Major Sections of Chapter
[Return to Syllabus]
Invertebrates and the origin of
Animal Diversity
[Sections]
Topics
Reminders
1. Introduction (fig. 29.2)
2. Defining "Animals"
3. General comments
4. Animal Phylogeny
5. Determination of Major Branches of the Animal
Kingdom
6. Major Branches of Animal Kingdom
[Return to Syllabus]
Reminders
- Brown chp 29, pp 598-631
- Emphasis: class outline
- Study Outline: pp 632-633
- Self Quiz: 633-634
[Topics]
1. Introduction (fig. 29.2)
[Topics]
2. Defining "Animals"
- multicellular
- carbohydrate reserve as glycogen
- lack cell wall, no cellulose
- specialized tissues, nervous and muscle
- sexual reproduction
- diploid stage dominate
- sperm and egg
- life cycle or development to a mature form
- zygote
- cleavage
- gastrula
- larva
- metamorphosis
- adult
[Topics]
3. General comments
- 35 phyla
- over 1,000,000 extant species
- Phylum Chordata is best known (5%)
- over 95% of described species are invertebrates
[Topics]
4. Animal Phylogeny
- origin of most phyla occurred in Precambrian and Cambrian, over 500,000
years ago
- most ideas and theory on animal evolution are based on:
- fragmentary fossil record
- comparative anatomy
- comparative embryology
- comparative biochemistry
[Topics]
5. Determination of Major Branches of the
Animal Kingdom
- (fig. 29.2)
- evolved from flagellated protozoa
- Branches based on the following
- tissue level
- symmetry
- development
- body cavity
- coelom formation
[Topics]
6. Major Branches of Animal Kingdom
- Parazoa
- Eumetazoa
- Radiata
- Bilateria
- Acoelomates
- Pseudocoelomates
- Protostomes
- Deuterostomes
- Parazoa
- No true tissue or loose tissue organization
- porifera -
- Eumetazoa
- true tissue
- diploblastic - two layers
- triploblastic - three layers
- Diploblastic Animals
- two true tissue (germ) layers
- ectoderm
- endoderm
- "mesoglea"
- radial symmetry
- representatives
- Triploblastic Animals
- three true tissue (germ) layers
- ectoderm
- mesoderm
- endoderm
- bilateral symmetry
- Triploblastic animals with no body cavity
- acoelomates -
- flatworms,
- planarians,
- tapeworms
- Triploblastic animals with body cavities
- advantages
- pseudocoelomates -
- rotifers,
nematodes,
ribbon worms
- coelomates - true body cavity
- Coelomates
- body cavity is a true coelom
- fate of blastopore, cleavage, and coelom formation
- blastopore forms mouth region, spiral cleavage, and schizocoelous
- protostome -
- annelids
- mollusks
- arthropods
- blastopore form anal region, radial cleavage, and enterocoelous
- deuterostomes -
- bryozoans
- brachiopoda
- echinoderms
- chordata - tunicates, vertebrates
[Topics] [Sections]
Parazoa to Acoelomates
[Sections]
Topics
I. Parazoa
II. Eumetazoa - Radiata
III. Eumetazoa - Bilateria - Acoelomates
[Return to Syllabus]
I. Parazoa
- Phylum Porifera
- General
- sponges
- sessile
- radial symmetry?
