(Mader, Chapter 29, Ed. 8, Introduction to Invertebrates)
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Students are required to read the textbook for the instructor to be able to teach the concepts the course encompasses. (From FOUNDATION SKILLS in the Biology Department Master Syllabus.)Students, do not just read these notes, to succeed in this class -- at least if you wish to have a high grade, you MUST use your textbook as a LEARNING TOOL!
MAIN TOPICS OUTLINE
23.1 General Characteristics
23.2 Movement to Land
23.3 Animal Structures
23.4 Classification
LECTURE OBJECTIVES
1. Discuss the characteristics of the kingdom Animalia, and some criteria used in classifying animals.
2. List the major phyla of the invertebrate animalia, and give some examples of each.
3. List the major classes of the Cnidaria, Mollusca, and Arthropoda, and give some examples of each.
4. List the way animalia differ from bacteria, protistans, fungi, and plantae.
5. Define selected key terms.
Key Terms:def. Acoelomate: Animals without a body cavity.
def. Asymmetry: Body plan having no particular symmetry.
def. Bilateral symmetry:
def. Blastopore: Embryonic opening to the primitive gut (archenteron) in an embryo in a gastrula stage.
def. Coelomate: Animals with a body cavity lying between the digestive tract and body wall that is completely lined with mesoderm (True body cavity).
def. Cnidocytes: Stinging cells in cnidarians.
def. Colony: Loose association of cells that remain independent for most functions.
def. Deuterostomes: Group of coelomate animals in which the blastopore is associated with the anus, a second opening is associated with the mouth.
def. Diploblastic: Organism with two germ layers.
def. Ectoderm: In animal embryos, the outermost primary tissue layer that gives rise to the nervous system and the outer layer of the integument.
def. Endoderm: In animal embryos, the innermost primary tissue layer that gives rise to the linings of the digestive tract and associated structures.
def. Endoskeleton: Protective internal skeleton, as in the vertebrates.
def. Exoskeleton: Protective external skeleton, as in the arthropods.
def. Germ layer: Primary tissue layer of animal embryos.
def. Mesoderm: In animal embryos, the middle primary tissue layer that gives rise to muscles, connective tissue layers (e.g., lining the body cavity), and several internal organs.
def. Parasites: Ecological relationship between two organisms where only one organism benefits, by deriving nourishment from the other, without killing it (at least not immediately) but usually doing harm to it.
def. Proterostomes: Group of coelomate animals in which the blastopore is associated with the mouth.
def. Pseudocoelomate: Animals with a body cavity lying between the digestive tract and body wall that is incompletely lined with mesoderm (False body cavity).
def. Radial symmetry: Body plan in which similar parts are arranged around a central axis, like spokes of a wheel.
def. Segmentation: Repetition of body units as is seen in the earthworms.
def. Tissue: Group of similar cells combined to perform a common function.
def. Triploblastic organism: Organism with three germ layers.
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23.1 General Characteristics
1. multicellular
2. eukaryotic
-- have a nucleus
-- DNA (in the form of chromosomes) inside the nucleus
3. have no cell wall (= protein structural molecule rather than cellulose)
4. aerobic (= must have oxygen)
5. heterotrophic (= ingest food)
6. large (compared to bacteria)
All animals are multicellular heterotrophs, and most INVERTEBRATES VERTEBRATES HUMAN EVOLUTION 23.2 Movement to land
-- Animals invaded land about 410 mya -- insects and amphibians (after fungi and plants)
• 23.21 Early animal forms lived in the oceans
1. no problem with dehydration
2. no problem with rapid temperature changes
3. no problem with extreme temperatures (narrower temp. range in the oceans)
• 23.22 Problems which needed to be overcome - (e.g., amphibians)
1. keeping membranes moist for gas exchange - (must keep skin moist)
2. supporting locomotion without buoyancy of water - (clumsy walkers)
3. transporting water in the body - (circulatory system)
4. conserving water in the body - (live near water)
5. reproduction in a dry environment - (reproduce in water -- not internal)
6. development of the early embryo - (no amniotic sac -- as in higher vertebrates)
7. surviving rapid environmental changes - (dormant, dig down or hide)
• 23.23 Evolutionary time table
1. 600 mya --------------------------------------------------------------------------
Age of invertebrates Age of Algae
2. 500 mya --------------------------------------------------------------------------
First Fishes (jawless) First plant fossils
Age of Fishes
First Amphibians & first Insects
3. 400 mya --------------------------------------------------------------------------
Age of amphibians Age of coal forming forests
