Mead AP Biology
Lap 9: Animal Classification and Evolution
Chapters 32-34
32. 1 What is an Animal?
A. Multicellular, Eukaryote
◦ Lack cell walls
◦ Structural proteins-collagen
◦ Intercellular junctions
 Tight, gap, desmosomes
 Fig 6.31, pg 121
B. Heterotrophic
◦ Most ingest
◦ Internal digestion
C. Specialized cells
◦ Muscle and nerve cells and tissues
D. Reproduction and development
◦ Sexual: Small flagellated sperm + Large non-motile egg
◦ Early embryonic development, Fig 32.2
 Zygote undergoes mitosis (cleavage)
 Forms blastula
 Undergoes gastrulation
 Forms gastrula
◦ Some metamorphosis
32.2 History of Animals
A. Common Ancestor
◦ Choanflagellate, Fig 32.3
◦ Colonial, flagellated protest, Fig 32.4
32.3 Body Plans
A.Symmetry, Fig 32.7
◦ Asymmetry
◦ Radial
◦ Bilateral
 Dorsal and ventral
 Right and left
 Anterior and posterior
 Cephalization
B. Tissues
◦ Def
◦ Sponges lack tissues
◦ All others = Eumetazoa
◦ Tissues layered by gastrulation (Fig 32.2)
◦ Called germ layers  form tissues/organs in body
1. Ectoderm
2. Endoderm (archenteron)
3. Mesoderm
◦ Radiata: only 2 germ layers (diploblastic)
◦ Bilateria: 3 germ layers (triploblastic)
C. Body cavities in Triploblasts, Fig 32.8
◦ Def
◦ Functions
◦ Acoelomates
 Platyhelminthes
◦ Pseudocoelomates
 Coelom
 Usually 2 openings
 Nematoda/Rotifera
◦ Coelomates
 True coelom
 Mesentary tissue
D. Patterns of Early Development
 Protosomes vs Deutersomes
 Differ in 3 ways
1. Cleavage
 Protosome: spiral and determinate
 Deutersome: radial and indeterminate
2. Coelom formation
 Protosome: coelom from mesoderm around archenteron
 Schizocoelous
 Deutersome: coelom from archenteron
 Enterocoelous
3. Blastopore
 Def
 Protosome: becomes mouth
 Protos= 1st
 Deuterosome: becomes anus
 Deuteros= 2nd
32.4 Animal Phylogeny
A. Different Hypotheses, Fig 32.10 and 32.11
B. Points of Agreement
◦ All animals share common ancestor
 Metazoa
◦ Sponges are basal animals
 From base of phylogeny
 Parazoa: “beside” the animals
 No tissues
◦ Eumetazoa have true tissues
◦ Most animals are bilateria
◦ Vertebrates are Deutersomia
C. 4 Main branches: One view, Fig 32.10
1. Tissue
◦ Parazoans: lack tissue (Porifera sponges)
◦ Eumetazoans: have true tissues
2. Symmetry of eumetazoans
◦ Radiata: radial symmetry (Cnidaria, Ctenophora)
◦ Bilateria: bilateral symmetry
3. Presence of body cavity in triploblasts
◦ Acoelomates: No body cavity (Platyhelminthes)
◦ Pseudocoelomates: Cavity not completely lined (Nematoda and Rotifera)
◦ Coelomates: True coelom
4. Coelomates divided by early development
◦ Protosomes
◦ Deutersomes (Echinodermata and Chordata)
33.1 Sponges: Porifera
A. Intro to Invertebrates
◦ Def
◦ Diversity
◦ Habitat
◦ Fig 33.2
◦ Fig 33.3
 Summarizes all phyla
B. Sponges are sessile
◦ No nerve/muscle
◦ Respond to stimulus
C. Structure, Fig 33.4
◦ Pores
◦ Central cavity = spongocoel
◦ Osculum
◦ Skeleton
 Spiculues
 CaCO3
 Spongin
D. Filter feeders
◦ Choanocytes (collar cells)
◦ Amoebocytes
E. Hermaphrodites
◦ Sexual: both sperm and egg
◦ Asexual: budding and regeneration
33.2 Cnidaria
A. Body plan
◦
◦
Gastrovascular cavity
