tatap muka 1 the history of life on earth 2015.ppt
TRANSCRIPT
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The History of Life on Earth
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Memahami dan mampu menjelaskan konsep kunci :
1. Conditions on early Earth made the origin of life possible
2. The fossil record documents the history of life
3. Key events in life’s history include the origins of unicellular and multicellular organisms and the colonization of land
4. The rise and fall of groups of organisms reflect differences in speciation and extinction rates
5. Major changes in body form can result from changes in the sequences and regulation of developmental genes
6. Evolution is not goal oriented
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Overview: Lost Worlds
• Past organisms were very different from those now alive
• The fossil record shows macroevolutionary changes over large time scales including• The emergence of terrestrial vertebrates • The origin of photosynthesis• Long-term impacts of mass extinctions
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Antarctica
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On what continent did these dinosaurs roam?
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Cryolophosaurus
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Conditions on early Earth made the origin of life possible• Chemical and physical processes on early Earth
may have produced very simple cells through a sequence of stages:1. Abiotic synthesis of small organic molecules
2. Joining of these small molecules into macromolecules
3. Packaging of molecules into “protobionts”
4. Origin of self-replicating molecules
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Synthesis of Organic Compounds on Early Earth
• Earth formed about 4.6 billion years ago, along with the rest of the solar system
• Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide)
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• A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment
• Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible
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• However, the evidence is not yet convincing that the early atmosphere was in fact reducing
• Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents
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Did life originate in deep-sea alkaline vents?
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• Amino acids have also been found in meteorites
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Abiotic Synthesis of Macromolecules
• Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock
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Protobionts
• Replication and metabolism are key properties of life
• Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure
• Protobionts exhibit simple reproduction and metabolism and maintain an internal chemical environment
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• Percobaan-percobaan laboratorium menunjukkan bahwa protobion dapat terbentuk secara spontan dari senyawa-senyawa organik yang dihasilkan secara abiotik
• Misalnya, beberapa tetesan kecil terlingkup-membran yang disebut liposom dapat terbentuk ketika lipid atau molekul-molekul organik lain ditambahkan ke air
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(a) Reproduksi sederhana dari protobion
(b) Metabolisme sederhana
Phosphate
Maltose
Phosphatase
Maltose
Amylase
Starch
Glucose-phosphate
Glucose-phosphate
20 µm
Protobion versi laboratorium
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RNA yang Bereplikasi-Sendiri dan Awal Kemunculan Seleksi Alam
• The first genetic material was probably RNA, not DNA
• RNA molecules called ribozymes have been found to catalyze many different reactions• For example, ribozymes can make complementary copies of
short stretches of their own sequence or other short pieces of RNA
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• Early protobionts with self-replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection
• The early genetic material might have formed an “RNA world”
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The fossil record documents the history of life
• The fossil record reveals changes in the history of life on earth
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Catatan Fosil
• Batuan Endapan adalah sumber fosil terkaya. Akibatnya, catatan fosil didasarkan terutama pada urutan terakumulasiny fosil di lapisan batuan endpam yang disebut strata
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Present
Dimetrodon
Coccosteus cuspidatus
Fossilizedstromatolite
Stromatolites Tappania, aunicellulareukaryote
Dickinsoniacostata
Hallucigenia
Cetakan amonit
Rhomaleosaurus victor, a plesiosaur
10
0 m
illi
on
ye
ars
ag
o2
00
17
53
00
27
04
00
37
55
00
52
55
65
60
03
, 500
1, 5
0 0
2.5 cm4.5 cm
1 cm
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Fossilizedstromatolite
Stromatolites Tappania, aunicellulareukaryote
Dickinsoniacostata
