EVOLUTION
Methods Used in Determining the Age of
Fossils
Experts make use of several methods to
determine the age of fossils. These methods are
the following:
1. Relative Dating - This method is used to
determine the age of rocks by comparing them
with the rocks present in the other layer. The
younger sedimentary rock layer is assumed to be
found on top and the older rock is found at the
bottom layer.
2. Radiometric Dating - This type of dating is
used to determine the age of rocks using the
decay of radioactive isotopes present among the
rocks such as Carbon-14. All organisms have
decaying Carbon-14 in them. Plants and animals
that are still alive constantly replace the supply of
carbon in their body while the amount of carbon14 in their body stays the same. When an
organism dies, carbon-14 will start to decay.
3. Carbon Dating- It is used to tell the age of
organic materials. Art collectors use carbon
dating to determine if a piece of artwork is
genuine or not
Geologic Time Scale
Out of the examinations of layers of rocks
and dating of fossils, scientists were able to
develop the Geologic Time Scale. This scale
shows the major events in the Earth’s history. It
also shows the appearance of various kinds of
organisms in a particular period of time on Earth.
Era, the largest division of the Geologic Time
Scale, has the following parts: Precambrian,
Paleozoic, Mesozoic, and Cenozoic. Each era is
further divided into periods.
The Precambrian is a term used to describe the
interval of geologic time that extends from the
formation of the Earth, around 4.6 billion years
ago, to the beginning of the Phanerozoic eon,
approximately 541 million years ago. It is the
longest span of Earth's history and is divided into
three eons: the Hadean, Archean, and
Proterozoic. During the Precambrian, the Earth
underwent significant changes, including the
formation of the first continents, the evolution of
the atmosphere and oceans, and the emergence
of life. The earliest life forms were unicellular
organisms such as bacteria and algae, which
appeared around 3.5 billion years ago.
The Hadean eon represents the earliest stage of
Earth's history, from its formation around 4.6
billion years ago to about 4 billion years ago.
During this time, the planet was subject to intense
bombardment by asteroids and comets, which
caused widespread volcanic activity and the
formation of the first oceans and atmosphere.
The Hadean eon is named after Hades, the
Greek god of the underworld, due to the extreme
conditions that prevailed on Earth at that time.
The Archean eon followed the Hadean and lasted
from about 4 billion years ago to 2.5 billion years
ago. It is characterized by the emergence of life
on Earth, the formation of the first continents, and
the stabilization of the atmosphere and oceans.
During the Archean, the first microbial life forms
evolved, and the earliest evidence of
photosynthesis and oxygen production by
cyanobacteria appeared.
The Proterozoic eon followed the Archean and
lasted from about 2.5 billion years ago to the
beginning of the Phanerozoic eon, around 541
million years ago. It is marked by the emergence
of eukaryotic cells, the diversification of life forms,
and the formation of the supercontinent Rodinia.
During the Proterozoic, Earth's climate alternated
between ice ages and warmer periods, and the
first multicellular organisms appeared.
The oldest fossils discovered to date are from
approximately 3.5 billion years ago, Precambrian
Era. These fossils are microbial mats found in
Western Australia and were described in a study
published in 2018. The fossils consist of
structures that resemble modern microbial
communities, suggesting that life on Earth was
present and diverse as early as 3.5 billion years
ago. However, it is possible that even older fossils
exist but has not yet been discovered.
AGE OF DINOSAURS
The Phanerozoic eon is the current eon of
Earth's history, and it began approximately 541
million years ago with the Cambrian explosion, a
period of rapid diversification and evolution of
complex life forms. The Phanerozoic eon is
characterized by the presence of abundant fossil
records, and it is divided into three major eras: the
Paleozoic, Mesozoic, and Cenozoic.
The Paleozoic era lasted from about 541 to 252
million years ago and saw the evolution of many
new types of animals, including fish, amphibians,
reptiles, and the first insects. During the
Paleozoic, the supercontinent Pangaea formed
and then began to break apart, leading to the
emergence of separate continents.
The Mesozoic era lasted from about 252 to 66
million years ago and is often called the "Age of
Dinosaurs." Dinosaurs were the dominant land
animals during this era, and many other new
types of plants and animals evolved. The
Mesozoic also saw the rise of mammals, birds,
and flowering plants.
