Download Scientific Evidence from Anatomy, Embryology, Biochemistry, and

Scientific Fields
 Different fields of science have contributed
evidence for the theory of evolution
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Anatomy
Embryology
Biochemistry
Paleontology
Anatomy
 Anatomy: study of the structures of organisms
 Provides one type of data for the support of biological
evolution
 Homologous structures
Anatomy and homologous
structures
 Homologous structures: one form of evidence to determine
the possible relationships between the evolutionary paths of
two species
 Organisms diverged from a common ancestor often have
homologous structures
 Homologous structures: similar characteristics resulting from
common ancestry
 The greater the numbers of shared structures between two
species, the more closely the species are related
Anatomy: Vestigial organs
 Many species have vestigial organs
that are parts of structures that had
important functions in an ancestor of
the species
 Vestigial organ: structure with little
or no function to the organism
 The vestigial organs of one species
are often homologous with structures
in related species where the structure
has remained functional
Anatomy and Evolution
 Study of species located in different geographical locations
reveals that species living in different locations under similar
ecological conditions developed similar structures and
behaviors
 If a species encountered a different ecosystem due to a change
in geographical location, favorable anatomical traits become
established.
 A new species evolves with a shared common ancestor from the
original population
Embryology
 Embryology: study of
embryonic development of
organisms
 Provides support for
biological evolution by
comparing anatomies of
embryos
 Embryos: an early stage
(pre-birth) of organism
development
Embryology and Evolution
 Patterns of development or structures may not be obvious
in adults but can be observed in embryos
 Embryos of vertebrates are similar in appearance but may
grow into different structures in the adult form
 The similar structures of these embryos may suggest that
these species evolved from common ancestors
Biochemistry
 Biochemistry: study of the chemical processes in
organisms
 Studies genes and proteins to provide support for
biological evolution
Biochemistry and Evolution
 The more similar the DNA and amino acid sequences in
proteins of species, the more likely they are to have diverged
from a common ancestor
 Biochemistry provides evidence of evolutionary relationships
among species when anatomical structures may be hard to use
 Examples:
 When species are so closely related that they do not appear to be
different
 When species are so diverse that they share few similar structures
Paleontology
 Paleontology: study of prehistoric life
 Another tool that can be used to provide support for
biological evolution
Paleontology and Evolution
 Fossil record provides good evidence of life forms and
environments along a timeline
 Also supports evolutionary relationships by showing the
similarities between current species and ancient species
 Comparing current and ancient species shows a pattern of
gradual change from the past to the present
 Fossil record of Earth shows a history that tells a story of the
types of organisms that have lived on Earth (including extinct
species) and the relative ages of those fossils.
Paleontology and Evolution
 The fossil record is not complete because most organisms do
not form fossils
 Many gaps have been filled in as more fossils have been
discovered
 The older the fossils, the less resemblance there is to modern
species
Phylogeny
 Scientists study data to trace the phylogeny of a species or a group
of related species
 Phylogeny: evolutionary history
 An evolutionary theory has been developed that states all forms of
life on Earth are related because the ancestry of organisms can be
traced back to a common origin
 Evidence of the shared history is found in all aspects of living and
fossil organisms
 Physical features
 Structures of proteins
 Sequences found in RNA and DNA
 Scientists must use multiple sources of evidence in drawing
conclusions concerning evolution
Anatomy and Phylogeny
 Phylogenies constructed
assuming anatomical
differences increase with time
 The greater the similarity, the
more recently a pair of species
share a common ancestor
 Evolutionary difference =
divergence
Anatomy and Phylogeny
 Observations on as many anatomical
structures as possible are used to construct
phylogenies
 Sometimes individual structures suggest
relationships that differ from bulk of
evidence
 This may result from convergence
(structures becoming more similar with
time)
 Convergence: when organisms with
different evolutionary histories adapt to
similar environments
Embryology and Phylogeny
 Embryonic development allow scientists to reconstruct the
phylogenies of highly divergent taxa (groups) that may have
evolved so many anatomical differences that they are difficult
to compare otherwise
 Selection for successive new stages at the end of embryonic
development = a mechanism of evolution
 Ontogeny recapitulates phylogeny
 Ontogeny: growth and development of an individual organism
 As we go through development from embryo to adult, animals
go through stages representing stages in the evolution of their
remote ancestors.
Ontogeny recapitulates phylogeny
Paleontology and
Phylogeny
 Fossil record provides information regarding the dates and
order of divergence for phylogenies
 Transitional fossils: fossils that show links in traits used to
document intermediate stages in the evolution of a species
 Used to confirm evolutionary relationships
Paleontology and Evolution
 Challenge of using fossil record as a map of evolutionary history =
record is incomplete
 Millions of fossils have been discovered, but still large gaps exist
 Many environmental conditions must be to create a fossil and the
chance of all of these conditions being met at once is very rare
 Fossil records favor species that were long lasting, abundant, and had
hard shells/skeletons
 Gaps do not indicate weakness in the theory of evolution
 Instead indicate opportunities for more research
 Fossils still being found that help fill in existing gaps = transitional
fossil
Biochemistry and
Phylogeny
 Evolutionary history can be constructed assuming that
differences in DNA, proteins and other molecules increase over
time.
 The greater the genetic similarity, the more recently a pair of
species shares a common ancestor
 “Molecular clock” = time since a pair of species diverged
Biochemistry and
Phylogeny
 Comparison of DNA sequences provides reliable evidence, but
challenges exist:
 Genes evolve at different rates making it difficult to yield
information about groups of organisms
 Insertions and deletions results in homologous genes of different
lengths, making it hard for comparison
 Different assumptions = different phylogenetic trees
 Natural selection can cause convergence in molecules
Theory of Evolution
 One piece of evidence does not mean an accurate picture of
the history of evolution
 The more pieces of evidence collected from all of the different
fields, the more reliable the hypothesis becomes
 Theory of evolution = a well-tested explanation that accounts
for a wide range of observations
 No scientists suggests all parts of theory are understood and
still many unanswered questions remain