Download EVOLUTION a.What is evolution and what is natural selection

EVOLUTION
a.What is evolution and what is natural selection? (8 marks)
The theory of evolution a
rises out of man's need to explain the origins of both the Universe and Life. Evolution may be defin
ed as that continual natural process through which organisms have acquired their peculiar structure
and functions. Whilst this is the generally accepted explanation to the origins of the Universe and
Life in history there have been many other theories put forward, such as spontaneous generation that
is the belief that living matter can be generated from non-living matter. In layman's terms evoluti
on is the process responsible for the changes over the extent of Earth's existence. Evolution began
with the development of certain conditions on Earth which were favourable to the formation of life a
nd the changing of these simple life forms over time into the organisms observable on earth today, i
ncluding humans. Darwin, though not the first to contribute to the idea of evolution is often credit
ed with its development. It was after his joint presentation with Wallace that evolution really bega
n to gain widespread acceptance in society. In his book "Origin of Species" Darwin proposes a two-pa
rt argument to support his evolutionary theory, 'Struggle for Existence' and 'Natural Selection'. Th
e 'Struggle for Existence' argument proposes two principles; the principle of reproduction which sta
tes all living things are potentially able and possess the drive to reproduce at rapid rates. The se
cond principle of dependence states that all organisms depend on natural resources such as air, wate
r and a source of energy. To these principles three factual observations were made. The first is tha
t there are limited numbers of places on earth where there are these natural resources exists. The s
econd states that the locations where these natural resources exist may fluctuate over time. Thirdly
much variation exists in the form and behaviour of organisms. When combined these principles and ob
servations led Darwin to two conclusions. The first is that because there are more organisms produce
d than the natural resources can support a struggle for existence must ensue. The second conclusion
says that the struggle for existence may explain the patterns of quantities and variations found amo
ngst organisms on the planet. In the second part of his argument ' Natural Selection' he identifies
three principles. The first was that some organisms possessed certain traits that allow them to obta
in more resources that others do not. The second states that organisms tend to reproduce very simila
r offspring. Thirdly he stated that organisms possessing advantageous traits have higher survival ra
tes and thus higher reproduction than those without. Following these three principles he offered thr
ee factual observations. The first was that struggle for existence exists in nature. Second was that
a good deal of variation occurs in the traits and behaviours possessed by organisms. Thirdly, some
traits and behaviours when assessed relative to others can be classified as advantageous, neutral or
disadvantageous in securing natural resources. The conclusion derived from these principles and obs
ervations is that there will be a natural selection in favour of those organisms that possess the mo
st advantageous traits and behaviours relative to those possessed by other organisms. Natural select
ion is not only the process through which new species evolve it also explains why poorly adapted spe
cies become extinct.
b.what reasons do we have for believing that there has been evolution of li
fe on earth and what reasons do we have for believing that much of evolution has been a result of na
tural selection.
There are many points of evidence that are used to prove that evolution of life
on earth has occurred and these points stem from many different specialized fields in biology. For
instance, there is evidence of evolution that is based on findings made from taxonomy, which is conc
erned with the defining, describing and classifying species. Taxonomy reveals that it is possible to
group certain species together on the basis of some similar feature that they share. For instance a
ll pine trees have needlelike leaves arranged in clusters, this and many other classifications of ot
her organisms present overwhelming evidence for descent of related species from a common ancestor. A
second account for the evidence of evolution is findings based on comparative anatomy. Study of the
anatomy of plants and animals reveals certain basis plans of body structure that have become the es
tablished features of large groups of plants and animals, for instance features of organ systems in
all mammal, irrespective of weather they live on land, in water or even fly are similar. Vestigial o
rgans also exist, that is structures without an existing function occur in many plants and animals,
for instance the existence of the tail bone in humans which points to humans being descendents of cr
eatures with tails. Homologous organs, which are organs with similar basic feature that are modified
for different uses also points to evolutionary change through the diversification of the species. T
hirdly there is evidence based on embryology. The embryos of higher organisms show marked similariti
es in the stages they pass through to other animals related to them but at a lower developmental sca
le. This is the theory of recapitulation, which states that an organism in its development from egg
to adult repeats the stages that correspond to early periods in the evolution of its group. The geog
raphic distribution of organisms also exhibits many peculiarities that can be best explained as a re
sult from evolution. For instance, what explains why areas with similar climates and conditions are
not inhabited by the same type of organisms, or why do similar creatures not live near each other, f
or instance alligators habitats are found in the South of the USA and China. These anomalies are exp
lained by assuming these animals descended from the same ancestors and subsequent offspring spread o
ut to find desirable habitats until stopped by actual land barriers. Changing landscapes, which sepa
rate the species into different groups, causes their offspring to vary from each other. Lastly there
is evidence based on fossils. Fossils reveal the type of plant and animals that have lived on earth
and at what point in time they existed. Using dating equipment scientists have been able to develop
a geologic time scale that establishes the sequence in which evolutionary changes have taken place.
