Week 5
才赶完一份Term paper。。。
俺还有四个要赶啊鸡蛋糕
Evolution Transition
Chin Chun Ming
003F11713
Evolutionary Psychology
Introduction
Evolution is a change
in population on Earth. It can happen in large major groups of living things,
or as well occur in minority species. Since Earth was formed 4.54 billion years
ago, living things started to emerge and grow. Nowadays, living things from a
single unicellular organism already developed into million types of various
species. All of these changes are positive and essential for living things to
survive. Yet, throughout these changes and evolution process, there were many
of the living things fail to adapt and eventually extinct. The reason behind
these failures is mainly caused by drastic changes in environment, weather, and
geological features.
Earth has been through
many stages within these 4.54 billion years. In different stages of Earth, the
geological features and condition are different too. There were four eras which
are Hadean, Archean, Proterozoic and Phanerozoic era. Each era has different
geographical condition, which was highly influence towards living things on
Earth. For example, the temperature on Earth during Hadean era was too high due
to frequent volcanism and outer asteroids collision. Proterozoic era Earth was
covered in ice, with very low temperature.
According to
evolutionary theory, humans did not appear as human on Earth “suddenly”. Humans
evolved from another type of organism throughout billions of years. In the same
time, other organisms nowadays such as cat, dog, dolphin, and monkey also
evolved from same ancestor billion years ago. According to Darwin (1859), all
species evolved from the same ancestor during Archean era of Earth, which are
the protozoa. From protozoa to humans, there were many transitions happened and
this paper is focusing on those evolution transition topics.
Transition of Earth
To describe Earth in an
easy way, Earth is just like a rental house. At first there was tenants lived
in there, after a while the old tenants moved out and new tenants moved in. The
reasons why they moved out maybe because of the weather is too hot, the air conditioner
is not cold enough, or the environment is not suitable. Similar to Earth, the
transition happened on Earth might provide a good environment for some
organisms to live but also sometimes provide bad environment which caused most
organisms faced extinction. To get a deeper view in it, we need to understand
the stages that the Earth had undergone and events that happened during that
time.
1) Hadean eon
According to University
of California Museum of Paleontology (2011), Hadean eon (4.6 to 4 billion years
ago) was the early formation of the Solar System. The sun appeared as a cloud
of gas and space dust, attracting and compressing into one giant gas ball and
started to undergo nuclear fusion. As a result of nuclear fusion, massive
amount of heat was released. At the same time, space particles around the sun
started to merge by gravity into planets and smaller particles united into
asteroids and comets.
Once
Earth was formed, the core emitted very high amount of heat energy and the
surface of the Earth is in molten rock state. This stage is known as Hadean
era. During Hadean era, the condition of the Earth is under very high
temperature and there was no breathable air. Hadean era lasted for 2 million
years and throughout the years uncountable volcanism and asteroid collision has
happened. These harsh conditions and phenomenon could not allow any organism to
live on Earth. Thermophilic organisms (organisms that preferably live in high
temperature environment) might have originated in this period, yet the
temperature range favored by thermophilic organisms did not appear for most of
the history of the Earth (Pace, 1991). This statement leaves several hypotheses
that life did not start at Hadean eon.
During early 4.4
billion years ago, the Earth started to cool down and the water vapor started
to condense into liquid. According to an extraction activity in 2014, a
fragment of zircon crystal has been discovered in Jack Hills, Australia.
Zircons have highly resistant towards chemical changes just like gold, also
shows that the zircon crystals crystallized 4.4 billion years ago. This
statement reinforce that 4.4 billion years ago the Earth had started to cool
down and water was present during that time. Besides from water, there were
several important elements and compounds appeared abundantly in the atmosphere
such as nitrogen, nitrogen oxide, carbon dioxide, methane, ammonia, hydrogen
and hydrogen sulfide (Zamora, 2014). Amino acids are the first organic
molecules to exist on the Earth. As the structuring of proteins, amino acids
are the basic unit of it and linked to almost every single life on Earth which
consists of protein. According to Nature Education (2010), amino acids appeared
between 4 billion and 3.5 billion years ago in Hadean eon through chemical
synthesis of ammonia, hydrogen, methane, and water vapor. Because of existence
of amino acid, single-stranded protein which is ribonucleic acid (RNA) had
developed and later on developed into deoxyribonucleic acid (DNA). It was the
first genetic material exists on Earth and also known as the beginning of life.
