42:163 This Old Earth Quiz 2 - Fossils and Evolution

fossils

fossils

remains, traces, or imprints of once living organisms preserved in the earth’s crust since some past geologic or prehistoric time

from fossa = hole, or to dig

loosely means any evidence of past life

body fossils

soft bodied or skeletal

exoskeletons, endoskeletons, or basal skeletons

microfossils or macrofossils

trace fossils

in sediments (signs of organic activity, burrowing, motion - tracks, trails - boring, footprints, recycling (coprolites)) - ichnofossils

two factors - fossil preservation

possession of hard parts

quick burial

possession of hard parts

animals which possess hard parts (shell, teeth, bony skeleton), stand a much better chance of fossilization than do soft tissues

quick burial

helps prevent or retard the decay, scavengers cannot disturb the remains

unaltered remains

the hard skeleton of the organism or its soft part or both remains unchanged

unaltered remains - soft part examples

mammoth: in the Pleistocene glaciers of Siberia

insect in amber: the insects are preserved in the resin (amber) such as those found in the Oligocene deposits of Baltic province

unaltered remains found in tar pools, oil seeps, or tar pits

mummified remains preserved in desert climates

unaltered remains - soft part

not as common as a type of preservation

important style of preservation because they can provide us with detailed information on the nature of the organism

fleshy, soft bodied parts of organisms may be preserved if bacterial decay has been inhibited

hard skeleton

this is characteristic for Cenozoic shells which underwent little or no alteration of the original mineral substance

hard skeleton examples

bivalve chlamys antiaustralis, from the Miocene of Victoria

altered remains

the soft parts decay and the hard skeletons are altered

most fossils have undergone some degree of alteration since the death of original organisms

carbonization

removal of volatile constituents such as oxygen, hydrogen, and nitrogen from the organic compound leaving only carbon as a thin black film

carbonization examples

in burguss shale

graptolites, fishes, and plants (in anaerobic environments)

recrystallization

the alteration of less stable inorganic compounds into more stable ones without any chemical/compositional change

recrystallization example

aragonite → calcite

replacement

the original mineral of skeleton is dissolved and replaced by other minerals substances

→ dissolved by ground waters

→ forms a replica of the original → silicified/petrified wood (stone forest)

replacement examples

silica (silification)

pyrite (pyritization)

iron

dolomite

permineralization (replacement +)

the deposition of minerals in the interstices of skeleton

if organic material is porous, mineral matter carried by percolating solutions may be deposited in voids, without altering the original material

permineralization (replacement +) examples

bone pore spaces filled in with minerals

chemical precipitation into pore spaces

resulting fossil is heavy and dense

fossil said to be permineralized

commonly calcium carbonate is deposited

other minerals such as silica, glauconite, and iron compounds are also deposited

imprints, moulds, and casts

organic structure may leave an impression if it is pressed into a soft material that is capable of receiving and retaining the imprint

imprints

impression made by thin objects such as fish, leaf

mould

the impression of skeletal remains on rocks

→ may represent the external or internal surface of the organism

cast

if a mold is infilled with sediment or mineral, the infilling produces a cast

→ can be natural or artificial

→ replica of the original - exact copy

→ will exhibit the same form or ornamentation as the original, but the internal structure of the shell is not preserved

age - main geological uses for fossils

based on the principle of biologic succession

specific groups of macrofossils and micro fossils are characteristic of certain time periods

in age determination, fossil assemblages are more reliable than individual species

correlation - main geological uses for fossils

based on the principle of biologic succession - biostratigraphy

fossils used in the construction of the geologic time scale (relative time scale)

microfossils are used for subsurface correlation

paleo-environmental analysis - main geological uses for fossils

fossils are critical in paleoenvironmental analysis

widely used to determine the following: paleo-climate, paleo-ecology, paleo-geography, paleo-depositional environment

record of life and evolution - main geological uses for fossils

a record of prehistoric life, especially those forms that have no living representatives

evidence of organic evolution

succession of fauna and flora

linnean taxonomic hierarchy (1758)

kingdom

phylum - first used by haeckel, 1876

class

order

family - chambers, 1753

genus

species

five kingdoms

monera (bacteria)

protista

fungi

plantae

animalia

life into two main divisions

prokaryote (bacteria, etc.)

eukaryote (animals, plants, fungi, and proctotists)

prokaryote

cell represents the simplest grade of organization of life, in which the genetic material (DNA) is not gathered together in a nucleus, but distributed throughout the whole cell

were the earliest life forms on earth, and they still constitute the bulk of the biomass of life on earth

eukaryote

organisms in which the genetic material is contained within a nuclear membrane, the name means “true kernel”

three-domain paradigm of woese

prokaryotae now divided into two domains → the bacteria and the archaea

different from either is the eukarya, or eukaryotes

first proposed by Dr Carl Woese in late 1970s

bacteria

are of immense importance because of their extreme flexibility, capacity for rapid growth and reproduction, and great age - the oldest fossils known, nearly 3.5 BYO, are fossils of bacteria-like organisms

bacteria example

cyanobacteria from the bitter springs chert of central Australia, late Proterozoic, ~850 MYO

oldest known fossils

3.465 BYO

cyanobacteria (?)

