Vertebrates and Fish: Zoology

• Zoology is the branch of biology that studies the animal kingdom.
• Focus areas include structure, embryology, evolution, classification, habits, and distribution of animals, both living and extinct
• Animals are generally multicellular, eukaryotic, and heterotrophic organisms.
• Zoology encompasses the study of both vertebrate and invertebrate animals.
• Vertebrates and invertebrates are distinguished by the presence or absence of a vertebral column or backbone.

Vertebrates

• Vertebrates possess a spinal column or backbone.
• The vertebral column is part of an internal skeleton.
• The internal skeleton is mostly bone, cartilage or both.
• Fish, amphibians, reptiles, birds, and mammals are types of vertebrates.

Fish

• Fish are aquatic animals with gills, fins, and scales.
• Examples include salmon, tuna, sharks, and rays.

Amphibians

• Amphibians undergo metamorphosis from a larval stage to adulthood.
• They live both in water and on land.
• Frogs, toads, and salamanders are amphibians.

Reptiles

• Reptiles are air-breathing vertebrates with scales or scutes.
• They lay eggs on land.
• Snakes, lizards, turtles, and crocodiles are reptiles.

Birds

• Birds have feathers, wings, beaks, and lightweight skeletons.
• They lay hard-shelled eggs and have a four-chamber heart.
• Eagles, parrots, and penguins are birds.

Mammals

• Mammals possess hair or fur, mammary glands, and a three-bone middle ear.
• Most give birth to live young, with monotremes being the exception.
• Humans, dogs, whales, and bats are mammals.

Characteristics of Vertebrates

• Endoskeleton: internal skeleton provides support and protection.
• Bilateral Symmetry: left and right sides of their bodies are mirror images.
• Closed Circulatory System: a heart pumps blood through vessels.
• Nervous System: complex, including a brain and spinal cord.
• Respiratory System: utilizes gills or lungs.
• Sensory Organs: well-developed sensory organs enable environmental perception.

Invertebrates

• Invertebrates lack a backbone or vertebral column.
• They make up the vast majority of animal species.
• They exhibit an enormous range of diversity.
• Major phyla include Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, and Echinodermata.

Porifera

• Porifera include simple aquatic animals with porous bodies.
• They lack true tissues and organs.
• Sponges belong to this group.

Cnidaria

• Cnidaria are radially symmetrical animals.
• They possess stinging cells called cnidocytes.
• Jellyfish, corals, and sea anemones are cnidarians.

Platyhelminthes

• Platyhelminthes are flat-bodied worms, some of which are parasitic.
• Tapeworms and flukes are examples of Platyhelminthes.

Nematoda

• Nematoda include cylindrical worms with a complete digestive system.
• They are found in various habitats.
• Roundworms are Nematoda.

Annelida

• Annelida are worms with segmented bodies.
• Earthworms and leeches are Annelida.

Mollusca

• Mollusca are soft-bodied animals, many of which have a hard shell.
• Snails, clams, and squids are mollusks.

Arthropoda

• Arthropoda are characterized by jointed appendages and a chitinous exoskeleton.
• This is the largest phylum in the animal kingdom.
• Insects, arachnids, and crustaceans are arthropods.

Echinodermata

• Echinodermata are radially symmetrical marine animals with a water vascular system.
• Starfish and sea urchins are echinoderms.

Characteristics of Invertebrates

• Exoskeleton: external skeleton made of chitin in some groups.
• Open or Closed Circulatory System.
• Diverse Respiratory Structures: gills, tracheae, or simple diffusion across the body surface.
• Varying Levels of Nervous System Complexity: from simple nerve nets to more complex brains.
• Absence of a Backbone.

Key Differences Between Vertebrates and Invertebrates

• Presence of a Backbone
  • Vertebrates: Have a vertebral column or backbone
  • Invertebrates: Lack a vertebral column or backbone
• Skeleton
  • Vertebrates: Possess an endoskeleton (internal)
  • Invertebrates: May have an exoskeleton (external) or a hydrostatic skeleton, or lack a skeleton
• Body Symmetry
  • Vertebrates: Bilateral symmetry
  • Invertebrates: Exhibit bilateral or radial symmetry
• Circulatory System
  • Vertebrates: Closed circulatory system
  • Invertebrates: Open or closed circulatory system
• Nervous System
  • Vertebrates: Complex nervous system with a brain and spinal cord
  • Invertebrates: Varying levels of nervous system complexity
• Diversity
  • Vertebrates: Represent a smaller portion of animal diversity
  • Invertebrates: Comprise the vast majority of animal species