Vertebrate Origins and Evolution

A flexible, rod-like structure made of mesoderm cells. It runs along the dorsal side of the body, below the nerve cord, and above the digestive tract. Provides structural support and serves as a muscle attachment axis. In vertebrates, it's replaced by the vertebral column during development.

A tube-like, hollow structure located along the back (dorsal) side of chordates. It forms from infolding ectoderm and is positioned above the notochord. In vertebrates, it develops into the brain and spinal cord, forming the central nervous system.

Openings or grooves in the pharynx, the region just behind the mouth. They are used for filter feeding in some chordates, and in vertebrates, they are modified for other functions like hearing and breathing.

A tail that extends beyond the anus. It helps with swimming and balance in aquatic chordates, and in some terrestrial vertebrates, it can be used for balance or communication.

The group of animals that includes vertebrates and a few other closely related groups (like tunicates and cephalochordates). All chordates share four key derived traits: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

A group of animals that are members of the Chordata phylum and are characterized by a vertebral column (spine) that encloses and protects the spinal cord.

Animals that do not have a backbone (vertebral column). They include a wide range of organisms, such as insects, worms, mollusks, and jellyfish.

The process of development where the first opening in the embryo becomes the anus, while the mouth forms later. Deuterostomes include chordates, echinoderms, and hemichordates.

The pharyngeal slits form during embryonic development from the endoderm, but mesoderm and ectoderm also contribute to their structure. In aquatic species, they function as gills for respiration. In terrestrial chordates, they contribute to structures like the ear and throat.

A post-anal tail is an extension of the body beyond the anus, composed of muscles and skeletal elements. It's located at the rear of the body, posterior to the anus. In aquatic species, it provides propulsion. In terrestrial species, it can be involved in balance, signaling, or other roles. In vertebrates, it may be reduced or vestigial in some adults, like the 'tailbone' in humans.

Lancelets and tunicates are chordates that lack a backbone.

Vertebrates have a backbone, called a vertebral column or spine, made of vertebrae. It protects the spinal cord, taking over from the notochord.

An endoskeleton is an internal skeleton made of bone or cartilage. It provides support and structure.

A cranium, or skull, is a protective structure for the brain.

Vertebrates have a complex central nervous system, including a well-developed brain and spinal cord.

Vertebrates have a closed circulatory system where blood circulates through vessels. It usually has a heart to pump the blood around the body.

Amphibians have skin that allows them to breathe and absorb water.

Amphibian life starts in water as a larva (tadpole) with gills, then transforms into an adult with lungs.

Amphibians rely on external heat sources like the sun to regulate their body temperature.

The Amniotic Egg allows reptiles and mammals to reproduce on land by providing a protective and moist environment for the developing embryo.

Reptiles have scales that protect them from water loss and allow them to survive in dry environments.

Most reptiles lay eggs on land after internal fertilization within the female's body.

Mammals have hair or fur that helps them retain body heat.

Female mammals produce milk to nourish their young.

Specialized sensory organs in sharks and rays that detect weak electrical fields generated by other organisms. These organs help locate prey, navigate, and sense environmental changes.

Tooth-like scales covering the shark's body. They reduce water resistance and provide protection.

Five to seven slits on the sides of the head, allowing sharks to breathe by extracting oxygen from the water

A bony skeleton made of bone, in contrast to the cartilage skeleton of sharks and rays.

A gas-filled sac that helps bony fish control their buoyancy in the water.

Fins supported by thin, flexible rays, providing efficient movement in the water.

Fleshy, lobed fins with a central bone structure. Muscles extend into the fin, providing powerful movement.

Strong, weight-bearing structures with distinct digits. Evolved from lobed fins used for movement on land.

Mammals that lay eggs, have fur but no nipples, and milk is secreted from a gland on the abdomen.

Mammals that give birth to live young, have nipples, and have a placenta but it is simpler and less developed than eutherians.

Mammals that give birth to live young, have a complex placenta, a long gestation period, and no pouch.

A complex structure that allows nutrient, gas, and waste exchange between the mother and developing embryo in eutherian mammals.

Primates that walk upright on two legs, a defining feature that sets them apart from other primates.

Opposable thumbs and toes allow for grasping and manipulation of objects, a key trait of primates.

Having eyes that face forward provides depth perception, a common trait in primates.

Primates have large brains relative to their body size, enabling complex cognitive abilities.

A flexible, rod-like structure made of mesoderm cells that runs along the dorsal side of the body below the nerve cord providing structural support and a muscle attachment axis. During development, it's replaced by the vertebral column in vertebrates.

A tube-like, hollow structure located along the back (dorsal) side of chordates. It forms from infolding ectoderm and is positioned above the notochord. In vertebrates, it develops into the brain and spinal cord, forming the central nervous system.