage-gated ionic channels. Sufficient membrane depolarization to threshold opens enough to these channels to produce an action potential. Non myelinated axon; the currents associated with the action potential spread to the depolarized region of the axon. In myelinated axon; the currents associated with the action potential spread to the next Node of Ranvier. The action potential travels down the axon to the axon terminals.