The Cenozoic era began about 66 million years
ago and continues to the present day. It is
characterized by the diversification and
dominance of mammals, the emergence of
humans, and significant climate change. During
the Cenozoic, the continents continued to move
and separate, leading to the formation of modernday continents and oceans.
The Phanerozoic eon is a critical period in the
Earth's history, as it saw the evolution and
diversification of complex life forms, the formation
and separation of continents, and significant
geological and climate changes. It provides a
wealth of information for scientists to study the
evolution and history of our planet.
Hint of Evolution from Comparative
Another hint of evolutionary concept is from
comparative anatomy. Comparative anatomy is
the study of the similarities and differences
present in the anatomy of various species. It is an
important tool that helps to determine the
evolutionary relationships between organisms
and whether or not they share common
ancestors. Meanwhile, anatomical similarities
between organisms support the idea that these
organisms evolved from a common ancestor.
When referring to anatomical structures, they can
either be homologous or analogous.
1. Homologous structures - These refer
to structures from different species which
have similar internal framework, position,
and
embryonic
development.
Homologous structures may have the
same origin or ancestors but different
functions. This type of evolution is called
divergent
evolution.
Divergent
evolution is the splitting of an ancestral
population into two or more subpopulations that are geographically
isolated from one another. The following
is an example of a homologous structure:
The forelimbs belonging to a dog, man,
cat, bat, bird, lizard, and whale are
structurally the same, but are functionally
different.
2.
Analogous structures – The structures
of unrelated species may evolve for them
to look somewhat the same because the
structure has adapted to similar
functions. In another words, analogous
structures have similar functions but
different in origin. In convergent
evolution, analogous structures of
unrelated organisms from different
ancestors developed a similar function.
This is one example: The wings of birds,
bats, and insects exhibit the same
functions.
Evidence from Embryonic Development
Embryology is the study of the anatomy
development of an organism to its adult form. It
provides evidence for evolution as embryo
formation in widely-divergent group of organisms
tends to be well conserved. That is to say,
structures that are absent among adults of some
groups often appear during their embryonic
forms. An embryo is an early stage of
development among organisms Due to these
manifestations, embryonic development is
considered to be very useful when studying the
relationship of organisms.
Studies have also shown that closely-related
species
can
exhibit
similar
embryonic
development but their adult structures can
become quite different later on. Amino Acid
Sequence Another evidence for evolution is
provided by the biochemical analysis and amino
acids sequence of an organism’s DNA. For
example, it is clear that the evolution of the new
functions of proteins commonly occurs after gene
duplications. These types of duplication allow the
free modification of one copy by mutation,
selection, or drift (changes in a population’s gene
pool resulting from chance), while the second
copy continues to produce a functional protein.
This means that the greater the similarity present
in the amino acid sequence, the closer the
relationship is among the organisms. Also,
organisms
with
similar
structures
and
biochemical compositions could have probably
descended from a common ancestor. To increase
your understanding on amino acid sequences
and their determining factor to the relationship of
organisms, perform the activity in the next
section.
Theories of evolution attempt to explain how
and why evolution occurs. Here are some of the
most well-known theories of evolution:
1. Theory of Evolution by Natural
Selection: This theory, proposed by
Charles Darwin in the 19th century,
states that the process of natural
selection determines which traits
become more or less common in a
population over time. Individuals with
traits that help them survive and
reproduce are more likely to pass on
those traits to their offspring, while
individuals with less advantageous traits
are less likely to do so.
2.
Lamarck's Theory of Evolution: This
theory, proposed by Jean-Baptiste Lamarck in
the 18th century, posited that traits acquired
during an organism's lifetime can be passed
down to its offspring.



Inheritance of acquired traits (Theory
of Acquired Characteristics): Lamarck
proposed that an organism can pass on
traits acquired during its lifetime to its
offspring. For example, if a giraffe
stretches its neck to reach leaves on a
high tree, its neck would become longer,
and this acquired trait would be passed
on to its offspring. However, this theory
has been disproven by modern genetics,
which has shown that acquired traits
cannot be passed down to offspring
through genes.
Use and disuse (Theory of Use and
Disuse): Lamarck suggested that the
use or disuse of a particular body part
can influence its development over time.
For example, if a bird stops using its
wings for flight and instead relies on its
legs to move around, its wings would
gradually
shrink
and
eventually
disappear over time. This theory has also
been discredited, as it has been shown
that changes in body structures are
driven by genetic mutations rather than
use or disuse.
