Evidence for Evolution
Natural Selection
Variation exists in the populations
There is a selection pressure exerted on the population, e.g. competition for food.
More offspring are produced than can survive
Those offspring that are better adapted to their environment will survive and reproduce
Favourable adaptations are passed onto the next generation
Over time favourable adaptations will increase in the population.
Species
A species is defined by the ability to interbreed and produce fertile viable offspring.
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Different species develop by the accumulation of microevolutionary changes over time → genetic isolation
Isolation is critical for the species of an e…
Comparative Embryology
Comparative
Paleontology
Palaeontology
(Transitional Forms)
Fossils or organisms
that show the
intermediate states
between ancestral for
and that of its
descendants are
referred to as
transitional forms
Evidence that
supports
Transitional fossils
demonstrate
intermediary forms
that occurred over the
evolutionary pathway
taken by a single
genus. They establish
the links between
species by exhibiting
traits common to both
an ancestor and its
predicted descendants
As new fossils are
discovered, new
evolutionary patters
are emerging,
therefore supporting
the theory of
evolution.
E.g. archaeopteryx →
dinosaur → bird
Comparative
anatomy
Comparing structural
similarities of
organisms to
determine their
evolutionary
relationships.
specie which share
many similarities are
closely related by a
relatively recent
common ancestor.
similar body parts
may be homologous
structures or
analogous structures.
i.e. the pentadactyl
limbs of humans and
apes which are
homologous
structures. Evidence
Limitations
There are only a few
transitional fossils
that have been
discovered: This is as
the formation of
fossils require
particular conditions
(e.g. an environment
where sedimentary
accumulation can
occur)
Some organisms are
more successful u
forming fossils due to
hard parts (teeth,
shell, bone) which
are able to withstand
the weathering of the
chemical and
physical assaults
from the surface of
the Earth
Some transitional
fossils may have not
been found yet.
Fossils may have
been destroyed due to
tectonic place
movement.
Some parts of the
animal fossils cannot
be found. Therefore,
limitations I no. of
fossils available.
doesn’t prove the
theory of evolution
on its own
assumes the theory of
evolution in order to
support it.
Questions
Palaeontology
Study of fossils
they come from
common ancestor,
Analogous structures
are structures in
unrelated organisms
that are similar, i.e.
wings in birds and
bats
Absolute dating
(radiometric dating)
Enables the actual
age of a specimen to
be determined using
the radioactive
elements that are
present in the
specimen
Fission-type dating
Used to establish he
age of a mineral
sample from its
uranium content.
Microscope used to
coudn th tracks left
behind by uranium
fission fragments –
conc. Determined by
bombarding the
sample with neutrons
can be used to date
volcanic minerals.
potassium-argon
dating
used to determine the
age of a rock by
measuring the ratio of
radioactive argon to
radioactive potassium
in the rock sample.
Relative dating
relies on the
assumption that
fossils found up
higher in rock strata
are younger than the
lower fossils, so
fossils are dated
relative to one
another.
→ Stratigraphy
Relies on
sedimentary rocks
being formed in
layers with the oldest
rocks being at the
bottom and and
youngest on top.
Biochemical
sequencing
→ Paleomagnetism
Study of the record of
Earth’s changing
magnetic field in rock
sediments.
Compares different
molecular features
Many different types
of bases that any
(e.g. nucleotide
sequence of genes) to
show how
evolutionarily related
species are.
Biogeography
The study of the
geographical
distributions of the
biological organisms
which provides
evidence about how
and when specie may
have evolved.
Biochemical DNADNA Hybridisation
Comparative
Embryology
Comparison of the
developmental stages
of different species.
Fossils
Evidence provided by
biogeography
includes the
discovery/recovery of
fossils, Fossils which
resemble modern
organisms are found
in regions separate
from locations
currently
uninhabited. This
supports the
hypothesis of how
species evolve from
common ancestors.
Different climates
changed
characteristics
Different selection
pressures
Molecular fossils had
commonalities with
each other.
Evolutionary changes
will be reflected in
changes in the base
pairs of DNAs.
Species not closely
related share some of
the same molecules
from DNA to
proteins. Amino acids
make up proteins,
most organisms have
the same set of amino
acids.
Fish, amphibians,
birds and mammals
all show the presence
of gill slits, tails and
distinct muscle
blocks during
embryonic
development. Thus,
the prediction is that
their early
developmental
stages.
variation in bases
cannot accurately
indicate major
differences.
Alterations such as
duplications,
deletions and
inversions can affect
large segments of
DNA.
It is all based on
hypotheses.
Technique is
inaccurate for the
comparison of
closely related
species. Large range
of data/huge margin
of error
These drawings are
now considered to be
inaccurate; they were
not an accurate
representation of the
embryos but were
interpretive.