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)