Transcript What are the main ideas of the following Scientists about

Evolution of life?
What is evolution?
What are the main ideas of the following
Scientists about the evolution of life?
Aristotle
Lamarck
Darwin
Mendel
Lysenko
Aristotle (384-322 BC)
• "Aristotelianism”
– Partly based on Plato's world of
ideas
– The species are given categories in
nature and are unchangeable
– There are only variation in mature
and perfection of individuals
– The only development is the mature
of each individual where the aim is
to reach perfection which is given in
the ideal types of the species
Aristotle’s epigenesis I.
• All living creatures, whether they swim, or
walk, or fly, and whether they come into
the world with the form of an animal or of
an egg, are engendered in the same way.
• Concept of epigenesis and that in the
embryo, more generalized structures
appear before the more specialized ones.
• Epigenesis was one correct idea of
Aristotle that was often discarded.
Aristotle’s epigenesis II.
• His concepts of heredity were even sounder than
Darwin's (!)
• Darwin believed in pangenesis (gemmules from all parts
of the body migrate to the semen and account for
paternal characteristics).
• This was an old idea that Aristotle had refuted by fairly
sound reasoning, among them:
– children sometimes resemble distant relatives more than their
parents. This couldn't occur if the genetic particles were obtained
by direct transmission.
– children of mutilated/crippled parents do not display these
mutilations
– both male AND female contribute to the characteristics of the
offspring.
Jean-Baptiste de Monet, chevalier de Lamarck
(1744-1829)
• "Lamarckism“
– French enlightenment
– Naturalist and pre-Darwinian
evolutionist
– Studied fossils and invertebrates
– Species change over time by adapting
to new environments
– Parents pass their traits on to their
offspring
– If an organ is used, it will become
stronger, and if it is not used, it will
weaken and may disappear in future
generations
– He postulated that acquired characters
can be inherited by future generations
Charles Robert Darwin (1809-1882)
• “Natural selection" / "Darwinism“
– By variation in the population there
is an adaption to the environment
through a natural selection of
acquired characters represented in
the variation of the species
– Darwin's concepts of heredity were
that gemmules from all parts of the
body migrate to the semen and
account for paternal characteristics
– Evolution purely mechanistic
process
Gregor Mendel (1822-1884)
• “Mendelian genetics“
– His principle of factorial
inheritance and the
quantitative investigation of
single characters have
provided the basis for
modern genetics.
Recognition came many
years after his death, when
his key article, ‘Experiments
with plant hybrids’ (1866),
was discovered.
The major insights attributed to Mendel
are often summarized in two "laws":
• Principle of Segregation:
– observable traits are passed down to offspring
via (discrete, non-blending) particles, one
from each parent.
• Principle of Independent Assortment:
– the particles (later dubbed genes by
American geneticist T. H. Morgan) from each
parent are equally likely to be passed down to
offspring.
T. H. Morgan 1866-1945
• Through study of “Drosophila”
• Made an elegant proof that the
chromosomes are indeed the bearers of
the hereditary factors or genes as they are
now known
Trofim Denisovich Lysenko (1898-1976)
• “Lysenkoism“
– developed a doctrine, compounded of
Darwinism and the work of Michurin, that
heredity can be changed by good
husbandry.
– As director of the Institute of Genetics of
the Soviet Academy of Sciences (1940–
65), he declared the accepted Mendelian
theory erroneous, and ruthlessly silenced
any Soviet geneticists who opposed him.
– He was dismissed by Khrushchev in 1965,
having gravely hampered scientific and
agricultural progress in the USSR.
James Watson 1962- &
Francis Crick 1916-2004
• Figured out the structure
of deoxyribonucleic acid,
DNA.
• And that structure — a
"double helix" that can
"unzip" to make copies of
itself — confirmed
suspicions that DNA
carries life's hereditary
information.
Discussion questions
1. What is evolution? Explain and
exemplify!
2. Does evolution have an aim?
3. Does evolution have a purpose?
Modern view on evolution
• Our very best evidence indicates that, in
reality, all species in this world have equal
lengths of evolutionary history.
• The differences are the result of
coincidence in the pathways evolutionary
movement takes.
• Evolution is ultimately about diversity, not
about progress and without purpose or
aim