• Classification
o Why do we classify species?
• Levels in our classification system:
o Domain
o Kingdom
o Phylum
o Class
o Order
o Family
o Genus
o Species
• How can we tell if two organisms belong to the same species?
o Binomial nomenclature
• Vertebrates
o Chordates – phylum
• Invertebrates
• Ectotherms Endotherms
• Endoskeleton Exoskeleton
• Mammals
o Marsupials
o Monotremes
o Placental
• Dichotomous key
o Can you create one?
o Can you interpret one?
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Why do we classify species? Classification is essential for organizing the incredible diversity of life on Earth. It helps scientists understand relationships between organisms, study them more effectively, communicate using a universal naming system, and trace evolutionary history and patterns.
The classification system uses eight main hierarchical levels, from broadest to most specific. Domain is the highest level, grouping organisms by fundamental cellular characteristics. Kingdom groups by general traits like cell type and nutrition. Phylum groups organisms with similar body plans. Class, Order, Family, Genus, and Species become increasingly specific, with Species being organisms that can interbreed and produce fertile offspring.
A species is defined as a group of organisms that can interbreed in nature and produce fertile offspring. Scientists use binomial nomenclature to give each species a unique two-part name. The first part is the genus name, which is always capitalized, and the second part is the species name, which is lowercase. Both parts are written in italics, like Homo sapiens for humans or Canis lupus for gray wolves.
Animals are divided into vertebrates and invertebrates. Vertebrates belong to phylum Chordata and have a backbone, including mammals, birds, fish, and reptiles. Invertebrates lack a backbone and include insects, spiders, and jellyfish. Animals also differ in temperature regulation: ectotherms rely on external heat sources while endotherms generate their own heat. Skeleton types include endoskeletons, which provide internal support in vertebrates, and exoskeletons, which form external coverings in insects and crustaceans.
Mammals are divided into three main groups. Placental mammals develop fully in the uterus with a placenta, like humans and dogs. Marsupials give birth to undeveloped young that complete development in a pouch, like kangaroos. Monotremes are unique mammals that lay eggs, such as the platypus. Dichotomous keys are identification tools that use paired choices to systematically identify organisms. By following the appropriate choice at each step, you can accurately identify unknown species.