Transcript Document 7370251

Rooting the Tree of Life
Rooting the Tree of Life
• Natural Selection has
been going on since the
beginning of life. It is not
unique to just any species
but it is an evolutionary
aspect of adaptation.
• After several scientific
investigations, it is
believed that all forms of
organisms now evolved
from earlier forms of
organisms dated back to
approximately 3.85
billions years ago.
• “evidence…in the form of
gene sequences, fossils,
and ancient traces of
Earth’s chemistry”
enables scientist to
rewrite the timeline of
history.
Tree of Life
• Three Main Branches
– Eukaryotes
•
•
•
•
Plants
Fungi
Animals
Single-celled protozoa
–
–
–
–
Amoebae
Parasites
Dysentery
giardia
– Prokaryotes
– Microbes Archaea
–1970- Carl Woese
• University of Illinois
• Biologist found that these simple
organisms may look like bacteria, but
they have cellular machinery that is
radically different. Woese named these
microbes archaea, meaning “first” for
the branch on which they appear. (103)
• Most of the diversity of life, not to
mention the sheer physical mass, is
microbial
In Search of Life’s Origin
Chemical Evolution
• Many of life’s origin could have came from
space. Astronomers discovered a number of
basic ingredients of life on meteorites, comets,
and interplanetary dusts.
• Ingredients from these foreign objects could
have seeded the planet w/components for
crucial parts of the cell
– Phosphate backbone of DNA
– Information-bearing bases
– Amino acids for making proteins
cont…
• Concentrated in raindrops or the spray of ocean
waves
• Life could have began at the mid ocean ridges
where hot magma emerges from the mantle
• Bacteria and archaea that live in extreme
conditions such as boiling water or acid
• Pre biological molecules became
organized into cycles of chemical
reactions that could sustain
themselves independently
Cont…
Biological Evolution
• DNA
– Capable of carrying information from one generation
to another
• RNA
– Carries information
– Produces proteins and amino
– Thomas Cech (1982) discovered that RNA can also
edit their own code
• ENZYMES
– Edit useless sequences after DNA is copied into RNA
The Mangrove of Life
• Evolution continues to be a story of and
about microbes
• Possible reasons for evolution of our
genetic sequencing and changes
– Examination of early bacteria show that
bacteria sometimes scoop up its genes and
integrate then into their own genomes
– Parasites can sometimes inject genetic
materials from one hosts to another
• Malaria
Evolution on Double Time
• Gene Duplication
– Create genes that are essential to the functioning of
the organism. Those are good for the organism will
be duplicated to do new jobs but those that are
superfluous will be eradicated because they are not
necessary.
– Mutations to useless genes that are already in the
organism systems are “pseudogenes”
– Duplicate Genes can be grouped into families and
they reflect a common descendant.
– Genes do not simply mutate, they multiply because of
duplication and a change in life could have caused a
transformation by coming in contact with another
organism or it was essential for their function in life
due to change.
Fusion Evolution
• Bacteria living inside cells and they both
benefit each other “symbiosis”
• Mitochondria
– Respiration: sausage-shaped blobs in our body
system that manages the use of oxygen and
other chemicals to create fuel for fuel
– All eukaryotes has mitochondria
• Chloroplast
– Captures sunlight in plant to create food for
plants in the process of photosynthesis
Cont…
• Both Mitochondria and Chloroplast has
DNA of their own and duplicate itself within
the cells of the organism.
• Dalhousie Univ. Novia Scotia (mid 1970)
– Carl Woese and W. Ford Doolittle
• Found that the DNA in chloroplasts does not
resemble the algae’s nucleus. Instead, it is
cyanobacteria DNA
• (1998-Siv Andersson) Mitochondria is also a
relative of Rickettsia prowazekii, a bacteria that
causes typhus.
Mitochondria cont…
• It is believed that a long-lost oxygenbreathing bacterium , gave rise to the
ancestors of both Rickettsia and
mitochondria. Both were free-living
microbes, feeding on the nutrients that
surrounded them. Eventually each lineage
began to live inside other organisms.
