ne of the first evolutionary trees of life conceived from a Darwinian (genealogical) perspective ... more ne of the first evolutionary trees of life conceived from a Darwinian (genealogical) perspective was published by Ernst Haeckel in 1866 (Figure 1.1). Haeckel's famous tree of life began a tradition of depicting phylogenetic hypotheses as branching diagrams, or trees, a tradition that has persisted since that time. We discuss various ways in which these trees are developed in Chapter 2. Since Haeckel's day, many names have been coined for the larger branches that sprout from these trees. We will not burden you with all of these names, but a few of them need to be defined here, before we launch into our study of the invertebrates. Some of these names refer to groups of organisms that are probably natural phylogenetic groups (i.e., groups that include an ancestor and all of its descendants), such as Metazoa (the animal kingdom). Other names refer to unnatural, or composite, groupings of organisms, such as "microbes" (i.e., any organism that is microscopic in size, such as bacteria, most protists, and unicellular fungi) and "protozoa" (a loose assemblage of primarily unicellular heterotrophic eukaryotes). The discovery that organisms with a cell nucleus constitute a natural group divided the living world neatly into two categories, the prokaryotes (those organisms lacking membrane-enclosed organelles and a nucleus, and without linear chromosomes), and the eukaryotes (those organisms that do possess membranebound organelles and a nucleus, and linear chromosomes). Investigations by Carl Woese and others, beginning in the 1970s, led to the discovery that the prokaryotes actually comprise two distinct groups, called Eubacteria and Archaea (= Archaebacteria), both quite distinct from eukaryotes (Box 1A). Eubacteria corre-Kingdom Archaea (Archaebacteria) Anaerobic or aerobic, largely methane-producing microorganisms. Never with membrane-enclosed organelles or nuclei, or a cytoskeleton; none use chlorophyll-based photosynthesis; without peptidoglycan in cell wall; with several RNA polymerases. THE EUKARYOTES (the "domain" Eukaryota, or Eukarya) Cells with a variety of membrane-enclosed organelles (e.g., mitochondria, lysosomes, peroxisomes) and with a membraneenclosed nucleus. Cells gain structural support from an internal network of fibrous proteins called a cytoskeleton. Kingdom Fungi The fungi. Probably a monophyletic group that includes molds, mushrooms, yeasts, and others. Saprobic, heterotrophic, multicellular organisms. The earliest fossil records of fungi are from the Middle Ordovician, about 460 mya. The 72,000 described species are thought to represent only 5-10 percent of the actual diversity.
ne of the first evolutionary trees of life conceived from a Darwinian (genealogical) perspective ... more ne of the first evolutionary trees of life conceived from a Darwinian (genealogical) perspective was published by Ernst Haeckel in 1866 (Figure 1.1). Haeckel's famous tree of life began a tradition of depicting phylogenetic hypotheses as branching diagrams, or trees, a tradition that has persisted since that time. We discuss various ways in which these trees are developed in Chapter 2. Since Haeckel's day, many names have been coined for the larger branches that sprout from these trees. We will not burden you with all of these names, but a few of them need to be defined here, before we launch into our study of the invertebrates. Some of these names refer to groups of organisms that are probably natural phylogenetic groups (i.e., groups that include an ancestor and all of its descendants), such as Metazoa (the animal kingdom). Other names refer to unnatural, or composite, groupings of organisms, such as "microbes" (i.e., any organism that is microscopic in size, such as bacteria, most protists, and unicellular fungi) and "protozoa" (a loose assemblage of primarily unicellular heterotrophic eukaryotes). The discovery that organisms with a cell nucleus constitute a natural group divided the living world neatly into two categories, the prokaryotes (those organisms lacking membrane-enclosed organelles and a nucleus, and without linear chromosomes), and the eukaryotes (those organisms that do possess membranebound organelles and a nucleus, and linear chromosomes). Investigations by Carl Woese and others, beginning in the 1970s, led to the discovery that the prokaryotes actually comprise two distinct groups, called Eubacteria and Archaea (= Archaebacteria), both quite distinct from eukaryotes (Box 1A). Eubacteria corre-Kingdom Archaea (Archaebacteria) Anaerobic or aerobic, largely methane-producing microorganisms. Never with membrane-enclosed organelles or nuclei, or a cytoskeleton; none use chlorophyll-based photosynthesis; without peptidoglycan in cell wall; with several RNA polymerases. THE EUKARYOTES (the "domain" Eukaryota, or Eukarya) Cells with a variety of membrane-enclosed organelles (e.g., mitochondria, lysosomes, peroxisomes) and with a membraneenclosed nucleus. Cells gain structural support from an internal network of fibrous proteins called a cytoskeleton. Kingdom Fungi The fungi. Probably a monophyletic group that includes molds, mushrooms, yeasts, and others. Saprobic, heterotrophic, multicellular organisms. The earliest fossil records of fungi are from the Middle Ordovician, about 460 mya. The 72,000 described species are thought to represent only 5-10 percent of the actual diversity.
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