The first life form is known as protobionts.
2) Archaean eon and Proterozoic eon
During 3.9 to 3.5
billion years ago, the Earth had entered a new eon, which was the Archaean eon.
Protobiont organisms had developed into a more complicated organism called
prokaryotes. Prokaryotes have the ability to undergo asexual reproduction,
which is binary fission to divide themselves into two offspring (Bult,et al,
1996). By using this reproduction method, the ocean of the Earth was full with
prokaryotic organisms during Archaean eon. A very amazing phenomenon was
happened during this time which was the level of oxygen in the atmosphere shot
up from none to 10%. This phenomenon was happened because of the development of
a new prokaryote called cyanobacteria. Cyanobacteria have the ability to make
food through photosynthesis, which is the process by taking in carbon dioxide
gas and release oxygen gas (Kendall, et al, 2010).
During 3.5 to 2.1
billion years ago, a new type of organism had emerged which is the eukaryote.
Eukaryote can be comprehended as the “ancestor” of all plant and animal.
Eukaryotes developed a digestion process called endosymbiosis, which means one
eukaryote will parasitize another eukaryote and become a more complex organism.
As the endosymbiosis process continues, the eukaryote become more complex and
eventually develop several organelles in one single cell and possess different
function in each of them (Bult,et al, 1996). By 1.5 billion years ago,
multicellular organisms grew abundantly according to fossil record. According
to Smithsonian National Museum of Natural History (2007), the oldest known
multicellular eukaryote is Grypania spiralis, a coil and ribbon-like fossil was
found in Michigan. The dating system shows that the eukaryote fossil was formed
2.1 billion years ago. Thanks to evolution of multicellular organism, sexual
reproduction ability was developed to replace asexual reproduction. Sexual
reproduction is very important because it can induce variation among organisms
and variation is essential for evolutionary process.
3) Phanerozoic eon
a. Cambrian Explosion
Phanerozoic eon is the
last eon and also the current eon that we are living under. 535 million years
ago, eukaryotic organisms began to bloom rampantly. This phenomenon is known as
Cambrian explosion. For 10 million years, aquatic animals evolved most of the
elementary body forms like nowadays worms, starfish, crustaceans, algae, and
sponges (Wang, et al, 1999). Also in Cambrian period, prey-predatory became
more vicious and multicellular organism started to use seawater and mineral to
build up “weapons” such as claws, and prey built up defensive “shield” such as
hard plates and shell.
b. Ordovician period and Devonian
period
At Phanerozoic eon’s
period, Ordovician period approximately 505 to 540 million years ago was the
period where animals and plants started to colonize together to avoid
predation. Until 365 million years ago, it was the Devonian period. At Devonian
period, there were two major dominant species living on the Earth, which were the
tetrapods (animals with four limbs) dominating the land and brachiopods
(animals with two hard shells located top and bottom) dominating the ocean
(Speer, 1998). Animals started to live
on land since there was a formation of land masses in this period. During
Devonian period, there were three major continent masses which were
Paleosiberia (a portion of modern Siberia), Euramerica (combination of modern
North America and Europe), and Gondwana (combination of South America, Africa,
Antarctica, India, and Australia). There was no mammal, reptile, or amphibian
organism developed in this period, only fish-like organisms. Besides, plants
also began to spread on the land in very small amount and sizes. Those plants
did not have roots or stem and did not grew more than few centimeter tall. But
then, during late Devonian period plants started to increase in population and
started to grow roots and leaves.
c. Carboniferous period
In 399 to 259 million
years ago, the Earth stepped into a period known as Carboniferous period, the
Coal age. The increasing of animals caused the amount of carbon dioxide
increase, which was extremely favorable by plants, as a result causing plants
to grow rampantly on land. As population of plants increases, the
photosynthesis process (process which plants make food by taking in carbon
dioxide and releasing oxygen under sunlight) became much more frequent. In a
very long geological time, the oxygen level in the atmosphere was too high and
reached 35% portion of air. According to National Geographic Society (2014),
insects and spiders grew in massive size due to high amount of oxygen in the
air. Centipedes can grow into maximum size of 2 meter long and dragonflies can
develop into 0.75 meter long. After over several million years, the climate started
to change and the amount of carbon dioxide in the atmosphere was harshly
decreasing due to excess growth of plants. The declination of carbon dioxide
caused the collapse of whole carboniferous forests kingdom and those remains of
dead trees buried under the land. Nowadays, those remains have become very
precious energy resources like coals and petroleum because of the thermal
pressure. Also, the collapse of carboniferous forest caused the formation of
wetlands, marsh, and swamps, which lead to evolution of reptiles and amphibian.