Hallucigenia
500
525
565
600
3,50
0 1,
500
2.5
cm
4.5 cm
1 cm
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Present
Dimetrodon
Coccosteus cuspidatus
Casts ofammonites
Rhomaleosaurus victor, a plesiosaur
100
mill
ion
yea
rs a
go
200
175
300
270
400
3754.5 cm
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Rhomaleosaurus victor, a plesiosaur
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Dimetrodon
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Casts of ammonites
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Coccosteus cuspidatus
4.5 cm
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Hallucigenia
1 cm
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Dickinsonia costata 2.5 cm
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Tappania, a unicellular eukaryote
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Stromatolites
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Fossilized stromatolite
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• Few individuals have fossilized, and even fewer have been discovered
• Catatan fosil yang diketahui cenderung pada spesies-spesies yang bertahan lama, berjumlah melimpah, dan tersebar luas di lingkungan-lingkungan tertentu, serta memiliki cangkang, rangka atau bagian lain yang keras sehingga mudah terfosilisasi
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Bagiamana Umur Bebatuan dan Fosil ditentukan
• Strata sedimen mengungkapkan umur relatif fosil• Umur yang sesungguhnya (absolut) dari fosil
dapat ditentukan dengan penentuan umur radiometrik, yang didasarkan pada peluruhan isotop radioaktif
• Sebuah Isotop ‘induk’ radioaktif meluruh menjadi isotop ‘anakan’ dengan laju yang konstan
• Laju peluruhan dinyatakan sebagai waktu-paruh (half-time), waktu yang diperlukan bagi 50% isotop induk untuk meluruh
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Waktu (waktu-paruh)
Isotop “anak” yang terakumulasi
Sisa isotop “induk”
Fra
ksi
dar
i si
sa
iso
t op
in
du
k
1 2 3 4
1/2
1/41/8 1/16
Penentuan umur radiometrik
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• Radiocarbon dating can be used to date fossils up to 75,000 years old
• For older fossils, some isotopes can be used to date sedimentary rock layers above and below the fossil
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• Magnetisme bebatuan juga menyediakan informasi penentuan umur
• Pengukuran magnetisme berbagai lapisan bebatuan mengindikasikan bahwa kutub magnetik utara dan selatan telah berganti-ganti posisi berulang kali di masa lalu.
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The Origin of New Groups of Organisms
• Mammals belong to the group of animals called tetrapods
• The evolution of unique mammalian features through gradual modifications can be traced from ancestral synapsids through the present
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Very late cynodont (195 mya)
Later cynodont (220 mya)
Early cynodont (260 mya)
Therapsid (280 mya)
Synapsid (300 mya)
Temporalfenestra
Temporalfenestra
Temporalfenestra
EARLYTETRAPODS
Articular
Key
Quadrate
Dentary
Squamosal
Reptiles(includingdinosaurs and birds)
Dimetrodon
Very late cynodonts
Mammals
Sy
na
ps
ids
Th
era
ps
ids
Ea
rli er c
yn
od
on
ts
The origin of mammals
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Therapsid (280 mya)
Synapsid (300 mya)
Temporalfenestra
Temporalfenestra
Articular
Key
Quadrate
DentarySquamosal
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Very late cynodont (195 mya)
Later cynodont (220 mya)
Early cynodont (260 mya)
Temporalfenestra
Articular
Key
Quadrate
Dentary
Squamosal
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Key events in life’s history include the origins of single-celled and multicelled organisms and the colonization of land
• The geologic record is divided into the Archaean, the Proterozoic, and the Phanerozoic eons
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• Fanerozoikum meliputi kehidupan eukariotik multiseluler
• Fanerozoikum dibagi menjadi tiga era: Paleozoikum, Mesozoikum, dan Kenozoikum
• Batas utama antara divisi geologi sesuai dengan peristiwa kepunahan dalam catatan fosil
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Animals
Colonizationof land
Paleozoic
Meso-
zoic
Humans
Ceno-zoic
Origin of solarsystem andEarth
ProkaryotesProterozoic Archaean
Billions of years ago
1 4
32
Multicellulareukaryotes
Single-celledeukaryotes
Atmosphericoxygen
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The First Single-Celled Organisms
• The oldest known fossils are stromatolites, rock-like structures composed of many layers of bacteria and sediment
• Stromatolites date back 3.5 billion years ago• Prokaryotes were Earth’s sole inhabitants from 3.5 to about 2.1 billion years ago
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Prokaryotes
Billions of year
s ag
o
4
32
1
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Photosynthesis and the Oxygen Revolution
• Most atmospheric oxygen (O2) is of biological origin
