InvertebratesDomain Eukarya

Kingdom Animalia

The Metazoans

Evoln of Animals

• Animals of Kingdom Animalia are multicellular euakaryotic heterotrophs that ingest their food

• Animals have the diploid life cycle and usually reproduce sexually

• Muscle and Nerve Tissues characterize animals

Enables animals to

1) search actively for their food and

2) prey on other organisms

• Animals are monophyletic

–Both invertebrates and vertebrates can trace their ancestry to the same ancestor

• Adult vertebrates have a spinal cord (backbone)

• Invertebrates do not have a backbone

Ancestry of Animals• The colonial flagellate hypothesis states that

animals are descended from an ancestor that resembled a hollow spherical colony of flagellated cells

• Colonial flagellate hypothesis implies that radial symmetry preceded bilateral symmetry in the history of animals

Radial Symmetry

• Any longitudinal cut produces two identical halves

Bilateral Symmetry

• Only one longitudinal cut yields two identical halves

Remember the Choanoflagellate?

• The choanoflagellates (collared flagellates) resemble the last unicellular ancestor of living animals, and molecular data illustrates that they are the closest living relatives of animals

• As water moves

through the microvilli,

they engulf bacteria

and debris from the water

Phylogenetic Tree of Animals-Cladogram-

• Based on molecular and morphological data

• The more closely related two organisms are, the more rRNA nucleotide sequences they will have in common

It’s all genetic and chemical

Morphological Data

• Asymmetry

• Radial Symmetry

• Bilateral Symmetry

Asymmetry

• There is no particular body shape (e.g., sponges)

Radial Symmetry• Body parts arranged

around an axis, like spokes of a wheel (e.g., starfish)

– May be sessile –attached to a substrate or less motile

– Enables the animal to reach out in all directions from one center

Bilateral Symmetry• Body plan having a right and left, or

complementary halves

– Only one longitudinal cut down the center produces mirror halves

– Tend to be active

– Have anterior (front) and posterior (back) ends

– Development of head to localize the brain and sensory organs at the anterior end (Cephalization)

Embryonic Development• The first three tissue layers are called germ

layers.

• They give rise to the organs and organ systems of complex animals

Diploblastic

• Animals with two tissue layers (ectoderm and endoderm) as embryos

Triploblastic

• Animals that develop further and have all three tissue layers (ectoderm, mesoderm, and endoderm) as embryos

• Can be further divided into protostomes or deuterostomes

• A coelom forms by the splitting of the mesoderm.

Protostomes exhibit the following events during embryological development

• Spiral cleavage in which the cells divide w/o an ↑ in size

• Fate of cells is fixed – each contributes to development in only one particular way

• blastopore is associated w/ the mouth

• A coelom forms by splitting of the mesoderm, which has arisen from cells near the blastopore

Coelom• A body cavity

• Lies between the gut and body wall and has a lining (the peritoneum) derived from the mesoderm

• Organs that developed w/in this cavity are cushioned and protected

Deuterostomes exhibit the following events during embryological development

• Radial cleavage - the new daughter cells sit atop the previous cells

• Fate of cells is indeterminate

• Blastopore is associated with the anus, mouth appears later

• Coelom forms by the fusion of mesodermal pouches from the primitive gut

Body Cavities - Acoelomate

epidermisgut cavity

no body cavity; region between gut

and body wall packed with organs

Fig. 25-6, p.406

Body Cavities - Pseudocoelomate

epidermis gut cavity

unlined body cavity

(pseudocoel) around gutFig. 25-6, p.406

Body Cavities - Coelom

gut cavity

peritoneumlined body cavity

(coelom)

Fig. 25-6, p.406

Phylum Porifera

The Sponges

• No symmetry

• No tissues – Cells line all body surfaces but don’t form distinct tissues

• No organs

• Aquatic

• Sessile Filter feeders – water enters through tiny pores and exits through one or more large openings

• Collar cells trap food

• Cells engulf bacteria or other organic debris

• Collar cells release some of it to amoeba-like cells that process food and carry out other tasks that benefit the sponge