- "plant-like"
- 9000 species - mostly marine
- filter feeder
- Anatomy (fig. 29.8)
- two layers and a gelatinous layer
- No true tissue or loose tissue organization
- spicules
- pores
- spongocoel
- choanocytes
- amoebocytes
- Physiology and Reproduction
- hermaphroditic - monoecious
- regeneration
[Topics]
II. Eumetazoa - Radiata
Phylum Cnidaria
- General
- Three classes
- Hydrozoa - hydra,
- Scyphozoa - jellyfishes
- Anthozoa - corals
- least specialized eumetazoans
- diploblastic - two layers
- gastrodermis - derived from endoderm
- epidermis - derived from ectoderm
- "mesoglea" - no mesoderm
- radial symmetry
- 10,000 species - mostly marine
- hydra freshwater species - 16 species
- carnivores
- Anatomy and characteristics
- planula larva
- dimorphic life cycle
- polyps
- medusa
- important in evolution of phylum
- Hydrozoa - hydra
- Scyphozoa - jellyfishes
- Anthozoa - corals, anemones
- oral and aboral
- no cephalization
- gastrovascular cavity
- mouth opening, no anus
- cnidocytes and nematocysts
- muscles and nerves
- balance organs
- corals, calcium skeleton
- symbiotic with algae
Phylum Ctenophora
- General
- 100 species
- marine
- comb jellies
- 1-10 cm
- diploblastic
- "mesoglea"
- Anatomy and characteristics
- eight rows of fused cilia
- balance sensory organ
- two tendacles
- bioluminescence
[Topics]
III. Eumetazoa - Bilateria - Acoelomates
Phylum Platyhelminthes
- General
- flatworms
- bilateral symmetry
- acoelomates
- triploblastic - endoderm, mesoderm, ectoderm
- 20,000 species
- freshwater and marine
- Anatomy and characteristics
- cephalization
- larval stages
- no respiratory or circulatory system
- incomplete digestive system - no anus
- three taxonomic classes
- Turbellaria - free living flat worms, planarians
- Trematoda - parasitic flukes
- Cestoda - parasitic tapeworms
- Class Turbellaria
- carnivores
- pharynx
- locomotion - undulation and cilia
- tremendous powers of regeneration
- Class Trematoda
- parasitic flukes
- suckers for attachment
- thick cuticle
- complex reproductive system
- complex life cycle
- immune system resistance
- Schistosoma 200,000,000 people infected with blood flukes-body pains,
anemia, and dysentery
- swimmers itch
- Class Cestoda
- parasitic tapeworms
- no digestive system
- complex life cycle
- uncooked meat contains encysted larvae
- mature worms may be 20 meters
- proglottids loaded with eggs
- scolex
[Topics] [Sections]
Pseudocoelomates
[Sections]
Topics
Characteristics of Pseudocoelomates
A. Phylum Rotifera
B. Phylum Nematoda
C. Phylum Nemertea
[Return to Syllabus]
Characteristics of Pseudocoelomates
- eumetaoa
- bilateral symmetry
- body cavity other than digestive cavity
- advantage of a cavity (pseudocoele)
[Topics]
A. Phylum Rotifera
- general
- wheel bearers animals
- 1800 species
- microscopic - 0.05-2.0 mm
- freshwater, usually high quality water
- characteristics
- complete digestive tract
- pseudocoele
- hydrostatic skeleton
- organs located in pseudocoele
- parthenogenesis
- crown of cilia
[Topics]
B. Phylum Nematoda
- general
- 80,000 species
- 1 mm - 1 meter in length
- freshwater, marine, terrestrial, and parasitic
- characteristics and anatomy
- complete digestive tract
- tough cuticle
- only longitudinal muscles
- pseudocoele
- hydrostatic skeleton
- important in decomposition and recycling
- agriculture pest
- parasitic
- hookworms
- pinworms
- trichinosis
- plant parasites
[Topics]
C. Phylum Nemertea
- general
- classification is questionable
- no pseudocoele
- body is acoelomate
- has coelom-like structure for storing probosis
- resembles protostomes
- probably evolved from flat worms
- characteristics and anatomy of Nemertea
- freeliving
- few cm to meter in length
- freshwater and marine
- complete digestive tract
- circulatory system - hemoglobin
[Topics] [Sections]
Eucoelomates-Protostome
[Sections]
Topics
Characteristics of Protostomes
A. Phylum Molluska
B. Phylum Annelida
C. Phylum Arthropoda
[Return to Syllabus]
Characteristics of Protostomes
- eumetazoa
- triploblastic
- bilateral symmetry
- cephalization
- blastopore becomes mouth
- eucoelomates
- schizocoelous (fig. 29.6)
- spiral cleavage
- determinate cleavage
- Three phyla - Molluska, Annelida, and Arthropoda
[Topics]
A. Phylum Molluska
- General
- 50, 000 species
- marine, freshwater, and terrestrial
