Ch. 18 : Classification of Living Organisms

Millions of organisms Only thousands named and studied Grouping makes its easier to study TAXONOMY = the branch of biology

that names and groups organisms according to their characteristics and evolutionary history.

taxonomy Aristotle ; plants or animals, animals where

either land-dwellers, water-dwellers or air-dwellers.

Carolus Linnaeus ; Swedish naturalist, mid 1770’s, realized that every area had their own name/language for organisms. Converted everything to latin so that names were universal.

Linnaeus’s system used morphology( form and structure) to classify organisms.

Today we are reclassifying some organisms based on their DNA sequences.

Levels of classification Domain – largest level of classification based on cell type

(eukaryotic and prokaryotic) Eukarya, Eubacteria and Archeobacter

Kingdom – big groups based on cell type, cell number, nutrition and reproduction

Animalia, Plantae, Protista, Fungi, and Bacterias Phylum – kingdoms are subdivided

animal kingdom is divided into vertebrates and invertebrates Class – smaller groups Order – more similar

There are orders of birds Family – still smaller and more similar

You are familiar with families like feline, canine, equine, bovine, etc Genus – like a last name Species – very specific, each organism belongs to its own

species

Levels of classification Domain - Kingdom - Animalia Phylum - chordata Class - mammalia Order - carnivora Family – felidae Genus - Panthera Species – P. leo Scientific name = Panthera leo

terms Phylogeny: using evidence and

hypotheses to evaluate morphology and that of ancestral organisms (related because of structures and shapes)

Systemics: organizing the diverse life forms around their evolutionary tree (thing of ‘branching or branches’)

Morpholgy: shape or form Cladistics: uses features to determine

common ancestors ( feathers – bird family)

6 Kingdom System

Archaebacteria* – prokaryotic cell Eubacteria – prokaryotic cell Protista – 1 , eukaryotic cell Fungi – 1 to many, eukaryotic cells Plantae – many eukaryotic cells Animalia – many eukaryotic cells

* You will see variety of spellings

Types of cells * see Ch. 1 notes for a detailed table

Prokaryotic Prokaryotes have prokaryotic cells which have

a cell membrane, cytoplasm with ribosomes and DNA in the form of 1 chromosome – there is NO nuclear membrane and no membrane bound organelles.

Eukaryotic Eukaryotes have eukaryotic cells which have a

cell membrane, cytoplasm full of membrane bound organelles and many chromosomes that are contained in a nucleus surrounded by a nuclear membrane.

Prokaryotic (bacteria) and eukaryotic cells (animal)

Domain

Relatively new in the classification system is the idea of domain. There are three domains Archae Prokaryae eukarya

Archaebacteria Unicellular Prokaryotes Unique DNA Ancient chemotrophic Harsh environments, often without O2

reproduce using binary fission

Eubacteria Unicellular Prokaryotes “true” Binary fission Many modes of nutrition May move with flagella or be spirochetes Unique cells walls that are either Gram

positive or Gram negative depending on ratio of starch to lipid

Protista Eukaryotic cells Single celled organisms ‘don’t fit elsewhere’ Lots of variety Algae (plant like) Zooplankton (animal like) Variety of cell walls – sometimes pellicle

and sometimes silica Various modes of reproduction

Fungi

Single celled (yeast) and multi-celled (mushrooms)

Eukaryotic cells Heterotrophic – even the green ones eat – they are not photosynthetic Absorptive nutrition- digest food

outside

Plantae Multicellular organisms eukaryotic Cell walls of cellulose Photosynthetic – have chlorophyll Cells are organized into tissues

called roots, stems and leaves with specialized functions.

Reproduce sexually and asexually

Animalia Heterotrophic ( eat ) Multicellular eukaryotic Sexual reproduction (a few have limited regeneration capabilities) Respond with movement and have muscle and nervous tissue Never have cell walls