Water injected with fluorescien dye to watch the filtering process

Sponge Skeleton• All sponges have

fibers made of spongin – a protein that gives the sponge its flexibility

• The endoskeleton contains spicules –tiny needle shaped structures with 1-6 rays

Sponge Predators

• Sea Slugs • Very few b/c of spicules and production of foul smelling and toxic substances

Asexual Reproduction - Budding

• Small buds or pieces break away and grow into new sponges

• Can produce large colonies

• Fragmentation

• Production of Gemmules -encapsulated amoebocytes

Sexual Reproduction• Eggs and sperm are

released into the central cavity

• Zygote develops into a ciliated larva – free living, sexually immature stage of animal development

• Larvae are flagellated, can swim briefly until settle in suitable substrate

central cavity

water out

water in

flagellum microvilli nucleus

glasslike structural elements

amoeboid cell

pore

semifluid matrix

flattened surface cells

Fig. 25-10, p.409

Stepped Art

Fig. 25-9d, p.408

The Jellies

Phylum Ctenophora• The Comb Jellies

• The largest animals propelled by beating cilia

• Range in size from a few cm to 1.5 m in length

• Most of their body is jelly-like material called mesoglea

• Long tentacles covered with sticky filaments –or an entire body covered by sticky mucus –captures prey

Phylum Cnidaria• Cnidarians

• Tubular or bell-shaped

• Can be marine, freshwater or brackish forms

• Gastrovascular cavity digests food, circulates nutrients and serves as supportive hydrostatic skeleton

Phylum Cnidaria• Only animals

that produce nematocysts

• Nerve net

• Hydrostatic skeleton

• Saclike gut

barbed thread inside capsule

capsule’s lid at free surface of epidermal cell

trigger

nematocyst Fig. 25-13, p.410

• Have cnidocytes – specialized cells containing nematocysts

– The nematocyst is a fluid-filled capsule containing a long, spirally coiled hollow thread

– When the trigger of cnidocyte is touched, the nematocyst is discharged

– Some threads merely trap prey or predators; others have spines that penetrate and inject paralyzing toxins

What can the nematocysts do to humans?

Two Main Body Plans

outer epithelium (epidermis)

mesoglea(matrix)

inner epithelium (gastrodermis)

Medusa

Polyp

Fig. 25-12, p.410

• Polyp is vase-shaped

• Mouth is upward

• Sessile

• Produces the medusae

• Medusa is bell-shaped

• Mouth is downward

• Has more mesoglea

• Tentacles found around margin of bell

• Motile

• Produces eggs and sperm

Phylum

Class

Class Anthozoa – Sea Anemones

• Solitary polyps

• Upward turned oral disk contains mouth surrounded by hollow tentacles containing nematocysts

Class Anthozoa - Corals• Resemble sea anemones encased in CaCO3

• Responsible for coral reefs by slow accumulation of limestone

Class Hydrozoa - Hydra• Dominant polyp stage

• Portuguese Man of War is colony of polyps

– Original polyp becomes the

gas-filled float

Nerve Net of Hydra

Class Scyphozoa – True JelliesHelmet Jelly

Class Cubozoa – Box Jellies

The Flatworms

The Simplest Organ Systems

Phylum Platyhelminthes• Bilateral Symmetry

• Moderate cephalization

• Triploblastic

• Possess several distinct organs, organ systems and true muscles

• Possess an incomplete digestive tract – only one opening

• No coelom

Class Turbellaria

• Marine or freshwater and moist terrestrial habitats

Planarians• Carnivorous – eat small animals and carrion

• Breathe by diffusion through skin

– Flattened body places all cells close to water

• Flame cells – excretory apparatus – fxn to maintain water balance

– Ammonia wastes diffuse from cells to water

• Move by means of cilia on ventral surface to glide along film of mucus

• Pharynx – sucks up food and expels wastes

• Reproduce asexuallyby transverse fission

• Mid-body constriction separates the parent into two halves, each of which regenerates the missing portion

