An Introduction to Animal Diversity and Invertebrates

1
An Introduction to Animal Diversity and
Invertebrates

• By Genetically Superior

2
Common Characteristics of Animals

• 1. multicellular
• 2. no cell wall
• 3. heterotrophic eukaryotes
• 4. sexual reproduction
• 5. tissues develop from embryonic layers

3
Cambrian Explosion

• 1. Occurred in the Paleozoic Era (542-251mya)
• 2. Animal diversification accelerates
• 3. Possible causes
•             a) new predator-prey relationships
  emerge that trigger natural 
•                 selection
•                                  -forms of
  locomotive had to evolve (for predators) and
  shell defensees (for prey)
•             b) 02 in atmosphere
•             c) evolution of the Hox Gene Complex
  provided developmental 
•                 flexibility that led to
  variations
• 4. Arthropods begin to adapt to terrestrial
  habitats (example millipedes and centipedes)

4
Cambrian Explosion

•     Neoproterozoic Era (1 bya-542mya)
•             -Generally accepted fossils of
  animals are only 575 mya 
•              (known as Ediacaran fauna)
•             -Related to cnidarians and corals,
  soft- Neoprotozoic bodied 
•               molluscs
•             -Numerous tunnels and tracks indicate
  forms of worms
•        -570mya embryos discovered in China show
  basic structural 
•         organization of present-day embryos
  (scientists not certain 
•         which clade)                  

5
Embryonic Development 

• 1. most animals produce sexually
• 2. diploid stage dominates life cycle
• 3. zygote undergoes cleavage

6
Characterization of Invertebrates

• 1. grade group of animal species that share same
  level of organizational complexity
• 2. body plans a set of morphological and
  developmental traits that define a grade
•      
•         a) symmetry
•                     -radial
•                     -bilateral
•                                 
•                 
•                 
•                                    
  - cephalization bilaterally symmetrical animals
  (anthropods and mammals) 

7
Invertebrates

• Diploplasts vs. triploblasts
• diploplasts
• animals with two germ layers (endoderm and
  ectoderm)
• cnidarians
• jellies, corals
• triploblasts
• three germ layers (third one being the mesoderm)
•  bilateral symmetry animals and cephalization
•  three categories of triploblasts based off of
  coeloms
•  acoelomates
•  do not have coeloms
• coelomates
• have a true coelom
• body cavity formed from mesoderm
• HUMANS!

8
All Triploblasts
9
Some Triploblasts are Chordates...

• two ways of development of chordates (have spinal
  cord)
• protostome development
• mouth develops from blastopore (opening of
  gastrula)
• deuterstome development
• anus develops from blastopore 
•            

10
Chordates
11
Sponges (Porifera)

• -Are sessile (fixed in one place, immobile)
• Symmetry
•         -none
• Diploplast
•         -2 germ layers and no coelom
• Cephalization
•         -none
• Special adaptations
•         -unlike eumetazoans (all other animals),
  sponges lack true tissues
•         
• Examples
•         -azure vase sponge (Callyspongia
  plicifera) 

12
Cnidarians

• Symmetry
•          -radial
• Diploblast
•          -2 germ layers and no coelom
• Cephalization
•          -none 
• Special Adaptations
•          -tentacles sting, thread punctures prey
• Examples
•          -jellies, sea anemones
•     

Hydrozoa Man O' War
13
Flatworms

•     -In addition to many free living forms, some
  are also parasitic
• Symmetry
•     -bilateral
• Triploblast
•     -triploblastic development
•     -acoelomates (lack body cavity)
• Cephalization
•     -is evident (head ganglion attached to nerve
  cords)
• Special Adaptations
•     -Their flat shape/thin bodies enables gas
  exchange and elimination of nitrogen waste      
      
•       to occur through diffusion
• Examples
•     

Tapeworm
Marine flatworm
14
Annelids (segmented worms)

•     -life cycle includes the trochophore stage
  (ciliated larval stage)
•   
• Symmetry
•         -bilateral
• Triploblastic
•         -3 germ layers
•        -pseudocoelomates
• Cephalization
•         -have some (pair of cerebral ganglia at
  their anterior end)
• Special Adaptations
•         -well-developed coelom provides a
  hydrostatic skeleton 
• Examples
•         -Earthworm
•        -Bristleworm    

15
Molluscs

•       -are soft-bodied animals, some have
  protective shell
•     -four classes     
•         1. Polyplacophora (chitons)
•         2. Gastropoda (snails and slugs)
•         3. Bivalvia (clams, oysters, other
  bivalves)
•         4. Cephalopoda (squids, octopuses,
  cuttlefish, chambered nautiluses)
•  
• Symmetry
•         -depends upon the organism
• Triploblasts
•         -3 germ layers
•         -coelomates
• Cephalization
•          -is evident
• Special Adaptations
•          -share same body plans    
•         -foot (muscular, used for movement)

16
Nemotodes (round worms)

•         -most are parasitic
• Symmetry
•         -bilateral
• Triploblastic
•         -3 germ layers
•         -pseudocoelomates
• Cephalization
•         -some (only two small anterior cerebral
  ganglia from which neural chords 
•          split)
• Special Adaptations
•         -digestive system is complete (has both
  anus and mouth)
•         -can redirect some cellular functions of
  their host
• Examples
•         -Parasitic Trichinella spiralis

17
Echinoderms

•         -slow moving or sessile marine animals
•   
• Symmetry
•         -radial as adult (not perfectly),
  bilateral as larvae
• Triploblastic
•         -3 germ layers
•         -coelomates
• Cephalization
•         -none  
• Special Adaptation
•         -water vascular system (tube-like
  extensions that function in locomotion,      
•         feeding, and gas exchange)
• Example
•         -star fish
•         -sea urchin

18
Arthropods (insects, arachnids, crustaceans)

•   
• Symmetry
•         -bilateral
• Triploblastic
•         -3 germ layers
•         -coelomates 
• Cephalization
•         -is extensive (concentration of diverse
  sensory structures at the anterior 
•          end)
• Special Adaptations
•         -hard, external shell (exoskeleton or
  cuticle) and the molting process
• Examples        

19
Grasshoppers

•         

20
Arthropods coelomates
21
Earthworms                coelomates

• Annelids