• Diversity in Body Plans
• A. Two types
• 1. Vertebrates (Backbone)
• 2. Invertebrates (No Backbone)
• Body Symmetry and Cephalization
• A. Two types of Symmetry
• 1. Radial (Bike wheel)Fig. 26.2
• 2. Bilateral (Halves)Fig.26.2

• Most Animals Who Have Bilateral Symmetry: Anterior End (Head)
• B. Posterior End (Butt)
• This Evolved after forward crawling creatures
• Cephalization: Evolutionary Process where nerves and sensory structures evolved in the head.
• Type of Gut (Region where food is digested &Absorbed) A. Saclike Gut (One Opening)
• B. Tubelike Gut (mouth & Anus)
• Body Cavities (Separate the Gut From Body Wall)
• A. Example
• 1. Coelom (Cintains distinctive lining called periotoneum)
• Segmentation(Series of Body units, may be similar or dissimilar)
• A. Example of Organism
• 1. Earth Worm
• 2. Insects (Head, thorax and abdomen)-

• Animals arose from protisanlike ancestors before Cambrian Era
• 560 million years ago all phylums were established

• Placozoan ( A soft bodied marine animal that is 3mm long)
• Trichoplax adhaerens (3mm short bodied marine animal found gliding acrossed anaqium tank)A. 2-layer
• B. no symmetry
• C. no organs
• D. breaks down food with enzymes
• E. Most simple Organism

Porifera (Sponges)

• Sponges ( Invertebrate, no symmetry, no organs, and gets food throw flagellated collar cells)
• Size
• A. Finger Nail to Chair sized
• More complex cell layers than Trichoplax
• Feed by filtering water
• Amoebocytes is where digestion and distribution of nutrients occur
• Spiccules are skeletal needles made of CaCO₃ or SiO₂
• Cannot form tissue because it is not organized enough

• Def- radial, tentacled animals and most live in the sea.
• Over 11,00 species, fewer 50 live in fresh water
• Members of phylums (jellyfish, anemones, & hydra)
• Produce nematocysts (toxin ladden treads used to capture prey and fend off predators)

• Cnidarian Body Parts
• Two Common Body Forms, both form around a saclike gut.
• 1.Medusa look like an upside down saucer. All float in water, mouth is in middle of the bottom of the saucer. Have oral arms.
• Gut is like a permanent food processing chamber, has a complex lining with glandular cells that secrete digestive enzymes.
• 2. Polyp (tube like), Tentacle fringed mouth at one end and the other is attached to a substrate.
• These organisms are like moving guts as its trichoplax drapes over the ground digesting mounds of food.
• Epithelial tissue- found in all animals more complex than a sponge. Examples: gatrodermis and the epidermis
• Cnidarians have a simple nervous system call a nerve net that responses to stimuli
• It is made up of nerve cell that run through the epithal tissue
• Along with sensory and contractile cells movement and shape changes are controlled
• Between epidermis and gastrodermis lays a secreted material called mesoglea
• This gives jellyfish heir buoyancy and serve as a deformable skeleton
• Not abundant in most polyps, who use their guts to propel them
• Hydrostatic skeleton- fluid-filled cavity or cell mass, most polyps have them

• Colonial anthozoans show variation of a basic body plan
• Examples: Corals are made up of interconnected polyps that secrete their own calcium reinforced skeletons. They serve as the building material for reefs.
• Cniderian Life Cycles
• Most Cniderians have a polypstage or a medesa stage
• Medesa- sexual form

• Marine predators that show radial symmetry
• Has eight comblike structures, made of thick, fused cilia
• All comb move together to propel it forward
• Some have feeding nets (two tentacles that branch out)
• Don’t produce nematocysts, but can store it from jelly fish it has eaten
• Evolutionary gave rise to muscles and organs in the circulatory, excretory and reproductive systems
• Resemble mesoderms

• 15,000 known species, are turbellarians, flukes and tape worms
• Have saclike gut and food usually enter through the pharynx
• Most have flat bodies
• Are bilateral and cephalized unlike sponges and Cniderians
• Simplest animals with organs, that are formed by different tissues and are organized inspecific proportion and pattern
• Also have organ systems, two or more organs interacting to do one task