• O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations
• The source of O2 was likely bacteria similar to modern cyanobacteria
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• By about 2.7 billion years ago, O2 began accumulating in the atmosphere and rusting iron-rich terrestrial rocks
• This “oxygen revolution” from 2.7 to 2.2 billion years ago
• Menimbulkan tantangan bagi kehidupan• Memberikan kesempatan untuk mendapatkan energi dari
cahaya• Organisme diperbolehkan untuk mengeksploitasi ekosistem
baru
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Atmosphericoxygen
Billions of year
s ag
o4
32
1
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Formasi lajur-lajur besi: bukti fotosintesis
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The First Eukaryotes
• The oldest fossils of eukaryotic cells date back 2.1 billion years
• The hypothesis of endosymbiosis proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells
• An endosymbiont is a cell that lives within a host cell
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Single-celledeukaryotes
Billions of year
s ag
o
4
32
1
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• The prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell as undigested prey or internal parasites
• In the process of becoming more interdependent, the host and endosymbionts would have become a single organism
• Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events
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Nucleus
Cytoplasm
DNAPlasma membrane
Endoplasmic reticulum
Nuclear envelope
Ancestralprokaryote
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Aerobicheterotrophicprokaryote
Mitochondrion
Ancestralheterotrophiceukaryote
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Ancestral photosyntheticeukaryote
Photosyntheticprokaryote
Mitochondrion
Plastid
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Ancestral photosyntheticeukaryote
Photosyntheticprokaryote
Mitochondrion
Plastid
Nucleus
Cytoplasm
DNAPlasma membrane
Endoplasmic reticulum
Nuclear envelope
Ancestralprokaryote
Aerobicheterotrophicprokaryote
Mitochondrion
Ancestralheterotrophiceukaryote
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• Key evidence supporting an endosymbiotic origin of mitochondria and plastids:• Similarities in inner membrane structures and functions
• Division is similar in these organelles and some prokaryotes
• These organelles transcribe and translate their own DNA
• Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes
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Asal-usul Multiselularitas
• Setelah eukariota pertama muncul, beraneka ragam bentuk uniselular berevolusi, memunculkan keanekaragaman eukariota bersel tunggal
• A second wave of diversification occurred when multicellularity evolved and gave rise to algae, plants, fungi, and animals
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The Earliest Multicellular Eukaryotes
• Comparisons of DNA sequences date the common ancestor of multicellular eukaryotes to 1.5 billion years ago
• The oldest known fossils of multicellular eukaryotes are of small algae that lived about 1.2 billion years ago
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• The “snowball Earth” hypothesis suggests that periods of extreme glaciation confined life to the equatorial region or deep-sea vents from 750 to 580 million years ago
• The Ediacaran biota were an assemblage of larger and more diverse soft-bodied organisms that lived from 565 to 535 million years ago
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Multicellulareukaryotes
Billions of year
s ag
o
4
32
1
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The Cambrian Explosion
• The Cambrian explosion refers to the sudden appearance of fossils resembling modern phyla in the Cambrian period (535 to 525 million years ago)
• The Cambrian explosion provides the first evidence of predator-prey interactions
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Animals
Billions of year
s ag
o
4
32
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Sp
on
ge
s
LateProterozoiceon
EarlyPaleozoicera(Cambrianperiod)
Cn
idar
ian
s
An
nel
ids
Bra
ch
iop
od
s
Ec
hin
od
erm
s
Ch
ord
ate
s
Mill
ion
s o
f y
ears
ag
o
500
542
Art
hro
po
ds
Mo
llus
cs
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• DNA analyses suggest that many animal phyla diverged before the Cambrian explosion, perhaps as early as 700 million to 1 billion years ago
• Fossils in China provide evidence of modern animal phyla tens of millions of years before the Cambrian explosion
• The Chinese fossils suggest that “the Cambrian explosion had a long fuse”
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(a) Tahap dua-sel 150 µm 200 µm(b) Tahap lebih lanjut
Fosil-fosil Proterozoikum yang mungkin merupakan embrio hewan yang berumur 575 jut tahun (SEM)
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The Colonization of Land
• Fungi, plants, and animals began to colonize land about 500 million years ago
