" ADAPTATION" can be a confusing term because of the many ways it is used. For example, "adaptation" can refer to both processes and products: (1) a "developmental" change such as that of a sense organ that make it less responsive to repetitive but irrelevant stimuli, or (2) an evolutionary change such as those caused by selection pressures on some attribute of a trait that helps the organism cope with a changing environment over the generations, or (3) a biological TRAIT that exists because it confers or is linked to a trait that now (or in the past) has conferred a biological advantage enhancing an organism's
FITNESS.
Evolution generally refers to any process of change over time. In the context of life science , evolution is a change in the genetic makeup of a population of interbreeding individuals within a species . Since the emergence of modern genetics in the 1940s , evolution has been defined more specifically as a change in the frequency of alleles from one generation to the next.
The word "evolution" is often used as a shorthand for the modern theory of evolution of species based upon Charles Darwin 's theory of natural selection , which states that modern species are the products of an extensive process that began over three billion years ago with simple singlecelled organisms , and
Gregor Mendel 's theory of genetics .
As the theory of evolution by natural selection and genetics has become nearly universally accepted in the scientific community, it has replaced other explanations including creationism and Lamarckism .
Skeptics, often creationists, sometimes deride evolution as "just a theory" in an attempt to characterize it as an arbitrary choice and degrade its claims to reality. Such criticism overlooks the scientificallyaccepted use of the word "theory" to mean a falsifiable and well-supported hypothesis .

Natural selection Definition A process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency , and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations .
Supplement It is the process by which heritable traits that increase an organism’s chances of survival and reproduction are favoured than less beneficial traits . Originally proposed by Charles Darwin, natural selection is the process that results in the evolution of organism.
Phylogeny Definition noun, plural: phylogenies (1) The evolutionary history of a taxonomic group of organisms. (2) The evolutionary development of a species or of a taxonomic group of organisms. (3) The history of development of a tribe or racial group. Supplement Word origin: Ancient Greek phylon (tribe)
+ geneia (producing). Related forms: phylogenetic (adjective)

Homologous structure Having similar structure and anatomical position (but not necessarily the same function) in different organisms suggesting a common ancestry or evolutionary origin
(e.g. wings of bats and arms of humans are homologous).
Analogous Structures Corresponding in function but not in evolutionary origin ;Analogous structures are similar or resembling in certain respects, e.g. in function or in appearance but not in evolutionary origin or developmental origin. An example is wings of a butterfly and wings of a hummingbird are analogous .

Embryology (Science: study) The study of the embryo and its development from a single-celled zygote (fertilized ovum) to the establishment of form and shape (at which point, if it is an animal, it becomes a foetus). a subfield of developmental biology. The branch of biology that studies the formation and early development of living organisms.The study of embryos and related factors.
Vestigial refers to an organ or part (for example, the human appendix ) which is greatly reduced from the original ancestral form and is no longer functional or is of reduced or altered function. Vestigial structures provide a clue to the evolutionary history of a species because they are remnants of structures found in the ancestral species.

Fossil (1) Any preserved evidence of life from a past geological age, such as the impressions and remains of organisms embedded in stratified rocks . (2) The mineralized remains of an animal or plant .
Having the characteristic, or pertaining to the nature, of a fossil. Fossils include shells , imprints, burrows , coprolites and organically-produced chemicals. The oldest fossils were bacteria that existed 3.8 billion years old. Fossils are once thought of to be all from extinct species until some were found to belong to species that are still living.
DNA Sequence A double-stranded nucleic acid that contains the genetic information for cell growth , division , and function . Structure: DNA is composed of two strands that twist together to form a helix .
Each strand consists of alternating phosphate (PO4) and pentose sugar (2-deoxyribose), and attached on the sugar is a nitrogenous base , which can be adenine , thymine , guanine , or cytosine . In DNA, these bases pair; adenine pairs with thymine and guanine with cytosine . Hence, DNA is a ladder-like helical structure. Location: DNA is found in the cytoplasm of prokaryotic cells , and chiefly in the nucleus of eukaryotic cells . A small fraction of total DNA is present in mitochondria and chloroplasts . Function: DNA is a long polymer of nucleotides to code for the sequence of amino acid during protein synthesis . DNA is said to carry the genetic ‘blueprint’ since it contains the instructions or information (called genes ) needed to construct cellular components like proteins and RNA molecules .

Anatomical Similarities There are many forms of evidence for evolution . One of the strongest forms of evidence is comparative anatomy ; comparing structural similarities of organisms to determine their evolutionary relationships . Organisms with similar anatomical features are assumed to be relatively closely related evolutionarily, and they are assumed to share a common ancestor . As a result of the study of evolutionary relationships, anatomical similarities and differences are important factors in determining and establishing classification of organisms.

P
hysiological Similarities between different species of plants or animals. Comparative anatomy, which is the study of physiological similarities, is the source of most traditional evidence for evolution and common descent. Anatomical homologies continue to provide many examples of deep relationships between species which are best or only explained through evolutionary theory when the similarities simply don't make sense from a functional perspective.