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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

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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
How can I make nanorobot?
why and for what was five kingdom of classification of organisms introduced
give the ans as fast as possible
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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