Most animals are invertebrates, no vertebral column (backbone). 

            A.  Sponges - Phylum Porifera

                        1.  most are marine (oceanic), but some are freshwater

                        2.  most live singly or in clusters formed by budding.  Many can regenerate completely if                                                      fragmented into pieces

                        3.  Vase- shaped or cylindrical sponges have radial symmetry - body arranged like pieces of a                                     pie around radial axis. (any imaginary plane passed vertically through the body will produce                                                 mirror images

                        4.  simple animals - generally, 3 loosely associated layers of cells

                                    a.  outside layer of flattened cells provides protection

                                    b.  middle body layer has motile cells called amoebocytes and skeletal components                                                      composed of a flexible protein called spongin or mineral containing particles. 

                                    c.  third cell layer consisting of  flagellated cells called choanocytes or collar cells,                                                                    have collar like structure surrounding base of flagella.  Aided by the flagella                                                                 on  choanocyte, water flows throughout the pores into the central cavity and  
                                                             then out of the sponge through its one large opening.                           

                                    d.  biologists believe sponges arose very early in animal evolution, from multicelled                                                         organisms

                                                1).  lack digestive tract

                                                2).  lack gastrula stage

                                                3).  3 cell layers are not homologous to body layers of other                                                                                         animals

                                                4).  lack nerves and muscles

                                                5).  not true tissues

            B.  Phylum Cnidaria:  hydras, jellies, sea anemones and corals.  All have radial symmetry and cnidocytes

                        1.  Radial symmetry is a hallmark of this phylum; any vertical cut will produce mirror images.                                                 Body forms:

                                    a.  polyps - columnar with radiating arms called tentacles

                                    b.  medusas - umbrella like, fringe of tentacles around umbrella -  motile

                        2.  some cnidarians have life cycles with both polyps and medusas

                        3.  carnivores  - use tentacles -capture small animals and protists, to push prey into mouth

                                    a.  polyp - mouth at top of column, at hub of radiating tentacles

                                    b.  medusa-  mouth in center of underside of umbrella

                        4.  in both body plans, mouth leads to digestive cavity called gastrovascular cavity

                                    a.  undigested food exits thru mouth, no anus;  digestive system is said to be                                                                  incomplete

                                    b.  cavity circulates body fluid that services internal cells

                                    c.  fluid in cavity provides body structure and support, like water in a balloon

                        5.  All cnidarians have cnidocytes- specialized cells, found on surface of tentacles of polyps                                       and medusas- fine thread coiled within a capsule.  When discharged, thread can sting or                         capture prey; some big enough to catch fish

                                    a.  defense

                                    b.  prey capture

                        6.  several features absent in sponges, present in other phyla:

                                    a.  digestive cavity

                                    b.  gastrula stage of development

                                    c.  presence of tissues.  eg sea anemone has well developed nerve and muscle                                      tissue, it can creep, swim, roll, burrow or somersault away from danger.

                                    d.  tissue animals - though some have  organs, most cnidarians have tissues that                                                       perform vital functions.

            D.  Most animals are bilaterally symmetrical - can be divided equally by a single cut into mirror image

            right and left side

                        1.  head end - anterior

                                    a.  head is prominent part of bilateral animals

                                                1.  sensory structures

                                                2.  brain

                                                3.  mouth

                                    b.  brain and sensory structures along with nerves = organ system = nervous system

                        2.  tail end - posterior

                        3.  dorsal side - back

                        4.  ventral side - front or underside

                        5.  lateral- side surfaces

6.  Radial animals lack forward orientation, sit on surface of seafloor or drift, waiting for action to come to them. Bilateral animals - generally quite active and travel head first through environment.  crawl, swim, run, walk, or fly.  Sense organs contact environment first and help animal respond.  Humans are bilateral.  Why don’t we move head first through the environment?

            E.  Platyhelminthes- flatworms are simplest bilateral animals.  Leaf or ribbonlike animals.

                        1.  unusually simple bodies for bilaterals

                        2.  incomplete digestive tract - no anus; most bilateral animals have a complete digestive system

                        3.  flatworms lack an internal cavity;  digestive cavity is only space in body, similar to cnidarians it      

                        is a gastrovascular cavity;  most bilateral animals have another body space called the body                         cavity between digestive system and body wall.

