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The biological species concept, which was first introduced by Ernst Mayr, defines a species as a population whose members have the potential to interbreed to produce viable, fertile offspring, but do not produce healthy offspring with other species.
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The basic context in which evolutionary biology works is phylogeny, a system of classification based on evolutionary relationships rather than phenotypic similarity. The central tenet of evolution is that all life is derived from a single common ancestor, and all life is therefore related
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according to the view ordinarily received, the myriads of organisms peopling this world have been created by so many distinct acts of creation. As we know nothing of the Ā«illegibleĀ» will of a Creator.
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In the first place I shall endeavour to state the laws of the distribution of existing beings, as far as our present object is concerned; in the second, that of extinct; and in the third section I shall consider how far these laws accord with the theory of allied species having a common descent.

Evolutionary Biology

Evolutionary Biology

Life on Earth is astonishingly complex. There are tens of millions of living species, or kinds of organisms. Some endangered species have just a few individual organisms, while others have quadrillions. Every individual organism is, all by itself, an extremely complicated object, with many interacting parts.

THE FOUNDATIONS OF THE ORIGIN OF SPECIES

DNA - The foundation of origin of species

Changes within a gene pool occurring from generation to generation is called microevolution. Allele frequencies in a population may change due to gene flow, genetic drift, natural selection and mutation. These are referred to as the four fundamental forces of evolution.....full story

Natural Selection & The Evidence

Natural Selection - Gene Tree

An individual organism placed under new conditions [often] sometimes varies in a small degree and in very trifling respects such as stature, fatness, sometimes colour, health, habits in animals and probably disposition. Also habits of life develope certain parts. Disuse atrophies. [Most of these slight variations tend to become hereditary.].....full story

VARIATIONS OF ORGANIC BEINGS & INSTINCTS

DNA - Variations of Beings

Most organic beings in a state of nature vary exceedingly little{218}: I put out of the case variations (as stunted plants &c., and sea-shells in brackish water{219}) which are directly the effect of external agencies and which we do not know are in the breed{220}, or are hereditary..... full story

GALLERY OF SPECIES & EVOLUTION

Human Echo System Genes Tree Dinosaurs
DNA Development of Races Darwin
Dinosaur Dinosaur Prehistoric times
prehistoric times museum dinosaur stegosaurus
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THE GEOGRAPHICAL DISTRIBUTION AFFINITIES & CLASSIFICATION

Geographical Distribution of Species

For convenience sake I shall divide this chapter into three sections. In the first place I shall endeavor to state the laws of the distribution of existing beings, as far as our present object is concerned; in the second, that of extinct; and in the third section I shall consider how far these laws accord with the theory of allied species having a common descent..... full story


MORPHOLOGICAL STRUCTURES & RUDIMENTARY ORGANS

somatoform dissociative disorders

Scarcely anything is more wonderful or has been oftener insisted on than that the organic beings in each great class, though living in the most distant climes and at periods immensely remote, though fitted to widely different ends in the economy of nature, yet all in their internal structure evince an obvious uniformity.... full story

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Evolution Girafee