• Plants and fungi likely colonized land together by 420 million years ago
• Arthropods and tetrapods are the most widespread and diverse land animals
• Tetrapods evolved from lobe-finned fishes around 365 million years ago
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Colonization of land
Billions of year
s ag
o4
32
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The rise and fall of dominant groups reflect continental drift, mass extinctions, and adaptive
radiations
• The history of life on Earth has seen the rise and fall of many groups of organisms
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Continental Drift
• At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago
• Earth’s continents move slowly over the underlying hot mantle through the process of continental drift
• Oceanic and continental plates can collide, separate, or slide past each other
• Interactions between plates cause the formation of mountains and islands, and earthquakes
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(a) Irisan bumi (b) Lempeng-lempeng benua utama
Innercore
Outercore
Crust
MantlePacificPlate
NazcaPlate
Juan de FucaPlate
Cocos Plate
CaribbeanPlate
ArabianPlate
AfricanPlate
Scotia Plate
NorthAmericanPlate
SouthAmericanPlate
AntarcticPlate
AustralianPlate
PhilippinePlate
IndianPlate
Eurasian Plate
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(a) Cutaway view of Earth
Innercore
Outercore
Crust
Mantle
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(b) Major continental plates
PacificPlate
NazcaPlate
Juan de FucaPlate
Cocos Plate
CaribbeanPlate
ArabianPlate
AfricanPlate
Scotia Plate
NorthAmericanPlate
SouthAmericanPlate
AntarcticPlate
AustralianPlate
PhilippinePlate
IndianPlate
Eurasian Plate
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Consequences of Continental Drift
• Formation of the supercontinent Pangaea about 250 million years ago had many effects• A reduction in shallow water habitat• A colder and drier climate inland• Changes in climate as continents moved toward and away
from the poles• Changes in ocean circulation patterns leading to global
cooling
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SouthAmerica
Pangaea
Mil
lio
ns
of
year
s ag
o
65.5
135
Mes
ozo
ic
251
Pal
eozo
ic
Gondwana
Laurasia
Eurasia
IndiaAfrica
AntarcticaAustralia
North Americ
a
Madagascar
Cen
ozo
ic
Present
Sejarah hanyutan benua selama eon fanerozoikum
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SouthAmerica
Mil
lio
ns
of
year
s ag
o
65.5
Eurasia
IndiaAfrica
AntarcticaAustralia
North Americ
a
Madagascar
Cen
ozo
ic
Present
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Pangaea
Mil
lio
ns
of
year
s ag
o
135
Mes
ozo
ic
251
Pal
eozo
ic
Gondwana
Laurasia
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• The break-up of Pangaea lead to allopatric speciation
• The current distribution of fossils reflects the movement of continental drift
• For example, the similarity of fossils in parts of South America and Africa is consistent with the idea that these continents were formerly attached
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Mass Extinctions
• The fossil record shows that most species that have ever lived are now extinct
• At times, the rate of extinction has increased dramatically and caused a mass extinction
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The “Big Five” Mass Extinction Events• In each of the five mass extinction events, more
than 50% of Earth’s species became extinct
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To
tal e
xtin
cti
on
ra
te(f
amili
es
pe
r m
illio
n y
ears
):
Time (millions of years ago)
Nu
mb
er o
f fa
mili
es:
CenozoicMesozoicPaleozoicE O S D C P Tr J
542
0
488 444 416 359 299 251 200 145
EraPeriod
5
C P N
65.5
0
0
200
100
300
400
500
600
700
800
15
10
20
Mass extinction and the diversity of life
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• The Permian extinction defines the boundary between the Paleozoic and Mesozoic eras
• This mass extinction occurred in less than 5 million years and caused the extinction of about 96% of marine animal species
• This event might have been caused by volcanism, which lead to global warming, and a decrease in oceanic oxygen
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• The Cretaceous mass extinction 65.5 million years ago separates the Mesozoic from the Cenozoic
• Organisms that went extinct include about half of all marine species and many terrestrial plants and animals, including most dinosaurs
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• The presence of iridium in sedimentary rocks suggests a meteorite impact about 65 million years ago
• The Chicxulub crater off the coast of Mexico is evidence of a meteorite that dates to the same time
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NORTHAMERICA
ChicxulubcraterYucatán
Peninsula
Trauma bagi Bumi dan kehidupan Kreta
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Apakah kepunahan Keenam sedang berlangsung?
