Chapter IV. Natural Selection
· Overview of the chapter*
· Brief statement of the main point*
· Outline*
· Quotes
*Taken from Kata's documentation
- Natural selection strives for preservation of favorable variations and rejections of injurious variations.
· Brief statement of the main point*
- Natural selection preserves more and rejects less.
· Outline*
- Natural Selection: preservation of favorable variations and rejections of injurious variations.
- 1. Modify the parent – young
- 2. Modify relationship young – parent
- 3. Adapt the structures of each individual for the benefit of the community
- Natural selection can’t modify the structure of the species without giving it advantage to other species.
- The process of modification is very slow.
- Illustrations: wolves, juice and plants (physiological division of labor)
- “Natural selection can act by the preservation and accumulation of infinitesimally small inherited modifications, each profitable to the preserved being…”
- Beings have modified in the same degree as its competitors, if not they are exterminated.
- Natural Selection does not happen at an indefinite period.
- 1. Intercrossing: it keeps individuals of the same species in a true and uniform character.
- 2. Isolation means that in an isolated area, all the species will modify in the same manner in relation to the same conditions and checks the immigration of better-adapted organisms.
- Largeness of the area.
- Divergence Character: Early differences, continued by time and natural selections, differences become greater, sub-breeds are formed, after centuries, sub-breeds become breeds.
- Principle: At first, the differences are barely noticed, then they increase and then breeds arise that are different from them and their parents.
· Quotes
- “How will the struggle for existence act in regard to variation? Can the principle of selection, which we have seen is so potent in the hands of man, apply in nature?” (page 47)
- “But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection.” (page 64)
- “Natural selection, also, leads to divergence of character; for more living beings can be supported on the same area the more they diverge in structure, habits, and constitution…the more diversified these descendants become, the better will be their chance of succeeding in the battle of life.” (page 64)
- "Natural selection leads to divergence of character and to much extinction of the less improved and intermediate forms of life.” (page 64)
*Taken from Kata's documentation
Chapter VI. Difficulties On Theory
· Overview of the chapter
In this chapter, Darwin would argument why his theory is the most probable theory among others. In order to do this, he explains why some difficulties that others have given rise from his theory are most probably not true. These difficulties are four (he only explains the first two in this chapter): 1. Gaps in the fossil record; 2. Complex structures; 3. Sterility of hybrids; and 4. Elaborate instincts.
· Brief statement of the main point
Darwin’s theory of Natural Selection is the most probable one that occurs in nature, and is the best suited to explain the differences between species.
· Outline
· Four difficulties and objections to his theory:
1. There are gaps in the fossil record (we don’t see everywhere the transitions).
2. Creation of complex structures (like the eye in the vertebrata group).
3. Modification and creation of instincts through natural selection.
4. The sterility of hybrids.
· First Difficulty: (on the absence or rarity of transitional varieties).
· Argument: he defends it by saying that the record of fossils is far less perfect than we think, so we are missing information.
· Second Difficulty: (organs of extreme perfection and complication)
· Argument: he argues that complex structures can be formed by from imperfect and simple structures by natural selection by inherited variations.
· Include: terms, phrases, examples, and mapping.
a. Terms
· Theory of “punctuated equilibria”: large-scale evolutionary changes are limited to short periods of time, interspersed with very long intervals during which not very much happens. (Stephen J. Gould)
· Theory of descent: variations are inherited and that species descent from a common ancestor (Tree of Life).
· “Natura non facit saltum”: Darwin’s claim that nature does not make a leap. He is referring to that all complex structures have transitional grades.
b. Mapping
· He states the four difficulties and objections to his theory.
· He explains the first one (on the absence or rarity of transitional varieties), and defends it.
· He explains the second difficulty (organs of extreme perfection and complication), and defends it.
· Conclusions on why nature does not make leaps.
c. Examples and Phrases
· “The crust of the earth is a vast museum; but the natural collections have been made only at intervals of time immensely remote.” (page 72)
· The eye (comparison between the eye in the Vertebrata and Articulate class)
· Comparing the eye with the telescope.
· “But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man?” (page 73-74)
· The swimbladder in fishes (purpose of floating that evolved to respiration and even as an accessory for auditory organs)
· The neuter insects
· The electric organs of fishes
In this chapter, Darwin would argument why his theory is the most probable theory among others. In order to do this, he explains why some difficulties that others have given rise from his theory are most probably not true. These difficulties are four (he only explains the first two in this chapter): 1. Gaps in the fossil record; 2. Complex structures; 3. Sterility of hybrids; and 4. Elaborate instincts.
· Brief statement of the main point
Darwin’s theory of Natural Selection is the most probable one that occurs in nature, and is the best suited to explain the differences between species.
· Outline
· Four difficulties and objections to his theory:
1. There are gaps in the fossil record (we don’t see everywhere the transitions).
2. Creation of complex structures (like the eye in the vertebrata group).
3. Modification and creation of instincts through natural selection.
4. The sterility of hybrids.
· First Difficulty: (on the absence or rarity of transitional varieties).
· Argument: he defends it by saying that the record of fossils is far less perfect than we think, so we are missing information.
· Second Difficulty: (organs of extreme perfection and complication)
· Argument: he argues that complex structures can be formed by from imperfect and simple structures by natural selection by inherited variations.
· Include: terms, phrases, examples, and mapping.
a. Terms
· Theory of “punctuated equilibria”: large-scale evolutionary changes are limited to short periods of time, interspersed with very long intervals during which not very much happens. (Stephen J. Gould)
· Theory of descent: variations are inherited and that species descent from a common ancestor (Tree of Life).
· “Natura non facit saltum”: Darwin’s claim that nature does not make a leap. He is referring to that all complex structures have transitional grades.
b. Mapping
· He states the four difficulties and objections to his theory.
· He explains the first one (on the absence or rarity of transitional varieties), and defends it.
· He explains the second difficulty (organs of extreme perfection and complication), and defends it.
· Conclusions on why nature does not make leaps.
c. Examples and Phrases
· “The crust of the earth is a vast museum; but the natural collections have been made only at intervals of time immensely remote.” (page 72)
· The eye (comparison between the eye in the Vertebrata and Articulate class)
· Comparing the eye with the telescope.
· “But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man?” (page 73-74)
· The swimbladder in fishes (purpose of floating that evolved to respiration and even as an accessory for auditory organs)
· The neuter insects
· The electric organs of fishes