                        4.  3 major groups of flatworms

                                    a.  freeliving (nonparasitic) flatworms - planaria

                                                1).  nervous system - dense clusters of nervous tissue (brain), eyespots, small                                                                         nerves that branch throughout the body

                                                2).  digestive system - highly branched.  mouth located not in head, but ventral                                                       surface;  muscular tube protrudes through mouth and pulls food in.  Planaria live                                                       on undersurfaces of rocks in ponds and streams.  Using cilia, they crawl in                                                                   search of food.   Muscles allow them to twist and turn.

                                    b.  flukes - parasites.  e.g. Schistosoma - female spends much of time in a groove in the                                       male’s body;  they copulate frequently producing over 1000 eggs/day.  Females and                                         males have suckers to attach to the inside of the blood vessels near the host’s                                       intestines.  Blood flukes infect humans and cause severe disease called schistosomiasis                                      (blood fluke disease).  It’s widespread in Africa, Southeast Asia and South America - 250                                         million people in 70 countries:  severe abdominal pain and dysentery.

                                    Complex life cycle, often involves > 1 host.

                                                1).  blood flukes living in a host reproduce sexually, eggs pass out through                                                                         feces. 

                                                2).  eggs in ponds or stream- hatch, ciliated larvae enter  nearby snail.

                                                3).  larvae in snail reproduce asexually, produce other larvae that enter humans.

                                                4).  Infection occurs when larvae penetrate skin

                                    c.  tapeworms are 3rd type of flatworms, also parasitic.  Inhabit the digestive tracts of                                     vertebrates, including reptiles, birds and   mammals. 

                                                1).  Long, ribbon like bodies with repeated parts.

                                                2).  no digestive tracts themselves - absorb partially digested nutrients directly

                                                3).  head is armed with suckers and teeth to attach to host.

                                                4).  behind head, a short neck generates the repeated parts;

                                                5).  youngest repeated part is behind the neck, oldest part at the posterior                                                      end of the worm. 

                                                6).  Repeated parts filled with male and female reproductive parts.

                                                7).  parts at posterior end filled with eggs;  break off, pass from body in feces.

                                                8).  Like flukes, complex life cycle- may have more than one host.  Many benefit                                                 from predator-prey relationships-  sheep or rabbit may become infected by                                                        eating grass containing tapeworm eggs.  Larval tapeworms develop, and when a                                                 predator eats an infected prey, say a coyote, tapeworm completes its life cycle.

                                                9).  Humans can become infected by a large tapeworm (20 m)  Taeniarhynchus

F.  Most animals have a body cavity, fluid filled space between digestive tract and body wall.  Sponges, cnidarians and flatworms lack them.   Fig. 18.7 shows structures of 3 animals - color of cells indicates same tissue layers:  outside covering region- blue, middle region (pink), and lining of digestive cavity (yellow).  These tissue layers form from cell layers of gastrula in embryonic development

                        1.  flatworms lack a body cavity

                        2.  roundworms have a cavity called pseudocoelom (false, hollow),

                                    a).  an internal space in direct contact with wall of the digestive tract

                                    b).  the outer edge of pseudocoelom contacts muscle layer, part of body wall

                        3.  other animals have more complex body structure than either of the two above

                                    a).  body cavity - coelom - completely lined by a middle tissue layer, which extends from                                                      the body wall and wraps the digestive tract.

                                    b).  suspends organs from the body wall

                                    Advantages of coelom:

                                                1).  more flexible- animals can crawl and burrow more easily

                                                2).  organs grow and move independently of outer body

                                                3).  fluids cushion organs, preventing injury;  animals with skeletons would do                                                                 serious damage to organs without fluids to protect organs during even mild                                                                 exercise           

                                                4).  fluids help circulate O2, waste and nutrients - amoeboid cells help in these                                                                  functions

                                                5).  fluids provide structure to some animals (like earthworms).

                                    c).  structure related to function - small size of flatworms means they don't need a body                                     cavity, all nutrients and O2 can diffuse in and waste out.  Even long ones, like                                              tapeworms, are very thin.

            G.  Nematodes - roundworms -pseudocoelom and complete digestive tract

                        1.  cylindrical worms with a finely tapered tail;  head is more blunt.

