must suppose that when the Author
of Nature creates an animal or plant, all the possible circumstances in
which its descendants are destined to live are foreseen, and that an
organization is conferred upon it which will enable the species to
perpetuate itself and survive under all the varying circumstances to
which it must be inevitably exposed."
|"Why should the enlightened
Christian, who has a correct idea of the firm foundation on which the
Bible rests, fear that any disclosures of the arcana of nature should
shake its authority or weaken its influence? Is not the God of
revelation the God of nature also?"
Trilobites appear in the early Cambrian era, the oldest stratum of "visible" hard-shelled fossils (the Phanerozoic eon, beginning about 545 Ma). They first appear as complete, fully-developed arthropods. They are unique among the Arthropods in that the body plan consists of 3-lobed segments (hence the name), but otherwise they have features similar to modern Crustaceans.
Perhaps trilobites are the most famous of the early fossils. They first show up as fully formed complex fossils in the early Cambrian Era (521 Ma) and become extinct in the Permian Era (251 Ma) in a clataclysmic extinction that marks the end of the Palaeozoic Age, after about 300 million years. Thus the abundant and very long trilobite fossil record is an opportunity to observe the great range of species changes that can occur over a very long time[FOOTNOTE: For illustration of the changes, see S.M. Gon III, Evolutionary Trends in Trilobites].
Evidence for Evolutionary Development. If one assumes that the observable changes in trilobite species over the 300 My of the fossil record amount to an extended example of Evo-Devo[FOOTNOTE: Evo-Devo attributes evolutionary change to changes in gene expression of a limited number of highly conserved genes. The gene expression is controlled by homeobox (hox) genes (also conserved, although not so highly as the gene packages) combined with development parameters that are recorded in the portions of DNA that do not code for genes] (which I do), then this long record gives a good opportunity to examine the implications of such potential for change, and is a good example of how the Silent Speech of Psalm 19 is woven into the natural world. Of course it is not possible to study this development at the genetic level on trilibotes themselves, but it should still be possible to reduce the observed changes into plausible hypotheses that can be tested in the laboratory using living species.
Recent work in Evo-Devo implies that most animal species -- extending back to the first appearance in the Cambrian era -- use a small packages of genes in the development of eyes and appendages (and, I suspect, many other major systems). These gene packages are virtually identical across a broad swath of species within and across many radically different body plans (phyla). The differing end results are the result of homeobox (hox) gene expression, which follow instructions contained in portions of the DNA that do not code for genes. Apparently, the instructions are subject to some natural variation, and the variations can be passed to future generations. The beneficial (or neutral) variations tend over time to survive and the unbeneficial variations tend to die out. These give rise over time to different families, genera and species[FOOTNOTE: The use of DNA profiling to identify individuals is based on variations between individuals in non-coding portions (so-called "junk" dna)].
A surprising conclusion of Evo-Devo work is that many animal features that appear to be quite different, in fact are at root different expressions of the same underlying gene packages: such as, for example, compound eyes and simple eyes, and even focusing and non-focusing eyes. The trilobites display a broad variety of eyes over their long history, and these appear (I assume) to be the accumulation of small variations in gene expression of the basic (and largely unchanging) gene package for eye development. For example, at another place I argue that computer simulation might be able to investigate testable hypotheses that emulate the evolution of the trilobite eye from a conical shape (the holochroal eye) to the bi-layered elliptical or spherical shape (the schizochroal eye) -- a case, I believe, of paedomorphosis.
Life Cycle. Most trilobite fossils are trilobite molts. Trilobites molt repeatedly nearly from the time they hatch, which shows how they grow and mature. Thus the fossil record provides abundant documentation of the growth and molting process.
