DOMAINS AND KINGDOMS CHAPTER 18-3

THINK ABOUT IT The process of identifying and naming all known organisms, both living and extinct, is a huge first step toward the goal of systematics. The real challenge, however, is to group everything—from bacteria to dinosaurs to blue whales—in a way that reflects their evolutionary relationships.

CHANGING IDEAS ABOUT KINGDOMS What are the six kingdoms of life as they are now identified? The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia.

CHANGING IDEAS ABOUT KINGDOMS During Linnaeus’s time, living things were classified as either animals or as plants. As biologists learned more about the natural world, they realized that Linnaeus’s two kingdoms—Animalia and Plantae—did not reflect the full diversity of life.

CHANGING IDEAS ABOUT KINGDOMS Classification systems have changed dramatically since Linnaeus’s time, and hypotheses about relationships among organisms are still changing today as new data are gathered.

CHANGING IDEAS ABOUT KINGDOMS Classification systems have changed since Linnaeus’s time, and hypotheses about relationships among organisms are changing today as new data is gathered. This diagram shows some of the changes in kingdoms since the 1700s.

THREE DOMAINS

THE TREE OF ALL LIFE What does the tree of life show? The tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of life.

THE TREE OF ALL LIFE Modern evolutionary classification is a rapidly changing science with the difficult goal of presenting all life on a single evolutionary tree. The tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains.

THE TREE OF ALL LIFE

3 DOMAINS; 6 KINGDOMS

PROKARYOTES Prokaryotes (cells without a nucleus) comprise the first two domains.

ARCHAEA

DOMAIN ARCHAEA Unicellular, Prokaryotic, Ancient Cell walls lack Peptidoglycan Unusual lipids in cell membrane Examples: Extremophiles Halophiles Thermophiles Absence of oxygen

DOMAIN BACTERIA These bacteria are ecologically diverse, ranging from free-living soil organisms to deadly parasites. Some photosynthesize, while others do not. Some need oxygen to survive, while others are killed by oxygen.

DOMAIN BACTERIA KINGDOM: EUBACTERIA Unicellular, Prokaryote Cell walls thick, rigid WITH Peptidoglycan Ex: blue-green algae, e.coli

DOMAIN EUKARYA The domain Eukarya consists of all organisms that have a nucleus. It comprises the four remaining kingdoms of the six-kingdom system: “Protista,” Fungi, Plantae, and Animalia. Kingdoms in this domain have different ways of obtaining energy.

 AUTOTROPHS CAPTURE THE LIGHT ENERGY FROM SUNLIGHT AND CONVERT IT TO CHEMICAL ENERGY THEY USE FOR FOOD.  Heterotrophs must get energy by eating autotrophs or other heterotrophs.  Decomposers, aka saprobes, are heterotrophs that recycle dead organisms by breaking them down.

PROTISTA Unicellular or Multicellular Eukaryotic (has a nucleus in cells) Very Simple cell structure “Catchall” for anything that doesn’t fit

THE “PROTISTS”: UNICELLULAR EUKARYOTES The kingdom Protista has long been viewed by biologists as a “catchall” group of eukaryotes that could not be classified as fungi, plants, or animals. Recent molecular studies and cladistics analyses have shown that “the eukaryotes formerly known as “Protista” do not form a single clade.

THE “PROTISTS”: UNICELLULAR EUKARYOTES Most “protists” are unicellular, but one group, the brown algae, is multicellular. Some “protists” are photosynthetic, while others are heterotrophic. Some display characters that resemble those of fungi, plants, or animals.

PLANTAE Multicellular Eukaryotic HAS a cell wall with cellulose Autotrophic Nonmotile (sessile)

FUNGI Multicellular or Unicellular Eukaryotic Cell wall WITH chitin Heterotrophic

FUNGI Most feed on dead or decaying organic matter. Secrete digestive enzymes into their food source, which break the food down into smaller molecules. The fungi then absorb these smaller molecules into their bodies.

ANIMALIA Multicellular Eukaryotic NO cell wall Heterotrophic

ANIMALIA Antarctica Hydrothermal Vents: A "lost world" of life Most animals can move about, at least for some part of their life cycle. There is incredible diversity within the animal kingdom, and many species of animals exist in nearly every part of the planet