H OLT B IOLOGY
U NIT 5-E XPLORING D IVERSITY
C HAPTER 19
I NTRODUCTION T O T HE K INGDOMS O F L IFE
I.
Introduction to Kingdoms and Domains
Objectives:
•
Identify the characteristics used to classify kingdoms.
•
Differentiate bacteria from archaebacteria.
A.
The Six Kingdoms of Life
1.
Living organisms are divided into six kingdoms and are grouped according to their cell type, complexity, and method for obtaining nutrition. a.
Organisms are either prokaryotes, which have prokaryotic cells, or eukaryotes, which have eukaryotic cells. b.
The cells of the organisms in four kingdoms have a cell wall, which may be composed of different materials. c.
The cells of the organisms in one kingdom do not have a cell wall.
2.
Organisms are either unicellular or multicellular.
3.
Many organisms are autotrophs. a.
Autotrophs make nutrients from inorganic materials.
4.
Many other organisms are heterotrophs. a.
Heterotrophs get nutrients by consuming other organisms.
B.
The Three Domains of Life
1.
Biologists have adopted a classification system that divides all organisms into three superkingdoms, or domains. a.
The domain thought to be the oldest is Bacteria, which is composed of the organisms in the kingdom Eubacteria. b.
Archaea is the second prokaryotic domain and is also composed of a single kingdom,
Archaebacteria. c.
A third domain, Eukarya, contains all four of the eukaryotic kingdoms: i.
Animalia (animals) ii.
Fungi (fungi) iii.
Plantae (plants) iv.
Protista (protists).
C.
The Domain Bacteria
1.
Characteristics of Bacteria a.
Bacteria have strong exterior cell walls made of peptidoglycan, a weblike molecule complex made of carbohydrate strands cross-linked by short peptide bridges. b.
Unlike the genes of eukaryotes and archaebacteria, bacterial genes have no introns. c.
The amino acid sequences of the ribosome proteins and RNA polymerases found in bacteria differ from those found in eukaryotes or in archaebacteria.
2.
Kinds of Bacteria a.
Bacteria are the most abundant organisms on Earth. b.
Some bacteria cause disease. c.
Other bacteria are used by humans to process foods. d.
Bacteria are used to control agricultural pests, to produce various chemicals, and to perform genetic engineering. e.
Some bacteria are chemoautotrophs, some are photosynthetic, and others are heterotrophic.

D.
The Domain Archaea
1.
Characteristics of Archaebacteria a.
The cell walls of archaebacteria do not contain peptidoglycan, as the cell walls of bacteria do. b.
Archaebacteria contain lipids very different from those of bacteria or eukaryotes. c.
As with the genes of eukaryotes, the genes of archaebacteria are interrupted by introns.
2.
Kinds of Archaebacteria a.
Methanogens obtain energy by combining hydrogen gas, H
2
, and carbon dioxide, CO
2
, to form methane gas, CH
4
. b.
A group of extremophiles called thermophiles lives in very hot places—up to 106ºC. c.
Halophiles inhabit very salty lakes that can be three times as salty as seawater. d.
Nonextreme archaebacteria grow in all the same environments that bacteria do.
E.
The Domain Eukarya
1.
Characteristics of Eukarya a.
All eukaryotes have cells with a nucleus and other internal compartments. b.
True multicellularity, in which the activities of individual cells are coordinated and the cells themselves are in contact, occurs only in eukaryotes. c.
Eukaryotes have a life cycle that involves sexual reproduction.
2.
Kinds of Eukarya a.
Protista contains both unicellular and multicellular organisms, many of which are aquatic. b.
Fungi are a group of heterotrophs that are mostly multicellular and are composed of cells with cell walls of chitin. c.
Almost all plants are autotrophs and have cells with cell walls composed of cellulose. d.
All animals are heterotrophs composed of cells that do not have cell walls.
II.
Advent of Multicellularity
Objectives:
•
Contrast the terms colony and aggregate.
•
List the characteristics of protists.
•
List the characteristics of fungi.
A.
The Many Forms of Multicellularity
1.
Colonies a.
Occasionally, the cell walls of bacteria adhere to one another. b.
These formations cannot be considered truly multicellular, however, because few cell activities are coordinated. c.
Such bacteria may properly be considered colonial. d.
A colonial organism is a group of cells that are permanently associated but that do not communicate with one another.
2.
Aggregations a.
An aggregation is a temporary collection of cells that come together for a period of time and then separate. b.
For example, a plasmodial slime mold is a unicellular organism that spends most of its life as single-celled amoebas. c.
When starved, however, these cells aggregate into a large group. d.
This weblike mass produces spores, which are then dispersed to distant locations where there may be more food.