• Reproduces sexually by cross-fertilization of hermaphroditic forms

• Muscular contractions produce undulations which allow some to swim

• Eyespots on head detect light

• Pair of lateral auricles detect environment

• Rudimentary brain (ganglia) capable of simple learning

Class Trematoda

• PARASITIC – feed on a host

– Cause weight loss

• BLOOD FLUKES and LIVER FLUKES

• Suckers present for attaching to host internal organs

• Majority are hermaphroditic

Human is the definitive (1°)host – where the mature parasite lives

Snail is the intermediate (2°) host –where the immature stage lives

Life cycle of Schistosoma japonicumInfects 200 million people/year

Class Cestoda• TAPEWORMS

• Parasites of vertebrate digestive systems

• Scolex – head armed with suckers and/or hooks that help maintain position by attaching to intestinal lining

• Proglottids – long ribbon of units located behind scolex

– Filled with reproductive organs

• No digestive system

Life Cycle• Mature proglottids fill with eggs, are released

from posterior end of worm, pass from body with feces

• Eggs are eaten by intermediate host and larva develops, usually in muscle tissue

• Definitive host becomes infected when it eats an intermediate host containing the larvae

*Cook your beef and pork WELL DONE

Life cycle of the beef tapeworm Taenia saginata. Can grow to be 25 meters long.

The Annelids

Segmented worms

Phylum Annelida• True coelom – well-developed and fluid-filled

– serves as hydrostatic skeleton,

– permits development of complex organ systems,

– protects internal structures,

– permits internal organs to fxn separately from the body wall muscles

• Segmented (repeated body parts) – provides for specialization of diff body regions

Class Oligochaeta / Clitellata

• The earthworms - (scavengers)

• Feed on soil and detritus – decaying org matter Aerate the soil – important to farmers

• Few bristles (setae) per segment – used for traction while crawling and burrowing

Complete digestive system divided into parts

Each part specialized for a specific fxn in digestion

Pharynx esophagus crop gizzard intestine

*Excretory system found in each segment

Closed Circulatory System

• Hgb present in blood cells

• Dorsal and ventral longitudinal vessels connected by pairs of vessels

• 5 pairs of hearts circle the esophagus

• gas exchange thru skin

Nervous System

• Pair of cerebral ganglia (rudimentary brain) lie above pharynx

Reproduction• hermaphroditic

• Worms X∆ sperm and store it

• The clitellum secretes a mucous cocoon -slides along worm picking up its eggs and then the stored sperm

• Cocoon slips off worm into soil and protects embryos during development

Movement

• Muscles in each segment contract and elongate

Class Hirundinea• Leeches

• Carnivorous predators &/or

parasites

• Blade-like jaws - slit the host’s skin or secrete enzyme that digests a hole in the skin

• Secretes numbing chem to prevent detection of the incision

• Secrete hirudin

– protein that

prevents blood

clotting

Medicinal Use• Used to treat bruised tissues and for stimulating

circulation of blood to fingers and toes reattached after being severed

Colored SEM of teeth of medicinal leech UP CLOSE AND PERSONAL

Following failed venous reconstruction with vein grafts, leeches were applied and color improved dramatically. Application continued every 4 to 6 hours. 5 days postoperatively, active range of motion was begun. 8 days postoperatively, venous flow was sufficiently restored.

3 weeks postoperatively, a skin graft was performed. 6 weeks postoperatively, following treatment with active and passive movement as well as coban taping, the finger has a TAM of 224 degrees.

Leeches U.S.A. LTD

A 45-year-old, white male patient who suffered a complete avulsion of the upper two-thirds of his right ear. The ear was reattached….

