Segmentation
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Transcript Segmentation
Chapter 18
Defining Animals
Multicellular, heterotrophic eukaryotes that obtain
nutrients by ingestion or eating food
No cell walls for structure
Joined by extracellular proteins and intercellular
junctions
Most have muscle cells for movement and nerve cells
for signal conduction
About 35 phyla in kingdom animalia; we examine 9
All but 1 are invertebrates or lack a backbone
Animal Life Cycles
Haploid gametes fuse into zygote
Mitosis forms a hollow ball of cells
= blastula
Invagination produces a gastrula
Becomes GI system lined with
endoderm
Ectoderm for outer covering,
some nervous systems
Mesoderm for muscles and
internal organs
Larva stage metamorphosis to
adult (some animals)
Constructing Phylogenetic Trees
Morphological similarities
and differences in body
plans
Symmetry
Tissue organization
Embryonic development
Body cavity is an additional
body plan feature
Kingdom Animalia
Symmetry
Radial often sedentary
Bilateral (most) often
mobile
Anterior and posterior
Ventral and dorsal
Location of brain, sense
organs, and mouth
Tissue Organization
True tissues are
specialized cells,
separated by layers
Absent in Porifera (level
of organization?)
Formed during
gastrulation
2 layers is ecto- and
endoderm
3 layers is ecto-, meso-,
and endoderm
Body Cavity
A coelom or fluid filled space
between GI tract and outer
body wall
Allows organ movement,
protection, and development
Presence or absence divides 3
tissue layer organisms
True coelom is completely
lined with mesoderm
Pseudocoelom not
completely lined
Platyhelminthes (flat worms)
lacks (acoelomate)
Embryonic Development
Based on gastrula
opening formed
Protostomes: opening
becomes mouth
E.g Arthropoda
Deuterostomes: opening
becomes anus
Mouth forms elsewhere
E.g Chordates
Phylum Porifera (Sponges)
Most are stationary (sessile), marine, and asymmetrical
Draws water in through pores and out an osculum
Suspension feeders
Choanocytes pull in food and
water
Amoebocytes provide support
Spicules is mineralized material
Spongin is flexible protein
No muscles or nerves
Toxins and antibiotics release
for protection
Phylum Cnidaria (Cnidarians)
Radial symmetry and 2
tissue layers
Jelly like substance between
Contractile and nervous
tissue (simple)
Exist as polyps or medusas
Carnivorous, use
cnidocytes
Incomplete GI tract
http://www.youtube.com/w
atch?v=fBkmzzAh8Eo&feat
ure=related
Phylum Platyhelminthes (flatworms)
3 tissue layers, acoelomate, incomplete GI tract
Class Turbellaria (free living)
Simple brain, branched GI, shared mouth/anus
http://www.youtube.com/watch?v=axBaCD4wYXE&feature=PlayList&p
=E9E1093124E2F9C9&playnext=1&index=10
Class Trematoda (flukes)
Animal parasites
Suckers to attach and interior all repro. organs
Larval intermediate stage
Class Cestoda (tapeworms)
Vertebrate GI tract parasites
Scolex, no mouth (absorption), hermaphrodite, eggs released from end
in feces
Multiple hosts
http://www.youtube.com/watch?v=GMSc2RZ19Us
Tapeworm
Phylum Mulluska (Mollusks)
Coelomates, separate sexes, larval stage (trochophore),
circulatory and advanced sensory systems
Muscular foot, visceral mass, mantle, radula (chitinous
tongue)
Class Gastropoda (snails and slugs)
Live on land and in all waters
Class Cephalopoda (squids and octopuses)
http://www.youtube.com/watch?v=9-azBDt0kik&feature=related
http://www.youtube.com/watch?v=5mBhKe4DxQ4
Mouth at end of foot, shell small or absent
Most advanced invertebrate brain and sense organs (eyes)
Class Bivalva (scallops, oysters, and clams)
2 shells hinged together
Suspension feeders, mantle has gills for food and gas exchange
Phylum Nematoda (Roundworms)
Pseudocoelomate, GI tract with 2 openings, separate
sexes, and lateral muscles
Free-living (C. elegans)
Parasitic
Dog heartworm
50 species in humans
Trichinella spiralis
Hook worms
Pinworms
Phylum Annelida (Segmented Worms)
Segmentation, longitudinal and circular muscles, closed
circulatory system
Class Polychaeta
Marine organisms, live in tubes, can be colonial
Class Oligochaeta (earthworms)
Segmented excretory, circulatory, repro, and nervous systems;
unsegmented GI tract
Hermaphroditic, thickened region gathers gametes and is left
in soil
Class Hirudinea (leeches)
Blood-sucking, releases an anesthetic and anticoagulant
Consume 10X’s weight, can go months w/o another meal
Medicinal uses
Phylum Arthropoda (Arthropods)
Most successful phylum
Exoskeleton
Protects and allows joint attachment
Protein and chitin that Is molted with growth
Segmentation
Head, thorax (fused is cephalothorax), and abdomen
Sensory, protection and walking, and swimming
respectively
Open circulatory system, blood not contained in vessels
Aquatic species with gills, terrestrial with air sacs
Subphylums
Chelicerates (arachnids)
Hollow mouth appendages
First terrestrial carnivores, deliver venom or toxins
E.g scorpions (night), spiders (day), and ticks/mites
Mandibulata
Solid mouth organs
Examples
Millipedes are herbivores with 2 leg sets per segment
Centipedes are carnivores with 1 leg set per segment
Lobsters, and insects
Classes
Crustacea (Crustaceans)
Aquatic (mostly) and have gills (rolly-polly)
Include lobsters, crayfish, shrimp, barnacles, and crabs
Insecta (Insects)
Most diverse group
Wings, advanced sensory organs, communication, and
social structure
Waterproof cuticle, short lives, complex life cycles, and
large offspring broods
Class Insecta
Life cycles
Only adults can reproduce or have functional wings
Multiple molts allow for metamorphosis, complete or
incomplete
Food sources differ so enhances adaptability
Body plan
3 parts: head, thorax, and abdomen
Embryonic segments develop independently
Connects with mutation and evolution
3 pairs of legs, not at cost to legs
Coloration
Camouflage, mimicry, and coloration from independent
development
Phylum Echinodermata
E.g sea stars, sand dollars, sea urchin and sea
cucumber
Radial symmetry internally and externally as an adult
Bilateral symmetry in larval stage
Calcium containing plates form endoskeleton
Tube feet that are extensions of a water vascular
system
For locomotion, feeding, and gas exchange
Mouth and stomach adaptations
deuterostomes
Capable of regeneration
Phylum Chordata
4 characteristics
Dorsal, hollow nerve cords
Notocord between GI tract and nerve cord
Pharyngeal slits
Post-anal tail
Tunicates (Sea squirts)
Adult has pharyngeal slits only,
larva has all four
Lancet
Suspension feeders
Mucus net to trap food
Phylogeny Review