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In this section you will be introduced to some scientific theories about life’s history. One of the popular theories of life’s history isthe theory of Evolution. Another is the theory of Intelligent Design. In order to be able to evaluate information critically, it is important to firstunderstand how people form knowledge, and to be able to differentiate between data and conclusions.

How do we know?

How do we know what happened in life’s history? We cannot do experiments on the origin of life. There are also no historical records about the origin oflife. We have to rely on data we find. From this we draw conclusions about what might have happened in life’s history.


How do we know?

This is a clip movie about how people get knowledge in general, and how people can get knowledge about origins, in particular.

Data and conclusions

Data means information people collect using their senses : sight, touch, hearing, feeling, smell. Usually when a scientist collects data, other scientists will agree with him/her about this data. Sometimes other scientists might question whether the data was correctly recorded, or whether the data is a forgery, but usuallyscientists trust that the data was collected correctly.

Conclusions are patterns people think up to help to make sense of data. When a scientist draws a conclusion from some data, he/she makes various assumptions. Assumptions are thoughts which peopletake to be true, without proof. Assumptions should be justified so that people can evaluate their validity (how likely they are to be true). It is common for scientists to disagree on the validity of assumptions and conclusions, even when they do agree on the data from which the conclusions are made. This is because different conclusionscan often be drawn from the same data.


Data conclusion

Life’s history

APBiology: Molecular Evolution and the early earth: (External Link)

The extremely long period of time over which life has developed on earth can be represented in various ways. Examine the diagrams below:

Taken from (External Link)

The various time periods are related to dramatic climate changes that the earth has experienced over time. This is partly due to what is called continental drift :

Continental drift:

This theory proposed that all land was at one stage joined to form the supercontinent Pangaea , which split into Laurasia in the north and Gondwana (or Gondwanaland) in the south. See (External Link)

There is much evidence that continental drift occurred and is still continuing today:

There is biogeographic evidence of related species in widely isolated areas, such as the very similar flightless birds like the rhea in South America, the ostrich in Africa, the moa in NewZealand, the emu and cassowary in Australia. They are thought to have developedfrom a common ancestor on Pangaea. As the climate gradually changed, organisms slowly adapted and underwent speciation in response to changes in thetemperature and vegetation around them.

OTHER EVIDENCE for continental drift include the following, showing that the climate in some areas is now very different from what it once was:

  • The discovery of fossilized tropical plants under Greenland’s ice caps
  • Glacial landscapes in central Africa and Central America
  • Whale fossils in the Sahara desert
  • The discovery of subtropical plant fossils in Antarctica, indicating that it once had a much warmer climate and lush vegetation.
  • South African examples of continental drift include the discovery of the fossils of marine organisms in places that are VERY far from the sea, such as bivalves and ammonites in the Makhatini flats in northern KZN, and marine trilobite fossils in the Karoo.
Ammonite fossil
Trilobite fossil

Plate tectonics

This theory provides a mechanism for continental drift. The continents we know today rest on large, interlocking plates of land called tectonic plates, whichfloat on a hot, molten layer that shifts them. Slow movements of these plates move continents further apart, but more rapid movements of the plates areevident when earthquakes occur. The continents are still moving apart at the rate of just a few cm per year.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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why and for what was five kingdom of classification of organisms introduced
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Comment on the ozone depletion over the period of 1982 to 1996
Mpho Reply

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Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
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