Soft-body parts. Normally, details of soft-body parts are not preserved in fossils. Discovery of pyritized trilobites provides another example of the Silent Speech. By a miraculous preservation, some trilobites discovered near Rome, New York (and a few other places globally) have had the hard and soft-body parts replaced by finely crystaline pyrite (FeS2) (commonly known as fool’s gold because of its golden color). They display finely detailed external appendages and gills. X-rays reveal details of soft tissue -- muscular, digestive, nervous and circulatory systems. As a result of this providential gift, much is known about trilobite anatomy despite the fact that they have been extinct for 250 million years (Figure ??)[FOOTNOTE: Rolf Ludvigsen, Fossils of Ontario Part 1: the Trilobites, Royal Ontario Museum, 1979, pg. 22. Also see various internet discussions of pyritized trilobites.].
anticipatory gene packages (these, molluscs, insects), hox gene scheme
appendage package: antennae, jointed legs, gills, senses (touch, ???)
flexible dev't -- not yet specialized (cf remarks by ??? about pattern of specialization in fossil record).
[cf rmk by Gon] Begin general, develop to special. GET WUOTE
changes over the 200 My of existence: number, location (some on stalks) & type of compound eyes.
appendages - jointed legs, claws, antennae (appear to be genetically controlled by similar gene package)
respiration - gills
vision - compound eyes (change over the existence)
senses: vision, smell, touch, hearing?,
nervous - ganglia, primitive brain?
primitive digestive system - lack chewing parts, proper stomach, etc.
I believe the Creator left this fossil record so that we could learn how much variation natural processes generate. As time passes, I believe that many details will be filled into the narrative. Already scientists are discovering something about the range of possibilities in the formation, location and type of eyes and the various appendages (antennae, legs).
It is useful to keep in mind that the distance between species may not be so close to appearance as might be thought. The maturation of a species is a complicated function of the gene pool and the gene expression (gene regulation). Laboratory experiments demonstrate that very small changes can result in radically different expression. For example, two trilobite species with radically different numbers of compound eyes (say, 500 or 5000) may not in fact be very far apart genetically: it boils down not to radically different genetic code, but to a difference in when the genetic expression was "turned off." An analogy would be in the difference between a faucet producing a cup of water and a bucket of water: we are not talking about radically different faucets, but just when the faucet was turned off. On the other hand, the difference between a cup of water and an ocean of water is probably a radical difference.
Common Animal Phyla Originating in the Cambrian Explosion (~542-530 Ma)The Phyla designations listed here are in approximate order of complexity.*
Animal Body Systems1. Regulatory
a. Body topography - orientation, symmetry, segmentation, etc.2. Digestion
b. Body parts -- appendages, defenses (stingers, claws, etc.)
c. Glands (skin) etc.
d. Life cycle
a. Gastrovascular cavity -- one opening3. Respiration - intake of oxygen, release of carbon dioxide
b. Digestive tract (gut) -- two openings (mouth for food intake, coelom for digestion, anus for elimination)
a. Diffusion across moist surfaces (earthworm)4. Circulation - transport of oxygen and nutrients throughout the body
b. Gills in aquatic animals
c. Lungs in terrestrial animals
a. Open circulatory system -- some vessels; body cavity is "washed" with blood and lymph5. Muscular
b. Closed circulatory system -- blood enclosed in vessels, capillaries deliver to organs, recycled to heart.
6. Nervous system -- coordinate activities of the body
a. Neurons -- nerve cells that send impulses7. Sensory systems -- (part of nervous system?)
b. Nerve net -- network of neurons, very little coordination
c. Ganglia -- clusters of neurons (simple brain)
d. Brain -- sensory structures and neutrons located at anterior end, complex coordination and behavior.
a. Sight8. Support -- maintain body shape and support, aid in locomotion
sensory pitsd. Taste
a. Hydrostatic skeleton -- water pressure (jellyfish, worms)9. Reproductive (Genital)
b. Exoskeleton -- outside skeleton (insects, crabs)
c. Endoskeleton -- internal skeleton (vertebrates)
a. Asexual -- reproduction of offspring from one parent. Offspring are idenical
(1). Regeneration -- fragmentation and regrowth (sponges)b. Sexual -- reproduction by mating egg and sperm. One or two parents.