4. 300 mya --------------------------------------------------------------------------
Amphibians decline
First Reptiles
First Dinosaurs
First Mammals Age of gymnosperms
5. 200 mya --------------------------------------------------------------------------
Age of Dinosaurs
First Birds First flowering plants
First Placental Mammals
6. 100 mya --------------------------------------------------------------------------
Age of Angiosperms
7. 66 mya --------------------------------------------------------------------------
Dinosaurs become extinct
Age of Mammals (and Insects)
(All modern orders of mammals represented,
including rodent-like Primates)
8. 30 mya --------------------------------------------------------------------------
First monkey-like Primates
9. 15 mya --------------------------------------------------------------------------
First Hominoids (Apes)
10. 4 mya --------------------------------------------------------------------------
First Hominids (Chimpanzee and human evolutionary lines separate)
11. 3 mya --------------------------------------------------------------------------
Homo habilis
12. 2 mya --------------------------------------------------------------------------
Homo erectus
13. 0.2 mya --------------------------------------------------------------------------
Homo sapiens
Age of Human civilization Destruction of natural habitats (e.g., tropical rain forest)
by humans accelerates extinctions
23.3 Animal Structures
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def. Acoelomate: Animals without a body cavity.
def. Asymmetry: Body plan having no particular symmetry.
def. Bilateral symmetry:
def. Blastopore: Embryonic opening to the primitive gut (archenteron) in an embryo in a gastrula stage.
def. Coelomate: Animals with a body cavity lying between the digestive tract and body wall that is completely lined with mesoderm (True body cavity).
def. Cnidocytes: Stinging cells in cnidarians.
def. Colony: Loose association of cells that remain independent for most functions.
def. Deuterostomes: Group of coelomate animals in which the blastopore is associated with the anus, a second opening is associated with the mouth.
def. Diploblastic: Organism with two germ layers.
def. Ectoderm: In animal embryos, the outermost primary tissue layer that gives rise to the nervous system and the outer layer of the integument.
def. Endoderm: In animal embryos, the innermost primary tissue layer that gives rise to the linings of the digestive tract and associated structures.
def. Endoskeleton: Protective internal skeleton, as in the vertebrates.
def. Exoskeleton: Protective external skeleton, as in the arthropods.
def. Germ layer: Primary tissue layer of animal embryos.
def. Mesoderm: In animal embryos, the middle primary tissue layer that gives rise to muscles, connective tissue layers (e.g., lining the body cavity), and several internal organs.
def. Proterostomes: Group of coelomate animals in which the blastopore is associated with the mouth.
def. Pseudocoelomate: Animals with a body cavity lying between the digestive tract and body wall that is incompletely lined with mesoderm (False body cavity).
def. Radial symmetry: Body plan in which similar parts are arranged around a central axis, like spokes of a wheel.
def. Segmentation: Repetition of body units as is seen in the earthworms.
def. Tissue: Group of similar cells combined to perform a common function.
def. Triploblastic organism: Organism with three germ layers.
23.4 Classification
-- Zoologists divide the animal kingdom into about 35 phyla. (Below are 12.)
• 23.41 The trunk of the animal evolutionary tree
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- evolutionary step 1: Multicellular -- but no true tissue, and no symmetry
-- previous: unicellular
Phylum Porifera (Sponges)
1. Asymmetry
2. No true tissue (digestion within cells)
3. No body cavity
-- Almost all are sessile
All other animal groups have true tissue and symmetry
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- evolutionary step 2: Radial Symmetry (no head)
-- previous: asymmetry (= no symmetry)
Phylum Cnidaria
1. Radial symmetry
2. True tissue (Diploblastic)
3. No body cavity
Class Hydras (Hydrozoa), e.g. • Hydra, • Obelia
Class Jellyfish (Scyphozoa)
Class Sea Anemones & Corals (Anthozoa)
-- Have stinging cells (Cnidocytes)
-- Have two life stages (Medusa, Polyp)
Phylum Ctenophora (Comb Jellies)
1. Radial symmetry
2. True tissue (Diploblastic)
3. No body cavity
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-Evolutionary step 3: Bilateral Symmetry
(definite head)
-- previous: radial symmetry
Phylum Platyhelminthes (Flatworms -- flukes, tapeworms)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. No body cavity (Acoelomate)
-- Have an incomplete digetsive tract (no anus)
Parasites
def. Parasites: Ecological relationship between two organisms where only one organism benefits, by deriving nourishment from the other, without killing it (at least not immediately) but usually doing harm to it.
