The Cenozoic Era began 65 million years ago after the extinction of the dinosaurs. During this era, mammals diversified and grew larger to fill ecological niches as the dominant land animals. Birds also flourished. The era is divided into periods and epochs where species evolved or went extinct based on environmental changes. During the Paleogene period after dinosaurs, mammals and birds were small but evolved into ancestors of modern groups. In the Neogene, grasslands expanded and large mammals like horses and rhinos evolved. The Pleistocene ice ages drove many large mammals like mammoths and saber-toothed cats to extinction. The current Holocene epoch since the last ice age has seen human impacts drive further extinctions.
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardized international units of geologic time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective[1] is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)[2] that are used to define divisions of geologic time. The chronostratigraphic divisions are in turn used to define geochronologic units.[2]
While some regional terms are still in use,[3] the table of geologic time presented in this article conforms to the nomenclature, ages, and color codes set forth by the ICS as this is the standard, reference global geologic time scale – the International Geological Time Scale.[1][
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardized international units of geologic time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective[1] is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)[2] that are used to define divisions of geologic time. The chronostratigraphic divisions are in turn used to define geochronologic units.[2]
While some regional terms are still in use,[3] the table of geologic time presented in this article conforms to the nomenclature, ages, and color codes set forth by the ICS as this is the standard, reference global geologic time scale – the International Geological Time Scale.[1][
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. Background
The total life span of the earth from the time of its origin is
called geological time.
The available evidence indicates that age of earth is 5000
million(5 billion) years .
Geologists have divided the geographical time into different
divisions based on the different types of fossils available in
the different strata of the earth.
Each division has its own duration and feature and it differs
from other divisions.
3. Major divisions are called eras.The eras are
divided into periods and the periods into epochs.
The eras,periods and epochs of the geological
time are arranged in an orderly manner and this
arrangement is called geological time scale.
4.
5.
6.
7.
8.
9. Cenozoic Era (65 million years ago to present)
The KT Event set the stage for the Cenozoic Era that began
65 million years ago. As the dinosaurs perished at the end of
the Cretaceous, the mammals took center stage. It is
represented upto present.It is called “Age of Mammals”.
Even as mammals increased in numbers and diversity, so too
did the birds, reptiles, fish, insects, trees, grasses, and other
forms of life. Species changed as the epochs of the Cenozoic
Era rolled by, with the mammals eventually becoming the
largest land animals of the Era, as the dinosaurs had been
during the Mesozoic.
10. Flowering plants strongly influenced the evolution of both
birds and herbivores throughout the Cenozoic era by
providing a rich abundance of food.
Those that could adapt to the changes in the environment
survived; those that could not were doomed to extinction.
The era is divided into 3
periods(Paleogene,Neogene,Quaternary) and 7 epochs.
12. TERRESTRIAL AND AQUATIC LIFE
Terrestrial Life During the Paleogene Period
Mammals.
Mammals didn't suddenly appear on the at the start of the Paleogene period; primitive mammals
dated back as far as the Triassic period, 230 million years ago. In the absence of dinosaurs,
though, mammals were free to radiate into a variety of open ecological niches. During the
Paleocene and Eocene epochs, mammals still tended to be fairly small, but had already started
evolving along definite lines: the Paleogene is when you can find the earliest ancestors
of whales, elephants, hoofed mammals.
By the Oligocene epoch, at least some mammals had begun to grow to respectable sizes, though
they weren't nearly as impressive as their descendants of the ensuing Neogene period.
13. Birds.
During the early part of the Paleogene period, birds, and not mammals, were the
dominant land animals on earth .
One early evolutionary trend was toward large, flightless, predatory birds
like Gastornis, which superficially resembled meat-eating dinosaurs, but
subsequent eons saw the appearance of more diverse flying species, which were
similar in many respects to modern birds.
