Burd BIOL 191 Study Guide – Lecture 16

Tetrapods

• Definition: Tetrapods are vertebrate animals adapted for life on land.

• Distinguishing Characteristics:

  • Limb structure: Four limbs used to support weight on land.

  • Musculoskeletal adaptations: Muscle force transmitted to limbs for movement.

  • Skeletal structure: Separation of the head from the shoulder girdle.

  • Frogs are noted for adaptations allowing them to live in trees or adapt to an underground lifestyle (fossorial).

Characteristics of Amphibians

• Main Traits:

  • have Moist skin for gas exchange.

  • have Positive pressure lungs

  • have to gulp air into lungs

Gas Exchange in Amphibians

• Amphibians exchange gases via skin (cutaneous respiration) and lungs.

• Their moist skin facilitates gas exchange with the environment.

Buccal Pumping

• Definition: A method of respiration:

  • Involves gulping air into the lungs.

  • Breathing process includes using cheek muscles to push air into the lungs.

Thermoregulation Terms

• Ectothermic Organism: Animals that rely on external sources like sunlight for temperature regulation.

• Endothermic Organism: Animals that maintain body temperature through internal sources, like mammals.

• Poikilothermic Organism: Organisms with body temperature that varies according to the environment.

• Homeothermic Organism: Organisms with a constant body temperature.

Amphibian Reproduction

• Amphibians typically reproduce in wet environments.

• Fertilization:

  • External Fertilization: Eggs fertilized outside the female's body (e.g., frogs).

  • Internal Fertilization: Sperm fertilizes eggs within the female's body.

Amphibians and Water Dependency for Reproduction

• Many amphibians require moist conditions for egg laying to prevent desiccation.

Metamorphosis in Amphibians

• Complete Metamorphosis: Involves major transformation from larval to adult form (e.g., tadpoles to frogs).

• Direct Development: Eggs hatch into a juvenile form that resembles the adult, without a distinct larval stage.

Amphibian Diversity

• Classes:

  • Anura: Frogs and toads, typically lack tails as adults.

  • Urodela: Salamanders and newts, characterized by tails.

  • Apoda: Caecilians, legless and worm-like amphibians.

Importance of Amphibians as Bioindicators

• Sensitive to environmental changes, amphibians are good indicators of ecosystem health.

Amniotic Egg Adaptation

• Definition: An egg structure allowing for reproduction on land, providing protection and nourishment to the embryo.

• Components:

  • Amnion: Fluid-filled cavity providing cushioning.

  • Yolk Sac: Nutrient source for the developing embryo.

  • Albumen: Protects and provides water to the embryo.

  • Shell: Offers physical protection while allowing gas exchange.

Mammals and Amniotic Eggs

• Some mammals, like monotremes (e.g., platypus), lay eggs, while most are viviparous (giving live birth).

Synapsids and Examples

• Definition: A class of mammals characterized by the presence of single temporal fenestra.

• Examples: Humans, cats, and dogs.

Diapsids and Examples

• Definition: Reptiles characterized by two temporal fenestrae in their skull.

• Examples: Birds, crocodiles, and lizards.

Anapsids

• Definition: Reptiles with no temporal fenestrae (e.g., turtles).

Keratin in Reptiles

• Keratin is found in scales and helps to protect against desiccation and abrasion.

Ectothermic vs. Endothermic in Reptiles

• Most reptiles are ectothermic, regulating body temperature behaviorally (e.g., basking in the sun).

Lepidosaurs

• Definition: A group of reptiles that includes lizards and snakes, characterized by overlapping scales.

Squamates

• Characteristics include:

  • Movable eyelids.

  • External ear openings.

  • Diverse diet and habitats.

Jacobson's Organ

• A sensory organ in reptiles used to detect chemical signals in the environment, enhancing their sense of smell.

Pit Vipers and Their Loreal Pits

• Loreal pits are specialized structures in pit vipers used to detect infrared radiation, assisting in locating warm prey in low light conditions.

Archosaurs

• Definition: A clade that includes birds and crocodilians, characterized by certain skull features and a derived ankle structure.

General Characteristics of Testudines (Turtles)

• Protected by a hard shell composed of a carapace (upper) and plastron (lower).

• Can withdraw their head and limbs into the shell for protection.

Difference Between Carapace and Plastron

• Carapace: The dorsal shell covering the turtle’s body.

• Plastron: The ventral shell covering the belly.

General Characteristics of Crocodilians

• Aquatic adaptations.

• Notable parental care behaviors.

• Territorial and often solitary, hunting in groups under specific conditions.

• Ectothermic metabolism allows for energy conservation in warmer aquatic environments.