Transcript Chapter 19
Chapter 19 Introduction to the Kingdoms of Life I. The Three Domains of Life • For decades, scientists recognized two basic forms of life, prokaryotes and eukaryotes that were grouped into five kingdoms • All prokaryotes were grouped into the Kingdom Monera • Comparisons of ribosomal RNA sequences showed that there was a distinction between two ‘types’ of prokaryotes • There is now a classification system that divides all organisms into three superkingdoms, or domains A. Bacteria • The domain thought to be the oldest • First prokaryotic domain • Composed of organisms in the kingdom Eubacteria B. Archaea • Second prokaryotic domain • Composed of organisms in the kingdom Archaebacteria C. Eukarya • Consists of four eukaryotic kingdoms 1. Animalia 2. Fungi 3. Plantae 4. Protista II. The Six Kingdoms of Life A. Cell Type • Prokaryotes or Eukaryotes B. Cell Walls C. Body Type • Unicellular or multicellular D. Nutrition 1. Autotrophs make nutrients from inorganic materials 2. Heterotrophs get nutrients by consuming other organisms III. The Domain Bacteria (the kingdom Eubacteria) A. Characteristics of Bacteria 1. Cell Wall Strong exterior cell walls made of peptidoglycan 2. Gene Structure • Bacteria genes have no introns • The entire gene is transcribed 3. Gene Translation Apparatus • Evolutionary relationships between organisms are based on their amino acid sequences • Amino acid sequences of bacteria’s ribosome proteins and RNA polymerases differ from sequences found in archaea and eukaryotes B. Kinds of Bacteria • Most abundant organisms on Earth • Used for: 1. processing food (turns milk into yogurt) 2. controlling agricultural pests 3. producing various chemicals 4. performing genetic engineering • Source of energy 1. from inorganic compounds i.e. ammonia and methane (autotrophic) 2. photosynthesis (autotrophic) - found in ocean and freshwater ecosystems 3. heterotrophic a. capable of living in the absence of oxygen (anaerobic) b. must have oxygen to live (aerobic) IV. The Domain Archaea (The Kingdom Archaebacteria) A. Characteristics of Archaebacteria 1. Cell wall and membrane • Archaebacteria cell walls do not contain peptidoglycan • Instead contain lipids very different from those of bacteria or eukaryotes 2. Gene Structure and Translation • Genes are interrupted by introns B. Kinds of Archaebacteria 1. Methanogens • Obtain energy by combining hydrogen gas, H2 and carbon dioxide, CO2, to form methane gas, CH4 (autotrophic) • Live deep in the mud of swamps • Poisoned by oxygen (anaerobic) 2. Extremophiles a. thermophiles – live in very hot places b. halophiles – inhabit very salty lakes that can be three times as salty as seawater c. other live in very acidic places d. others live under enormous pressure 3. Nonextreme Archaebacteria • Grow in all the same environments that bacteria do • Some are heterotrophic V. The Domain Eukarya • Made up of the kingdoms Protista, Fungi, Plantae, and Animalia A. Characteristics of Eukarya 1. Highly organized cell interior • Cells have a nucleus and other internal compartments - allows specialization of functions 2. Multicellularity • Occurs only in eukaryotes • Cells are in contact with one another • Activities of individuals are coordinated 3. Sexual Reproduction • Meiotic cell division forms haploid (n) gametes, and two gametes unite to form a diploid (2n) cell in fertilization B. Kinds of Eukaryotes 1. Protista 2. Fungi 3. Plantae 4. Animals Sponges Arthropods Mollusks Worms Echinoderm Vertebrates VI. Forms of Multicellularity A. Colonies • Occasionally, the cell walls of unicellular bacteria adhere to one another permanently • Few cell activities are coordinated; there is a lack of communication B. Aggregations • An aggregation is a temporary collection of cells that come together for a period of time and then separate C. True Multicellularity • A multicellular organism is an organism composed of many cells that are permanently associated with one another • Occurs only in eukaryotes • Cells are in contact with each other and their activities are coordinated • Enables cells to specialize in different functions • Cell specialization begins as a new organism develops, or undergoes differentiation D. Complex Multicellularity • Specialized cells of most plants and animals are organized into structures called tissues and organs • Various organs that carry out a major body function make up an organ system VII. Kingdom Protista • Most diverse kingdom • Defined as eukaryotes that are not fungi, plants, or animals • Some are multicellular but others are unicellular • All protists have a cell membrane - some also have strong cell walls i.e. algae and slime molds - others also produce shells of glassy silica i.e. diatoms • Some are autotrophs while others are heterotrophs • Most move around using flagella, cilia, or pseudopods • Normally reproduce asexually by mitotic cell division • Some are photosynthetic - algae is distinguished by the kinds of chlorophyll they contain • Some are fungus like • Some are spore-forming i.e. sporozoans VIII. Kingdom Fungi • Most are multicellular, yeasts are unicellular • Cell walls contain chitin • The bodies of fungi consist of hyphae, long strands of cells that are connected end to end and that share cytoplasm • Reproduce asexually or sexually • Lack the green pigment chlorophyll and do not conduct photosynthesis • All are heterotrophic A. Kinds of Fungi 1. Zygomycetes i.e. bread mold • Form structures called zygosporangia for sexual reproduction 2. Basidiomycetes • Form mushroom structures for sexual reproduction 3. Ascomycetes • Form sexual pores in special saclike structures called asci IX. Kingdom Plantae • Complex multicellular organisms with specialized cells and tissues ex. Vascular tissue is made up of specialized cells that play a role in transporting water and dissolved nutrients • Cell walls composed of cellulose • Portable reproductive structures, such as spores and seed, enable the dispersal of plants • Autotrophs, primary producers - provide nutritional foundations for most terrestrial ecosystems A. Kinds of Plants 1. Nonvascular Plants i.e. mosses • Lack the tissue to transport water and nutrients 2. Seedless Vascular Plants i.e. ferns • Reproduce with spores that are resistant to drying 3. Nonflowering Seed Plants i.e. Pine trees • Called gymnosperms • Produce seeds in cones 4. Flowering Seed Plants i.e. Bluebonnets, grasses, oaks • Called angiosperms • Produce seeds in fruits X. Kingdom Animalia • Multicellular; cells are mostly diploid (2n), lack a cell wall, and are organized as tissues • Most reproduce sexually - gametes fuse with one another to form a zygote that then gradually develops into an adult through several developmental stages • 99% are invertebrates; that is, they lack a backbone • The rest are vertebrates that have a backbone A. Kinds of Animals 1. Sponges and Cnidarians • Sponges are the only animals that do not have tissues - they do however, have specialized cells • Cnidarians include jellyfish, sea anemones, and corals 2. Mollusks • Have a saclike tissue called a coelom that encloses internal organs • Include snails, oysters, clams, octopuses, and squids 3. Worms • Includes worms with a specialized internal sac for organs and segmented worms 4. Arthropods • Most diverse of all animals • Have external skeletons • Jointed appendages i.e. antennae and jaws 5. Echinoderms • Include sea stars, sea urchins, and sand dollars • Many are able to regenerate a lost limb 6. Vertebrates • Include mammals, fish, birds, reptiles, and amphibians • Have an internal skeleton made of bone • A vertebral column that surrounds the spinal cord • Have a head with a brain contained in a bony skull