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18.3

18.3. From 5 to 6. In recent years, as evidence about microorganisms continued to accumulate, biologists came to recognize that the Monera were composed of two distinct groups.

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18.3

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  1. 18.3

  2. From 5 to 6 • In recent years, as evidence about microorganisms continued to accumulate, biologists came to recognize that the Monera were composed of two distinct groups. • So, the Monera have been separated into two kingdoms, Eubacteria and Archaebacteria, bringing the total number of kingdoms to six.

  3. The 6 Kingdoms • The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

  4. Using a molecular clock model, scientists have grouped modern organisms according to how long they have been evolving independently. • The three domains are: • Eukarya ,which includes protists, fungi, plants, and animals • Bacteria, which includes Eubacteria; • Archaea, which includes Archaebacteria.

  5. The members of the domain Bacteria • are unicellular and prokaryotic. • Their cells have thick, rigid cell walls that surround a cell membrane. • The cell walls contain a substance known as peptidoglycan. • The domain Bacteria corresponds to the kingdom Eubacteria. • 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.

  6. Domain Archaea • Also unicellular and prokaryotic, members of the domain Archaea live in some of the most extreme environments you can imagine—volcanic hot springs, brine pools, and black organic mud totally devoid of oxygen. • many of these bacteria can survive only in the absence of oxygen. • The domain Archaea corresponds to the kingdom Archaebacteria.

  7. Domain Eukarya • The domain Eukarya consists of all organisms that have a nucleus. • It is organized into the four remaining kingdoms of the six-kingdom system: Protista, Fungi, Plantae, and Animalia! • .Organisms in these kingdoms are diverse and varied.

  8. Protista • The kingdom Protista is composed of eukaryotic organisms • Of the six kingdoms, Protista is the least satisfying classification, because its members display the greatest variety. • Most protists are unicellular organisms, but some, such as the multicellular algae, are not. • Some protists are photosynthetic, while others are heterotrophic. Some share characteristics with plants, others with fungi, and still others with animals.

  9. Kingdom Fungi • Fungi Members of the kingdom Fungi are heterotrophs. • Most feed on dead or decaying organic matter. • Unlike other heterotrophs, these fungi secrete digestive enzymes into their food source. They then absorb the smaller food molecules into their bodies. • The most recognizable fungi, including mushrooms, are multicellular. S • ome fungi, such as yeasts, are unicellular.

  10. Kingdom Plantae •  Members of the kingdom Plantae are multicellular organisms that are photosynthetic autotrophs. • Plants are nonmotile—they cannot move from place to place. • They also have cell walls that contain cellulose.

  11. Kingdom Animalia •  Members of the kingdom Animalia are multicellular and heterotrophic. • The cells of animals do not have cell walls. • Most animals can move about, at least for some part of their life cycle. • and many species of animals exist in nearly every part of the planet.

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