Rickettsia became a ruthless parasite
while mitochondria became a helping
component in eukaryote organisms.
• During the age of the microbes, there were
countless number of changes that
occurred that create our world today.
• It is only after microbes had gone through
all of this evolution that our own multi
cellular ancestors-the first animal could
appear.
Evolution
Intro to evolution
• All animals descended form a common
single-celled ancestor, but scientists are
still learning how it was that they
diversified into so many different bodies
• All animals use a standard tool kit of bodybuilding genes
• The tool kit must have evolved in the
millions of years that preceded the
Cambrian explosion
Evolution’s monsters
• To learn how animals evolve, biologists
make monsters
– Flies with legs sprouting from their heads
– Spinal cord in a frogs belly
• All they have to do is alter a single gene
• These genes control the development of
animal bodies
• The process of creating these “monsters”
is called homeosis
• This process was first discovered in 1915,
when mutant fruit flies were discovered
growing extra wings
• 1980 biologists figured out how to isolate
the gene that is responsible for mutations
• These genes are called HOX genes
Hox genes
• By altering hox genes,
biologists could create
mutated flies
• By doing so, biologists
were able to figure out
how normal Hox genes
work
• It is the Hox genes job to
tell the cells of an embryo
(baby) what they are
going to become
– Abdomen or leg
• Hox genes exert their power
by acting like master control
switches for other genes
• A single Hox gene can
trigger a chain reaction of
many other genes, and
together they form a
particular part of the body
• Hox genes are lined up on
their chromosome in the
same order as they are
expressed in the body
– Head genes in front
– Tail genes in back
• When Hox genes were
first discovered, biologists
thought that they were
only in flies
• Biologists soon began to
find that Hox genes are in
many other types of
animals, from worms to
humans
• The Hox gene does the
same job in all of these
animals
• It specifies different
sections of the head-totail axis
• The genes are so similar
in these animals that they
could replace a defective
gene from a fly with a
mouse gene and it would
still grow properly
Master Control Genes
• In the 1980’s and 90’s
scientists discovered
many other mastercontrol genes at work,
just as powerful as Hox
genes
• While hox genes work
from head to tail, other
genes mark the left and
right sides, and others
establish top and bottom
• These genes help build
organs
• Each of these master
control genes also exists
in our own DNA
• these genes are able to
use the same bodybuilding instructions to
build very different kinds
of animal bodies
• This common genetic tool
kit is so intricate that it
couldn’t have evolved
independently…
The genes behind Cambrian
explosion
• Once biologists
discovered the genetic
tool kit, they realized that
it might have made the
Cambrian explosion
possible
• The genetic tool kit
emerged in the common
ancestors of all animals
about 535 million years
ago
• Evolution did not build a
new network of body
building genes from
scratch, it simply tinkered
with the original genetic
tool kit to build different
body parts
• An example of this is our
own nervous system: all
vertebrae have a nerve
cord running down their
backs, while heart is on the
front; insects have the
opposite arrangement
The dawn of Vertebrates
• Vertebrae acquired
eyes, complex brains,
and skeletons during
the Cambrian
explosion
• To figure out how this
happened biologists
studied our closest
living relative, the
lancelet
• Looks like a headless
sardine
• Shares key traits with
vertebrae
– Has slits near the front
of its body
corresponding to gills
– Has a nerve cord
running along its back
• It also has precursors
to eyes and a brain
Cont
• Hox genes and other
genes that map out the
vertebrate brain do the
same job in the lancelet
embryo
• Once the ancestor of
vertebrates and lancelets
divided, our ancestors
went through an
extraordinary evolutionary
experience
• Hox and master-control
genes duplicated
themselves, forming new
body parts and organs
• Thanks to this,
vertebrates could start
hunting and growing
bigger
• Big mobile predators
appeared on earth for the
first time
Flaws and Fingers
• Although were are
very well developed
were are
fundamentally flawed
– Eyes: human and
squid
• Biologists looked
back at lancelets to
figure out how come
vertebrates had this
flaw
• It has been argued
that fish evolved legs
and toes to move
underwater, not on
land
• One biologists has
even found fossils of
a separate lineage of
fish that evolved
fingers independently
of our own ancestors
Cont…and whales
• Evolution borrows things
adapted for one function
to perform a new one
• Whales are thought to be
descended from
mammals that lived on
land
• A paleontologist found the
first fossil of a land whale
in 1979
• Cows and hippos are
their closest ancestors
• Although whales went
through lots of evolution,
they had limits
• They didn’t change until
after the dinosaurs were
gone
• Ever since then, all types
of mammals have
dominated the land and
sea
• This domination only
happened because
millions of other species
disappeared
Extinctions
Extinctions
• Suspects behind extinctions include volcanoes,
asteroids, and sudden changes to the oceans
and the atmosphere
• Extinctions divide Earth’s history into three great
eras: the Paleozoic, “ancient life”, the Mesozoic,
“middle life”, and the Cenozoic, “early life”.
