Classification of Living Things

Classification of Living Things

• Scientists classify living things based on shared characteristics.
• Carl Linnaeus developed the binomial system of classification in the 18th century. This system uses two Latin names to identify each species.
• For example, humans are Homo sapiens.

Kingdoms

• Organisms are classified into five kingdoms based on: cell structure (single or multicellular), how they obtain nutrients, and movement.
• Two notable kingdoms are Animalia and Plantae.

Animal Kingdom

• Contains approximately nine to ten million species.
• All members are multicellular and obtain nutrition by consuming other organisms.
• They can move using muscles or other means.
• Divided into invertebrates and vertebrates.

Vertebrates

• Mammals:
  • Examples include cows, mice, and humans.
  • Feed young with milk.
  • Characteristics may include hair, live birth, regulating body temperature, and red blood cells without nuclei.
  • About 5,500 species worldwide.
• Birds:
  • Examples include sparrows, chickens, and ostriches.
  • Have wings and feathers.
  • Lay hard-shelled eggs.
  • Adaptations may include flight, beaks suited for specific diets, and hollow bones.
  • About 10,000 species worldwide.
• Fish:
  • Examples include cod, sharks, and salmon.
  • Live in water and have gills for breathing.
  • Cold-blooded (cannot regulate temperature).
  • Swim using tails and fins.
  • Covered in scales.
  • Lay many soft eggs outside the body.
  • About 32,000 species worldwide.
• Reptiles:
  • Examples include iguanas, tortoises, and crocodiles.
  • Breathe air and are cold-blooded.
  • Lay soft, leathery eggs.
  • Covered in scales.
  • Have a cloaca (single opening for excretion and reproduction).
  • About 8,700 species worldwide.
• Amphibians:
  • Examples include frogs, toads, and newts.
  • Live both in water and on land.
  • Moist, permeable skin allows gas exchange.
  • Offspring develop in soft eggs, often laid in water.
  • Undergo metamorphosis.
  • About 8,100 species worldwide.

Invertebrates

• Animals without backbones.
  • Examples include arthropods (insects, spiders, crabs), mollusks (snails, octopuses, shellfish), nematodes (parasitic worms), and annelids (earthworms, leeches).

Plant Kingdom

• Flowering Plants: This large group is further divided into monocots and dicots.
• Non-Flowering Plants: Includes plants not in the flowering plant classification.

Other Kingdoms (from the text)

• Fungi: A kingdom with its own set of characteristics
• Prokaryotes: Single-celled organisms without a nucleus.
• Protists: Diverse group of single-celled or simple multicellular organisms.