                        2.  tough, nonliving skin called cuticle, resists drying or crushing

                        3.  pseudocoelomates

                        4.  complete digestive tract;  mouth near head, anus near tail.  food travels one way;                                   specialization in digestive tract - highly efficient

                                    a. anterior region churns and mixes food w/enzymes

                                    b.  posterior region absorbs nutrients and disposes of waste

                        5.  Nematodes are among the most numerous of animals in terms of number of individuals and                                       number of species;

                                    a.  important decomposers, they live wherever there is rotting organic matter - soil, lakes,                                     rivers, oceans

                                    b.  also parasites of plants and in body fluids of animals.

                                    c.  90,000 species are known and likely that 10x exist; freeliving worms are most                                     abundant

                                    d.  humans are host to at least 50 species, many of which cause major health problems

                                                1).  hookworms

                                                2).  heartworms in dogs

                                                3).  trichinella - trichinosis (NASTY!!  worms may infect heart or brains)-                                                              undercooked pork may contain juveniles - cook meat until no longer pink

                                    e.  conservation of body form among nematodes - all look pretty much as described

H.  Phylum Mollusca - snails, slugs, oysters, clams, octopus and squids are examples of great variety -             body structure NOT conservative in this group!

                        1.  most have soft bodies protected by hard shell

                        2.  molluscus in latin means “soft”

                        3.  Fig. 18.9 shows basic body plan -

                                    a.  muscular “foot” - locomotion

                                    b.  mantle - outgrowth of body surface that protects animal

                                                1).  produces shell in clams and snails

                                                2).  also:  respiration, waste disposal and sensory reception.

                                                3).  mantle cavity - created by mantle formation - may house a gill to extract O2                                                 in water and dispose of fluid wastes

                                                4).  many molluscs have radula- a rasping tongue for scraping

                                    c.  true coelom - 3 small cavities

                                                1).  for heart

                                                2).  for reproductive organs

                                                3).  one forms part of kidney

                                    d.  circulatory system - distributes nutrients and water - has taken over the function of a                                                       large coelom

                        4.  Different body features in different groups

                                    a.  gastropods - fresh water, salt water, terrestrial.  In fact, this group has the only                                                      molluscs that live on land;  75,000 species

                                                1).  terrestrial snails, slugs lack gills; mantle cavity has evolved into a huge lung

                                                2).  most are marine; sea slugs are unusual mollusks, lacking a mantle, mantle                                                               cavity and shell

                                    b.  bivalves - (bi = double, valva = leaf of folding door);  include clams, oysters, mussels,                                                           scallops. 

                                                1). have shells divided into 2 halves, hinged together

                                                2).  sedentary, live in sand or mud

                                                3).  muscular foot used for digging/anchoring

                                                4).  mucus coated gills to trap fine food particles

                                                5).  scallop - many eyes around mantle edges.  can clap its shell shut and squirt                                                                water from its mantle cavity, jetting itself a short distance away

                                    c.  cephalopods (greek - kephale = head, pous = foot) - built for speed and agility

                                                1).  a few have large, heavy shells, but most have small internal shell (squid), or                                                             lack it all together (octopus)

                                                2).  marine predators - beaklike jaws and radula to crush or rip prey apart

                                                3).  mouth at base of foot, which is divided into numerous tentacles for catching                                                                        and holding prey

                                                4).  squids -

                                                            a).  draws water into mantle cavity, fires it out - fast sreamlined animal

                                                            b).  large complex brain

                                                            c).  among  most complex sense organs in animal kingdom - lens (focus                                                                           light) and retina (images)

                                                5).  all cephalopods have complex brains and sense organs, contribute to                                                                  success as predators

                                                6).  Octopuses have larger, more complex brains, proportionate to body size                                                                      than almost any animal.  good learners!

I.  Segmentation - subdivisions of the body along its length; this feature played a major role in evolution of many complex animals.

            1.  Earthworms are segmented (Fig. 18.10)

                        a.  coelom is partitioned by walls

                        b.  nervous system (yellow) has a cluster of cells in each segment

                        c.  excretory organs (green) repeated in each segment

                        d.  digestive tract is not segmented;  it passes through the segment walls from the mouth                                       to the anus. 

                        e.  circulatory system - dorsal and ventral blood vessels; 

                                    1. accessory hearts

                                    2.  main heart

            2.  Dragonfly - also segmented, though less uniformly than earthworm

                        a.  segments most pronounced in abdomen. 