(2). Budding -- growth and release of a clone (hydras)
(3). Parthenogenesis (rare) -- individual develops from unfertilized egg
(1). Hermaphrodite -- single parent produces both egg and sperm (earthworm)
(2). External fertilization -- sperm and egg released into water.
(3). Internal fertilization -- sperm and egg mate within the female body.
a. External (eggs, etc.)
Internal Structure of Eukaryotes during cell divisionThere are two forms of cell division.
A mitotic spindle separates the chromosomes of a eukaryotic cell during cell division. The spindle is formed of microtubules.
The internal structure of eukaryotes ...s.
Cell Division -- Mitosis. The mitotic spindle, made up of microtubules, forms during cell division.
When cells divide a-sexually, the chromosomes appear to be pulled apart
Internal Structure of Eukaryotes:
The internal structure of
... Of course the science was unknown in his day, but the following observation fits right into the theory (and capsulizes my principle objection to evolution as it is usually presented).
Lyell's point, translated into modern terms, is even more powerful: that the only evolution that is observed in the fossil record can be expressed in terms of evolutionary development. "Substitutions of a new sense, faculty or organ" simply does not occur. Evo-devo may produce remarkable divergences, but they develop from a common, conserved package of genes. Totally new gene packages represent a quite different and higher level of achievement, and (arguably) simply do not arise.
The Cnidaria are relatively simple animals -- they have few of the body parts of higher animals. But a defining feature of the phylum is the presence of stingers (nematocysts) used for food-gathering and other tasks. The nematocysts are complex marvels of engineering sophistication.
The Cnidaria are relatively simple animals -- they have few of the body parts of higher animals -- no enclosed digestive tract, nerve network, circulatory system, vision, skeletal structure, or appendages to aid in movement -- but they have a means of communication to coordinate actions. They are radially symmetric and digest food in an open interior sac. The phylum includes corals and jellyfish (= medusas).They are soft-bodied, but corals secrete calcium carbonates that form the hard coral reefs that house millions of individual animals. A few corals show up in the Cambrian era (520 Ma) , but become abundant about 100 My later, in the Ordovician era . The modern corals date from the Devonian era (about 240 Ma).
There are a large variety of nematocysts, which may even vary geographically for the same or similar species. This implies that there is a robust evolutionary mechanism at work which supports variability around a basic gene package. I conjecture that this evolutionary variation occurs primarily in the parameters of gene expression.
The geologist Buckland once marvelled at the exquisite attention to engineering detail that is revealed in ancient fossils.
Our own fascination is with the Cnidarians - Phylum A-4, which includes corals and medusas. All species in this phylum are radially symmetric and have stingers, called nematocytes. The cnidarians are (relatively) immobile, and gather food with stingers which inject neuro-poisons (hypnotoxin) to immobilize their victims.
The nematocysts have been called the "most complex organelles of animal cells[FOOTNOTE: Stefan Berking & Klaus Herrmann, Formation and dischare of nematocysts, (2005) ]." They are small -- about the size of an average bacterium (up to 60 µm in length).
A cnidarian may have many thousands of these nematocysts with various specialized functions. When fully mature they appear able to function somewhat independently of the host. Some species eat cnidarians and preserve immature nematocysts (called "kleptocnidae") for their own defensive use[FOOTNOTE: "Certain types of sea slugs, such as the nudibranch aeolids, are known to undergo kleptocnidae (in addition to kleptoplasty), whereby the organisms store nematocysts of digested prey at the tips of their cerata." http://www.answers.com/topic/nematocyst].
