Comparative embryology is the branch of
embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos an ...
that compares and contrasts
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
s of different species, showing how all animals are related.
History
Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical Greece, Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatet ...
was the earliest person in recorded history to study embryos. Observing embryos of different species, he described how animals born in eggs (
oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), a ...
ly) and by live birth (
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
ly) developed differently. He discovered there were two main ways the egg cell divided:
holoblasticly, where the whole egg divided and became the creature; and
meroblasticly, where only part of the egg became the creature. Further advances in comparative embryology did not come until the invention of the microscope. Since then, many people, from
Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new s ...
to
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...
, have contributed to the field.
Misconceptions
Many erroneous theories were formed in the early years of comparative embryology. For example, German biologist and philosopher
Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new s ...
proposed that all organisms went through a
"re-run" of evolution he said that 'ontogeny repeats phylogeny' while in development. Haeckel believed that to become a
mammal, an embryo had to begin as a single-celled organism, then evolve into a fish, then an amphibian, a reptile, and finally a mammal. The theory was widely accepted, then disproved many years later.
Objectives
The field of comparative embryology aims to understand how embryos develop, and to research the inter-relatedness of animals. It has bolstered
evolutionary theory
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation te ...
by demonstrating that all
vertebrate
Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...
s develop similarly and have a putative common ancestor.
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See also
*
Embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos an ...
References
{{Reflist
* Comparative Embryolo
Retrieved 5/21/14
* Embryolo
Retrieved 5/21/14
* Comparative Embryology: The Vertebrate Bo
Retrieved 5/22/14
* Embryolo
Retrieved 5/22/14
* Evidence for Evoluti
Retrieved 5/22/14
* Comparative Studies Insigh
Retrieved 5/23/13
External links
Medpedia Article
Embryology