Anurans
Frog and toad
External fertilization
Urodeles
Salamander
Internal fertilization
Environmental hazard affecting
amphibian development
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Loss of wetland
Increased ultraviolet radiation
Pollution of breeding sites
Low PH
Toxicity of aluminum
Dry weather
Sudden temperature changes
Stages in amphibian development
1. Unfertilized
2. Gray crescent
3. 2-cell
4. 4-cell
5. 8-cell
6. 16-cell
7. 32-cell
8. Mid cleavage
9. Late cleavage
10. Early gastrula ,
dorsal lip forming
11. Mid gastrula
12. Late gastrula
13. Neural plate
14. Neural fold
15. Rotation
16. Neural tube
17. Tailbud
18. Muscular response
19. Heartbeat
20. Gill circulation, hatching
1. Unfertilized
• Mesolecithal type
• Telolecithal type
2. Gray crescent
3. 2 – blastomers stage
4. 4 – blastomers stage
5. 8 – blastomers stage
6. 16 – blastomers stage
7. 32 – blastomers stage
8. Mid cleavage (Morula stage)
9. Late cleavage (blastula stage)
10. Early gastrula , dorsal lip forming
11. Mid gastrula
12. late gastrula
13. Neural plate
14. Neural fold
15. Rotation
16. Neural tube
17. Tailbud
18. Muscular response
19. Heartbeat
20. Gill circulation, hatching
Organization on tadpole
Examine cross section of frog embryo at hatching stage through head and
developing eye
Neural tube
notochord
somites
Heart
foregut
Adhesive
glands
Examine cross section of frog embryo at hatching stage through region of heart and
gills
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12.
Examine cross section of fertilized egg of frog
Examine cross section of 2 – blastomers stage of frog
Examine cross section of 4 – blastomers stage of frog
Examine cross section of 8 – blastomers stage of frog
Examine cross section of 16 – blastomers stage of frog
Examine cross section of blastula stage of frog
Examine cross section of Mid gastrula of frog
Examine cross section of late gastrula of frog
Examine cross section of frog embryo shows neural plate
Examine cross section of frog embryo shows neural fold
Examine cross section of frog embryo shows neural tube
Examine cross section of frog embryo at hatching stage
through head and developing eye
13. Examine cross section of frog embryo at hatching stage
through region of heart and gills
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