24 hrs after surgery 48 hrs 72 hrs 6 days

2 months after surgery

Leeches U.S.A. LTD

Phylum Nematoda

The Roundworms

The Nematodes• Cylindrical, bilateral

bodies with tapered ends

Caenorhabditis elegans –species used by scientists for experiments

– Small, tiny, transparent, only 959 body cells

– Easy to observe and manipulate

http://tuebingen.mpg.de/en/homepage/detail/the-reason-worms-dont-have-legs-and-are-still-able-to-accomplisch-everything.html

• Many are agricultural pests

• Some are animal parasites:

Ascaris lumbricoides –largest intestinal worm to infect humans

Cause stomach pain, vomiting, fever, wheezing, and abdominal tenderness and worm move through intestines

• Trichinella spiralis –Attach to intestines of pigs and game animals

• Eggs develop and migrate to blood and muscles – CausesTrichinosis

• Wuchereria bancrofticauses elephantiasis

Pinworms caused by

Enterobius vermicularis –live in the human rectum

– Common in young children

Phylum Mollusca

Phylum Mollusca

• Snails, slugs, oysters, clams, octopuses, squids

• Bilateral Symmetry

• Soft bodied,

– most protected by hard CaCO3 shell

– Squids and octopuses have reduced, internalized shell or no shell

Molluscan Body Plan• 3 parts

– Foot for locomotion

–Visceral Mass containing most of the internal organs

–Mantle – heavy fold of tissue that surrounds the visceral mass and secretes the shell

• Radula – present in many molluscs – fxns as a rasping tongue to scape food from surfaces

Class Bivalvia• Clams, oysters, mussels, scallops• Shell divided in 2 halves• May extend foot for mobility or anchorage• Mantle contains gills for gas X∆ and feeding• Most are suspension feeders

– Traps small food particles in mucus coating of gills and use cilia to move particles to mouth

– Water enters incurrent siphon, moves over gills, exits an excurrent siphon

• No radula or distinct head

• Sedentary lives

– Use foot as anchor in sand/mud

– Sessile mussels secrete threads that anchor them to rocks, docks or other hard surfaces

• Scallops propel themselves along the sea floor by flapping their shells

Light sensitive “eyes” of scallop

Class Gastropoda• Snails and Slugs

• Herbivores - use radula to scrape food

• Torsion during embryonic development

– Causes anus to develop above head of adult

• Most have shell (exceptions are slugs and nudibranchs)

• Many have distinct heads with eyes at tips of tentacles

Class Cephalopoda• Squids and octopuses

• Carnivores

– Use beaklike jaws to crush prey

– Mouth is at center of several long tentacles

• Mantle covers visceral mass

• Shell reduced and internal in Squids

• Shell totally absent in Octopuses

• Closed circulatory system – blood is always contained in vessels

• Well developed nervous system – complex brains capable of learning

• Well developed sense organs

Chambered Nautilus

• Only shelled cephalopod alive today

Squids• Swim backward in open

water

Octopuses• Usually move along sea

floor in search for food – instead of swimming in open water

Phylum Echinodermata

• 1°ly bottom dwelling marine animals

• 5-pointed radial symmetry as adults

• Larvae are free-swimming, bilateral, filter-feeders

• Endoskeleton of calcium-rich ossicles

Class Asteroidea

• Sea stars – 5 or more arms extending from a central disc

• Tube feet on undersurface of arms

• Regeneration abilities

Class Holothuroidea

• Sea Cucumbers

Class Echinoidea

• Sea urchins and sand dollars

Class Ophiuroidea

• Brittle stars

• No suckers on tube feet

Class Crinoidea

• Sea Lilies

• Mouths point upward Used in suspension

feeding

Class Concentricycloidea

• Sea daisies

Phylum Arthropoda

The most successful phylum

Arthropods

• Segmented bodies

• Jointed appendages modified for walking, feeding, sensory reception, copulation and defense.

• Covered by cuticle – exoskeleton constructed of layers of chitin and protein

Exoskeleton

• thin and flexible in joints, thick and hard elsewhere

• Provides protection and points of attachment for muscles

• Impermeable to water

• Must be shed for animal to grow (molt) and new one is secreted

Cephalization

Gas X∆

• Feathery gills in aquatic species

• Tracheal system in insects

• Book-lungs in other terrestrial forms (spiders)