                        b.  head and thorax - fused segments

                        c.  Each pair of legs and wings emerges from a segment in the thorax

            3.  Humans have segments, not homologous with earthworm’s or dragonfly’s

                        a.  Backbone is repeated series of knobs called vertebrae, and muscles associated with                                                 vertebrae are segmented.

                        b.  stomach muscles are segmented

            4.  Advantages of segmented bodies

                        a.  great bodily flexibility

                        b.  mobility;  probably an adaptation for movement

J.  Phylum Annelida (annelus = ring) - segmented worms;  15000 species. Terrestrial (damp soil), freshwater and marine (some swim, most are bottom dwelling scavengers) habitats; separate head and tail; body segments all very similar

                        1.  Earthworms one of 3 large annelid groups

                                    a.  eats its way through soil extracting nutrients as soil passes thru digestive tube.                                                  Undigested material passes through anus at posterior end. 

                                    b.  earthworms are incredibly valuable-

                                                1).  they till the soil and enrich it

                                                2).  they improve the texture;  Darwin estimated that an acre of land (Britain) had                                                                   about 50,000 earthworms that produced about 18 tons of feces/yr.

                        2.  Polychaetes (gk- poly = many, chaeta = hair) most live on the seafloor; some freshwater or                                             estuaries.  Most annelids are polychaetes. 

                                    a.  segmented appendages help worms wriggle

                                    b.  segmented appendages increase surface area for taking up  O2 and dispose of                                                         wastes

                                    c.  many marine species live in tubes; extend feathery appendages to trap suspended                                                 food particles

                                    d.  tubes formed by sticky proteins secreted near mouth

                        3.  Leeches are 3rd group of annelids;  blood suckers, some are freeliving, eating snails and                          insects.  Most leeches are fresh water;  a few terrestrial species inhabit moist vegetation in the tropics

                                    a.  until this century, leeches were used to remove “bad blood” from patients

                                                1).  razor-like jaws cut through skin

                                                2).  saliva contains strong anesthetic

                                                3). and strong anticoagulant - prevent heart attacks

                                    b.  leeches used on burn victims and in reattachments

            K.  Phylum Arthropoda -

                        1.  nearly a million types of segmented animals - includes crayfish, lobsters, crabs, barnacles,                                 spiders, ticks and insects.            

                        2.  arthropod population of earth is about a billion billion 10¹⁸ ! most successful phylum of animals                          ever, in terms of diversity, distribution and sheer numbers.

                        3. Fossils indicate intermediates btn annelids and arthropods - Cambrian, 550 mya.  But                                   molecular analysis shows an earlier ancestor of both, two different evolutionary lines.

                        4.  Arthro = jointed, pod = foot; jointed appendages in this phylum.  Appendages in lobster for                                   walking, feeding, swimming, sensory reception and defense. 

                        5.  exoskeleton - hard external skeleton- chitin: polysaccharide, w/proteins

                                    a.  protection

                                    b.  attachment for muscles to move appendages

                                    c.  thick in some places thin in others

                                    d.  molting- periodic shedding of exoskeleton, secretion of new one

                        6.  annelids have similar segments;  most arthropods have distinct groups

                                    lobster, e.g.

                                    a.  head- sensory parts: antennae, eyes and mouthparts

                                    b.  thorax-pincers for defense and 4 prs. legs for walking

                                    c.  abdomen- swimming appendages

                        7.  horseshoe - living fossil - survived w/ little change for hundreds of millions of yrs.  Only                                                     survivor of spiderlike arthros abundant in seas 300 mya

                        8.  closest living relative of horseshoe crabs - arachnids: spiders, ticks, mites, scorpions.  Most                                         arachnids live on land. 

                                    a.  Scorpions are nocturnal hunters.  eat mainly insects and spiders

                                    b.  mites- thousands can live in a few square centimeters of carpet or in a dust bunny;                                                       not disease carriers; many people are allergic

                        9.  crustaceans - nearly all aquatic- lobster, crayfish, shrimps, crabs, barnacles. 

                                    a.  barnacles live in limestone shell;  jointed appendages protrude from shell to catch                                         small invertebrates and suspended particles. body and appendages covered with                                          chitinous exoskeleton

                        10.  centipedes and millipedes- jointed legs identify them as arthropods

                                    a.  millipedes- plant eaters

                                    b.  centipedes - carnivores with poison claws used in defense and to paralyze prey like                                                cockroaches and flies.

