Reptiles

Chapter 41

Origin & Evolution of Reptiles

Section 41.1

History of Reptiles

• 350 million years old• Reptiles arose from amphibians• “Age of Reptiles” = Mesozoic era• Reptile means “to crawl”• Herpetology: study of reptiles &

amphibians

Evolution of Dinosaurs

• Dinosaurs: group of extinct reptiles that dominated life 235 mya

• Triassic dinosaurs: small, carnivorous

• Jurassic dinosaurs: large, carnivorous

• Cretaceous dinosaurs: large, herbivorous

Extinction of Dinosaurs

• 66 million years ago1. Asteroid-impact hypothesis:

huge asteroid hit the earth, creating lots of dust that reduced the amount of sunlight causing massive climatic changes

2. Multiple-impact hypothesis: multiple asteroid impacts

Success of Reptiles

• Only 4 orders of reptiles survived the mass extinction– Squamata, Chelonia, Crocodilia, &

Rhynchocephalia

• First totally terrestrial vertebrate

Amniotic Egg

• Egg that encases the embryo in a secure, self-contained aquatic environment

Draw this picture!

Parts of the Egg

• Amnion: membrane enclosing the fluid where the embryo floats

• Yolk sac: encloses the yolk (fat-rich food supply)

• Allantois: stores wastes produced by embryo

• Chorion: protects the embryo• Albumen: stores protein & water for

embryo

Characteristics of Reptiles

Section 41.2

Watertight Skin

• Thick, dry skin with keratin: – protein found in the outer surface cells

• Lipids & protein barrier• Protects from water loss, infections,

& injuries

Excretion

• Efficient systems to help conserve water– Little water loss in urine

• Lungs to breathe out CO2

Circulatory System

• Composed of two loops:

1. Pulmonary loop: deoxygenated blood from heart to lungs, oxygenated blood from lungs to heart

2. Systemic loop: oxygenated blood to body, deoxygenated blood to heart

Heart Structure & Function

• Most have a 3 chambered heart: – 2 atria & 1 ventricle (partially divided)

• Crocodiles have a 4 chambered heart: – 2 atria & 2 ventricles– Ventricle divided by septum tissue

• Reptiles can reroute blood flow away from lungs – Conserves energy– Raises body temperature quickly

Crocodile Heart

Septum

Respiration

• Large, several chambered lungs with small sacs called alveoli– Increases surface area for diffusion

• First vertebrae group to breath by expanding & contracting their chest– Air pressure gradient between outside

and the thoracic cavity

Nervous System• Sight is very important thus big eyes• Hearing is also important though snakes lack

a tympanum – Detect ground vibrations via jaw bones

• Jacobson’s organ: detects odor (smell), on roof of mouth

• Heat sensitive pits below eyes of some snakes

Thermoregulation

• Definition: control of body temperature

• Ectotherm: warms body by absorbing heat from the surroundings– Fish, reptiles, amphibians

• Endotherm: generates heat from within – Birds, mammals

Advantages & Limitations of Ectothermy

• Advantages:– Slow metabolism– Less food needed

• Limitations:– Cannot live in cold climates (become

dormant in winter)– No sustained exertion

Reproduction & Parental Care

1. Oviparity: egg surrounded by tough protective shell, no parental care

2. Ovoviviparity: eggs stored within female until just before hatching, limited parental care

3. Viviparity: eggs stored with female and receives nutrients from the placenta, most parental care

Welcome to the world!

Modern ReptilesSection 41.3

Order Chelonia

• Examples: turtles (water dwelling) & tortoises (land dwelling)

• Body covered by a 2 part shell: carapace (dorsal) & plastron (ventral)

• Vertebrae & ribs fused to carapace– Cannot leave shell!

• Sharp beak with no teeth• Lay eggs (oviparity)

Two parts of the shell

Some Ohio turtles on the next few slides…..

Eastern Box Turtle

Stinkpot Musk Turtle

Soft-shelled Turtle

Blanding’s Turtle

Spotted Turtle

Snapping Turtle

Painted Turtles

Tasha, Daisy, & Bowser – in the Maroons’ house!

Order Crocodilia

• Examples: crocodiles & alligators• Closest relatives to dinosaurs• All are carnivores

– Eat turtles, fish, etc.

Order Squamata

• Examples: lizards & snakes• Autotomy: the ability to detach a

body part often when a predatory is near

• Snakes swallow prey whole– Detachable jaw

Types of Snakes

• Constrictors: wrap body around prey and suffocate by increasing pressure– Boas, pythons, anacondas

• Elapsid: inject venom through two small, fixed fangs in front of mouth– Cobras, coral snakes

• Vipers: inject venom through large, mobile fangs in the front of mouth– Rattlesnakes, copperheads, water

moccasins

Order Rhynchoephalia

• Example: tuatara• Meaning “spiny crest”• Only two modern species• Live in New Zealand

4 Order Note Cards

• Front Side:– Name of order– Picture (in color) of animal

• Back Side:– Example organisms– Where on Earth?/habitat– Unique characteristics– Feeding patterns– Reproductive behavior