Reptiles and amphibian started to live on land and ocean through wetlands,
which allow them to adapt both environments. Amphibians in carboniferous period
grew in large size and developed amniote egg reproduction (National Geography
Society, 2014).
d. Permian period
In between 299 to 251
million years ago, the Earth stepped into Permian period. During the Permian, a
single supercontinent was formed by combining all land masses from all over the
world. The supercontinent called Pangaea meanwhile the combination of land
masses left a large single ocean called Panthalassa (Kazlev, 2012). The
combination of continents encouraged more organisms to start living on the
land. Non-flowering plants such as pines, conifers, and ferns became more
prominence in this period. Besides, two types of animal roaming widely on the
land which was Pelycosaurs (quadruped reptiles with large hard fin on the back)
and Archosaurs (the ancestor of dinosaurs and modern reptiles). At the same
time, giant carboniferous insects met their extinction due to collapse of
carboniferous ecosystem (Kazlev, 2012).
e. Permian Extinction
According to Hoffman (2014),
there was a huge extinction event happened even before evolution of mammals and
dinosaurs. During 252 million years ago, one of the huge extinction event of
species happened on Earth, Permian-Triassic extinction as we know nowadays.
Some unknown reason caused 90% of species on the planet met extinction. Only
less than 5% of organism lived in the ocean survive the extinction event
meanwhile almost all plants died. The speculation for the major extinction
event is most probably caused by acid rain, yet there are still many mysteries
remain unsolved (Chu, 2013).
f. Triassic period
According to
Smithsonian National Museum of Natural History (2007), the end of Permian
extinction was recovered slowly during the Triassic period (252 to 201 million
years ago). Brachiopods (two shells organism) went fully extinct. But then,
dinosaurs started to evolve and began to roam the land. Archosaurs evolved into
much diversity of dinosaurs and modern lizards meanwhile a new species called
lystrosaurus had evolved. Lystrosaurus was believed to be the ancestor of
mammals and it had features similar to pigs nowadays. According to Newitz
(2013), lystrosaurus in Triassic period did not have any natural predators who
fed on them meanwhile lystrosaurus was herbivore by the way. Besides, they had
no sharp teeth or tusk as defense mechanism. Yet, lystrosaurus had strong
adaptation abilities toward weather and environment. That is the reason why
mammals can survive from the major extinction.
g. Jurassic period
Until 199 to 145
million years ago, dinosaur became the dominant species on Earth in this
period, which known as Jurassic period. The name “Jurassic” is referring to the
Jura Mountains by Buch in 1839. The domination of huge and giant dinosaur on
the Earth threatened mammals’ life and mammals had to grow in smaller size to
maintain population (Department of Paleobiology, 2007). In the oceans, plenty
types of sharks and marine crocodiles evolved and grew in large number of
population. On the land, the first flying vertebrae animal was pterosaur, which
evolved to giant bird during late Jurassic period. In Jurassic period,
dinosaurs dominated the animal kingdom meanwhile ferns and conifers dominated
the plant kingdom. From the geological perspective, Pangaea had separated and
some low ground area flooded by sea water. This continental drift caused North
America drifted apart from South America and Africa, also formed Atlantic Ocean
in between those two continents (Department of Paleobiology, 2007).
h. Cretaceous period
During 146 to 65.5
million years ago, Earth undergone changes in geological and living organism.
According to University of California Museum of Paleontology (1995), cretaceous
period was the period whereby many types of new diversity appeared. For
example, here comes the first appearance of flowering plants and angiosperm,
butterflies, and bees. The presence of bees and butterflies encouraged the
increasing population of flowering plants because those insects acted as the
vector to transport pollen grains for reproduction.
i.