• Para saintis memperkirakan bahwa tingkat laju kepunahan adalah 100 sampai 1.000 kali lebih besar daripada laju latar tipikal yang terlihat dalam catatan fosil
• Data menunjukkan bahwa kepunahan massal keenam (akibat manusia) mungkin akan terjadi dalam beberapa abad atau melenium mendatang apabila tindakan dramatis tidak diambil
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Konsekuensi Kepunahan Massal
• Kepunahan massal dapat mengubah komunitas ekologi
• Catatan fosil menunjukkan bahwa biasanya diperlukan 5-100 juta tahun bagi keanekaragaman makhluk hidup untuk pulih setelah kepunahan massal
• Kepunahan massal dapat membuka jalan bagi radiasi adaptif
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Pre
dat
or
gen
era
(pe
rcen
tag
e o
f m
arin
e g
en
era
)
Time (millions of years ago)
CenozoicMesozoicPaleozoicE O S D C P Tr J
542
0
488 444 416 359 299 251 200 145
EraPeriod C P N
65.5 0
10
20
30
40
50
Kepunahan massal dan ekologi
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Adaptive Radiations
• Radiasi adaptif (Adaptive radiation) adalah periode perubahan evolusioner ketika kelompok-kelompok organisme membentuk banyak spesies baru dengan adaptasi yang memungkinkan mereka mengisi peran ekologis, atau relung, yang berbeda dalam komunitas
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Radiasi Adaptif berskala Dunia
• Mamalia mengalami radiasi adaptif besar-besaran setelah kepunahan dinosaurus darat 65,5 juta tahun lalu.
• Dengan lenyapnya dinosaurus (kecuali burung), mamalia berkembang pesat dalam keanekaragaman maupun ukuran, mengisi peran-peran ekologis yang sebelumnya ditempati oleh dinosaurus darat.
• Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods
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Millions of years ago
Monotremes(5 species)
250 150 100200 50
ANCESTRALCYNODONT
0
Marsupials(324 species)
Eutherians(placentalmammals;5,010 species)
Ancestralmammal
Adaptive radiation of mammals
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Radiasi adaptif Regional
• Radiasi adaptif dapat terjadi ketika organisme mengolonisasi wilayah yang hanya terdapat sedikit kompetisi
• Kepulauan Hawaii merupakan salah satu tempat pameran terbesar di dunia dari radiasi adaptif regional
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Close North American relative,the tarweed Carlquistia muirii
Argyroxiphium sandwicense
Dubautia linearisDubautia scabra
Dubautia waialealae
Dubautia laxa
HAWAII0.4
millionyears
OAHU3.7
millionyears
KAUAI5.1
millionyears
1.3millionyears
MOLOKAIMAUI
LANAI
Adaptive radiation on the Hawaiian Islands
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Close North American relative,the tarweed Carlquistia muirii
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Dubautia waialealae
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Dubautia laxa
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Dubautia scabra
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Argyroxiphium sandwicense
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Dubautia linearis
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Perubahan besar pada bentuk tubuh dapat menyebabkan perubahan di dalam sekuens dan regulasi gen
perkembangan
• Mempelajari mekanisme genetik perubahan dapat memberikan wawasan perubahan evolusioner skala besar
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Efek-efek Evolusiner dari gen-gen Perkembangan
• Gen-gen yang mengatur perkembangan mempengaruhi laju, waktu terjadi, dan pola spasial dari perubahan pada bentuk organisme ketika ia berkembang dari zigot menjadi dewasa
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Perubahan pada laju dan waktu terjadi
• Heterokroni (Heterochrony) adalah perubahan evolusioner dalam laju atau waktu terjadinya peristiwa perkembangan
• Sebagai contoh, bentuk suatu organisme sebagian bergantung pada laju pertumbuhan relatif dari bagian-bagian tubuh yag berbeda selama perembangan
• Perubahan kecil sekali pun dalam laju pertumbuhan relatif dapat mengubah bentuk dewasa secara substansial, seperti yang terlihat pada bentuk tengkorak manusia dan simpanse yang sangat kontras
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(a) Laju perkembangan diferensial pada manusia