                        11.  these 4 groups make up 170,000 living species.  Insect numbers dwarf all other groups 

                        L.  Insects- more total insects than all other animal species combined. prominent on land for 400 my. 

                        fewer in water, especially salt water                                        .

                                                1.  common features:  3 part body- head, thorax, abdomen

                                                2.  head- sensory antennae, eyes

                                                3.  several prs of mouthparts adapted for particular kinds of eating

                                                            a.  biting and chewing plants - grasshopper

                                                            b.  lapping up fluids- houseflies

                                                            c.  piercing skin and sucking blood- mosquito

                                                4.  adults- 3 prs legs, 1 or 2 prs wings.

                                                5.  ability to fly- evolutionary success

                                                6.  metamorphosis- part of development.  life stages may look like adult (incomplete)                                                  or  not (complete metamorphosis)

                                                7.  insect orders:

                                                            a.  Orthoptera- grasshoppers, crickets, locusts, cockroaches, preying                                                                             mantises.  most are herbivores. praying mantises are predators, use 
                                                                        forelegs to grip prey

                                                            b.  Odonata-  dragonflies and damselflies- two prs wings biting mouthparts,                                                                   carnivores.  Larvae of larger species eat tadpoles and small fish

                                                            c.  Hemiptera- true bugs- bedbugs, waterstriders, stink bugs.  Most feed on                                                                 plant sap;  bedbugs feed on blood.  Two pairs of wings, fore wing thickened 
                                                            and leathery. 

                                                            d.  Coleoptera- beetles- largest order in the animal kingdom.occur almost                                                              everywhere from high mtns to streams, seashores, forests, desert, etc.                                                              carnivores, herbivores, omnivores.  2 prs wings, only hindwings used in 
                                                              flight.   Forewings hard cover for hindwings.        

                                                            e.  Lepidoptera - moths and butterflies.  2 prs wings, hindwings smaller.  
                                                            wings and body covered w/scales- dust. Mouthparts form a long drinking tube-
                                                             nectar.  tube coils up when not in use.

                                                            f.  Dipteran- flies- houseflies, fruitflies, gnats, mosquitoes. single pr wings,
                                                            small club shaped organ - haltere- balance in flight.  mosquitoes- long
                                                            mouthparts, spread malaria. 

                                                            g.  Hymenoptera- ants, bees, wasps.  2 prs wings, use both in flight.  
                                                            hindwings smaller, hooked to rear of forewings- behave as a single functional
                                                            unit.  Thorax and abdomen separated by a narrow waist.  Herbivores and
                                                            omnivores. some have complex social organization

            M. Phylum Echinodermata- spiny skin, endoskeleton, water vascular system

                        1. eg sea urchins and sea stars,

                        2.  lack segments

                        3.  radially symmetrical as adults;  larval stage bilaterally symmetrical.  Echinoderms, therefore,                                               are not closely related to cnidarians. 

                        4.  spiny or rough skin, spines embedded

                        5.  spines part of endoskeleton

                        6.  vascular water system- network of water filled canals, that branch into tube feet

                                    a. sea stars grab bivalve with tube feet and push stomach through mouth, into bivalve.                                                        digests soft parts of prey.

                        7.  strong powers of regeneration- regrow feet and arms, and sea cucumbers can regrow organs.

                        8.  Sea urchins are spherical and have no arms; algae eaters

            N.  Phylum Chordata- our phylum.  4 distinctive features in embryos

                        1.  dorsal hollow nerve cord

                        2.  notochord - flexible longitudinal nod btn digestive tract and nerve cord

                        3.  gill structures-  in pharynx, region of digestive tube behind mouth

                        4.  post anal tail (posterior to anus). 

                                    a.  vertebrates

                                    b.  invertebrates

                                                1). tunicates- large gill apparatus; adhere to rocks and boats. tunicate larvae                                                               exhibit the above 4.   Eat fine organic matter caught by mucus around gills

                                                2).  lancets- marine chordates- feed on suspended particles;  have segmented                                                                    muscles to flex body side to side.  Gill apparatus traps food. 

Lesson Objectives Ch. 33