Kingdom Animalia Part I

Members of Kingdom Animalia are eukaryotic, multicellular, heterotrophic, and lack cell walls
Largest kingdom, with 95% of species being invertebrates (lack a backbone) and 5% being vertebrates (have a backbone)

Cell specialization: cells become more specialized to perform specific functions
Development: growth of a single celled zygote into a complete organism
Three types of germ tissues form after gastrulation:
- Ectoderm: becomes nerves, sense organs, and skin
- Mesoderm: becomes muscles, circulatory, reproductive, and excretory systems
- Endoderm: becomes digestive tract and respiratory system
Body symmetry:
- Early animals have no symmetry
- Radial symmetry appears first, with infinite lines of symmetry
- Pentaradial symmetry has 5 lines of symmetry
- Bilateral symmetry has only 1 line of symmetry and is the most advanced
Body cavity formation:
- Early animals are solid with no body cavity (acoelom)
- More advanced animals have a tube within a tube (pseudocoelom)
- The most advanced animals have the inner tube suspended within the outer tube (coelom)

Asymmetrical, sessile filter feeders with specialized cells:
- Epidermal cells cover the outside of the sponge
- Pore cells allow water to flow through the body wall
- Choanocytes are flagellated cells that create water flow
- Archaeocytes are amoeba-like cells that wander through the sponge and distribute nutrients and make spicules
Feeding, respiration, circulation, and excretion are all accomplished by water flow through the body wall and out the osculum
No nervous system, so minimal response to the environment
Can reproduce asexually or sexually

Soft-bodied carnivores with radial symmetry, stinging tentacles, and only one opening (mouth/anus)
Have cnidocytes (stinging cells) with nematocysts (harpoon-like poison-filled structure)
Three layers:
- Ectoderm (outer layer)
- Mesoglea (jelly-like with neural network)
- Gastroderm (where digestion takes place in gastrovascular cavity)
Two life stages:
- Polyp: sessile with tentacles up
- Medusa: motile with tentacles down

Circular and longitudinal muscles enable movement
Asexually: polyps can bud off new organisms
Sexually: separate medusa sexes release eggs and sperm into water (external fertilization)
Three classes of Cnidaria:
- Scyphozoa (jellyfish)
- Hydrozoa (branching polyp colonies, hydra, and Portuguese man-o-war)
- Anthozoa (anemones and corals)

Soft-bodied, flattened worms with bilateral symmetry and cephalization
Flatworms can be free-living or parasitic
Feeding:
- Free-living flatworms: carnivore scavengers that suck up material through a pharynx into a gastrovascular cavity
- Parasitic flatworms: do not have a complex digestive system, rather just absorb nutrients through body by diffusion
Respiration, circulation, and excretion:
- Bodies are thin and flat, relying on diffusion of materials through the body wall
- Some free-living flatworms have flame cells that act to filter metabolic waste and remove it
Response:
- Cephalized with an aggregation of neurons (ganglia) and sense organs
- Two nerve cords run down the body
- May have eyespots to detect light
- Parasitic flatworms have a much simpler nervous system
Movement:
- Free-living flatworms have cilia that allow them to glide through the water and muscles to wiggle
- Parasitic flatworms are usually non-motile
Reproduction:
- Asexual: fragmentation (fission) by splitting into 2 pieces
- Sexual: most are hermaphrodites (male and female)
- Parasitic: complex lifecycles with more than one host
Three classes of flatworms:
- Turbellaria (free-living marine or freshwater)
- Trematoda (Flukes, parasitic infecting internal organs of the host)
- Cestoda (parasitic tapeworms infecting the digestive system of the host)

Slender, unsegmented worms with a pseudocoelom
Feeding:
- Most nematodes are free-living (carnivores or decomposers)
- Some are internal parasites
Respiration, circulation, and excretion:
- Due to small size, they rely on diffusion of gases and waste through their body wall
Response:
- Simple nervous system consisting of several ganglia (groups of neurons), but no brain
Movement:
- Longitudinal muscles as well as a pseudocoelom filled with fluid acts as a hydrostatic skeleton
- Contraction of the muscles allows movement
Reproduction:
- All sexual
- Most have separate sexes
- Internal fertilization
Many species of nematodes are human parasites, including Trichinosis Worms, Filarial Worms, and Ascarid Worms

Segmented worms with a true coelom
Each segment has its own set of external appendages called setae
Feeding:
- Can be carnivores, decomposers, or filter feeders
- Pharynx has specialized feeding structures
- Food moves through an esophagus, then a crop (storage), and a gizzard (grinding)
- Nutrients are absorbed into each segment through the intestine
- Waste is removed out the anus
Circulation:
- Closed circulatory system (blood never leaves a vessel)
- Blood moves toward head in the dorsal blood vessel
- A set of 5 pairs of ring vessels act as hearts to pump blood
- Ventral blood vessel carries blood towards rear of worm
Respiration:
- Aquatic annelids have gills
- Terrestrial annelids require moist skin to allow transport across it
Excretion:
- Each segment has a pair of nephridia that remove waste
Response:
- Cephalized (brain and sense organs at anterior)
- Ventral nerve cord runs length of worm
Movement:
- Hydrostatic skeleton
- Setae evolve to aid movement
Reproduction:
- Sexual (separate sexes and hermaphrodites)
- External fertilization
Three classes of Annelids:
- Oligochaetes (mostly terrestrial or freshwater, relatively small or reduced number of setae)
- Polychaetes (mostly marine, many setae that have evolved into paddle-like structures)
- Hirudinea (leeches, external parasites)

Soft-bodied animals with a free-swimming trochophore larvae stage
Four basic body parts:
- Muscular foot: locomotion
- Mantle: thin layer of tissue that covers body
- Visceral mass: internal organs
- Shell: may or may not be present
Feeding:
- Snails have a rasp-like tongue called a radula to scrape
- Octopi have a beak for ripping and tearing
- Clams have a siphon that draws water in to be filtered
Respiration:
- Aquatic molluscs have gills inside the mantle cavity
- Terrestrial molluscs maintain a moist mantle to exchange gases
Circulation:
- Snails and clams have an open system (blood flows through a few vessels and a heart, but also leaves a vessel and is free to slosh around the body cavity)
- Octopi have a closed system as it is more efficient
Excretion:
- Nephridia release waste outside body
Response:
- Clams do not have a brain or complex nervous system
- Snails have a simple brain and senses
- Octopi have a well-developed brain and senses
Movement:
- Clams dig with their foot
- Snails glide on mucus and muscular contractions of the foot
- Octopi have their foot divided into tentacles as well as can shoot water out of their siphon
Reproduction:
- Many different strategies
- Separate sexes or hermaphrodites