The Classification of Plants and Other Organisms Chapter 18
LEARNING OBJECTIVE 1 Define taxonomy Explain why the assignment of a scientific name to each species is important for biologists
KEY TERMS TAXONOMY Science of describing, naming, and classifying organisms
Describing Plants
Scientific Names Biologists use scientific names to precisely identify organisms Each organism has only one scientific name Avoids confusion of many common names
LEARNING OBJECTIVE 2 Identify the biologist who originated the binomial system of nomenclature Describe the general scheme of the system
KEY TERMS BINOMIAL NOMENCLATURE System for giving each organism a two-word scientific name First used consistently by Carolus Linnaeus
Linnaeus
Binomial Nomenclature Species The basic unit of classification The scientific name of each species has two parts: generic name (genus) specific epithet
Tradescantia virginiana
Species and Subspecies
Gilia latiflora Gilia tenuiflora subsp. excellens subsp. davyi subsp. latiflora Fig. 18-4, p. 355
LEARNING OBJECTIVE 3 List and describe the hierarchical groupings of classification
Classification Hierarchical groups (most to least inclusive) domain kingdom phylum class order family genus species
Classification of Ginger
Domain Eukarya Kingdom Plantae 5 other kingdoms Phylum Anthophyta 9 other phyla Class Order Family Monocotyledones Zingiberales Zingiberaceae 1 other main class 18 other orders 4 other families (b) Each taxonomic level is more inclusive than the one below it. For example, the order Zingiberales consists of 5 families. The family Zingiberaceae contains 49 genera and a total of about 1300 species. Genus Zingiber (ginger genus) 48 other genera Fig. 18-5b, p. 356
A Dichotomous Key
Fig. 18-6a, p. 357
Fig. 18-6b, p. 357
LEARNING OBJECTIVE 4 Define systematics Describe the cladistic approach to systematics
KEY TERMS SYSTEMATICS Scientific study of the diversity of organisms and their natural (evolutionary) relationships A systematist seeks to reconstruct phylogeny
PHYLOGENY KEY TERMS Evolutionary history of a species or other taxonomic group MONOPHYLETIC Said of a group consisting of organisms that evolved from a common ancestor
KEY TERMS CLADISTICS Classification of organisms based on recency of common ancestry rather than degree of structural similarity
Cladistics Cladists emphasize phylogeny by focusing on when evolutionary lineages (lines of descent) divide into two branches Cladists develop cladograms
KEY TERMS CLADOGRAM A diagram that illustrates evolutionary relationships based on the principles of cladistics
Building a Cladogram
Characters TAXON VASCULAR TISSUES SEEDS FLOWERS Moss A A A Fern P A A Pine P P A Daisy P P P Fig. 18-7 (1), p. 358
Moss Fern Pine Daisy Node 1 Common ancestor with vascular tissues Common plant ancestor (a) All of the plant groups shown here except mosses have vascular Fig. 18-7a, p. 358
Moss Fern Pine Daisy Node 2 Node 1 Common ancestor with vascular tissues Common plant ancestor (b) Seeds are a shared character for all plant groups shown here except mosses and ferns. Fig. 18-7b, p. 358
Moss Fern Pine Daisy Node 3 Node 2 Common seedproducing ancestor Node 1 Common ancestor with vascular tissues Common plant ancestor (c) Of the plant groups shown here, only the daisy produces flowers. Fig. 18-7c, p. 358
LEARNING OBJECTIVE 5 List and briefly describe the three domains and six kingdoms recognized by many biologists
KEY TERMS DOMAIN BACTERIA Domain of metabolically diverse, unicellular, prokaryotic organisms
KEY TERMS DOMAIN ARCHAEA Domain of unicellular, prokaryotic organisms adapted to extreme conditions (such as very hot or very salty environments)
KEY TERMS DOMAIN EUKARYA Includes all eukaryotic organisms (protists, plants, fungi, and animals)
The Three Domains
Domain Bacteria Domain Archaea Domain Eukarya Common ancestor of all living organisms Fig. 18-9, p. 360
Six-Kingdom Classification Kingdom Bacteria (domain Bacteria) Kingdom Archaea (domain Archaea) Kingdom Protista (domain Eukarya) Kingdom Fungi (domain Eukarya) Kingdom Plantae (domain Eukarya) Kingdom Animalia (domain Eukarya)
The Six Kingdoms
Bacteria Archaea Protista Plantae Protista Animalia Fungi Common ancestor of all eukaryotes Common ancestor of all living organisms Fig. 18-8, p. 360
LEARNING OBJECTIVE 6 Summarize the scientific limitations of the kingdom Protista
KEY TERMS PARAPHYLETIC Said of a group consisting of a common ancestor and some, but not all, of its descendants
Kingdom Protista Ideally, all members of a kingdom should have a common ancestor Members of kingdom Protista are paraphyletic Some biologists think protists should not be grouped in a single kingdom
Animation: Constructing a Cladogram