K12 Comparative Embryology: Difference between revisions
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:[[:File:Ernst Haeckel.jpg|Ernst Haeckel (1834 – 1919)]] "ontogeny recapitulates phylogeny" claimed that an individual organism's biological development (ontogeny), parallels and summarises its species evolutionary development (phylogeny). First a single-celled organism, then evolve into a fish, then an amphibian, then a reptile, then a bird, and finally reach a mammal. | :[[:File:Ernst Haeckel.jpg|Ernst Haeckel (1834 – 1919)]] "ontogeny recapitulates phylogeny" claimed that an individual organism's biological development (ontogeny), parallels and summarises its species evolutionary development (phylogeny). First a single-celled organism, then evolve into a fish, then an amphibian, then a reptile, then a bird, and finally reach a mammal. | ||
:Current developmental biology shows that animals follow similar developmental programs, but do not go through | :Current developmental biology shows that animals follow similar developmental programs, but do not go through Haeckel's "species change" during development. | ||
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[[#Meiosis|Meiosis]] | [[#Mitosis|Mitosis]] | [[#Gastrulation|Gastrulation]] | [[#Body Plan|Body Plan]] | [[#Limbs|Limbs]] | [[#Tissue Development|Tissue Development]] | [[#Organ Development|Organ Development]] | [[#Meiosis|Meiosis]] | [[#Mitosis|Mitosis]] | [[#Gastrulation|Gastrulation]] | [[#Body Plan|Body Plan]] | [[#Limbs|Limbs]] | [[#Tissue Development|Tissue Development]] | [[#Organ Development|Organ Development]] | [[#Animal Models|Animal Models]] | [[K12_Human_and_Other_Animal_Development|Human and Other Animal Development]] | ||
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Also look at the [[K12 Human and Other Animal Development]] that simply compares development times and embryo structures. | Also look at the [[K12 Human and Other Animal Development]] that simply compares development times and embryo structures. | ||
See also online textbook - Gilbert SF. Developmental Biology. 6th edition. Sunderland (MA): Sinauer Associates; 2000. [https://www.ncbi.nlm.nih.gov/books/NBK9974/ Comparative Embryology]. | |||
[[K12 Professional Development 2016]] | [[K12 Professional Development 2014]] | [[K12 Professional Development 2016]] | [[K12 Professional Development 2014]] | ||
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| [[File:Inner cell mass cartoon.jpg|300px|alt=germ cell layers]] | | [[File:Inner cell mass cartoon.jpg|300px|alt=germ cell layers]] | ||
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{| class="wikitable mw-collapsible mw-collapsed" | |||
! Teacher Note | |||
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| colspan="2"|[[File:Mark_Hill.jpg|50px]] '''Triploblastic''' (three layer) organisms describe vertebrate embryos with these 3 germ layers. '''Diploblastic''' (two layers) lacy a mesoderm layer and occurs in some marine invertebrate animals: ''porifera'' (sponges), ''cnidarians'' (sea anemones, hydra, jellyfish) and ''ctenophores'' (comb jellies). | |||
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Here is a page with University level student information on [[Developmental Signals - Homeobox|Homeobox]] | Here is a page with University level student information on [[Developmental Signals - Homeobox|Homeobox]] | ||
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==Pharyngeal Arches== | |||
The vertebrate early embryo head region develops a series of transient structures called '''pharyngeal arches''' (branchial arches and gill arches). Each arch has a similar structure and is formed from all 3 germ layers. In fish, these arches develop into the gill apparatus. In mammals, these arches contribute many different head structures including the jaws, hearing components and endocrine organs. | |||
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| width=210px|[[File:Stage14 sem2l.jpg|200px]] | |||
| This is a human embryo (week 5) showing the pharyngeal arches numbered 1, 2, 3, 4. | |||
* The arches developmentally form in sequence, top to bottom (1 to 6). | |||
* The arches are then remodelled over the next 3 developmental weeks to form many different components of the head. | |||
* Other mammals form similar structures from each arch, but over a different time course. | |||
The cartoon below shows the repeated structure within each arch, germ layer contribution, and the special names given to each region. | |||
[[File:Pharyngeal arch structure cartoon.gif|480px]] | |||
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| '''Pharyngeal Arches''' are formed by all vertebrates, are temporary structures, contain all 3 germ layer, and contribute similar head components to all animal embryos. | |||
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{| class="wikitable mw-collapsible mw-collapsed" | |||
! Teacher Note | |||
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| colspan="2"|[[File:Mark_Hill.jpg|50px]] Note that humans do not have a 5th arch (numbered on the basis of structures formed) and arch 4 and 6 are present as a single structure on the above surface embryo view. | |||
The table below gives a detailed overview of adult structures formed from each arch in the human embryo. | |||
{{Pharyngeal Arch table}} | |||
[[Pharyngeal arches]] this page contains more detailed information about these structures. | |||
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| Many different animals form limbs (arms and legs). During embryo development there are common signalling molecules and regions that form the initial limb structure. A similar process occurs for both the upper (arm) and low (leg) limb development. | | Many different animals form limbs (arms and legs). During embryo development there are common signalling molecules and regions that form the initial limb structure. A similar process occurs for both the upper (arm) and low (leg) limb development. | ||
The final limb structures formed can appear different, but the bones shows that they share a pattern of development. | |||
| [[File:Stage16-17-limbs01.jpg|300px]] | | [[File:Stage16-17-limbs01.jpg|300px]] | ||
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| '''Limbs''' even though animal arms, legs, flippers and wings appear externally different their skeletons show common features and have a common function (motility). | | [[File:Mouse limb cartilage and bone E14.5L.jpg|300px]]<br> | ||
Mouse Embryo Limb | |||
