Darwin & Mendel: the two sides of a biological “coin”
– behavior & inheritance.
# 1, Darwin and Mendel's legacy–“lessons about limits in another person's
eyes” – Darwin nor Mendel ever met one another.
# 2, The Tangled Bank– more
lessons of natural laws from all around us
# 3, Our Distant Past– “rocks of ages”
unseen remnants of a forgone world
About the discovery of human descent, variation and our shared ecological conditions of existence.
Background | Body | Evidence | Food Webs | Detailed Analysis | Conclusion
Unknown to one another
Darwin and Mendel discovered that variability and selection work in tandem to produce viable offspring—members
of a potentially breeding population.
Eight significant points are
the heart of the chapter, foreshadowing the book: within limits,
“descent with modification” from a common ancestor leads to
diversity over time, random
mixture generates genetic variability, immunity or
resistance, and biotic potential.
Thus this hereditary composition of a population assures our effective survival, if not breeding.
moths, birds, anoles, fruit
flies, human blood cells, eye color, and enzymes.
Conditional (surroundings) change + genetic
inheritance = descent with deviations
“it is usually very hard to select for just one
“a gene consists of a series of
nucleotides with different bases
that determine the
sequence... proteins” [with alterations = modifications = deviations]
proteins (enzymes & hormones) are life’s essential
constituents, act as arbiters of what variations are sustained, & shared molecules, carbohydrates and proteins are the threads that tie ecological systems together.
Limits | thermodynamics | evolution | eight summary points | conclusion
Limits – The laws of thermodynamics are just one example of how ecological systems have a limited capacity to sustain life for a time.
divergence and convergence
do your eye colors differ only within a limited range?
There is evidence that as many as 16 different genes could be responsible for eye color in humans; however, the main two genes associated with eye color variation are OCA2 and HERC2, and both are localized in Chromosome 15.
Descent from a common ancestor creates a contingent inheritance of colors, shape, mass, or size, as Mendel realized with his peas. He grasped in his garden, what Darwin's saw in the world: a variety of traits inherited by descendents from a common, ancestral source.
The steam engine's widespread use in the 19th century led French, German, & British investigators to study the transfer of heat from the boiling water flashed into steam inside the steam engine's boilers as this was transferred into the mechanical motion of the drive shaft and gears.
From this curiosity into the amount of heat released as mechanical motion increased the gradual discovery of three laws of thermal mechanics were articulated about the characteristic behavior of energy. this was long before anyone associated the sun's spectrum of visible light with the existence of long wave or infrared radiation, that we know today as "heat."
Three laws of
(and matter) can neither be created nor destroyed; (E) energy is constant (k)
transfer of energy is ever completely efficient; so that heat, as a loss, or entropy accumulates
the universe will have insufficient energy for life
Said another way, by Garret Hardin
are bound to lose
cannot get out of the game
descendants vary with respect to
the traits they inherit and thus what survives depends
on what was produced earlier by variable parents and grandparents.
No living thing
really evolves, but its descendants vary greatly from them & their ancestors
of that variable inheritance is passed on
all traits are passed on, but natural selection favors functional assets, or at least non-lethal traits.
in a population many traits survive
that can endow future offspring with variety
is insurance against the storm
are no guarantees of success
has the capacity to adapt to conditions that are not too extreme
time due to isolation and variation, populations give rise to new species:
on the Galapagos Islands
Eight significant points:
1. Populations change within
limits [milieu’s limits + genome’s limits]
2. Natural selection favors
some traits among very variable offspring’s genomes
3. Isolation (loss) and the
pace of change among organisms can be rapid or slow
4. Linking evolution to
genetics is the Modern synthesis and a foundation of biology
5. Artificial selection by
humans and other organisms can change other creatures (fruit flies, cows, cats
& dogs, sheep, GMOs]
6. Change in the hereditary
composition of populations over time is due to DNA and RNA’s variability and functionally replicable chemistry.
7. Genotype & phenotype act
in such a way as phenotype is
selected for as an expression of genotype [eye color in humans].
8. Changes in
a population’s genome is the raw material of evolution or shifts–alterations–in populations
of organisms over time.
The new tree of life -- the five kingdoms of three Eukaryotes organisms and their cousins the bacteria and the Archaea, or bacterial-like creatures thriving in extreme conditions.
We like all of
nature’s species are the products of variation & selection. To know truly
what limits we have & how this biological treasure we are endowed with
functions, we must unravel a complex puzzle among: the earth, ethology (behavior), ecology (surroundings), &
molecular biology (competing means of regulatory feedback). Our task is to better know the world in us!
We are the
products of the world we see around us, limited by its conditions plus our inherited
and acquired traits to wither or prosper; as we can become proper caretakers,
or unreasonable exploiters of an unimaginably expensive endowment, which I will
call life’s diversity, beauty, and integrity on an imperiled planet.
Three ecological factors:
a. Laws enabling limits and optimization
b. descent from a common ancestor
c. inherited resistance
The complexity of life's diversity is the product of evolution despite environmental resistance.
Words to know and use:
- limitations of natural selection & inheritance,
U.K. & industrial melanism,
- genotype vs. phenotype,
- diversity, diversification,
- inorganic & organic limitations,
- biotic species,
- predator – prey relations,
- Warblers’ song,
- origins & loss in descent,
- fossils, missing links,
- deep time,
- Olduwan culture,