Invertebrates

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Invertebrates

• Packet 38

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Introduction I
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Introduction II
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Invertebrates- Animals Without Backbones

• Ninety five percent of all known animals species
  are invertebrates.
• Invertebrates have a worldwide distribution
  ranging from deep sea hydrothermal vents to the
  polar deserts of Antartica.

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Phylum Porifera (The Sponges)

• Major Clades of Coelimates
• Protosomes
• Lophotrochozoa

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Introduction I

• Phylum Porifera (pore bearer) sponges are sessile
  with porous bodies and choanocytes.
• Sessile animals
• They have no nerve or muscle tissue but
  individual cells can react to environmental
  changes.
• There are 9000 species approximately only 100
  live in freshwater, the rest are marine.
• Characterized by flagellate collar
  cellschaoanocytes
• Sponges are suspension feeders and they evolved
  from colonial choanoflagellate.
• Sponges range in size from a few mm to a few
  meters.
• They produce a variety of antibiotics and other
  defensive compounds.

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Introduction III

• Sponges are hermaphrodites and almost all exhibit
  sequential hermophroditism.
• Gametes develop from both choanocytes and
  amoebocytes.
• Eggs remain in the mesophyl while sperms are
  carried out of the sponge by water current.
• Cross fertilization occurs when sperm are drawn
  into others sponges.
• Fertilization occurs in the mesophyl forming
  zygotes that develop into flagella larvae.
• Once settled on a suitable substrate the larvae
  develop into a sessile sponge

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Introduction II

• The sponge body is a sac with tiny openings
  through which water can flow
• Central cavity
• Sponogocoel
• Water enters here
• Open end
• Osculum
• Water exits here
• The cells of the sponge are loosely associated
• They do not form true tissue

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Ingestion of Materials

• Water is drawn through the pores into a central
  cavity called spongocoel.
• Water flows out through a larger opening called
  the osculum.
• Sponges collect food particles with specialized
  food trapping cells called choanocytes (i.e.
  collar cells) which line the interior of the
  spongocoel.
• Choanocytes use their flagella to create a
  current and then use their collars to trap the
  particles which are ingested by phagocytosis.

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Phylum Cnidaria

• Major Clades of Coelimates
• Protosomes
• Lophotrochozoa

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Introduction I

• There are four classes of this phylum
• Hydrozoa
• Cubozoa
• Scyphozoa
• Anthozoa
• Characteristics
• Radial symmetry
• Two tissue layers
• Diploblasic
• Contain cnidocytes
• Cells that contain organelles with stinging
  abilities called nematocysts
• Gastrovascular cavity serves as both the mouth
  and anus.
• The nerve cells are irregular, non-directional
  (nerve nets)
• Connect sensory cells with contractile and gland
  cells

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Introduction II

• True tissue
• There are over 10,000 species
• Occur in two forms
• Polyps
• Sessile
• Medusa
• Floats
• Often canivorous

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Classes I

• Class Hydrozoa
• Hydras, hydroids, and Portuguese man-of-war
• Polyps
• May be solitary or colonial

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Classes II

• Class Scyphozoa
• Jelly fish Sea nettles
• Generally medusa
• Class Cubozoa
• Sea wasps box jellies
• Class Anthozoa
• Polyps
• May be solitary or colonial
• Sea anemones
• Most corals sea fans

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Classes III
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Phylum Ctenophora (The Comb Jellies)

• Major Clades of Coelimates
• Protosomes
• Lophotrochozoa

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Introduction

• Fragile
• Luminescent marine predators
• Display bi-radial symmetry
• Contain eight rows that resemble combs
• Diploblastic
• Have tentacles with adhesive glue cells.

