The Diversity of Life
The Diversity of Life
Edward O. WIlson
The Amazonian forest is
"one of the great surviving wildernesses of the world, stretching 500 kilometers…"
(3)
"This is the assembly of life that took a billion years to evolve. It has
eaten the storms -- folded them into its genes and created the world that created
us. It holds the world steady." (15)
§§§
Krakatoa
spiders are among the earliest
terrestrial life on deserted islands
"The thick green forest offers testimony to the ingenuity and resilience of life. Ordinary volcanic eruptions are not enough, then, to break the crucible of life." (23)
"The most wonderful mystery of life may well be the means by which it created so much diversity from so little physical matter. The biosphere, all organisms combined, makes up only about one part in ten billion of the earth's mass.… Yet life has divided into millions of species, the fundamental units, each playing a unique role in relation to the whole." (35)
An ecosystem is a collection of
biotic communities (organic features of a place) +
collection of habitats (inorganic features of a place)
existing dynamically over time due to the reuse of scarce nutrients & materials by either:
cooperating – symbiotic or,
competing – rival organisms (creatures, life, beings).
Biodiversity is due to: 1) habitat differences,
2) species richness, 3) genetic variety
species, the fundamental units, each playing a unique role in relation to the whole." (35)
"The hallmark of life is this: a struggle among an immense variety of organisms
weighing next to nothing for a vanishingly small amount of energy."
"Life operates on only 10% of the sun's energy reaching the earth's surface,
that portions fixed by the photosynthesis of green plants." (36)
"The free energy is sharply discounted as it passes through the food webs
from one organism to the next:"
"Top carnivores …. always … skirt the edge of extinction and they are
the first to suffer when the ecosystem around them starts to erode."
"biological diversity … is a side product of evolution"
What is the origin of biological diversity?
Natural selection
1859 –Darwin's - "On the Origin of Species: or the Preservation of favoured Races in the Struggle for
Life."
Evolution creates two patterns across time:
vertical change w/in the original population -- Homo erectus ------> Homo
sapiens
speciation & vertical chg. -- adaptive radiation ++ A. robustus; Homo habilis,
erectus
"A species can be altered so extensively by natural selection as to be
changed into a different species, said Darwin."
speciation’s relation to global diversity
“In conclusion, species can be created quickly, and diversity can therefore
expand explosively. Our knowledge of evolution, though imperfect, tells us at
the very least why life has that potential. Given the right circumstances, a
new species can arise in one to several generations.” (73)
“…new species are relatively cheap species.…If they fill a new
niche, they probably do so with relative inefficiency.” (74)
“Great biological diversity takes long stretches of geological time and
the accumulation of large reservoirs of unique genes. The richest ecosystems
build slowly, over millions of years. It is further true that by chance alone
only a few new species are poised to move into novel adaptive zones, to create
something spectacular and stretch the limits of diversity. A panda or sequoia
represents a magnitude of evolution that comes along only rarely. It takes a
stroke of luck and a long period of probing, experimentation, and failure. Such
a creation is part of deep history, and the planet does not have the means nor
the time to see it repeated.” (74)
genes are the accounting medium of micro-biology
"One gene can change
the shape of the skull. It can lengthen lifespans, restructure the color pattern
on a wing, or create a race of giants."
Changes in the frequency
of gene and chromosome combinations among populations are the underlying motive
power of evolution.
a gene -- is a portion of the nucleotide, DNA, that codes for a specific protein
point mutation -- a piece of the nucleotide bases is randomly substituted
by another
natural selection -- acts on genetic [genotype (raw) & phenotype
(environs)] matter
genetic drift -- random (chance) changes in the gene frequencies of populations
Darwin (1859) was unaware of Mendel's work (1865)
Darwin's theory requires:
1) variation in traits (eye color) exist across any population
2) the inheritability of traits from parents to offspring
3) differential reproductive success among individual offspring
"beauty arises from error."
"… a change in
the frequency of
genes and chromosome configurations in a population."
"The number of genes in a typical larger organism, such as
a human being, is on the order of 100,000."
"At least genes on different
chromosome positions affect
variation in quantitative traits
such as the date of flowering
in plants, fruit size, the eye
diameter of fish and skin color
of human beings. As many as
100 genes work together to
prescribe traits as complex as
ear structure or skin texture."
p. 59, 75-76.
"There are other causes of evolution but natural selection is overwhelmingly dominant."
"This is the question that Darwin answered in essence and twentieth century biologists have refined to produce the synthesis, called neo-Darwinism, with which we now live in uneasy consensus.”