NewbornAge (years)
Adult1552
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(b) Comparison of chimpanzee and human skull growth
Chimpanzee fetus Chimpanzee adult
Human fetus Human adult
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• Chimpanzee infant Chimpanzee adult
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• Heterokroni juga dapat mengubah waktu perkembangan reproduktif terhadap organ-organ nonreproduktif
• Pada pedomorfosis (paedomorphosis), laju perkembangan organ reproduksi lebih cepat daripada organ-organ yang lain, tahap kedewasaan secara seksual dari satu spesies mungkin tetap mempertahankan ciri-ciri tubuh yang merupakan struktur juvenil pada spesies nenek moyang
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Gills
Pedomorfosis pada salamander axolotl
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Perubahan Pada Pola Spasial
• Perubahan evolusioner yang substansial juga dapat terjadi akibat perubahan pada gen-gen yang mengendalikan penempatan dan penataan spasial bagian-bagian tubuh
• Gen-gen regulator induk yang disebut Gen homeotik (homeotic gene) menentukan ciri-ciri dasar seperti letak sepasang sayap dan sepasang kaki yang akan berkembang pada burung atau cara penataan bagian-bagian bunga dari suatu tumbuhan
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• Produk dari salah satu kelas gen homeotik, gen-gen Hox menyediakan informasi posisi pada embrio hewan
• Informasi ini mendorong sel-sel untuk berkembang menjadi struktur yang sesuai bagi lokasi tertentu
• Perubahan pada gen-gen Hox atau pada cara gen-gen tersebut diekspreasikan dapat memiliki dampak yang besar pada morfologi
• Misalnya, di antara krustasea, perubahan pada lokasi tempat 2 gen Hox (Ubx dan Scr) diekspresikan akan berkorelasi dengan konversi dari kaki renang menjadi kaki untuk makan
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• Evolusi vertebrata dari hewan invertebrata mungkin juga dipengaruhi oleh sejumlah perubahan pada gen-gen Hox dan gen-gen yang meregulasi mereka
• Dua duplikasi dari gen-gen Hox telah terjadi pada garis keturunan vertebrata, dan semua genom vertebrata yang sudah diuji telah memiliki kedua duplikasi ini
• Duplikasi-duplikasi ini mungkin berperan penting dalam kemunculan karakteristik baru pada vertebrata
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Vertebrata (berahang) dengan empat gugus Hox
Vertebrata awal hipotesis (tak berahang) dengan dua gugus Hox
Nenek moyang vertebrata hipotesi (invertebrata) dengan gugus Hox tunggal
Duplikasi Hox yang kedua
Duplikasi Hox yang pertama
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Evolusi Perkembangan
• The tremendous increase in diversity during the Cambrian explosion is a puzzle
• Developmental genes may play an especially important role
• Changes in developmental genes can result in new morphological forms
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Perubahan pada Gen
• Bentuk-bentuk morfologi baru mungkin berasal dari peristiwa duplikasi gen yang menghasilkan gen-gen perkembangan baru
• Sebuah mekanisme yang mungkin untuk evolusi serangga berkaki enam dari nenek moyang serupa-krustasea yang memiliki lebih dari enam kaki ditunjukkan dalam percobaan laboratorium
• Perubahan spesifik dalam gen Ubx telah diidentifikasi yang dapat “menekan" pembentukan kaki
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Hox gene 6 Hox gene 7 Hox gene 8
About 400 mya
Drosophila Artemia
Ubx
Asal-usul bangun tubuh serangga
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Perubahan dalam Regulasi gen
• Perubahan bentuk organisme mungkin disebabkan oleh mutasi-mutasi yang mempengaruhi regulasi, bukan susunan, gen-gen perkembangan
• Misalnya ikan stickleback berduri-tiga yang hidup di danau memiliki duri lebih sedikit dari kerabat mereka yang hidup di laut
• Sekuens gen tetap sama, tetapi regulasi ekspresi gen berbeda dalam dua kelompok ikan
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Uji Hipotesis A:Adakah perbedaan pada sekuens pengkode gen Pitx1 milik stickleback yang hidup di laut dan di danau?
hasil:tidak
Embrio stickleback laut
Tampak-dekat permukaan ventral
Uji Hipotesis B:Adakah perbedaan dalam hal regulasi ekspresi Pitx1?