| bgcolor="F5FFFA"|'''Limbs''' even though animal arms, legs, flippers and wings appear externally different their skeletons show common features and have a common function (motility). | |||
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{| class="wikitable mw-collapsible mw-collapsed" | |||
! Teacher Note | |||
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| colspan="2"|[[File:Mark_Hill.jpg|50px]] Even animals like snakes, that today don't today have limbs, express transiently the genes that are required to pattern limbs. Leal and Cohn, [http://www.cell.com/current-biology/abstract/S0960-9822(16)31069-7 Loss and Re-emergence of Legs in Snakes by Modular Evolution of Sonic hedgehog and HOXD Enhancers], Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.020 | |||
* Python legs are truncated due to early arrest of [[Developmental Signals - Sonic hedgehog|Sonic hedgehog]] (SHH) transcription | |||
* The python SHH limb enhancer has weak activity due to deletion of key binding sites | |||
* [[Developmental Signals - Homeobox|HOXD]] digit enhancers and the footplate expression domain are conserved in pythons | |||
* Python leg buds form transitory condensations of the tibia, fibula, and footplate | |||
See also notes on [[Musculoskeletal System - Limb Development|Limb development and patterning]]. | |||
Other animals, like salamanders ([[Axolotl Development|axolotl]] and newts) are capable of regenerating their entire limb. See the [https://youtu.be/byLDgtSMI0w HHMI Video] below. | |||
<html5media width="480" height="360">https://www.youtube.com/embed/byLDgtSMI0w</html5media> | |||
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The developmental signals that control say a connective tissue, like bone, are the same for all bones throughout the body. These mechanisms are the same in other animals. Therefore bone development will go through similar stages in all animals bodies even though different bones are eventually formed. | The developmental signals that control say a connective tissue, like bone, are the same for all bones throughout the body. These mechanisms are the same in other animals. Therefore bone development will go through similar stages in all animals bodies even though different bones are eventually formed. | ||
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'''Mouse limb tissue development''' | |||
[[File:Mouse limb tissue development.jpg|700px]] | |||
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{| | {| | ||
|-bgcolor="F5FFFA" | |-bgcolor="F5FFFA" | ||
| '''Tissue Development''' - the genes and signals that control embryonic development of these tissues are closely related in all animals. | | '''Tissue Development''' - the genes and signals that control embryonic development of these tissues are closely related in all animals and differ from the "patterning genes". | ||
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| [[File:Appendicular skeleton.jpg|200px]] | | [[File:Appendicular skeleton.jpg|200px]] | ||
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==Comparing Embryos== | ==Comparing Embryos== | ||
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Whats | | Whats difference in humans? | ||
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The long fetal growth period allows extensive neural growth and development, though humans are not the longest prenatal period, so its not just about time. | The long fetal growth period allows extensive neural growth and development, though humans are not the longest prenatal period, so its not just about time. | ||
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{| | |||
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| '''Developmental Times''' - the graph compares different animals time to reach the same stage in embryo development. | |||
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| [[File:Carnegie stages species comparison.jpg|500px]] | |||
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{{Animal development period table}} | {{Animal development period table}} | ||
{{CarnegieComparisonHRM}} | |||
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Now looks at [[K12_Human_and_Other_Animal_Development|Human and Other Animal Development]] | Now looks at [[K12_Human_and_Other_Animal_Development|Human and Other Animal Development]] |
Latest revision as of 09:21, 21 October 2016
Embryology - 26 Apr 2024 Expand to Translate |
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Introduction
All human and animal embryos go through very similar stages of early development. See also Humans and Animal Embryology.
This page introduces a few of the concepts of comparative development shared with all animals.
MeiosisMitosis
Gastrulation
Body Plan
Below is an example of what happens in a fly if these patterning signals get disrupted, putting legs from the body on the head where antenna should be located.
This fly mutation identified a common patterning gene family called Hox that establishes the head to tail axes in the embryo. This complicated picture shows how different Hox genes are expressed at different embryo levels in different species (worms, flies, mouse and human).
Pharyngeal ArchesThe vertebrate early embryo head region develops a series of transient structures called pharyngeal arches (branchial arches and gill arches). Each arch has a similar structure and is formed from all 3 germ layers. In fish, these arches develop into the gill apparatus. In mammals, these arches contribute many different head structures including the jaws, hearing components and endocrine organs.
Limbs
Tissue Development
Organ DevelopmentMany animals have common organs used for digestion (stomach, liver, pancreas), breathing (lungs), waste (kidneys) and cardiovascular (heart). The signalling mechanisms that are used to control their initial development and later internal patterning are the same in many different species embryos.
Animal ModelsThese shared signalling mechanisms allow us to use animal development to study both normal and abnormal human development. Common animal "models" used include mouse (mammal), chicken (bird) and zebrafish (fish). Though very different species, current research shows that these embryos share common signalling mechanisms that form similar structures in different animals.
Comparing Embryos
Now looks at Human and Other Animal Development
Cite this page: Hill, M.A. (2024, April 26) Embryology K12 Comparative Embryology. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_Comparative_Embryology
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