2 variations, Fig 33.5
 Polyp
 Medusa
B. Carnivores, Fig 33.6
◦ Tentacles
◦ Cnidocytes
◦ Nematocyst
C. Tissues
◦ No true tissue: Parazoan
◦ Nerve net
◦ Simple contractile tissue
 Epidermis
 Gastrodermis
D. Classes, Fig 33.7 & Table 33.1
◦ Hydrozoa
◦ Scyphozoa
◦ Cubozoa
◦ Anthozoa
33.3 Worms with Bilateral Symmetry
A. Flatworms: Platyhelminthes
◦ Habitat
◦ Triplobalstic: mesoderm
◦ Only 1 opening to digestive cavity
◦ Acoelomate: lack body cavity
◦ Major Classes, Table 33.2
1. Turbellaria, Fig 33.9, 33.10
 Free-living, marine
 Planaria
 Gastrovascular cavity
 Pharynx
 Flame cells
 Cilia and muscles
 Cephalization
 Eyespot
2. Trematoda, Fig 33.11
 Parasites
 Complex life cycle with human hosts
 Flukes
3. Cestoda, Fig 33.12
 Tapewroms
 Parasites
 Head/scolex
 Chain of repeating units


Complex life cycle in hosts
Eggs  larvae cysts in animal muscle
B. Rotifera, Fig 33. 12
◦ Habitat
◦ Pseudocoelomate: cavity without full lining
 Fluid functions as internal transport
◦ Complete digestive tract with 2 openings
◦ Reproduction
 Parthenogenesis
 Degenerate males
C. Roundworms: Nematoda
◦ Habitat
◦ Pseudocoelomates, 2 openings
◦ Reproduction
 Separate male/female
 Internal fertilization
◦ Importance
 Decomposition/recycling
 Parasites
 Pinworm, Hook worm
33.4 Molluscs
A. Habitat
B. Body plan
◦ Soft bodied with shell
◦ 3 main parts
 Muscular foot
 Visceral mass
 Mantle
◦ Radula
◦ Sex
C. Classes, Table 33.3
◦ Polyplacophora-chiton
◦ Gastropoda-single shell
◦ Bivalvia- shell with 2 parts
◦ Cephalopoda
 Closed circulatory system
 Well-developed nervous system with brain
33.5 Segmented Worms: Annelida
A. Habitat
B. Body
◦ Segmented
◦ Coelom separated by septae
◦ Closed circulatory system with 5 pumping vessels (heart)
◦ Skin as respiratory organ
◦ Metanephridia
◦ Brain-like ganglia
◦ Hermaphrodites that cross-fertilize
◦ Fig 33.23
C. Classes, table 33.4
◦ Oligochaeta
◦ Polychaeta
◦ Hirudinea
 Secrete hirudin
3.7 Arthropods
A. General characteristics
◦ Segmentation
 Cephalothorax and abdomen
 Head, thorax and abdomen
◦ Jointed appendages
◦ Cuticle/exoskeleton
◦ Cephalization and sense organs
◦ Open circulatory system
◦ Gas exchange varies
B. Sub-phyla, Table 33.5
◦ Trilobites
◦ Cheliceriforms
 Book lungs
◦ Millipede and Centipedes
◦ Hexapoda-Insects
 Complex organ systems
 Digestive
 Open circ/heart
 Malpighian tubules
 Tracheal system of gas exchange
 Nervous system
 Metamorphosis
 Reproduction
◦ Crustaceans
33.8 Echinodermata
A. Habitat
B. Structure
◦ Symmetry: larvae vs adult
◦ Calcareous endoskeleton
◦ Echino = spines
◦ Water vascular system
◦ Tube feet
◦
◦
Early development with deuterostomes
Sea Star anatomy, fig 33.39
 Central disk: nerve ring and nerve cords
 Ring canal
C. Examples, Fig 33.40
34.1Features of Chordates
A. Defined
◦ Eumetazoa, bilateria, deuterstomes
◦ 4 features, Fig 34.3
1. Notochord
2. Dorsal, hollow nerve cord
3. Pharyngeal slits
4. Tail
 Muscular
 Post-anal
B. Invertebrate chordates
◦ Tunicates: Subphylum Urochordata
 Fig 34.4
 Adult: sessile, Sea squirt
 Larvae: free swimming, non-feeding, 4 features
