Ehrlich on the discoveries of Darwin and Mendel
Biota “do not remain static in the face of environmental change.”
(p.10)
Nine main ideas are summarized.
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First. Population evolving
a. Pitcher plants and mosquitoes
b. Larvae and length of day for hibernation & awakening
Second. Darwin and Wallace’s Great Idea
a. Natural selection
b. Malthus on differential survival
i. "struggle for existence"
ii. "favourable variations"
iii. "Survival of the fortunate" (survival of the fittest was Herbert Spencer's term.)
Third. Islands in Time
a. Descent with modification + much extinction = varied traits among survivor populations
b. tragic consequences of selection in island rails
i. birds can evolve fast too – Grant’s study
ii. Bahamian island Anoles and predation
For more details see chapter 2.
Fourth. The Modern Synthesis
a. Conditional change + genetic inheritance (particulate materiality, chromosomes)
b. Industrial melanism and the peppered moths, 50 years
c. “raised the frequency of some genes in the population.” P. 20
Fifth. Artificial Selection (“have been changed by recent human activities. P. 20)
a. Fruit fly resistance to DDT and “higher fitness”
b. “it is usually very hard to select for just one characteristic.”
Sixth. Evolution in Human beings
a. “change in the hereditary composition of populations.” P. 22
b. erythrocyte (red blood cell) variability in humans
i. sickle cell recessive inheritance & malaria parasites
ii. human resistance to famine and the new situation of food abundance
For further details see chapter 3.
Seventh. What Genes (segments of molecules. . . DNA [p.27.]) Do
a. “linkage” makes it “difficult for selection to do only one thing.”
b. Genotype is not the same as phenotype (appearances)
i. Brown eyes are due to two different genotypes
ii. “the total number of genes is not tied to the complexity of organisms.” P. 27
iii. “a gene consists of a series of nucleotides with different bases that determine the sequence... proteins” p. 28
For further details see chapter 4.
Eighth. Environment: Evolutionary Partner of the Gene
a. Changes in the genomes in a population
b. “overuse of antibiotics has caused rampant antibiotic resistance in bacteria.” P. 30
c. “reproduction leads to random changes” (cross-over in meiosis) p. 30
d. “genetic variation is the raw material of evolution.” P. 31
For further details see chapter 9.
Ninth. The Evolution Explosion ( summary )
a. New techniques of molecular genetics
b. “complex lock and key systems can evolve...”
i. Joe Thornton: steroid hormones + receptors (evidence)
ii. “evolution is the foundation of all biology.” (2005-1973)
c. “an explanatory framework that has been exhaustively tested and can be used for making predictions.” P. 33
d. Darwin’s closing remarks “contemplate an entangled bank”
i. “dependent on each other in so complex a manner”
ii. “produced by laws acting around us...”
iii. “divergence of character and extinction of less-improved forms”
iv. “There is a grandeur in this view of life”
v. “from so simple a beginning endless forms...are being evolved.” p. 34.
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The Ehrlich’s presentation is based on their belief as expressed in this key chapter is grounded in the essential pieces of a complex puzzle. Like four dimensional chess, the four factors produce unanticipated changes in populations due to interacting forces among ethology, ecology, epigenesis, and molecular biology. *note.
They, as environmental scientists, express the simpler perspective of inheritance versus ecological change; or genetic variability (Mendel’s legacy) encountering changes in the surroundings (Darwin’s legacy) that have an impact on the survival rate of different (and variable populations) offspring. These legacies are also called biological potential versus environmental resistance.
The two lenses in the glasses symbolize environmental and inheritable (genetic) factors shaping nature.
But clearly the behavioral (ethology) role is a crucial mediator in the body of knowledge that reveals how surroundings (ecology) impact the sorts of creatures (molecular biology that reveals organism’s genetic [genotype & phenotype] endowment or genome) that are able to reproduce their offspring in sufficient numbers to repopulate their range.
The story is one drawn from Darwin, Wallace, Malthus, Mendel, and others who were since 1836 capable of seeing the natural world in a significantly new light: a paradigm shift in the biological, behavioral and social sciences. The ingredients are particulate heritable molecules & they combine with proteins, DNA and catalysts as an assembly of molecules called genomes.
That new light (sensibility), shedding understanding on biology, consisted of
1. Fathoming several kinds and rates of change (ours is not a static world)
a. Geological (climatic shifts)
b. Inherited (genetic variability, immunity, & instinctual behavior)
c. Acquired (appetites, learned behavior, “fitness” or adaptive traits)2. A redefinition of organisms as variant members of a breeding population
3. A profound role of chance (random variation) or stochastic transformation over time
4. Differential survival rates among members of the same and different populations leads to divergence and variability becomes more pronounced.
5. Complexity of inheritance as a form of selection (natural, sexual, artificial)
6. Recognizing the milieu of life is made of: two–never having lived, living, and dying–parts called an ecological system.
The Ehrlichs equate predictive concepts in science as definitive theories by linking heliocentric beliefs of Copernicus with biological laws of variation, inheritance, and evolutionary change by means of natural selection as discovered by Darwin, Wallace, and Mendel.
The view of contemporary biology is radically different from any previous concepts about this planet's native conditions and subsequent changes life has created and adjusted to over the extremely long period of time that life has coexisted on Earth.
Tie this idea to E. O. Wilson's Storm over the Amazon.
Students must be able to present examples of the tension between environmental and inheritable rates of change in the behavior of and adaptation for creatures to sustain abrupt change.
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Meanings:
ethology, the study of behavior in organisms and the physiochemical change and cognition that accompanies stimulus and response to new or familiar conditions.
ecology, the relation of an organism or species to its conditions: alive and inanimate.
epigenesis, the reaction of RNA and DNA to the chemicals in the cell or surroundings and
molecular biology, the actual chemistry of life, organic molecules, atomic elements.
stochastic, means proceeding by chance, any association of non-determined events, sporadic or clearly not intermittent occurrences.
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