Variation Under Domestication
The most important causes of variability are : the degrees of inheritance and reversion, by the laws of correlation of growth, conditions of life, and to the use and disuse.
Struggle for Existence
All organisms struggle for survival
A. Competition, if variability is always profitable, tend (variation) to profitable.
B. Natural Selection, Accepts and rejects. Struggle with same and different species.
C. Increase in geometrical ratio its number destruction and death is inevitable in each generation.
D. Climate and space, ever increase circles of complexity
Competition is always present, only the fittest survive and multiply.
A. Competition, if variability is always profitable, tend (variation) to profitable.
B. Natural Selection, Accepts and rejects. Struggle with same and different species.
C. Increase in geometrical ratio its number destruction and death is inevitable in each generation.
D. Climate and space, ever increase circles of complexity
Competition is always present, only the fittest survive and multiply.
Natural Selection
A There are two elements
The eleement of competition, and the environment.
Intercrossing: individuals breeding with one another of different species.
It is necessary (if population is small)
Too much intercrossing can blur the direction of a population's development.
Isolation
Evolve differently due to the conditions of life.
Intense competition= vigurous kinds of animals.
Divergence of Character
Natural Selection, leads to divergence of character and to much extinction of the less improved and intermediate forms of life.
Natural selection is the preservation of favourable variations and the rejection of injurious variations.
The eleement of competition, and the environment.
Intercrossing: individuals breeding with one another of different species.
It is necessary (if population is small)
Too much intercrossing can blur the direction of a population's development.
Isolation
Evolve differently due to the conditions of life.
Intense competition= vigurous kinds of animals.
Divergence of Character
Natural Selection, leads to divergence of character and to much extinction of the less improved and intermediate forms of life.
Natural selection is the preservation of favourable variations and the rejection of injurious variations.
Difficulties on Theory
On the theory of Natural Selection, we can clearly understand why she (nature) should not, for natural selection can act only by taking advantage of slight successive variations, she can never take a leap, but must advance by the shortest and slowest steps.
Geographical Distribution
Inheritance produces organisms quite like. The dissimilarity of the inhabitants of different regions may be attributed to modification through natural selection, and in a quite subordinate degree to the direct influence of different physical conditions.
The degree of dissimilarity will depend on the migration of the more dominant forms of life from one region into another having been effected with more or leess ease, at periods more or less remote, and in their action and reaction, in their mutual struggles for life, the relation of organisms to organism being.
Barriers comes into play by checking migration, time for the slow process of modification through natural selection.
The degree of dissimilarity will depend on the migration of the more dominant forms of life from one region into another having been effected with more or leess ease, at periods more or less remote, and in their action and reaction, in their mutual struggles for life, the relation of organisms to organism being.
Barriers comes into play by checking migration, time for the slow process of modification through natural selection.
Recap and Conclusion
We are always slow in admitting any grat change of which we do not see the intermediate steps.
It is so easy to hide our ignorance under such expressions as the plan of creation, unity of design, and to think that give an explanation when we only restate a fact.
When we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the smae way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen, when we then thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!
An untrodden field of inquiry will be opened, on the causes and laws of variation, on correlation of growth, on the effects of use and disuse, on the direct action of external conditions, and so forth.
And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.
....these eleborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.
These laws, taken in the largest sense, being Growth and Reproduction; Inheritance which is almost implied by reporduction, Variability from the indirect and direct action of the external conditions of life, and from use and disuse, a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows.
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one, and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and being, evolved.
It is so easy to hide our ignorance under such expressions as the plan of creation, unity of design, and to think that give an explanation when we only restate a fact.
When we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the smae way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen, when we then thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!
An untrodden field of inquiry will be opened, on the causes and laws of variation, on correlation of growth, on the effects of use and disuse, on the direct action of external conditions, and so forth.
And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.
....these eleborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.
These laws, taken in the largest sense, being Growth and Reproduction; Inheritance which is almost implied by reporduction, Variability from the indirect and direct action of the external conditions of life, and from use and disuse, a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows.
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one, and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and being, evolved.