Download What is an animal?

ANIMALS (INVERTEBRATES)
Characteristics of Animals
What is an animal?
 Multicellular
 Heterotrophs
 Lack cell walls
Symmetry
 Asymmetry
 Lack of symmetry
 E.g. sponges
Symmetry
 Radial symmetry
 Symmetrical in
multiple planes
 E.g. jellies
(cnidaria)
Symmetry
 Bilateral symmetry
 Symmetrical in one
plane
 E.g. platyhelminthes,
nemotoda, arthropoda,
etc.
Early Embryonic Development
Fertilization
Zygote
Cleavage
Blastula
Gastrulation
Gastrula
Early
Embryonic
Development
Frog Gastrulation
Early
Embryonic
Development
Early
Embryonic
Development
COPY
OUTLINE
Germ Layers
 Endoderm – gives rise to digestive tube
 Mesoderm - gives rise to musculature and
organ systems
 Ectoderm – gives rise to outer layer and
nervous systems
 COPY PICTURE
Cephalization
 Development of a head which
includes central nervous system and
sensory organs
 Occurs in bilaterally symmetrical
animals
Body Cavities
 Coelom
 Fluid-filled body cavity between the
digestive tract and the outer body
wall
Body Cavities
 Coelomate
 “true coelom”
 Coelom is surrounded by
mesoderm
 e.g. annelids
 COPY PICTURE
Body Cavities
 Pseudocoelomate
 Coelom is derived from blastocoel
 Coelom bordered by both endoderm and
mesoderm
 E.g. nematode
 COPY PICTURE
Body Cavities
 Acoelomate – animals without a coelom
 Gas exchange and nitrogenous wastes occur
across body surface
 E.g. platyhelminthes (flatworms)
 COPY PICTURE
Body Segmentation
 Repetition of identical body units
 Originated in the Ediacaran fauna (before Cambrian explosion).
 Cause?
Regulated by HOX genes
Body Segmentation
 Advantage?
New segments
can specialize
 What is this similar to? Gene duplication
Invertebrates
 Animals without a backbone
 Includes about 95% of species
 FILL IN THE PROVIDED TABLE USING
INFORMATION FROM THE FOLLOWING
SLIDES
Porifera
 Asymmetrical
 Lack true tissues
Cnidaria
 2 Germ Layers
 Radially symmetrical
 Not cephalized. Nerve net. No brain (CNS).
Cnidaria
Cnidaria
Cnidocytes harpoonlike
structure to
catch prey
Platyhelminthes
 Triploblastic
 Bilateral symmetry
 Cephalized
 Acoelomate
Platyhelminthes
Mollusca






Cephalized (usually)
Bilateral symmetry (usually)
3 germ layers
Coelomate
Protostomes
Have shells (usually)
Mollusca
 Include




chitons
snails and slugs
clams, mussels, oysters
squid, octopus, nautilus
Polyplacophora
Gastropoda
Conus geographus ("geography cone") gets its name from
map-like markings on its shell. It is one of the few snails
that can kill a human.
Bivalvia
Cephalopoda!
https://youtu.be/YcpzubpIhtI
Annelida




3 germ layers
Bilateral symmetry
Cephalization
Coelomate – use the coelom as a
hydrostatic skeleton for movement.
 Protostomes
 Segmented – repeated body
segments. Allows for specialization of
parts.
Annelida
 3 groups
 Earthworms
 marine worms
 leeches
Annelida
Annelida
Annelida
Nematoda








3 germ layers
Bilateral symmetry
Cephalization
Pseudocoelomate
Protostomes
Have outer cuticle
Molt (ecdysis)
Not segmented
Arthropoda (“jointed foot”)
 3 germ layers
 Bilateral symmetry
 Cephalization
 Coelomate
 Protostome
 Segmented
 Exoskeleton (of chitin) –grow via molting
(ecdysis)
Arthropoda (“jointed foot”)
 4 groups
 Cheliceraformes (spiders, scorpions,
horshoe crabs)
 Myriapoda (centipedes and
millipedes)
 Hexapoda (insects)
 Crustacea
Cheliceraformes
Myriapoda
Hexapoda
Crustacea
Echinodermata
 3 germ layers
 Bilateral symmetry as larvae
 Radial symmetry as adults
 No Cephalization
 Coelomate
 Deuterostome
 Water vascular system used for locomotion,
feeding, and gas exchange
Echinodermata
https://youtu.be/2DFXGafpGkQ
Echinodermata
Invertebrate Chordates
Chordates









3 germ layers
Bilateral symmetry
Cephalized
Coelom
Deuterostome
Not segmented
Dorsal hollow nerve cord (spinal cord)
Notochord (flexible rod in back)
Includes: Vertebrates
Invertebrate Chordates
 Lancelets
 Tunicates
Tunicate
Urochordata
<www.ucmp.berkeley.edu>
Cephalochordata
<www.ucmp.berkeley.edu>
Lancelet
Cephalochordata
Amphioxus
<www-biol.paisley.ac.uk>
END OF PART 1