In week 3, we learned about new topics which was about
History of Life. I able to describe the conditions thought to have existed on
early earth. How did life begin?? We never know how old our earth as well but
for this topic I had learned about that diversification of life started in 3.8
billion years ago. How did life begin?? It was begin from molecule to cells.
The first cells was from abiotic synthesis of small organic. Next, bonding
small molecules into macromolecules. Then, packaging macromolecules into
protobionts and lastly origin of self-replicating molecules.
Origins of
life means organic life sprung from non-organic matter exclusively through a
natural mechanistic process on a pre-biotic earth. This is called chemical
evolution. That original life form then evolved into more complex life forms
through a natural process of random mutations and natural selection.
Origin of
life in chemical evolution was from small inorganic molecules CO2, N2, H2, CO,
NH3, H2S, H2O and then into small organic molecules. Next, into larger organic
molecules which was RNA, DNA, proteins etc and then turn into life. It
approximate 4.6 billion years ago earth formed. How did organic molecules
formed on primitive earth? They could have formed from smaller molecules
present on primitive Earth, either very slowly over millions of years or
rapidly before the earth cooled down. Prebiotic broth hypothesis. Asteroids may
have brought them from outer space. According prebiotic broth hypothesis which
was proposes that organic molecules formed near earth’s surface-in a sea of
organic soup or on rock or clay surfaces.
Furthermore,
we also had being explained about Miller-Urey’s experiment (1953). It was
established an experimental reducing atmosphere. The mixture was subjected to
electrical sparks and cooled the systems. The simple organic compound reacted
in water to form amino acids. I had never heard this before so for me it was
quite interesting that I had learned in the class.
Miller-Urey’s
experiment
Next, I had learned about the RNA world. We always get
confused on which came first? RNA or DNA? So in this subtopic I knew that the
first genetic material was probably RNA, not DNA. DNA strands can only copy
themselves with the help of enzymes but single RNA strands can copy in
solutions containing nucleotides without enzymes. This theory is called the RNA
world theory.
The structures between DNA and RNA
Moreover, we had learned about protobionts. Protobionts were
from replication and metabolism and then aggregates of abiotically produced
molecules enclosed by a membrane. Next display simple replication and
metabolism and also maintain an internal chemical environment.
In this class, we knew the first prokaryotes. It could be
chemoheterotrophs-consume organic molecules for both energy and carbon. “ate”
ATP energy formed abiotically in the organic soup. The loss of abiotically
formed ATP, natural selection will favour those early prokaryotes that can
regenerate ATP from ADP using energy extracted from available compound.
So for
the origin of life by 2-2.5 billion years ago, there was a great diversity of
prokaryotes on earth which were firstly is anaerobic heterotrophs and
autotrophs and secondly aerobic heterotrophs and autotrophs. Starting from when
life began, until 2.1 billion years ago, all life was prokaryotic, unicellular
and aquatic!
For
the SCL activity, we are required to do the comic strips which were quite
interesting. We had to do the comic strips about evolution. For our group
members, we had chosen tortoise for the main character in our comic strips. It
was about a natural selection between saddleback tortoise and domed tortoise.
Our group was doing together for finished the task and submit it into the
putrablast website.
Natural selection for tortoises
For the next subtopic we had learned about systematics, taxonomy and
classification. At the end of this lecture, we will able to justify the use of
scientific names and classification of organisms, arrange the Linnaean
categories in hierarchical fashion, apply the concept of shared derived
characteristics to the classification of organisms and lastly able to describe
the present methods of molecular biology used by taxonomists.
All living things are classified by characteristics into 6 kingdoms of
life which were archaebacteria, eubacteria, Protista, fungi, animals and
plants. I had learned this topic which was biodiversity during my
matriculation. So it will be much easier for me to understand for this
particular topics. Biodiversity is very interesting because we can know all
about living things.
6 kingdoms of life
What
is systematics? Systematics is the study of biological diversity and its
evolution. Taxonomy, a subdivision of systematics, is the science of biological
classification-identification, nomenclature ( naming the organism ) and making
into a system.
Systematics, taxonomy and classification
Classifications
is the systems that help to clarify relationships among organisms; they help us
remember organisms and their traits; they unable us to communicate clearly the
identity of organisms being studied; they improve our predictive powers and
they provide.
Caralus
Linnaeus was the first to develop and publish the first comprehensive and
consistent classification system for both plants and animals. I also learned on
how to naming the organism for example Homo
sapien, Escheria coli. Genus is always capitalized, species
is usually not. Both names must be underlined or written in italics. Species
were arranged in an ascending series of inclusive categories of taxa.
Linnaeus classification categories
Lastly, we
had learned about phylogenetics. Phylogenetics is the study of evolutionary
relationships among and between species. Homology means similar structure and
position but different function-derived from a common ancestor. Analogy means
similar function but different origin which was not derived from a common
ancestor; convergent evolution-similar selection pressure.