3.
True Multicellularity a.
A multicellular organism is an organism composed of many cells that are permanently associated with one another. b.
Multicellularity enables cells to specialize in different functions. c.
These cells grow and undergo differentiation, the process by which cells develop a specialized form and function.
4.
Differentiation a.
The specialized cells of most plants and animals are organized into structures called tissues and organs. b.
A tissue is a distinct group of cells with similar structure and function. c.
Different tissues may be organized into an organ, which is a specialized structure with a specific function. d.
Various organs that carry out a major body function make up an organ system.
B.
Kingdom Protista
1.
Members of the kingdom Protista, protists, are defined on the basis of a single characteristic: they are eukaryotes that are not fungi, plants, or animals. a.
Many are unicellular; in fact, all single-celled eukaryotes (except yeasts) are protists. b.
Protists normally reproduce asexually by means of mitotic cell division.
2.
Kinds of Protists a.
Amoebas are protists that have flexible surfaces with no cell walls or flagella; they move by using extensions of cytoplasm called pseudopodia. b.
Many protists, including autotrophs and heterotrophs, move by using flagella. c.
Diatoms are photosynthetic protists with unique double shells made of silica, like boxes with lids. d.
Algae are photosynthetic protists and are distinguished by the kinds of chlorophyll they contain. e.
Slime molds and water molds are often confused with fungi because they aggregate in times of stress to form spore-producing bodies. f.
Sporozoans are nonmotile unicellular parasites that form spores.
C.
Kingdom Fungi
1.
The bodies of fungi consist of long strands of cells that are connected end to end and that share cytoplasm. a.
The slender strands of fungi are called hyphae. b.
Like plants, fungi do not move from place to place. c.
Like animals, fungi are heterotrophs.
2.
Kinds of Fungi a.
Zygomycetes form structures for sexual reproduction called zygosporangia. b.
Basidiomycetes include fungi that make mushrooms. c.
Ascomycetes form sexual spores in special saclike structures called asci.
III.
Complex Multicellularity
Objectives:
•
Summarize the characteristics of organic compounds.
•
Compare the structures and function of different types of biomolecules.
•
Describe the components of DNA and RNA.
•
State the main role of ATP in cells.
A.
Kingdom Plantae
1.
Plants are complex multicellular autotrophs; they have specialized cells and tissues. a.
Most plants have vascular tissue, which is made up of specialized cells that play a role in transporting water and dissolved nutrients. b.
Plants are sources of food for humans and other animals.

2.
Kinds of Plants a.
Plants without a well-developed system of vascular tissues are called nonvascular plants. b.
Mosses are the most familiar example of nonvascular plants. c.
Plants with a well-developed system of vascular tissues are called vascular plants. d.
Their larger, more-complex bodies are organized into roots, stems, and leaves. e.
Most plants are vascular plants. f.
Ferns are the most common and familiar seedless vascular plants and reproduce with spores that are resistant to drying. g.
Gymnosperms are vascular plants that reproduce using seeds but do not produce flowers. h.
The largest group of plants, called angiosperms, produce their seeds in flowers.
B.
Kingdom Animalia
1.
Animals are complex multicellular heterotrophs. a.
Almost all animals (99 percent) are invertebrates; that is, they lack a backbone. b.
Of the more than 1 million living species, only about 42,500 have a backbone; they are referred to as vertebrates.
2.
Kinds of Animals a.
Animals can range in size from 0.5 mm (0.02 in.) microscopic mites that live on your skin to enormous whales, which are vertebrates, and giant squids, which are invertebrates.
3.
The many kinds of animals can be roughly grouped into seven categories. a.
Sponges are the only animals that do not have tissues, but they do have specialized cells. b.
Cnidarians are mostly marine animals; they include jellyfish, sea anemones, and corals. c.
Mollusks have a saclike tissue called a coelom that encloses internal organs, and includes snails, oysters, clams, octopuses, and squids. d.
Worms include a variety of animals with cylinder-shaped bodies and that live in both aquatic and terrestrial habitats. e.
Arthropods have an external skeleton, jointed appendages, such as antennae and jaws and make up two-thirds of all named species of animals, most of them insects. f.
Echinoderms, a group of invertebrates includes sea stars, sea urchins, and sand dollars. g.
Vertebrates have an internal skeleton made of bone, a vertebral column (backbone) that surrounds and protects the spinal cord, and a head with a brain contained in a bony skull and includes mammals, fish, birds, reptiles, and amphibians.