• Turbelians
• Live in the seas and fresh water
• Carnivores that eat small animals of suck from dead ones
• Herbivorous types eat diatoms
• Bodyfluid regulated by a planarian organ system
• Reproduce asexually by fussion
• Each worm is a homophrodite, contain both gonads used in sexual reproduction
• Flukes
• Parasites, live in vertebrates guts, liver, lungs, bladder, and blood vessels
• Have many life cycles
• Have a sexual and asexual phase in two different host
• Definitive host is where it reaches sexual maturity
• intermediate host is where they develop in laral stage and become encysted
• Tapeworms
• Parasites in the intestines, not no gut because it is surrounded by predigested food
• Attaches to intestinal wall by a scolex (hook and sucker)
• Behind the scolex, proglottiod form by budding
• proglottoids are homophroditic
• Older proglottooids store eggs
• Eggs leave the host through feces
• Then the eggs are carried by an intermediate host
• Tapeworms resemble planlas of Cniderians.
• Some think bilateral animals evolved from planula ancestors

• Live in the snowfield, deserts and hot springs
• Thousands can be found in a cup full of dirt
• Parasitize plants and animals, 30 species parasitize humans
• Body plan- bilateral, cylindrical body, and tapered at both ends
• Have cuticle- tough flexible body covering
• Simplest animals with a digestion system
• Cause trichinosis in uncooked meats

• Predators in marine habitat
• Close relatives to flatworms
• Unlike flatworms they have a complete gut and circulatory system and are not hermaphrodites
• Have a proboscis (tubelike) to capture prey by injecting venom

Rotifera (Rotifers)

• One millimeter long, but multicelluar and have a complex digestive tract
• Abundant in plankton
• They eat bacteria and single celled algae
• Most have crown of cilia, help it swim and waft food in its mouth
• Have salivary glands a jawed pharynx, an esophagus, digestive gland, a stomach and an intestine and anus
• Protonephridia remove excess water
• Head is a cluster of nerves, some species have eyes
• Some have two toes that allow it to attach to substrate while feeding
• Evolutionary side step, show complexity of animals with a false colon

A Major Divergence

• After Cambrian to distinct evolutionary lineages formed
• 1. Protostomes (Mollusks, annelids and arthropods)
• 2. Deuterostomes (Echinoderms and chordates)
• Differences appeared in embro development
• Deuterostomes embryos divide parallel and perpendicular (radial cleavage)
• The first hole in embryo becomes the anus
• Colon forms in an out pouching of the gut
• Protostomes embryos divide in oblique wedges (spiral cleavage)
• First hole is the mouth
• Colon forms on side of the gut

Mullusca (Mollusks)

• Include snails, bivalves, octopus, and squid. Make up the second largest phylum besides arthropods
• Most mollusks have shells and have coelomate bodies with a complete digestive tract
• Bivalves are clams and muscles (2 part shells)
• Squids have a reduce shell and it is internal
• Octopus have no shell and a highly developed nervous system along with a large complex brain

Annelida (segmented worms)

• Leeches, earthworms, and polychaete worms are examples of annelida. All are bilateral and have true colons
• Leeches can be predators of small animals or blood-sucking parasites. They also have two suckers at opposite ends of their body. They are use for attachment and movement
• Polychaete worms are found in marine environments. Some are tube builders others crawl, burrow or swim
• Dine on small invertebrates and algae
• Sea nymphs are crawling polychaete

• Examples are spiders, insects, crustaceans, and other related organisms
• Have joint appendages, a well developed nervous system, specialization of body segments and an exoskeleton made of chitin.
• Two life cycles
• 1. nymphs- small version of the adults
• Larvae is another form some arthropods are born as. (maggots)
• 2. metamorphosis- they inclose themselves in a pupa and change into adults who can disperse gamete and reproduce

• Chelicerates have only one surviving marine animal is the horseshoe crab
• On land they are ticks, spiders, mites, and scorpions to name a few
• Spiders and Scorpions pump digestive enzymes into the guts of their prey. Some are also venomous to humans
• Ticks can transmit lyme disease and Rocky Mountain Spotted Fever
• Spider and Scorpions have book lungs

• Crustaceans include crabs lobsters, shimp and mud puppies
• Shell of barnacles is calcified to protect themselves for predator s when are attach to an object
• Eat tiny photosynthetic plankton
• Insects have a head, thorax and abdomen
• Also have a sensory antennae and paired mouth, use for chew biting or puncturing

Echinodermata (echinoderm)

• Examples are sea stars, sea urchins, and sand dollars
• All are coelomate Deuterostomes and have a complex digestive tract
• Adult echinoderms are radial symmetric
• Larvae show bilateral symmetry
• Ancestors are believed to be bilateral
• Starfish have tubefeet they are used for walking, burrowing clinging to rocks or grabbing clams or snails for a meal (Some sallow prey whole)
• Adults have no brain, but nervous system allow it to react to stimuli

• are vertebrates
• All members show the following 4 features some time during their life
• A notchord
• Dorsal hollow nerve cord
• Pharyngeal gill slits
• muscular tail