This document discusses the characteristics and classification of reptiles. It begins by introducing duckweed and materials needed for an investigative project. It then covers the defining features of reptiles, including having scales or scutes, being ectothermic, and having three-chambered hearts except in crocodiles. The document proceeds to outline the four orders of reptiles - Crocodilia, Testudines, Squamata, and Rhynchocephalia - providing key details about each order and the types of reptiles that fall within each order.

1. Science Investigative Project
• Duckweed (Lemna)

2. Preparation of Materials
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2 culture containers (basins or bowls) of equal size
20 fronds of duckweeds
Pond water
Record Notebook
Pen
Marker

3. Reptiles

4. Characteristics of Reptiles
• Amniotes- “amnions”-elastic sac where the embryo
develops.
• Most are oviparous but some are viviparous.
• Skin covered by scale or scutes.
• Ectothermic

7. Characteristics of Reptiles
• All have three chambered heart except for
crocodiles which have four.
• Absence of gill even during the juvenile stage but
presence of well developed lungs.
• Ear holes instead of external ear

8. Group of Reptiles

9. Orders of Reptiles
 Order Crocodilia
 Order Testudinia
 Order Squamata
 Order Rynchocephalia

11. Order Crocodilia
• Semi-aquatic predators
• Extra transparent eyelid
• Flap of skin at the back of their throat.
• Carnivorous

12. Characteristics
• Diapsids-two holes on each side of the skull.
• Oviparous
• Eyes on top of the head.
• Laterally compressed teeth

13. Characteristics
• Nostril at the tip of the snout.

14. Order Testudinia
• Upper and lower bony shells surrounding their body.
• Carapace-Dorsal
• Plastron-Ventral

15. Characteristics
• Absence of teeth instead keratinous beak.
• Oviparous
• Young are independent of the parent at hatching.
• Temperature sex determination

17. Order Squamata
• Lizards
• Snakes
• Worm Lizards

18. Lizards
• Two pairs of legs
• Upper and lower laws unite anteriorly
• Most are oviparous some are ovoviviparous

20. The only venomous lizard
Gila Monster (Heloderma suspectum)
American Beaded Lizard (Heloderma horridum)

21. Snakes
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Limbless but some have traces of hind limbs (python and boa)
Internal fertilization
Joints between vertebrae
Jacobson’s organ or vomeronasal organ
Movable upper jaws and loosely joined lower jaw

24. Worm Lizards
• Specialized burrowers
• Single median tooth in the upper
• Legless and skulls are wedge or shovel shaped
• Skin have ring like folds called annuli
• Oviparous

26. Order Rhynchocephalia
• Two rows of teeth on the upper jaw and one row of
teeth on the lower jaw.
• Oviparous