Chapters 18 & 19
Evolution of Animals and Humans
Domain Eukarya : Kingdom Animalia
I. Characteristics
- multicellular eukaryote
- Heterotrophs
- lack cell walls
- Digestive system (most)
- Dominant diploid
- Similar developmental stages
II. Evolutionary History
- Protozoan Protista
1. mobile
2. nucleic acid similarities
3. similar cell structures
4. similar metabolism
95% invertebrates
5% vertebrates
III. Major Evolutionary Trends
1. Symmetry
2. Cephalization
3. Digestive Systems
4. Body Cavity
5. Segmented
6. Skeleton
--------------------------------------------------------------------------SPECIFICS OF EACH TREND:
1. Symmetry
Asymmetric
Radial Symmetry
Bilateral Symmetry
2. Cephalization
None → Present
3. Digestive Systems
Intracellular
Extracellular incomplete
Extracellular complete
4. Body Cavity
Acoelom
Pseudocoelom
Coelom
5. Segmented
No segmentation
Segmentation
6.
Skeleton
Hydroskeleton
Exoskeleton
Endoskeleton
IV. 9 Animal Phyla
Figure 18.23
Porifera
Cnidaria
Platyhelmithes
Nematoda
Mollusca
Annelida
Arthropoda
Echinodermata
Chordata
PHYLUM
PORIFERA
Sponges
- Asymmetric to Radial
Symmetry
- 3 Cell Layers
outer epidermal
middle amoebocytes
inner choanocytes
- regenerate and reform easily
- Extracellular skeleton
spongin (collagen protein) & spicules
- aquatic filter feeders
- Colonial protista ancestor = Choanoflagellate
PHYLUM
CNIDARIA
Jellyfish, Sea Anemone, Hydra, Coral
- Radial symmetry
- Polyp & Medusa stages
- Carnivores:
tentacles w/ Cnidocyte cells (nematocysts)
- Gastrovascular Cavity
Extracellular Incomplete
st
- 1 Tissues level
- Hydroskeleton
PHYLUM PLATYHELMINTHES free-living flatworm, flukes,
tapeworm
- Bilateral Symmetry
- Hydroskeleton
- Gastrovascular Cavity (absent in some)
Extracellular incomplete
- Eyespots (ocelli)
- Simple CNS (brain & nerve cord)
- specialized suckers/hooks
- highly regenerative
PHYLUM
NEMATODA
Hookworm, Heartworms,
Trichonosis
- Outer tough cuticle
- Pseudocoelom
- Extracellular Complete
Digestion
- Decomposer, Parasitic
PHYLUM
-
MOLLUSKA
Gastropod, Bivalve,
Cephalopod
Muscular foot
Mantle w/ gills
Radula
Coelom (Eucoelom)
well-developed Nervous
System: complex eyes
- Hydroskeleton
(some supplement with a secreted shell)
PHYLUM ANNELIDAE
Earthworms, leeches,
Polychaetes
- Segmented
- Extracellular complete
digestive system
- Bilateral symmetry
- Hydroskeleton
- Decomposers & parasites
PHYLUM ARTHROPODA
Arachnid, Crustacean,
Milliped, Centiped, Insects
- Jointed Legs
Exoskeleton of Chitin
- Segmented:
Head, Thorax, Abdomen
- Extracellular Complete Digestion
- Compound eyes
- Molt for growth
- Sexual & Asexual Reproduction
- Most diverse group of all animal phyla!
PHYLUM
ECHINODERMATA
Starfish, Sea Urchin,
Sea Cucumber
- Spiny skinned
- Endoskeleton of calcified plates
- Bilateral juveniles,
radial adults
- Extracellular Complete Digestion
- Water-vascular System with tube feet
- regenerative to appendages
PHYLUM
-
CHORDATA
Dorsal Hollow Nerve Cord
Notocord
Gill Structures
Post Anal Tail
INVERTEBRATES:
Tunicates & Lancelets
VERTEBRATES:
Agnathans
Fish
Amphibian
Reptile
Bird
Mammal
Primates
Invertebrates &
Vertebrates
PRIMATE CHARACTERISTICS
-
Limber shoulder/hip joints
5 digit hand/foot
highly mobile
Opposable Thumb/Big Toe
Greater sensitivity in
Hand/Foot
Short snout
Close eyes w/ overlap in fields = increased depth perception
Increased Infant care, slow development
Large developed Brain