• Extinctions have destroyed as much as 90
percent of all species at one time.
Permian-Triassic Extinction
• Evidence of the Permian-Triassic extinction can
be found in the mountains of the Karroo Desert
in South Africa.
• This extinction destroyed 90 percent of all
species living on Earth around 250 million years
ago.
• The Permian-Triassic extinction was the biggest
mass extinction that was ever recorded.
Permian-Triassic Extinction cont’d
• Before the extinction hulky reptilian creatures,
called synapsids, were the dominant
inhabitants of the Karroo Desert.
• The mass extinction destroyed almost all
species of trees on Earth, along with most of the
smaller plants.
• Insects, which had not succumbed to any other
mass extinction in their history, disappeared in
great numbers.
Krakatau
• Krakatau was an island in the Sunda Strait
whose volcano erupted in 1883.
• During the eruption: a column of ash rose 20
miles, mud rained down, clouds of vaporized
rocks flew at 300 mph away from the island and
incinerated thousands of people.
• The eruption caused tsunamis around the world.
• The ash from the eruption turned sunsets
bloodred, making everything look like it was on
fire.
Krakatau cont’d
• The eruption killed every living plant and animal
on Krakatau.
• After a few years life began to return to the
island, starting with ferns, mosses, a few beach
plants, and spiders.
• By the 1890s fig and coconut trees were
scattered across the island and beetles,
butterflies, and a monitor lizard joined them.
Mammals
• Only a few synapsids came through the Triassic period, but
one that did continued to evolve the equipment for becoming
a mammal.
• These synapsids, known as cynodonts, evolved rib cages to
house diaphragms, which allowed them to develop more
stamina.
• The cynodonts developed hair and began to nurse their
young.
• They had a high metabolism that made it easier for them to
grow smaller, until eventually none of the early mammals
weighed more than 5 pounds.
• Their high metabolism also helped them fill a niche left empty
by their cold-blooded counterparts, they became able to hunt
at night.
Mammals cont’d
Monotremes
Placental mammals
• Placental mammals keep
• Oldest lineage of
their babies in the uterus
mammals still alive today.
until they are very
• They have less control
developed.
over their body
• They have a placenta that
temperatures.
surrounds the embryo and
• Female monotremes lay
gives the baby nutrients.
eggs instead of having a • They branched off from the
live birth.
other mammals somewhere
between 100 and 65 million
• Example: the platypus.
years ago.
• Example: the rabbit.
K-T Extinction
• The K-T Extinction occurred at the end of the
Cretaceous period, around 65 million years ago.
• This was when the dinosaurs disappeared along with 70
percent of all species.
• In the Bottaccione Gorge, in Italy, there are rocks that
are from the Cretaceous period and the Paleocene
period, but between these two rocks there is a half-inch
wide strip of clay which marks the K-T extinction.
