Classification of the Animal Kingdom

Animal Kingdom Overview

• Kingdom Animalia is one of the five kingdoms of living organisms: plants, fungi, protista, monera, and animalia.
• Animals are multi-cellular and cannot produce their own food, distinguishing them from plants.
• Animal cells lack cell walls, making them visually different from other life kingdoms.
• The animal kingdom is the largest, with many diverse species present in various environments around the globe.

Classification of Animals

• Animals are classified into two main groups: vertebrates (species with a backbone) and invertebrates (species without a backbone).
• Invertebrates comprise approximately 97% of all animal species, with over a million identified and many millions more estimated to exist.
• Vertebrates include around 60,000 known species and are categorized under the phylum Chordata.

Vertebrate Classes

• Fish:

  • Live in water, breathe through gills, covered in scales, and are ectothermic.
  • Most reproduce externally by laying fertilized eggs outside their bodies.

• Amphibians:

  • Examples include frogs and toads.
  • Begin life as larvae in water, breathing through gills; undergo metamorphosis to become adults.
  • Adults have lungs and can absorb water through their skin, allowing them to hibernate underwater.
  • Also ectothermic, with external reproduction.

• Reptiles:

  • Include snakes, turtles, lizards, crocodiles, and extinct dinosaurs.
  • Ectothermic, scaly, and breathe air using lungs.
  • Reproduce internally; eggs are fertilized within the female and typically laid outside.

• Birds:

  • Closely related to reptiles, characterized by feathers and endothermic nature.
  • Maintain a constant warm body temperature regardless of the environment.
  • Generally, birds can fly, but some, like penguins and ostriches, are flightless.

• Mammals:

  • Endothermic, breathe via lungs, and most reproduce internally, giving birth to live young instead of laying eggs.
  • Unique for feeding young with milk from specialized glands.
  • Varied environments: while many are hairy and terrestrial, others like whales are smooth-skinned and aquatic; some mammals like bats can fly.
  • Humans are classified as mammals in the order of primates and family of great apes.

Key Features Summary Table