The engineering challenges are as follows[FOOTNOTE: Following Fautin and Shimek]:
• The cell wall is super-strong, to resist extreme pressure without bursting. One scientist estimated that "the tip of the nematocyst thread is forced out of the capsule [by hydrolic pressure, although some authors assert that electrical repulsion initiates the explosion - dcb] at the astounding acceleration of 40,000g!" This is over 30 times the water pressure at the deepest part of the ocean (16,000 psi ~ 1,100 atm) and is strong enough to penetrate almost any biological structure, including shells and exoskeletons[FOOTNOTE: Shimek, ibid.]. Despite this, water can pass through the cell wall.
• A hollow tube is tightly coiled under tension inside the cell, which leads to the question: how does the coil get packed into the cell? (An analogous packing problem exists for packing of viral dna inside its capsule). This tube is packed inside-out with barbs along the inner surface (which will be the outer surface once the tube is discharged). The venom may be stored in the tube[CHECK].
• The propulsion is provided by a concentrate of calcium ions that are stored in a water-tight sac. When the cyst is triggered, these ions rush into the cell, and immediately cause a severe osmotic imbalance so that water rushes into the cell, swelling it rapidly to the point of explosion directed through the lid. The hollow piercing barb penetrates the victim's skin; the coiled tube passes through the tube and poison is ejected through the tip of the tube or through the tube wall.[GET REFS -- is this consistent with Fig below??]
• The activation time is the fastest in the animal kingdom: the entire process is complete in 3 ms[FOOTNOTE: Berking, ibid. Also Kurz, et. al., Mini-Collagens in Hydra Nematocytes, (1991): "The explosive discharge of cnidarian nematocysts is one of the fastest and most spectacular events in biology. High speed cinematographical analysis has shown that the whole exocytotic process takes <3 ms (Holstein and Tardent 1984)."]. Electric triggering causes the cell volume to increase by 10%, which opens the lid, and the dart ejects in a few µs, propelled by hydrostatic (osmotic) pressure."
• The triggering mechanism is generally a combination of mechanical and chemical response, so that discharge occurs when the trigger is touched by the right prey[FOOTNOTE: REF??]. Either mechanical or chemical response alone is not sufficient.[GET REF]
At present, the details of the nematocyst's life cycle are uncertain. Figure ?? summarizes one current view (expressed in general terms with some details missing). Ultimately, of course, every detail must be explained in terms of ordinary chemistry, but many questions remain.
There does not appear to be full concensus on the details of the discharge mechanism -- how the remarkably rapic high pressure impulse is created. The wikipedia article credits "a large concentration of calcium ions"; the above references assume electrical repulsion and osmotic pressure; other discussions assume a role for spring tension in the coil. It seems fair to conclude that this is still an unsettled question.
Similarly the storage of the toxins, or how it enters the victim does not appear to be fully settled.
is to fossils alone that must
attributed the birth of the theory of the earth; that, without them we
never have surmised that there were successive epochs in the formation
globe, and a series of different operations. Indeed, they alone prove
globe has not always had the same crust, by the certainty of the fact
must have existed at the surface before they were buried in the depths
they are now found. It is only by analogy that we extend to primitive
formations that conclusion which fossils enable us definitively to
secondary formations; and if there were only formations without
fossils, no one
could prove that these formations were not simultaneously produced.
is to fossils, small as has been our acquaintance with them, that we
little knowledge we have attained respecting the nature of the
the globe. They have taught us, that the layers which comprise them
undisturbedly deposited in a liquid; that their alterations have
with those of the liquid; that their exposure was occasioned by the
this liquid; that these exposures have taken place more than once. None
these facts could have been decided on without these fossils."
There were a number of major extinctions of animal and plant life over the nearly 3.5 billion year fossil record.
In my view these extinctions were part of God's plan, and in effect "cleared the deck" for the subsequent creation.
Fossil Record of Plant DevelopmentAll plants develop from embryos and are multi-cellular eukaryotes[FOOTNOTE: Margullis, Kingdoms and Domain, p. 413].