(75)
"The fundamental evolutionary event is a change in the frequency of genes
and chromosome configurations in a population."
"Individuals and their immediate descendants do not evolve. Populations
evolve, in the sense that the proportions of of carriers of different genes
change through time. This conception of evolution at the population level follows
ineluctably from the idea of natural selection, which is the coreof Darwinism."
"There is still a great deal more to evolution than its genetic mechanisms."
(89)
"How important is species selection? If the group is defined broadly enough,
such as all vascular plants or all land vertebrates, it is of overwhelming importance."
(91)
"Among insects, a shift from predatory behavior or scavenging, to plant feeding increases the rate of species formation." (coevolution of flowers & insects)
the rise, spread, decay and fall of species reveals patterns
"Organisms possessing
a common ancestry rise to dominance, expand their geographic ranges, and split
into multiple species." (94)
"A complex and strikingly beautiful pattern across the surface of the earth…
a palimpsest … as past {species} survive as faded traces…."
AR is the spread of related species (individuals that may interbreed successfully)
into a wide variety of open or unoccupied niches over evolutionary time.
a niche is the fundamental unit of ecological adaptive behavior:
role, function, place, range, habits & "job" of an organism throughout
its life.
hypervolumetric niche:
amount of energy transformed into matter
in a specific space over a given time by an organism
AR accounts for:
Poaceae (flowering plants) -- grasses; comprise 80% of the human diet
Galapagos island's Finches: 13 species
300 species of Cichlid fishes & 350 species of sharks (both endangered)
Galapagos island's Finches (Darwin) 13 species
"The most curious fact is the perfect gradation in the size of the beaks…"
Galapagos Volcanic islands
631 miles from Ecuador
family: Geospizinae 600 specimens of 2 species of finches on Dafne Island
1) Natural Selection: climatic or geological changes
1977-78 drought 555 days w/o rain
competition for scarcity (seeds) number available for birds
birds turn their attention to larger seeds in drought (xeric tolerant plants)
(small bills are selected against the large beaked birds are selected for)
large beaked finches' population increases
2) Genetic inheritance: beaks are altered (phenotypic) thus genome is changed
inherited DNA & RNA possess the nitrogen base code as a history of the race
Medium ground finch has hybridized with other finches and has a wider range
of beak variability -- after two generations the size of the beak became enlarged.
1983 severest El Nino in 400 years (3 times the rain as worst rains, 8 months)
Finches bread rapidly (8 broods in 10 months; 150 to 1000 birds) small beak
spread
After the wet years the smaller species grew; drier years the larger species
grew
"Population size is critical to genetic drift…"
pp 101-103
"I have begged the question of ultimate causation. If global cooling was the killing event, what caused the cooling? … the movement of land masses …"
"Today the land mass of the world is arrayed in a configuration that favors
high levels of diversity: widely separated continents with long shorelines and
stretches of shallow tropical water dotted with lots of islands."
Time required for the recovery from a mass extinction:
0 = state of widespread biotic differences among creatures and within species
5 million years = the initial period
20 million years = minimal time for complete recovery of preexisting biodiversity
30 million years = recovery for oceanic extinctions (Devonian)
100 million years = recovery for Permian & Triassic destruction due to frequency
"These figures should give pause to anyone who believes that what Homo sapiens destroys, Nature will redeem.… within any length of time that has meaning for contemporary humanity."
Pre-Cambrian extinctions
-- Burgess shale formation of Canada
Cambrian explosion of diversity (seas) -- may have been more diverse
than now.
Ordovician -- first worldwide ecosystem collapse, cessation of reef building!Devonian
-- another worldwide collapse -- end of reef building, 90% extinction.
terrestrial flora & fauna emerge
Permian -- 54% of the families perished; 77-96% of all marine organisms
it took over 10 million years for reef building organisms to rebound!
Cretaceous -- 1/3 of all families perished; dinosaurs, trilobites, &
ammonites gone
60% of all species perished
Pleistocene -- large animals died out: saber toothed tigers, mammoths,
& sloths
Great extinctions created
the:
age of fishes; the Devonian 405 mi. years ago
age of insects; the Carboniferous 310 mi. years ago
age of reptiles; the Mesozoic 230 mi. years ago
age of mammals; the Cenozoic 60 mi. years ago
age of primates; the Plio-pleistocene 2 mi. years ago
540 mil. years ago oxygen levels > to comprise the current 21% of air!