◦ Lanceletes: Subphylum Cephalochordata
 Fig 34.5
 Shows all 4 features
C. Early chordate evolution
◦ Ancestor of vertebrates liekly suspension/filter feeder
◦ Similar to adult lancelet and larvae tunicate
◦ Paedogenesis theory
 Evolutions from sexual maturity of larval form
 Changes in genes controlling development, Fig 34.6
34.2 Craniates
A. Features
◦ Chordates with a head
 Brain, skull
 Eyes, sensory organs
◦ Derived Characters
 2 clusters of Hox developmental genes
 Neural crest, Fig 34.7
 More active
 Organs
B. Hagfishes: Class Myxini
◦ Features
◦ 30 marine species
◦ Secrete slime
34.3 Vertebrates (Jawless)
A. Derived Features
◦ Craniates with a backbone
◦ Gene duplication allowed complex nervous system and skeleton (Dlx gene)
◦ Leading to backbone
B. Lampreys, Fig 34.10
◦ Jawless vertebrate fish
◦ Superclass Agnatha
◦ Larvae in streams
◦ Adults in lakes/seas
◦ Cartilage skeleton
34.4 Gnathostomes: Vertebrates with Jaws
A. Derived Characters
◦ Jaws
◦ Evolution: possible hypothesis, Fig 34.13
◦ Additional duplication of Hox genes
B. Chondricthyans: Cartilaginous fish
◦ Sharks, rays, relatives, Fig 34.15
◦ Feeding
 Filter feeders
 Carnivores
 Bottom dwellers
◦ Reproduction
 Internal fertilization
 Oviparous
 Oviviviparous
 Viviparous
C. Osteichthyans: Bony fish
◦ Characteristics
 Bony skeleton
 Gills and operculum
 Swim bladder
 Scales
 Varied reproduction
◦ Ray-finned fish, Fig 34.17
◦ Lobe-finned fish, Fig 34.18
34.5 Tetrapods: Gnathostomes with Limbs
A. Origin of tetrapods
◦ Limbs support weight on land
 Replace fins
 Pelvic bones
 Gill slits  ears, glands and other structures
◦ Lobe-fin fish evolve, Fig 34.19
B. Amphibians
◦ Classes, Fig 34.21
 Salamanders – Urodela
 Frogs – Anura
 Caelcilians- Apoda
◦ Metamorphosis
 Larval stage
 Adult
◦ Habitat
 Indicator species
34.6 Amniotes: Tetrapods with Amniotic Egg
A. Amniotic Egg, Fig 34.24
◦ Some have shells
◦ Specialized membranes
 Chorion
 Allantois
 Yolk sac
 Amnion
B. Reptiles
1. Features
 Scales with keratin
 Internal fertilization
 Snakes/some lizards are viviaprous
 Ecothermic
2. Groups, Fig 34.27
◦ Tuatara
◦ Squamata: snakes and lizards
◦ Turtles
◦ Alligators and crocodiles
C. Birds
◦ Derived Characters
 Reptile ancestor adapted for flight
 Weight-saving traits
 Wing/feathers, Fig 34.28
 Endothermic
 Acute vision and muscle control
 Complex mating behavior
◦ Origin
 2 theories
 Archaeopteryx, Fig 34.29
◦ Living birds, Fig 34.30
 Diversity of feet, Fig 34.31
34.7 Mammals: Amniotes with Milk and Hair
A. Evolved after Cretaceous crash
B. Characteristics
◦ Hair: made of keratin
◦ Endothermic
◦ Respiration and Circulatory system
 4 chambered heart
 Diaphragm
◦ Mammary gland: milk
◦ Internal fertilization
◦ Larger brain and learning
◦ Differentiation of teeth, Fig 34.32
◦ Ear: 3 bones
C. Evolution of Mammals
◦ Evolved from reptiles
 Earlier than birds
 From therapsids
◦ Existed with dinosaurs
◦ Diversified after mass extinction
D. 3 Types
◦ Monotremes
◦ Marsupials
◦ Eutherian (Placentals)
E. Phylogeny of Primates
◦ Features of primates
◦ Phylogeny
 Prosimians vs Anthropoids
 Fig 34.38