M Database Inspector (cheetah)
Not logged in. Login

OriginOfSpecies - 475 Rows
Column Type #Values Column Stats
id int(11) 475 Column Stats
subject varchar(80) 14 Column Stats
title varchar(250) 139 Column Stats
ordinal int(11) 30 Column Stats
description text 474 Column Stats

475 rows, page 71 of 119 (4/p)
1 20 30 40 50 60 65 66 67 68 69 70 71 72 73 74 75 76 77 80 90 100 110 119

Export to Excel select * from OriginOfSpecies order by ordinal desc limit 280, 4 (Page 71: Row)
subject
title
ordinal Desending Order (top row is last)
description
04 - Natural Selection 04-04 - Its Power at All Ages and on Both Sexes 20 Natural selection will modify the structure of the young in relation to the parent, and of the parent in relation to the young.

In social animals it will adapt the structure of each individual for the benefit of the whole community, if the community profits by the selected change.

What natural selection cannot do, is to modify the structure of one species, without giving it any advantage, for the good of another species; and though statements to this effect may be found in works of natural history, I cannot find one case which will bear investigation.

A structure used only once in an animal's life, if of high importance to it, might be modified to any extent by natural selection; for instance, the great jaws possessed by certain insects, used exclusively for opening the cocoon- or the hard tip to the beak of unhatched birds, used for breaking the egg.

insect
insect

bird
bird

beak
beak

egg
egg


It has been asserted, that of the best short-beaked tumbler-pigeons a greater number perish in the egg than are able to get out of it; so that fanciers assist in the act of hatching.

Tumbler Pigeon
Tumbler Pigeon


Now if nature had to make the beak of a full-grown pigeon very short for the bird's own advantage, the process of modification would be very slow, and there would be simultaneously the most rigorous selection of all the young birds within the egg, which had the most powerful and hardest beaks, for all with weak beaks would inevitably perish; or, more delicate and more easily broken shells might be selected, the thickness of the shell being known to vary like every other structure.

It may be well here to remark that with all beings there must be much fortuitous destruction, which can have little or no influence on the course of natural selection.

For instance a vast number of eggs or seeds are annually devoured, and these could be modified through natural selection only if they varied in some manner which protected them from their enemies.

egg
egg

seeds
seeds


Yet many of these eggs or seeds would perhaps, if not destroyed, have yielded individuals better adapted to their conditions of life than any of these which happened to survive.

So again a vast number of mature animals and plants, whether or not they be the best adapted to their conditions, must be annually destroyed by accidental causes, which would not be in the least degree mitigated by certain changes of structure or constitution which would in other ways be beneficial to the species.

But let the destruction of the adults be ever so heavy, if the number which can exist in any district be not wholly kept down by such causes,- or again let the destruction of eggs or seeds be so great that only a hundredth or a thousandth part are developed,- yet of those which do survive, the best adapted individuals, supposing that there is any variability in favourable direction, will tend to propagate their kind in larger numbers than the less well adapted.

If the numbers be wholly kept down by the causes just indicated, as will often have been the case, natural selection will be powerless in certain beneficial directions; but this is no valid objection to its efficiency at other times and in other ways; for we are far from having any reason to suppose that many species ever undergo modification and improvement at the same time in the same area.
06 - Difficutiles in Theory 06-05 - Diversified Habits in the Same Species 20 As we sometimes see individuals following habits different from those proper to their species and to the other species of the same genus, we might expect that such individuals would occasionally give rise to new species, having anomalous habits, and with their structure either slightly or considerably modified from that of their type. And such instances occur in nature.

Can a more striking instance of adaptation be given than that of a woodpecker for climbing trees and seizing insects in the chinks of the bark?

Yet in North America there are woodpeckers which feed largely on fruit, and others with elongated wings which chase insects on the wing.
North America
North America

woodpecker
woodpecker

fruit
fruit

insect
insect


On the plains of La Plata, where hardly a tree grows, there is a woodpecker (Colaptes campestris) which has two toes before and two behind, a long pointed tongue, pointed tail-feathers, sufficiently stiff to support the bird in a vertical position on a post, but not so stiff as in the typical woodpeckers, and a straight strong beak.

La Plata
La Plata

Colaptes Campestris
Colaptes Campestris


The beak, however, is not so straight or so strong as in the typical woodpeckers, but it is strong enough to bore into wood.

Hence this Colaptes in all the essential parts of its structure is a woodpecker.

Even in such trifling characters as the colouring, the harsh tone of the voice, and undulatory flight, its close blood-relationship to our common woodpecker is plainly declared; yet, as I can assert, not only from my own observation, but from those of the accurate Azara, in certain large districts it does not climb trees, and it makes its nest in holes in banks!

In certain other districts, however, this same woodpecker, as Mr. Hudson states, frequents trees, and bores holes in the trunk for its nest. I may mention as another illustration of the varied habits of this genus, that a Mexican Colaptes has been described by De Saussure as boring holes into hard wood in order to lay up a store of acorns.
Mexican Jay
Mexican Jay

acorn
acorn
06 - Difficutiles in Theory 06-10 - Natura Non Facit Saltum 20 Finally then, although in many cases it is most difficult even to conjecture by what transitions organs have arrived at their present state; yet, considering how small the proportion of living and known forms is to the extinct and unknown, I have been astonished how rarely an organ can be named, towards which no transitional grade is known to lead.

It certainly is true, that new organs appearing as if created for some special purpose, rarely or never appear in any being;- as indeed is shown by that old, but somewhat exaggerated, canon in natural history of "Natura non facit saltum."

We meet with this admission in the writings of almost every experienced naturalist; or as Milne Edwards has well expressed it, Nature is prodigal in variety, but niggard in innovation.

Why, on the theory of Creation, should there be so much variety and so little real novelty? Why should all the parts and organs of many independent beings, each supposed to have been separately created for its proper place in nature, be so commonly linked together by graduated steps?

Why should not Nature take a sudden leap from structure to structure? On the theory of natural selection, we can clearly understand why she should not; for natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps.
06 - Difficutiles in Theory 06-11 - Organs of Small Importance 20 In the first place, we are much too ignorant in regard to the whole economy of any one organic being, to say what slight modifications would be of importance or not. In a former chapter I have given instances of very trifling characters, such as the down on fruit and the colour of its flesh, the colour of the skin and hair of quadrupeds, which, from being correlated with constitutional differences or from determining the attacks of insects, might assuredly be acted on by natural selection.
peach
peach

nectarine
nectarine


The tail of the giraffe looks like an artificially constructed fly-flapper; and it seems at first incredible that this could have been adapted for its present purpose by successive slight modifications, each better and better fitted, for so trifling an object as to drive away flies; yet we should pause before being too positive even in this case, for we know that the distribution and existence of cattle and other animals in South America absolutely depend on their power of resisting the attacks of insects: so that individuals which could by any means defend themselves from these small enemies, would be able to range into new pastures and thus gain a great
advantage.
giraffe
giraffe

cattle
cattle


It is not that the larger quadrupeds are actually destroyed (except in some rare cases) by flies, but they are incessantly harassed and their strength reduced, so that they are more subject to disease, or not so well enabled in a coming dearth to search for food, or to escape from beasts of prey.