The fossil record reveals a progress from very simple life forms to the very complex forms. It also
reveals that many species became extinct indicating the struggle for existence results in the elimi
nating of species in addition to the creation of new ones. It can be seen that much of evolution has
been as a result of natural selection, that is the gradual accumulation of advantageous traits by v
arious populations that allowed some species to survive while those without the advantageous traits
become extinct. Other factors such as genetic factors and environmental factors have also contribute
d to evolution, so that not only the accumulation of the best traits is responsible for change but s
pontaneous natural mutations and also environmental changes impacted on species forcing them to adap
t to their surroundings.
evolution what evolution what natural selection marks theory evolution
arises need explain origins both universe life defined that continual natural process through which
organisms have acquired their peculiar structure functions whilst this generally accepted explanati
on origins universe life history there have been many other theories forward such spontaneous genera
tion that belief that living matter generated from living matter layman terms process responsible ch
anges over extent earth existence began with development certain conditions earth which were favoura
ble formation life changing these simple forms over time into organisms observable earth today inclu
ding humans darwin though first contribute idea often credited with development after joint presenta
tion with wallace really began gain widespread acceptance society book origin species darwin propose
s part argument support evolutionary theory struggle existence natural selection struggle existence
argument proposes principles principle reproduction which states living things potentially able poss
ess drive reproduce rapid rates second principle dependence states organisms depend resources such w
ater source energy these principles three factual observations were made first there limited numbers
places where there these resources exists second states locations where resources exist fluctuate o
ver time thirdly much variation exists form behaviour when combined principles observations darwin c
onclusions first because more produced than support struggle must ensue second conclusion says expla
in patterns quantities variations found amongst planet part argument selection identifies three some
possessed certain traits allow them obtain more others tend reproduce very similar offspring thirdl
y stated possessing advantageous traits have higher survival rates thus higher reproduction than tho
se without following three offered factual observations exists nature good deal variation occurs tra
its behaviours possessed thirdly some behaviours when assessed relative others classified advantageo
us neutral disadvantageous securing conclusion derived from will favour those possess most advantage
ous behaviours relative those possessed other only process through species evolve also explains poor
ly adapted species become extinct what reasons believing been reasons believing much been result man
y points evidence used prove occurred points stem from many different specialized fields biology ins
tance evidence based findings made taxonomy concerned defining describing classifying taxonomy revea
ls possible group certain together basis some similar feature they share instance pine trees needlel
ike leaves arranged clusters this other classifications present overwhelming evidence descent relate
d common ancestor account findings based comparative anatomy study anatomy plants animals reveals ba
sis plans body structure become established features large groups plants animals instance features o
rgan systems mammal irrespective weather they live land water even similar vestigial organs also exi
st structures without existing function occur plants animals tail bone humans points humans being de
scendents creatures tails homologous organs organs basic feature modified different uses also evolut
ionary change through diversification based embryology embryos higher show marked similarities stage
s they pass related them lower developmental scale this theory recapitulation organism development a
dult repeats stages correspond early periods group geographic distribution exhibits peculiarities be
st explained result explains areas climates conditions inhabited same type creatures live near each
alligators habitats found south china anomalies explained assuming descended same ancestors subseque
nt offspring spread find desirable habitats until stopped actual land barriers changing landscapes s
eparate into different groups causes their offspring vary each lastly fossils fossils reveal type pl
ant lived point time existed using dating equipment scientists able develop geologic scale establish
es sequence evolutionary changes taken place fossil record reveals progress very simple forms very c
omplex forms became extinct indicating results eliminating addition creation ones seen much result g
radual accumulation various populations allowed survive while without become extinct factors such ge
netic factors environmental factors contributed only accumulation best responsible change spontaneou
s mutations environmental changes impacted forcing them adapt their surroundingsEssay, essays, termp
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