• This strip does not contain any fossils of the plankton
that can be found below it or above it.
K-T Extinction cont’d
• American geologist Walter Alvarez and his father Luis tried
to identify the clay’s time period by measuring the iridium
levels but they found that the rate was 30 times that which
was found both above and below the strip of clay.
• Because iridium usually came from space the Alvarez duo
speculated that the huge dose of iridium at the end of the
Cretaceous period must have come from a giant asteroid
hitting the earth.
• This asteroid’s debris combined with the terrestrial rock its
crater gouged out flew into the air and created a dark
shroud around the planet. The dark cloud blocked out the
sun, which killed the plants, starving the herbivores, with
the carnivores disappearing afterwards. This was the K-T
extinction.
Ice Ages
• While mammals have been the dominant land vertebrates for
the past 65 million years, they have had to go through their
own changes.
• The climate was a lot warmer between 65 and 55 million
years ago, so warm that palm trees could grow north of the
Arctic Circle and Canada resembled Costa Rica today.
• After that the world’s average temperature has been dropping,
and it is partly the Himalayas fault. When they were first
created, the rains that fell on the Himalayas carried dissolved
carbon dioxide which the Himalayas removed from the
atmosphere. They removes so much that the climate
gradually cooled.
Ice Ages cont’d
Antarctica moved further south until it reached the South
Pole. Permanent ice began to form on it and the ice reflected
the sun back into space and cooled the atmosphere.
• While South America and North America joined together, after
their 60 million year separation, The Great American
Interchange occurred. The Interchange came from the
different species of animals that migrated from one continent
to another.
• At the time of the Interchange, the global climate found a new
pattern. The ice at the poles moved outward towards the
equator and then pulled back in a series of ice ages.
• These ice ages were controlled by the changing orbit of Earth
around the sun. The earth moves closer and farther away
from the sun in its 100,000 year cycle. These changes alter
how much sunlight the earth receives and this alters the
climate and results in ice ages.
•
Human Extinctions
The First Waves
• The latest mass extinctions began around
50,000 years
• It was from the latest mass extinction that
humans arrived
• The oldest evidence of humans comes from
Chile dated 14,700 years ago
• Humans did their part to wipe out the huge
animals that they coexisted with all around
the globe
• Human caused extinctions served as
catalysts for changing the environment of the
planet
History in a Hole
• Holes in the ground can do wonders as
a time machine
• Caves preserve bones, and lakes
preserve pollen from plants
• Hawaii’s isolation, like the Galapagos
provides a great place for study
• The arrival of Captain Cook in Hawaii
caused a mass extinction of native
plants and animals
Extinctions Accelerate
• Humans seem to be major catalysts for
animals extinctions
• Civilizations that began to appear 10,000
years ago caused environmental destruction
• Deforestation, and land exploitation for crops
destroyed many species
• Extinctions proceed based on a half-life many
times, in which during a period of time 50% of
the species will die, and then the remaining
50% will die in the second period
Alien Invasion
• Extinctions are sped up by biological invaders,
which are new species that are introduced to a
new environment
• Biological invasions were rare before humans
• Biological invaders killed much faster than even
the humans did
• Some biological invaders benefit more from
their introduced environment, because they
don’t suffer from normal predators
The Future of Extinctions
• We seem to be entering an era of mass
extinction on par with the die-offs of 600
million years ago
• Species are disappearing 100 to 1,000
times faster today than before the arrival
of humans
• Global Warming also stands to
substantially alter the worlds climate
Humanity Leaves its Mark
• The next few centuries could see the
largest number of animals lost ever, well
over half of all species
• Human can alter the course of biodiversity
• Over 90% of the world’s agriculture is
based on 20 species of plants and 6
species of animals
• Humans may not survive if ecosystems
that we rely on collapse due to lack of
biodiversity
In Conclusion
• Darwin is wrong and there is no theory of
evolution, there is just a list of animals that
Chuck Norris lets live…
Clip on Evolution