The document discusses several concepts in embryology including: 1. All animals develop from a single egg cell and pass through similar developmental stages. 2. The gastrula of all animals has three germ layers - ectoderm, mesoderm, and endoderm - that develop into different tissues and organ systems. 3. According to Von Baer's law and the biogenetic law, higher animal embryos pass through stages resembling the adult forms of lower animals from which they evolved.

1. Embryological Evidences
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2. Embryology deals with the development of organisms from the egg stage to the adult stage
it is also called ontogeny
1. Egg:
Each animal, whether a worm or fly or a frog or an elephant or a man start development from
single cell, the egg
2. Development stage:
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3. 3. Fate of Gastrula:
the gastrula of all animals consist of an archenteron, a blastopore and three germinal
layers, namely ectoderm, mesoderm and endoderm.
Archenteron: alimentary Cavity and the associated glands
Blastopore: Mouth in invertebrate except echinoderm and anus in all chordate
Ectoderm: nervous system, skin
Mesoderm: muscular system, skeleton
Endoderm: Alimentary canal
4. Similarity of embryos:
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4. 5. Von Baer's Law:
In the 18th century Von Bear, founder of comparative embryology, contributed much to the
field of embryology and evolution
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5. 6. Biogenetic law or Recapitulation theory:
Biogenetic law was postulated by Ernst Haeckel (1861)
This theory says that higher animals in their development passes through stages which
are similar to the adult stages of lower animals, which would be their ancestors.
Ontogeny
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6. Phylogeny:
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7. This theory can be substantiated by following example
1. Tadpole
2. Teeth in birds:
3. Embryonic stages:
4. Hair in whale embryo
5. Heart:
6. Kidney:
7. Yolk sac:
8. Aortic Arch:
9. Branchial grooves and visceral pouch:
10.Trochophore larva
11.Nauplius Larva
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8. 1. Tadpole
2. Teeth in birds
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9. 3. Hair in whale embryo
4. Embryonic stages
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10. 5. Heart:
6. Kidney
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11. 7. Yolk sac:
8. Aortic Arch:
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12. 9. Branchial grooves and visceral pouch:
10. Trochophore larva
11. Nauplius Larva
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13. Sandip Rathod