Progression
towards
complexity
(Theory of Need): Lamarck proposed
that all living things have a natural
tendency to become more complex and
sophisticated over time. He believed that
simple organisms gradually evolved into
more complex ones through a process of
increasing perfection. However, this
theory has been challenged by the
discovery of many simple organisms that
have remained relatively unchanged for
millions of years, as well as by the
understanding that evolution is driven by
natural selection rather than a pre-
determined
complexity.
goal
of
increasing
3.
Modern Synthesis: This theory, also
known as the Neo-Darwinian Synthesis,
combines Darwin's theory of natural selection
with the understanding of genetics that emerged
in the 20th century. It posits that genetic
mutations are the ultimate source of variation in
populations and that natural selection acts on this
variation to produce evolutionary change.
4.
Neutral
Theory
of
Molecular
Evolution: This theory, proposed by Motoo
Kimura in the 1960s, suggests that much of the
genetic variation within and between species is
the result of neutral mutations that do not have an
effect on an organism's survival or reproduction.
This theory has been supported by molecular
studies of DNA and protein sequences.
5.
Punctuated Equilibrium: This theory,
proposed by Stephen Jay Gould and Niles
Eldredge in the 1970s, suggests that evolution
occurs in relatively rapid bursts, followed by long
periods of stasis. This theory challenges the idea
of gradual, continuous evolution and posits that
major evolutionary changes happen relatively
quickly, in response to major environmental
shifts.
Charles
Darwin
JeanBaptiste
Lamarck
BIODIVERSITY
Biodiversity is the variety of life on earth and the
essential interdependence of all living things.
Short for biological diversity, includes all
organisms, species, and populations; the genetic
variation among these; and all their complex
assemblages of communities and ecosystems. It
also refers to the interrelatedness of genes,
species, and ecosystems and their interactions
with the environment.
Levels of Biodiversity
1. Genetic Diversity - different genes &
combinations of genes within populations.
Genetic diversity is all the different genes
contained in all individual plants, animals, fungi,
and microorganisms. It occurs within a species as
well as between species.
2. Species Diversity- organisms that have the
potential to interbreed in nature and produce
viable, fertile offspring. A number of different
species represented in a given community.
Population are a group of individuals of the same
species that live in the same area and interbreed,
producing fertile offspring. Species diversity is all
the differences within and between populations
of species, as well as between different species
3.Ecosystem
Diversity-variation
in
the
ecosystems found in a region. Ecosystem
diversity is all the different habitats, biological
communities, and ecological processes, as well
as variation within individual ecosystems.
Humans depend on biodiversity in countless
ways, yet species are being rapidly lost due to
human activities. The ecosystem services
approach to conservation tries to establish the
value that society derives from the natural world
such that the true cost of proposed development
actions becomes apparent to decision makers.
Species are an integral component of
ecosystems, and the value they provide in terms
of services should be a standard part of
ecosystem assessments.
Adaptation refers to the ability of an organism to
survive and reproduce in an environment. This
may involve changes in behavior or physical
structure to survive. For example, if we take a
street dog (that lives in a tropic place) in Alaska
(cold country), it will grow thicker fur to survive
cold temperature. Likewise, when a dog in a cold
country brought to the tropics, it will shed its fur to
adapt to the warm climate.
Variation increases the chance of survival.
Organisms with the most desirable traits would
likely survive environmental changes and
gradually become better suited to survive in a
given environment; this is called adaptation. The
differences among individuals in a population that
improve the species' fitness. These adaptations
can be physical, chemical, or behavioral.
Camouflage and mimicry are two forms of
physical adaptation.
-
Camouflage:
Structural
adaptation that enables an
individual to blend with its
surroundings, and that allows an
individual to avoid detection by
predators. Occurs when an
individual “blend” into the
environment in the eyes of a
potential predator.
-
Mimicry: A phenomenon in
which an individual gains some
sort of survival advantage by
looking like an individual of
another (often more harmful)
species. Is present when one
species has evolved to look like
another species in a way that will
provide some advantage. The
best-known examples of mimicry
are those in which a species
mimics another that is toxic or
harmful to a potential predator.
Camouflage and mimicry are
both adaptations because they
increase the likelihood of an
individual evading predation long
enough to reproduce.