Pitx1 diekspresikan pada wilayah duri ventral dan wilayah mulut stickleback laut yang sedang berkembang, namun hanya wilayah mulut pada stickleback danau yang sedang berkembang
Tidak. Ke-283 aasam amino protein Pitx1 pada populasi stickeback laut dan danau ternyata identik
Hasilt:Ya
Embrio stickleback danau
Tampak dekat mulut
RESULTS
Apa yang menyebabkan hilangnya duri pada ikan stickleback danau?
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Evolusi bukan berorientasi kepada tujuan• Evolusi bagaikan mengutak-atik proses kemunculan
bentuk-bentuk baru melalui modifikasi kecil dari bentuk-bentuk yang sudah ada.
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Hasil baru evolusi• Ketika spesies baru terbentuk , struktur-struktur yang baru
dan kompleks dapat muncul sebagai modifikasi bertahap dari struktur nenek moyang
• Dalam kingdom hewan, mata kompleks telah berevolusi secara mandiri dari gugusan sederhana sel-sel fotoreseptor yang ada pada nenek moyang bersama.
• Eksaptasi (Exaptations) adalah struktur-struktur yang berevolusi dalam suatu konteks namun menjadi terlibat untuk fungsi lain
• Seleksi alam tidak dapat memperkirakan masa depan, melainkan hanya bisa meningkatkan suatu struktur dalam konteks kegunaan saat ini
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(a) Topok sel-sel berpigmen
Saraf optiklapisan berpigmen (retina)
Sel-sel berpigmen (fotoreseptor)
Rongga berisi caira
Epithelium
Epitelium
(c) Mata tipe kamera lubang-jarum
Optic nerve
Cornea
Retina
Lens
(e) Mata tipe kamera kompleks
(d) Mata dengan lensa primitif
Saraf optik
KorneaMassa selular (lensa)
(b) Mangkuk mata
Sel-sel berpigmen
Serabut saraf Serabut sarf
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TREN EVOLUSI
• Mengambil satu progresi evolusi tunggal dari catatan fosil dapat menyesatkan
• Tren evolusi jelas harus diperiksa dalam konteks yang lebih luas
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Recent(11,500 ya)
NeohipparionPliocene(5.3 mya)
Pleistocene(1.8 mya)
Hipparion
Nannippus
Equus
Pliohippus
Hippidion and other genera
Callippus
Merychippus
Archaeohippus
Megahippus
Hypohippus
Parahippus
Anchitherium
Sinohippus
Miocene(23 mya)
Oligocene(33.9 mya)
Eocene(55.8 mya)
Miohippus
Paleotherium
Propalaeotherium
Pachynolophus
Hyracotherium
Orohippus
Mesohippus
Epihippus
Browsers
Grazers
Key
Evolusi Bercabang dari kuda
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Oligocene(33.9 mya)
Eocene(55.8 mya)
Miohippus
Paleotherium
Propalaeotherium
Pachynolophus
Hyracotherium
Orohippus
Mesohippus
Epihippus
Browsers
Grazers
Key
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Recent(11,500 ya)
NeohipparionPliocene(5.3 mya)
Pleistocene(1.8 mya)
Hipparion
Nannippus
Equus
Pliohippus
Hippidion and other genera
Callippus
Merychippus
Archaeohippus
Megahippus
Hypohippus
Parahippus
Anchitherium
Sinohippus
Miocene(23 mya)
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• seleksi spesies: spesies yang mampu bertahan paling lama dan menghasilkan spesies keturunan baru paling banyak akan menentukan arah tren evolusi utama
• Apapun penyebabnya, suatu tren evolusi tidak berarti bahwa ada suatu dorongan intrinsik menuju fenotip tertentu
• Evolusi adalah akibat dari interaksi antara organisme dan lingkungannya saat ini; jika kondisi-kondisi lingkungan berubah, suatu tren evolusi bisa berhenti atau mungkin berbalik
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Millions of years ago (mya)
1.2 bya:First multicellular eukaryotes
2.1 bya:First eukaryotes (single-celled)
3.5 billion years ago (bya):First prokaryotes (single-celled)
535–525 mya:Cambrian explosion(great increasein diversity ofanimal forms)
500 mya:Colonizationof land byfungi, plantsand animals
Pre
sen
t
500
2,00
0
1,50
0
1,00
0
3,00
0
2,50
0
3,50
0
4,00
0