Cretaceous
extinction
In late Cretaceous
period (65 million years ago), dinosaurs who dominating the Earth for several
periods met their extinction. Although this Cretaceous-tertiary extinction was
not as critical as Permian-Triassic extinction, but this extinction event
induced the evolution of mammals on Earth which indirectly induce the evolution
of humans. According to Smithsonian National Museum of Natural History (2007),
the reasons of the dinosaur’s extinction are still being argued by paleontologists.
Paleobiology researchers agree that a major cause was an asteroid
about 10 kilometers in diameter that collide with Yucatán peninsula in Mexico.
The aftermaths of the impact were catastrophic; possibly inducing global forest
fires, long-period of cold weather due to smoke and dust blocked the sunlight,
and followed by a period of hot temperature caused by the high levels of CO2
released into the atmosphere (greenhouse effect). Evidence for these statement
is the finding which paleontologist found cretaceous dinosaurs’ fossil under a
layer of asteroid rocks layer. Some paleontologists
claim that dinosaurs were deteriorating before the asteroid
collision; hence its environmental aftereffects quickened their extinction. Besides,
there is others fact to the plenty and diversity of dinosaur
species
fossil recorded in the sediments left underneath the asteroid impact layer in
the Hell Creek Formation of western North America.
4) Cenozoic era
a.
The
Age of Mammals
Lastly, it is the
Cenozoic era (65 million years ago to present). According to Hamilton (2010),
the early stage of Cenozoic era was still dominated by descendants of
dinosaurs, the birds even after the mass extinction of dinosaurs. But then, the
land nowadays is dominated by mammals. Different habitat diversified mammals to
herbivore, carnivore, and omnivore just in order to survive. During 65 million
years ago, a type of mammals diversified and evolved into Plesiadapiformes,
which believed it is the ancestor of primates (ape-liked mammals) (Dawkins,
2004). Throughout 50 million years of evolution, the first Hominidae (great
apes) diversified as the descendants of gibbons. For another 12 million years
of evolution, some great apes developed bipedal abilities (walking with two
legs) and they are known as the ancestor of Homo mammals.
b.
The
Age of Humans
The Homo genus
organisms was then evolved into Homo antessor, which as known as the ancestor
of Neanderthals and modern humans (Bermúdez de
Castro, et al., 1997). Until 200 thousand years ago, the first homo
sapien with Y-chromosomes evolved and they were originated from Ethiopia,
Africa. The population was then
increasing and starting to migrate to all over the continents. Till now, it is
the Age of Humans.
Reference
·
Chu, J., Massachusetts Institute
of Technology, A possible cause of the end-Permian mass extinction: Lemon
juice? 2013.
·
Darwin, C., On the Origin of
Species (By means of Natural Selection), London, 1859
·
Department of Paleobiology, the overview
of Jurassic Period, 2007
·
Hoffman,
H.J, National Geographic Society, The Permian
Extinction—When Life Nearly Came to an End,
·
Nature Education, An Evolutionary
Perspective on Amino Acid, The Origin of Nutrient Biosynthesis, 2010
·
Newitz,
A., Phenomena: A science salon hosted by National Geographic Magazine,
Lystrosaurus, 2013
·
Richard Dawkins "Fossils that might help us reconstruct what
Concestor 8 was like include the large group called plesiadapi-forms. They
lived about the right time, and they have many of the qualities you would
expect of the grand ancestor of all the primates" 2004
·
Sci-news, Jack Hills Zircon:
Scientist Discover Oldest-known Fragment of Earth, 2014
·
Smithsonian National Museum of Natural
History, Extinction and Recovery: Triassic Period, 2007
·
Smithsonian National Museum of Natural
History, Geologic Time: The story of a Changing Earth, the Overview of
Cretaceous period, 2007
·
Smithsonian National Museum of
Natural History, the Proterozoic:
Eukaryotes and the first multicellular life forms. 2007
·
Speer, B. R., University of
California Museum of Paleontology, The Devonian Period, 1998
·
University of California Museum
of Paleontology, Geological Timescale: The Archaean eon and Hadean eon, 1997
·
Zamora, A., Evolution of the
Earth Atmosphere: Atmospheric composition of the Earth, 2014.
