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Summary Evolution
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EVOLUTION BY NATURAL SELECTIONGENERAL
― Evolution is a general term defined as change over time. These changes may
occur in chemicals, matter, solar systems, or language etc.
― Biological evolution: genetic changes in a population [of living organisms] that are
inherited over successive generations due to natural selection and ultimately
resulting in the formation of new species.
― Biological evolution includes;
o Macro-evolution: the development of new life forms / species from
earlier life forms over many generations [extended geological periods].
o Micro-evolution: the variation that occurs w. in a species. Small changes
originate in the gene pool, resulting in small changes in the genotype of
the species. These changes are passed on to the offspring.
Speciation forms the basis of macro-evolution where new species develop from
existing species over time.
EVOLUTION – HYPOTHESIS OR THEORY?
DIFFERENCE BETWEEN A HYPOTHESIS AND A THEORY
Hypothesis
― A hypothesis is sometimes called an informal [educated] assumption because it
provides a proposed solution to a problem / an explanation of a specific
phenomenon, based on scientific evidence and observations.
― Is tested in a series of experiments / by repeated observation, i.e. it is testable /
falsifiable depending on further research.
― Depending on results, it is rejected / accepted.
Theory
― A well-substantiated [supported by evidence] explanation / hypothesis that makes
sense of a natural phenomenon.
― Based on scientific evidence and is usually tested and confirmed by independent
groups of researchers.
― It develops and is changed / replaced as new evidence is discovered.
Evolution is considered a scientific theory, as it is based on a series is hypotheses that
have been tested and verified over time.
Scientists acknowledge that some aspects of the theory of evolution are not easily
tested and verified. For example, the time frame of millions of years can not be
repeated / observed directly.
ORIGIN OF IDEAS ABOUT ORIGINS
― The origin and development of life on earth have been a great source of
speculation and conflict from the earliest times. Many scientists support the
theory that life on earth arose from a common ancestor 4,6 billion years ago.
― It’s also commonly accepted that the process of evolution occurred where one
kind of organism changed into another.
, ― Evolutionists believe this process led to the enormous biodiversity that currently
exists.
Evolution is change over time. It does not claim to explain the origin of
life.
EVIDENCE OF EVOLUTION
― Explained by different lines of evidence and contributions of many scientists;
o Fossil records.
o Modification by descent.
o Biogeography.
o Genetics.
o Other forms of evidence.
FOSSIL RECORDS
― Fossil: an organism / the remains, imprints or footprints of an organism, usually
preserved in rock.
― Fossils provide evidence of the history of extinct organisms on earth.
― Also give an indication of the climate and enviro. Millions of years ago.
― The fossil record is the accumulation of all listed and known fossils of different
ages that have been discovered by palaeontologists worldwide.
― Few individuals fossilise – possibly because they are soft-bodied and thus they
The study of plant and animal fossils is known as palaeontology and a scientist that
studies fossils is known as a palaeontologist.
decompose after death and their structures are not preserved.
― Very specific conditions [e.g. rapid burial, high pressure, and lower oxygen] are
essential for fossilisation to occur.
― The fossil record is a record of those organisms that were fossilised. However,
fossil records are incomplete and not an indication of all the organisms that
existed at a particular time.
― Scientists expect to find earlier, simpler fossils in the deeper, older rock layers
The fossil record provides info about extinct species as well as species that are still
living today.
and recent, more complex fossils in the upper, more recent rock layers.
― This indicates the order in which evolution occurred.
― The age of fossils may be determined from the age of the rock in which they
occur.
― Older rock strata display less biodiversity than the more recent rock strata. This
shows that there was an increase in biodiversity over time.
― The fossil record contributes to the compilation of a geographical time scale from
the origin of the earth until the present.
Evolutionary scientists like Stephen Jay Gould and Niles Eldredge have formulated
The geological time scale clearly shows the increase in complexity over time; the
alternative theories to explain the gaps in the fossil record.
simple, single-celled prokaryotes appear first. The increase in biodiversity can also be
observed.
The fossil record has many gaps, however, particularly where there is a change from
one type of organism to another. Fossils of these transitional forms are very rare.
archaeopteryx is an example of a transitional fossil. It is known as the earliest and
most primitive bird. It is considered a transitional form between reptiles and birds
from the Jurassic period [150 million years ago] and displays both bird and reptile
characteristics.
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