Marine Bio Unit 8

Lesson 1: Introduction to Marine Reptiles

Reptiles: Introduction

  • Marine reptiles - vertebrates mainly living in tropical and subtropical habitats

  • thought that reptiles evolved around 330 million years ago

  • first animals to live and multiply on land

    • amniotic eggs and the ability to breathe air

  • in modern times many species have returned to the sea and exist both in terrestrial and marine environments

  • only a few orders of marine reptiles remain belonging to class Reptilia

    • crocodiles

    • marine iguanas

    • turtles

Reptiles: Skin & Skeleton

  • dry skin covered with scales and cutaneous gland with high levels of keratin

    • glands - prevents water loss through the skin

  • scales are formed from the epidermis

    • protect the body

  • all reptiles have a spinal columns and a strong skeletal system with a rib cage

  • most have a min of two spinal bones in the pelvic area

Reptiles: Cardio-Respiratory System

  • reptiles do not pass through an embryonic stage with gills rather they breathe with well-developed lungs

  • most have two lungs but some snakes only have one

  • reptiles (except crocs) have three-chambered hearts

    • consists of two atria to recieve blood and one partially divided ventricle for pumping blood

    • croscs have a four-chambered hearts with two atria and two ventricles

Ectotherms vs. Endotherms

  • reptiles are ectothermic

    • why you may see snakes laying on the road or rocks attempting to warm up in the sun

    • metabolic rate and activity levels vary w/ temp

      • sluggish in the cold

  • endothermic animals regulate their temp internally through the metabolic process

Reptiles: Digestive system

  • reptiles have a digestive system similar to vertebrates

  • the main difference is the gut, ducts of urinary and sexual organs lead to a singular posterior chamber called the cloaca

    • cloaca - a muscular opening at the base of the tail

    • in arid regions water is further absorbed into the body from the waste and the waste waste is excreted

Reptiles: CNS & Senses

  • reptiles have a well-developed brain and centeral nervous system CNS

  • physical characteristics of reptiles included their keen sense

    • helps them find food and escape from predators.

  • eyes are one of the most important sense organ

    • front of the head

      • facilitate binocular vision

  • eardrum are internal and located near the eyes

Reptiles: Special Adaptations

  • marine reptiles also have adaptations that are specific to their life in the ocean

  • bc of their saltwater enviroment, sea turtles and marine lizards need to get rid of excess salt to conserve freshwater

    • salt glands (above the eye)

      • allows them to secrete large quantities of salty tears

      • allows them to live without access to freshwater,

      • wash sand from their eyes

    • concetrate urnine

Reptiles: Reproduction

  • first animals with amniotic eggs that can be laid on land and not in water

  • the eggs can survive w/o water as they have protective leathery shells and membranes that permit gases to enter

  • most lay eggs, but a few have give live birth

  • reptile reproductive characteristics:

    • internal fertilization

  • offspring resemble adults when born.