Class - Amphibia, Reptilia & Mammalia | Biology for JAMB PDF Download

Amphibians 

• Amphibians are a group of vertebrates that can live in both water and on land. They are cold-blooded animals.
• The word 'amphibian' comes from the Greek word 'amphibios', which means living a double life.
• There are around 8,698 species of amphibians worldwide, with the first known species appearing about 370 million years ago.
• Modern amphibians are classified into three orders: Anura, Caudata, and Apoda.
• Order Anura includes frogs and toads, Order Caudata includes salamanders and newts, and Order Apoda includes caecilians.
• These orders are distinguished by their physical characteristics.
• Frogs have no tails and have powerful hind limbs, while salamanders have tails and limbs of similar size, and caecilians are limbless and adapted for burrowing.
• Most amphibians have moist skin and rely on cutaneous respiration.
• Many develop gills in their larval stage for breathing underwater, which disappear as they mature into adults.
• Amphibians have unique sensory features, including a double hearing system and special retinal cells for color vision.
• They reproduce sexually through internal or external fertilization, using scents or calls to attract mates.
• Due to their porous eggs and permeable skin, amphibians are highly vulnerable to environmental changes.

Reptiles 

• Reptiles are ectothermic vertebrates that primarily inhabit terrestrial environments, characterized by epidermal scales covering their bodies.
• These creatures exhibit a diverse range of features; some share similarities with amphibians, while others display avian characteristics.
• Most reptiles are tetrapods, possessing two pairs of limbs, and they typically do not undergo an aquatic larval stage.
• There are over 10,000 known species of reptiles on Earth, with the earliest reptilian fossils dating back approximately 312 million years.

Classification of Modern Reptiles

• Order Squamata: Encompassing lizards and snakes, this order showcases a remarkable diversity in form and function.
• Order Crocodilia: This group includes formidable predators such as crocodiles and alligators, known for their semiaquatic lifestyles.
• Order Testudines: Turtles and tortoises belong to this order, characterized by their protective shells and unique body structures.
• Order Sphenodonta: Represented by tuataras, this order is a relict lineage with distinct physiological features.

Distinctive Characteristics

• Reptiles possess epidermal scales composed of beta-keratin, varying in shape and size among species.
• These creatures are air-breathing and rely on a developed pulmonary system for respiration.
• While some reptiles have limbs, others are limbless, adapting to diverse modes of locomotion.
• Regular shedding of the outer skin layer is a common phenomenon among reptiles, crucial for growth and maintenance.
• Due to their ectothermic nature, reptiles' metabolic processes are influenced by environmental temperatures.

Reproduction and Development

• Sexual reproduction is predominant among reptiles, involving internal fertilization through copulation.
• Parthenogenesis, a form of asexual reproduction, is observed in certain reptilian groups.
• While boas and pythons give live birth, most reptiles lay amniotic eggs with calcareous shells.
• The incubation period and sex determination of offspring are influenced by the temperature of the nesting environment.

Behavioral Traits

• Many reptiles are diurnal, exhibiting peak activity during daylight hours.
• These creatures possess advanced color vision and depth perception, aiding in various aspects of their behavior and survival.

Key Differences (Amphibians vs. Reptiles)