Aquatic Biology: Fishes and Reptiles

Study Notes

Internal Line System: A series of sensory receptors along the sides of the body detect water pressure, movement, and vibrations; aiding navigation, hunting, and predator avoidance.
Buoyancy: Lack a swim bladder; rely on a large, oily liver for neutral buoyancy and active swimming to maintain position.
External Anatomy: Cartilaginous skeleton, placoid scales (tiny, tooth-like scales), multiple gill slits, mouth on underside with teeth, nostrils, and well-developed eyes.

External Anatomy: Bony skeleton, operculum (bony flap covering gills), swim bladder (gas-filled sac for buoyancy control), scales, various fins for swimming, steering, and balance (dorsal, caudal, pectoral, pelvic).
Swim Bladder: A gas-filled sac allowing bony fishes to regulate buoyancy.

Oviparity (Egg-Laying): Female reptiles lay fertilized eggs, often in nests or buried in soil.
Viviparity (Live Birth): Female reptiles give birth to live young, with nourishment provided through a placental-like structure or yolk sac.
Ovoviviparity (Egg-hatching Inside the Mother): Female reptiles retain fertilized eggs inside their bodies until hatching.
Orders of Reptiles: Testudines (turtles and tortoises), Squamata (lizards and snakes), Crocodilia (crocodiles, alligators), Sphenodontia (Tuataras).
Internal Anatomy: Digestive system (mouth, esophagus, stomach, intestines, cloaca), respiratory system (lungs), circulatory system, excretory system, nervous system, reproductive system.
Parthenogenesis in Reptiles: A rare form of asexual reproduction, observed in some lizards and snakes. Unfertilized egg develops into an offspring.

Three Main Orders: Anura (frogs and toads), Caudata (salamanders and newts), Gymnophiona (caecilians).

Respiratory System: Lungs and air sacs; unidirectional airflow for efficient oxygen intake.
Circulatory System: Four-chambered heart, maximizing oxygen delivery.
Digestive System: Beak, crop, gizzard, and intestines.
Nervous System: Relatively large brain, well-developed senses.

General Characteristics: Hair or fur, mammary glands, endothermy, four-chambered heart.
Ways of Giving Birth: Placental mammals, marsupials, monotremes.
Groups: Rodentia (rats, mice, squirrels), Chiroptera (bats), Carnivora (dogs, cats, bears), Primates (humans, monkeys), Artiodactyla (cows, deer), Perissodactyla (horses, zebras), Cetacea (whales, dolphins), Sirenia (manatees).

Respiratory System: Adaptations to breathe air in water (e.g., complex social structures; echolocation). Examples include whales, dolphins, porpoises, seals, sea lions, walruses.