14. Reptiles.
Although dinosaurs and marine reptiles had gone completely extinct by
the start of the Paleogene period, the same wasn't true for their close
relative the crocodiles, which not only managed to survive the K/T
Extinction but actually flourished in its aftermath. The deepest roots
of snake and turtle evolution can be located in the later Paleogene, and
small, inoffensive lizards evolved.
Plant Life :
Flowering plants, which had already made an appearance toward the end
of the Cretaceous period, continued to flourish during the Paleogene. The
gradual cooling of the earth's climate paved the way for vast deciduous
forests, mostly on the northern continents, with jungles and rain forests
increasingly restricted to equatorial regions. Toward the end of the
Paleogene period, the first grasses appeared, which would have a
significant impact on animal life during the ensuing Neogene period,
spurring the evolution of both prehistoric horses and the saber-toothed
cats that preyed on them.
15. Marine Life :
Not only the dinosaurs went extinct 65 million years ago; so did their vicious marine
cousins, the mosasaurs, along with the last remaining plesiosaurs and pliosaurs.
This sudden vacuum at the top of the aquatic food chain naturally spurred the
evolution of sharks (which had already been around for hundreds of millions of
years, though in smaller sizes). Mammals had yet to venture fully into the water,
but the earliest, land-dwelling ancestors of whales survived the Paleogene
landscape, most notably in central Asia.
16. Terrestrial Life During the Neogene Period
Mammals.
Global climate trends, combined with the spread of newly evolved grasses, made the Neogene
period the golden age of open prairies and savannahs. These extensive grasslands spurred the
evolution of even- and odd-toed ungulates, including prehistoric horses and camels (especially in
North America), as well as deer, pigs and rhinoceroses.
During the later Neogene, the interconnections between Eurasia, Africa, and North and South
America set the stage for a confusing network of species interchanges, resulting (for example) in
the near extinction of South America's Australia-like megafauna.
17. Birds. While birds never quite matched the size of their distant mammalian cousins,
some of the flying and flightless species of the Neogene period were truly enormous (for
example, the airborne Argentavis and Osteodontornis both exceeded 50 pounds.) The
end of the Neogene marked the extinction of most of the flightless, predatory birds of
South America and Australia, the last ones being wiped out by the end Pleistocene.
Argentavis osteodontornis
18. Reptiles. A large part of the Neogene period was dominated by gigantic crocodiles,
which still never quite managed to match the size of their Cretaceous forebears. This
20-million-year span also witnessed the continuing evolution of prehistoric snakes and
(especially) prehistoric urtles, the latter of which began to reach truly impressive
proportions by the start of the Pleistocene epoch.
Plant Life:
There were two major trends in plant life during the Neogene period. First, plunging
global temperatures spurred the rise of massive deciduous forests, which replaced
jungles and rain forests in high northern and southern latitudes. Second, the worldwide
spread of grasses went hand-in-hand with the evolution of mammalian herbivores,
culminating in today's familiar horses, cows, sheep, deer, and other grazing and
ruminant animals.
19. Marine Life During the Neogene Period
Although prehistoric whales started to evolve in the preceding Paleogene period, they
didn't become exclusively marine creatures until the Neogene, which also witnessed the
continuing evolution of the first pinnipeds (the mammalian family that includes seals and
walruses) as well as prehistoric dolphins. Prehistoric sharks maintained their status at the
top of the marine food chain; Megalodon, for example, had already appeared at the end of
the Paleogene, and continued its dominance throughout the Neogene as well.
21. Terrestrial life During the Pleistocene Epoch
Mammals. The dozen or so ice ages of the Pleistocene epoch destroyed megafauna
mammals, the largest examples of which were simply unable to find enough food to
sustain their populations. The wolly mammoth lived during this period.Conditions were
especially severe in North and South America and Eurasia, where the late Pleistocene
witnessed the extinction of Smilodon (the Saber-Toothed Tiger), the Giant Short-
Faced Bear, Glyptodon (the Giant Armadillo) and Megatherium (the Giant Sloth).