450 mil. years ago the first plants colonized the dry land; insects followed
Should ours, instead, be the age of ants? (they farm, build nests, & recycle)
small animals are more diverse than large
Area is required for diversity to increase & not decrease over time:
640 acres = 1 square mile or 250 hectares
100 hectares = 1 square kilometer 10,000 Hectares. = 25,000 Acres = ?
"We live on a largely
unexplored planet"
“a common vocabulary, the nucleic-acid code”
“Wilderness is a metaphor of unlimited opportunity. . . . not just the
body but the spirit”
there are 290,000 known
species of coleopterans! [beetles]
they pollinate primitive flowers & recycle organic (waste) nutrients
Is our world maintained by arthropods (invertebrates, insects, crabs, spiders,
etc.?
What would happen to vertebrate & fungal populations if arthropods become
extinct?
We know between 10% & 1.4% of all probable species on earth (labor intensive)
habitat: 1 Gram of Soil
biocenose: 10 billion bacteria representing 4,000 to 5,000 known bacterial
species
What are the five kingdoms (macro-divisions) of life? (make an analogy to a
hand)
Three measure of diversity:
alpha -- species richness in a particular habitat
beta -- rate of increase in the number of species as habitats are added
gamma -- number of species in all habitats across a wide area (sp. equitability)
Ecosystem creation and maintenance
“In the study of communities, this strategy requires greater attention to context, history, and chance.”
An ecosystem combines the habitat (inorganic) with the biotic community (organic) parts of any place, area, or region.
Over evolutionary (20 generations or more) time ecosystems change due to biotic and abiotic factors that affect the differential survival rates of all individuals.
But! key individuals may affect the character of the ecosystem: starfish, Pisaster *see 3 Sea Otters in Pacific coastal kelp beds
Elephants & driver ants (probably leaf cutter ants in the Rain Forests of
Americas)
Gopher Tortoises in Florida sand & scrub habitats; alligators in seasonal
swamps
Assembly rules: 1) specialized predator prey 2) competitive (species) exclusion 3) checks on growth of populations
Complexity of biotic communities increases over time due to symbiosis: [living together]
example are seen in coral reefs, lichens (tundra & forest), termites, mycorrhizae (root fungi).
3 types of symbiosis are:
Food webs and chains of dependency reveal how little we know about communities!
Two approaches to life's diversity:
1. ecological stage -- the quest for habitat, sustenance, security, comfort, procreation, lifecycle, range, longevity, gestation, and generational quality, the bio geographical dispersal of populations.
arena of the tangled bank { interdependencies are manifold }
2. evolutionary stage -- the biogeochemical heritage as encoded in DNA & RNA inheritable traits, reflexive behavior, historical or accidental, contingent character,
genetic & bio geological heritage
When combining these two ways of viewing the world, a sort of binocular vision reveals the totality & depth perception of a viewpoint.
See also: dialectic, argument, method, dualism, spectrum, bias
"Its potential is brilliantly illustrated by the maize species Zea diploperennis, a wild relative of corn discovered in the 1970s by a Mexican College student in the west central state of Jalisco, south of Guadalajara."
The new species is resistant to diseases and unique among living forms of maize in possessing perennial growth.
The Jalisco maize was found just in time, however. Occupying no more than 10
hectares (25 acres) of mountain land, it was only a week away from extinction
by machete and fire."
"For a start we need to reclassify environmental problems in a way that
more accurately reflects reality. There are two major categories and two only.
One is the alteration of the physical environment to a state uncongenial to life."
The second category is the loss of biological diversity. Its root cause is the
despoliation of the physical environment, but is otherwise radically different
in quality." permanent loss of genetic information on past ecological conditions
p. 281
Humans are part of nature.
Nature's past is enfolded into our genetic "blueprint"
The special qualities of humans arise from:
Every
country has three forms of wealth
"the substance of our every day lives:"
1) material -- capital, resources, money, consumer goods, inventories, structures.
2) cultural -- public places, food, medicine, religious shrines, museums, amenities.
"is passing through a bottleneck:"
3) biological -- species, biotic communities, soil, reefs, plant associations, fungi
nitrogen fixing bacteria, gene pools, or "Vavilov centers" (ch. 13)
Sustainable development
-- minimize extinction rates while minimizing costs
Rapid Assessment Program: Conservation International
BIOTROP - identify ecological hot spots in danger of loss
designing reserves
protect & sustain indigenous peoples
encourage extractable resources (cashews, mushrooms, rubber, drugs)
restoration ecology -- recreate biological wealth
bio regions & characteristic ecosystems to be protected to preserve keystone
species.
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