Invertebrates

• Sponges, Cnidarians, Worms, Mollusks, Annelids, Arthropods, Echinoderms

• Each group of organisms have specific forms and functions

• Feeding• Respiration, circulation and excretion• Response• Movement• Reproduction

Worms

• Free-living or parasites• Segmented or unsegmented• Flatworms – soft, flattened worms that have

tissues and internal organ systems,• simplest animals to have three embryonic germ

layers (ectoderm, endoderm, mesoderm), bilateral symmetry and cephalization

• Carnivores – single opening for digestive system• Use diffusion to move materials• Use ganglia (bundle of nerve cells) to respond to

external stimuli

Cont.

• Cilia and muscles are used for movement• Reproduce using sexual (hermaphordites)

or asexual by the process of fission (splitting)

• Three groups;• Turbellarians – free-living, fresh or marine

water• Flukes – parasitic, internal organs (blood)• Tapeworms-parasitic, intestines

Nematoda

• Roundworms are unsegmented worms that have two opening, anus and mouth

• Have specializes tissue and organ systems• Consumers• Diffusion to move materials• Very simple nervous systems for response• Muscles allow for movement• Sexual reproduction – individuals (male and

female)• Diseases – trichinosis, elephantiasis,

Annelids

• Segmented bodies, complex organ systems that are unique due to segmented body plan

• Filter feeders and predators• Closed circulatory system – dorsal vessel

moves toward head and ventral moves toward tail

• Aquatic breathe through gills, land through skin

Cont.

• Removes waste from digestion through anus and cellular waste by nephridia

• Have a well developed nervous system and fundamental brain to respond to stimuli

• Have two major groups of body muscles that function as part of the hydrostatic skeleton for movement – longitudinal head to end (fatter or short) circular around body contract to make worm longer and thinner

Cont.

• Hermaphrodites: have both sperm and eggs

• 3 Types of Annelids

• Oligochaetes

• Leeches

• Polychaetes

Mollusks

• Soft-bodied animals that usually have an internal or external shell

• Have four parts: foot, mantle, shell, visceral mass

• Herbivores, carnivores, filter feeders, detritivores or parasites

• Breathe through gills or across skin

• Open or closed circulatory systems

Cont.

• Cells release Nitrogen containing waste into the blood in the form of NH3 and removed by nephridia

• Simple organisms (clams) have nervous systems made of ganglia, more complex organisms have (octopi) have very complex nervous systems and a highly developed brain

Cont.

• Movement depends on species – snails secrete mucus and move with a rippling motion along – octopus use jet propulsion

• Reproduction depends on species – some are hermaphrodites, other release egg and sperm by external fertilization

• 3 types of mollusks –

• Gastropod, bivalves, cephalopods

Arthropods

• Insects, crabs, centipedes and spiders

• Segmented body, tough exoskeleton and jointed appendages

• Natural selection and other process has led to fewer body segments, highly specialized appendages for feeding, movement and other functions

Cont.

• Herbivores, carnivores and omnivores

• Breathe oxygen through specialized organs (tracheal tubes, book lungs)

• Open circulatory system

• Excretes waste through specialized organs

• Well developed nervous system, ALL have a brain

Cont.

• Movement provided by well developed muscles controlled by nervous system

• Internal or external reproduction depending on the species

• growth - outgrow exoskeleton by molting

• Classified by number and structure of segments and appendages (specifically mouth parts)

Cont.

• Crustaceans, spiders (and relatives), insects (relatives)

Insects

• Body divided into 3 parts – head, thorax (3 pairs of legs attached), abdomen

• Use sense organs to respond to stimuli compound eyes, chemical receptors, sensory hairs, well developed ears (beyond human range)

• Mouth part used for feeding• Movement uses legs (walking, jumping,

holding prey)

Cont.

• Metamorphosis – complete (look nothing like parent) or incomplete (look a lot like parent)

• Complex social order system called societies using a “language” to communicate information

Echinoderms

• Spiny skin, internal skeleton, water vascular system, suction structures, exhibit five-part radial symmetry (star fish)

• Water vascular system carries out essential body functions respiration, circulation and movement

• Sea urchins, sea cucumbers, sea stars

• Crown of thorns – major threat to coral

Evolution

• 575 to 543 million years old – Ediacaran

• Soft bodied with little specialization

• By Cambrian (544 mil yrs) period many had formed shells, skeletons and other hard body parts

Evolutionary Trends

• Specialized cells, tissues, organs • Body symmetry - All invertebrates except sponges exhibit some type of body symmetry

• Cephalization – respond to environment in more sophisticated ways

• Segmentation – increased body size• Complex animal phyla have a true coelom that is

lined completely with tissue derived from mesoderm

Form and Function

• Digestion: Intercellular (digested inside cell) or extracellular (in digestive cavity then absorbed) design

• Respiration: large moist surface area in contact with air and water where diffusion can take place

• Circulation: move blood through one or more hearts and an open or closed circulator system

Cont.

• Excretory: removal of ammonia aquatic-diffusion / terrestrial ammonia is converted to urea (less toxic) released through excretory pores

• Response: 3 trends – centralization (simplest nervous system), cephalization (brain), specialization (sense organs)

Cont.

• Movement and support: 3 main kinds of skeletal systems – hydrostatic (fluid filled), exoskeleton (outside body), endoskeletons (inside body)

• Reproduction: sexually and asexually depending on organism – external (outside body) internal (inside body)