five mass extinctions

late Ordovician - 440 MYA

late Devonian - 370 MYA

end Permian - 245 MYA

end Triassic - 210 MYA

end Cretaceous - 65 MYA

inheritance of acquired characteristics - lamarck’s ideas on evolution

new features arise in organisms because of their needs, and somehow these features are passed along to their descendants → characteristics acquired during the lifetime of an individual are in inheritable

origins of species (1859)

published by darwin 20 years after his voyage on the beagle

descent with modification - natural selection

those with favorable variations are more likely to survive and pass on their favorable variation

natural selection

evolution by natural selection is largely a matter of reproductive success, for only those who reproduce pass on their favorable variations

darwin-wallace’s vs. lamarck’s

darwin correctly thought that the variation already existed in the population and that nature just selected for the most suitable ones against less useful ones

lamarck’s incorrectly thought that the environment altered the characteristics of individuals and that these acquired changes were then inherited

examples of natural selection

darwins 13 species of finches in the galapagos islands

→ adaptive radiation

moths

chernobyl black frogs reveal evolution in action

→ the dark coloration is typical of frogs from within or near the most contaminated areas at the time of the accident

evolution of camouflage

mendel and the birth of genetics

george mendel’s work in the 1860s explained some of the inheritance problems, but went unnoticed until 1900

mendel’s experiments with garden peas led him to conclude that traits are controlled by a pair of factors - genes

mendel’s experiments

showed that genes controlling the same trait occur in alternate forms, or alleles

→ coined recessive and dominant in reference to certain traits

chromosomes are complex molecules of DNA

the cells of all organisms contain threadlike chromosomes, which are complex, double-stranded, helical molecules of DNA

the number of chromosomes is the same for a single species but varies among species

meiosis

a type of cell division in which sex cells form; each cell contains one member of each chromosome pair

only one of the four final cells is a functional one

mitosis

results in the complete duplication of a cell

a cell with four chromosomes (2 pairs) produces two cells, each with four chromosomes

mitosis occurs in all body cells except sex cells

once an egg is fertilized, the developing embryo grows by mitosis

phyletic gradualism

evolution is a slow, gradual process

this idea has been challenged recently

the nuclear rabbit

a rabbit born after the nuclear explosion was born with no ears and is sending fear throughout the world of the mutations and deformities to come

speciation

the origin of new species

species

species are groups of interbreeding natural populations that are reproductively isolated from other such groups

if group organisms belong to another species, they can NOT mate and form another generation and species to continue descendants since they are different species

→ offspring will not be fertile/sterile

liger

result of male lion and female tiger mating in captivity

offspring are infertile

for new biological species to be formed, there must be what

reproductive isolation

mutation - reproductive isolation

in some cases, can cause instant reproductive isolation and speciation because mutant individuals are genetically blocked from mating with members of the non-mutant population

geographic barriers - reproductive isolation

including distance, prevents new traits that evolve in one population from being introduced to other populations

in time, geographically separated populations may develop genetic traits that preclude interbreeding

allopatric speciation

the formation of new species by geographic isolation

gene flow is interrupted or reduced because of

isolation by distance

extrinsic barriers

vicariance

isolation by distance

limited vagility produces polytypic subspecies

extrinsic barriers

physical barriers to gene flow

→ mountains, canyons, rivers, deserts, etc.

vicariance

populations move, or are moved apart

→ continental drift, land bridges, range expansion, change of watercourse, movement of glacier

example of allopatric speciation

the grand canyon of northwestern arizona serves as a geographic barrier to gene flow

the kaibab squirrel lives on the north rim of the grand canyon while the abert squirrel lives on the south rim

the two forms are variously regarded as full species or as subspecies of sciurus aberti

darwinian evolution theory

evolution and speciation via natural selection occurred mainly as a slow and gradual process

new traits arise by mutations, and traits that infer greater productive success are selected for and eventually become dominant over many generations - gradualism/phyletic gradualism

punctuated equilibrium

fossil record shows that new species appear suddenly, then persist unchanged for millions of years, and disappear just as suddenly

niles eldredge + stephen gould suggested in 1972 that evolution was not gradual, and proposed new mode of evolution

divergent evolution

ancestral species giving rise to diverse descendants adapted to various aspects of environments

convergent evolution

the development of similar characteristics in distantly related organisms, due to adapting to similar environments

is the development of similar characteristics in distantly related organisms

parallel evolution

similar characteristics arising in closely related organisms but not from a common ancestor - due to adapting to similar environments

is the development of similar characteristics in closely related organisms

homologous organs

similar arrangement of bone, muscle, and tissue in different organisms modified for different functions and indicate derivation from a common ancestor

analogous organs

serve the same function in different organisms, wings of insects and birds, quite different in structure and developments

vestigial structures

nonfunctional or partly functional remnants of structures that were functional in their ancestors