Owen Lyke
1st Period
11/29/10
Investigation 6
Evolution Essay
Evolution
Evolution is the process that has genetically diversified every organism on the
planet. Without evolution the first life forms that existed on this planet would never have
branched out and adapted to the various conditions that exist on the planet, the first life
forms that appeared on earth would still be the same now. The diversity of life on earth is
important because all of the different life forms are working together to maintain the
balance of Earth’s systems. For example, animals absorb the oxygen from the air and use
it to make energy for them to move. That process crates carbon dioxide, which is
absorbed by plants and trees to use in photosynthesis. Photosynthesis then creates energy
for the plant and oxygen, which is released back into the atmosphere for consumption by
other organisms. Evolution is an important process that is critical for the development of
life on Earth and the stabilization of Earth systems.
What is evolution? Evolution is the process of natural selection, where naturally
superior individuals conquer their habitat and out-live less competent individuals. Natural
selection acts on variations in the genes of different species called mutations. Mutations
occur in the genes of parents and then the mutated genes are passed down to offspring.
Also, when two parents produce offspring the process of meiosis mixes up the genes of
the two parents offering a chance for new mutations to be created. These changed genes
can either help an organism or put them at a disadvantage. When a certain gene puts an
individual at a disadvantage, it has a lower probability of surviving to produce more
offspring and spreading its DNA. On the other hand, when an organism receives a
mutation that enables it to survive longer in it’s environment, such as the ability to see
better at night to avoid predators, it has a better chance of passing its DNA on to further
generations. This process applies to all forms of life that inhabit the world. Even asexual
organisms can be affected by evolution due to mutations that occur because of mutagens
in the environment that change the sequence of DNA by damaging it.
The theory of natural selection was developed by Charles Darwin, a naturalist,
after sailing on the navy vessel Beagle. He took notes on the many forms of life that he
encountered on his trip, but he was puzzled when he reached the Galapagos Islands.
There he found many different types of finch that inhabited each island. On each island
the finch had a slightly different beak structure. Back at his home he pondered the reason
for these differences. At the time it was believed that god had created every creature
perfect, and there was no reason for these finches to all be different. Darwin then went
back to the Galapagos Islands to find out why the finches were all different. He found
that on each island the type of food that was available to the finches was different and
required different ways of obtaining it. For example, on one island the finches fed on
nuts, which required a short, powerful beak to crack. On another island the finches ate
nectar from flowers. On that island the finches had long slim beaks to reach deep inside
flowers. He eventually developed the idea that the finches were diversified because the
ones who could most easily obtain food on each island had lived longer and passed on
their DNA more successfully than others. This was the basis for the theory of evolution
that has now become globally accepted as the reason there are so many forms of life on
Earth today.
All life that currently inhabits Earth has descended from one form of life. About
four billion years ago, through the process of abiogenesis, the first life appeared on earth.
Abiogenesis is the process that occurs naturally under the right circumstances and creates
life from inanimate matter. The building blocks of simple life, amino acids, can be
formed by natural chemical reaction unrelated to life as demonstrated by the Miller-Urey
experiment. These acids were then organized into proteins by nucleic acids. These
proteins created the first very basic forms of life. Later, around three billion years ago the
first organisms developed chloroplasts and the ability to create energy through the
process of photosynthesis. Around one and a half billion years ago life branched out to
include eukaryotic cell types, where the organelles are enclosed in membranes, in
addition to the prokaryotic cells that existed before. Around one billion years ago multicellular organisms developed. This allowed the organism to develop special tissues to do
specific jobs such as movement. 750 million years ago multi-cellular organisms have
grown more complex and been able to adapt to changing environments more efficiently
than previously. 500 million years ago life separated into plants and animals. About 250
million years ago dinosaurs appeared and ruled earth for about 200 million years. Around
the same time that dinosaurs appeared, mammals were developing and are still around
today. 125 million years ago some plants evolved into flowers, and 200,000 years ago
humans started to look like we do today. Lastly, around 25,000 years ago, Neanderthals
died out. This is just a basic overview of the way that life has spread out over time to be
as diverse as it is today. It is impractical to go much farther into detail about specific
evolutions, because life has evolved an unfathomable number of times throughout the
history of the Earth. The number of time that a new species has been created due to
evolution cannot be accurately recorded today because we don’t even know to the fullest
extent what species currently inhabit our world.
Evolution has affected the life on Earth since it started almost 450 million years
ago. Without evolution life on Earth would be limited to simple, one-celled organisms.
Evolution is important because it helps balance out the planet’s systems; i.e. predators vs.
prey, oxygen consumers vs. oxygen creators etc.