Phylum Nemertea (Ribbon worms)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. No body cavity (Acoelomate)
-- Have an complete digetsive tract (comp. w flatworms)
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- evolutionary step 4: False Body Cavity -- Pseudocoelome
-- previous: no body cavity (acoelomate -- only two germ layers)
Phylum Nematoda (Roundworms -- e.g., Ascaris, Trichinella)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. False body cavity (Pseudocoelomate)
Parasites
def. Parasites: Ecological relationship between two organisms where only one organism benefits, by deriving nourishment from the other, without killing it (at least not immediately) but usually doing harm to it.
Phylum Rotifera (Rotifers)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. False body cavity (Pseudocoelomate)
- evolutionary step 5: True Body Cavity -- Coelome
-- previous: false body cavity (pseudocoelomate)
-- All organisms below are COELOMATES
• 23.42 The “left” branch of the animal evolutionary tree
Protostomes (Blastopore develops into a mouth)
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Phylum Mollusca (Mollusks)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. True body cavity (Coelomate)
Class Gastropods (Gastropoda)
Class Pelecypods (Pelecypoda, or Bivalvia)
Class Cephalopods (Cephalopoda)
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- evolutionary step 6 - P: Segmentation
-- previous: no segmentation
Phylum Annelida (Segmented Worms -- earthworms, leeches)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. True body cavity (Coelomate)
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- evolutionary step 7 - P: Exoskeleton (-- including legs)
-- previous: no legs
Phylum Arthropoda (Arthropods, Jointed-legged animals)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. True body cavity (Coelomate)
Class Horse-shoe crabs (Merostomata)
Class Crustaceans (Crustacea) lobsters, crabs, crafish, shrimp
Class Arachnids (Arachnida) spiders, scorpions, ticks, mites
Class Insects (Insects, or Hexapoda) beetles, butterflies, bees, flies
Class Millipeds (Diplopoda)
Class Centipeds (Chilopoda)
• 23.43 The “right” branch of the animal evolutionary tree
Deuterostomes (Blastopore develops into an anus)
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Phylum Echinodermata (Echinoderms -- sea stars, sea urchins, sand dollars, sea cucumbers)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. True body cavity (Coelomate)
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- evolutionary step 6 - D: Endoskeleton (-- including legs or fins)
-- previous: no legs
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Phylum Chordata (Chordates -- tunicates, lancelets, vertebrates)
1. Bilateral symmetry
2. True tissue (Triploblastic)
3. True body cavity (Coelomate)
Characters in common (at least part of their life cycle -- sometimes secondarily lost):
1. gill slits
2. dorsal nerve cord
3. dorsal notochord (backbone supporting the nerve cord)
Subphylum Urochordata
-- tunicates, sea squirts
Subphylum Cephalochordata
-- lancelets
Subphylum Vertebrata
-- vertebrates
Class Jawless fishes (Agnatha) lamprey, hagfish
Class Cartilaginous fishes (Chondrichthyes) sharks, rays
Class Bony fishes (Osteichthyes) all fishes with bony skeleton
Class Amphibians (Amphibia) frogs, toads, salamanders
Class Reptiles (Reptilia) snakes, lizards, turtles
Class Birds (Aves) all organisms with feathers
Class Mammals (Mammalia) Platypus, Marsupials, Placentals
Note: Newer research remove the hagfishes from the vertebrates but include them in a new group called "craniates". This nullifies the name Agnatha for the lampreys. The lampreys (have a cranium and vertebrae) instead become the class Cephalaspidomorphi. Hagfishes (have a cranium but no vertebrae) become class Myxini. This classification is followed in next chapter ("the vertebrates").
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The most successful group? -- Arthropoda
Animals with backbone? -- Chordata (evolved late)
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