- chitons, snails, slugs, clams, oysters, octopuses, and squids
- Characteristics of mollusks
- most have external shells of calcium carbonate, although some have
internal shells and some have none
- three body parts - foot, visceral mass, and mantle
- mantle cavity - houses gills and other organs
- no body segmentation
- Classification of mollusks
- Class Gastropoda
- snails and slugs
- 40,000 species
- freshwater, marine and terrestrial
- tortion
- radula
- locomotion by gliding on foot
- mantle cavity houses gills or function as lungs (terrestrial)
- Class Bivalvia
- clams and oysters
- two shells
- sessile
- head reduced or absent
- filter feeder
- locomotion limited to foot
- Class Cephalopoda
- squids and octopi
- head-foot
- complex camera eye
- largest invertebrates - squid 17 meters, 2 tons
- body - mantle, tentacles, siphon,
- jet propulsion for locomotion
- well developed behavior - active predator
[Topics]
B. Phylum Annelida
- General
- 15,000 species
- freshwater, marine and terrestrial
- earthworms, polychetes, leeches
- Characteristics of annelids
- segmentation - major evolutionary step
- body segment - specialization
- coelom
- locomotion
- earthworms, polychetes, leeches
- Classification of annelids
- Class Oligocheta
- freshwater and terrestrial
- recycle soil
- Class Hirudinea
- blood sucking parasite
- scavengers
- hirudin
- freshwater and terrestrial
- anterior and posterior suckers
[Topics]
C. Phylum Arthropoda
- General
- 1-2,000,000 species
- most diversified group
- most individuals 1018
- freshwater, marine, and terrestrial
- Characteristics of arthropods
- segmentation
- hard exoskeleton
- jointed appendages
- specialized appendages
- antennae, mouthparts, legs
- moulting
- variety of gas exchange or respiratory structures
- Classification of arthropods
- Subphylum Trilobitomorpha
- extinct trilobites
- Subphylum Chelicerata
- chelicerae - mouth appendage
- sucking mouthparts
- no antennae
- cephalothorax and abdomen
- usually four pairs of legs
- horse shoe crabs, spiders, mites, scorpions
- Subphylum Uniramia
- one pair of antennae
- head, thorax, and abdomen
- insects, millipeds, centipedes
- wings in insects
- insects with three pairs of legs and two pairs of wings
- metamorphosis
- Subphylum Crustacea
- two pairs of antennae
- cephalothorax and abdomen
- usually five pair of legs
- crabs, lobsters, crayfish, shrimp, barnacles
[Topics] [Sections]
Eucoelomates-Deuterostome
[Sections]
Topics
Characteristics of Deuterostomes
A. Phylum Bryozoa
B. Phylum Brachiopoda
C. Phylum Phoronida
D. Phylum Echinodermata
E. Phylum Chordata
[Return to Syllabus]
Characteristics of Deuterostomes
- bilateral symmetry
- some have secondary radial symmetry
- enterocoelous
- blastopore becomes anus
- radial cleavage
- indeterminate cleavage
- Classification of deuterostomes
- lophophorates - have a feeding structure from the body wall which
surrounds the mouth - no well developed head
- Phylum Bryozoa
- Phylum Brachiopoda
- Phylum Phoronida
- spiny skin or echinoderms
- chordates
[Topics]
A. Phylum Bryozoa
- General
- moss animals
- 5000 species
- freshwater and marine
- Characteristics
- exoskeleton
- sessile and colonial
- excellent ecological indicator
[Topics]
B. Phylum Brachiopoda
- General
- 330 species
- marine
- Lingula - 400,000,000 years old
- Characteristics
- resemble bivalve clams
- two shells surrounding lophophore
[Topics]
C. Phylum Phoronida
- General
- Characteristics
- tube-dwelling marine worms
[Topics]
D. Phylum Echinodermata
- General
- 7000 species
- sanddollars, sea urchins, sea stars
- spiny skin
- marine
- Characteristics
- sessile or sedentary-like
- radial symmetry as adults
- pentagonal, five sides or five arms
- endoskeleton
- water vascular system
- sea stars - regeneration
- Water Vascular System
- Classification
- starfish or sea stars
- sea urchins
- brittle stars
- sea cucumber
- sea lilies
[Topics]
E. Phylum Chordata
- General
- very diversified
- freshwater, marine, terrestrial
- Amphioxus, sea squirts, vertebrates
- Characteristics of chordates
- notochord
- dorsal hollow nerve chord
- pharynx slits
- muscular postanal tail
- Classification of Chordates
- Subphylum Cephalochordata
- Subphylum Urochordata
- Subphylum Vertebrata
- lampreys, sharks, fish, amphibians, reptiles, birds, and mammals
[Topics] [Sections]