Camels disappeared from North America, as did horses, which were only reintroduced
to this continent during historical times, by Spanish settlers.
22.
23.
24.
25.
26.
27. Birds. During the Pleistocene epoch, bird species continued to flourish around the
globe, inhabiting various ecological niches. Sadly, the giant, flightless birds of
Australia and New Zealand, such as Dinornis (the Giant Moa) and Dromornis (the
Thunder Bird), quickly succumbed to predation by human settlers. Some
Pleistocene birds, like the Dodo and the Passenger Pigeon, managed to survive
well into historical times.
.
28. Reptiles. As with birds, the big reptile story of the Pleistocene epoch was the extinction of
oversized species in Australia and New Zealand, most notably the giant monitor
lizard Megalania(which weighed up to two tons) and the giant turtle Meiolania (which "only"
weighed half a ton). Like their cousins around the globe, these gigantic reptiles were doomed by
a combination of climate change and predation by early humans
29. Plant Life During the Pleistocene Epoch
There were no major plant innovations during the Pleistocene epoch; rather, during these two million
years, grasses and trees were at the mercy of intermittently plunging and rising temperatures. As
during preceding epochs, tropical jungles and rain forests were confined to the equator,
with deciduous forests and barren tundra and grasslands dominating northern and southern regions.
30. Marine Life During the Pleistocene Epoch
The Pleistocene epoch witnessed the final extinction of the giant shark Megalodon, which had
been the top predator of the oceans for millions of years; otherwise, though, this was a
relatively uneventful time in the evolution of fish, sharks and marine mammals. One notable
pinniped that appeared on the scene during the Pleistocene was Hydrodamalis (aka Steller's
Sea Cow), a 10-ton behemoth that only went extinct 200 years ago.Dugong
32. Holocene epoch:- “the age of man”
Plant and animal life
Animal and plant life have not changed much during the relatively short
Holocene, but there have been major shifts in the distributions of plants and
animals. A number of large animals including mammoths and mastodons, saber-
toothed cats like Smilodon and Homotherium, and giant sloths disappeared in
the late Pleistocene and early Holocene—especially in North America.
The Holocene extinction event is a name customarily given to the
widespread, ongoing extinction of species during the modern Holocene epoch.
The genera vary from mammoths to dodos, to species in the rainforest dying
every year. Because some believe the rate of this extinction event is
comparable to the "Big Five" mass extinctions, it is also known as the Sixth
Extinction, although the actual numbers of extinct species are not yet similar
to the major mass extinctions of the geologic past.
33.
34.
35. In broad usage, the Holocene extinction event includes the remarkable
disappearance of large mammals, known as megafauna, by the end of the
last ice age 9,000 to 13,000 years ago. Such disappearances have been
considered as either a response to climate change, a result of the proliferation of
modern humans, or both. Also, some scientists have considered the possibility of
new diseases and super-viruses. These extinctions, occurring near the
Pleistocene/Holocene boundary, are sometimes referred to as the Pleistocene
extinction event, or Ice Age extinction event. The Ice Age extinction event is
characterized by the extinction of many large mammals weighing more than 40
kg. Among the major megafauna exterminated about 9,000 to 15,000 years ago
were the woolly mammoth, the woolly rhinoceros, the Irish elk, the cave lion,
the cave bear, and saber-toothed cats.
39. Within the past 2,000 years, a large number of species have become extinct
in ways more clearly linked to human dispersal or activity.
The observed rate of extinction has risen dramatically in the last 50 years.
Only during these most recent parts of the extinction have plants also
suffered large losses.
Among the human activities currently considered as impacting extinctions
are overhunting (either directly, or indirectly by decimation of prey
populations), introduction of infectious diseases (perhaps carried by
associated animals such as rats or birds), increased interspecific
competition, habitat destruction. The destruction of large mammals could
have had even wider impacts on the ecosystems of which they were part.