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Protostome Coelomates
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Introduction

• Spiral cleavage
• Determinate cleavage
• Mouth develops from the blastopore

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CoelomateEvolutionary Adaptations

• Allowed the formation of
• The tube-within-a-tube body plan
• The hydrostatic skeleton
• Provides space for the organs and gonads to
  develop
• Helps transport materials
• Protects internal organs

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LophotrochozoaPhylum Nemertea (Ribbon Worms)

• The Protostomes

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Introduction

• Characterized by proboscis
• Muscular tube used in capturing food
• Muscular tube used in defense
• Coelom is reduced
• Consists of the rhynchocoel
• Space surrounding the proboscis
• Have a tube-within-a-tube body plan
• Have complete digestive tract with mouth and anus
• Have a circulatory system

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Phylum Platyhelminthes (The Flatworms)

• Protosomes

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Introduction I

• Commonly referred to as the flatworms because
  their bodies are thin between the dorsal and
  ventral surfaces
• Some are free living or parasites
• Live in marine, freshwater and/or damp
  terrestrial habitats
• Divided into four classes (No details this year
  ?)
• Turbellaria
• Monogenea
• Trematoda
• Cestiodea (Tapeworms)

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Introduction II

• Acoelomate animals
• Bilateral symmetry
• Cephalization
• Connection of the head
• Concentration of nervous tissue at the front end
  of the animal
• Have a ladder-type nervous system
• Sense organs and a simple brain
• Consists of two nerve cords that extend the
  length of the body
• Many are hermaphrodites
• Animal develops both sperm and eggs
• Have protonephridia
• Organs that function in osmoregulation and
  disposal of metabolic wastes

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Phylum Mollusca (The Mollusks)

• Protosomes

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Mollusks
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Introduction I

• Soft-bodied animals usually covered by a shell
• Have a ventral foot for locomotion
• Have a mantle that covers the visceral mass
• Visceral mass
• Concentration of body organs
• Open circulatory system
• Exception Cephalopods (squids, octopods)
• Have paired excretory tubules and metanephridia
• Have rasplike radula
• Functions as a scraper in feeding
• Marine mollusks are free-swimming, ciliated
  trochopore larva

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Introduction II

• Class Polyoplacophora
• Sluggish marine chitons
• Class Gastropoda
• Largest group of mollusks
• Snails slugs
• Bodies undergo torsion
• Visceral mass rotates up to 180º causing the
  animals mantle and head to end up above its
  head
• Class Bivalvia
• Aquatic clams scallops oysters
• 2 part shell, hinged dorsally, encloses the
  bodies of these suspension feeders
• Class Cephalopoda
• Squids Octopods
• Active and predatory swimmers
• Tentacles surround mouth

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Major Classes of Phylum Mollusca
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Phylum Annelida (The Segmented Worms)

• Protosomes

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Introduction I

• 15,000 species that include
• Many aquatic worms
• Others live in freshwater or terrestrial habitats
• Earthworms
• Leeches
• Conspicuous long bodies with segmentation
  internally and externally
• Large compartmentalized coelom serves as a
  hydrostatic skeleton

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Classes Annelida

• Class Polychaeta
• Marine worms
• Have appendages called parapodia
• Used for locomotion and gas exchange
• Bear setae
• Class Oligochaeta
• Earthworms
• Named for their sparse setae which are bristles
  composed of chitin
• Important to farming
• Castings, aeration, soil texture and tilling
• Class Hirudinea
• Leeches
• Characterized by the absence of sate and
  appendages
• Parasitic leeches are equipped with suckers at
  anterior and posterior ends.

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Evolutionary Connection

• Adaptations
• Development of coelom
• Provides a hydrostatic skeleton
• Body space for storage and complex organ
  development
• Protection
• Cushion for internal structures
• Segmentation
• Allows for a high degree of specialization of
  body regions

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Phylum Nematoda (The Roundworms)

• Protosomes
• Lophotrochozoa

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Introduction I

• Non-segmented psuedocoelomates covered with a
  tough cuticle that prevents desiccation
• Over 90,000 species
• Bilateral symmetry
• Triploblastic
• Complete digestive system
• Zygotes are able to survive harsh conditions
• Parasitic Nematodes
• Ascaris, hookworms, trichina worms, pinworms
• Agricultural pests
• Attack plant roots.

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Phylum Arthropoda (Jointed Feet)

• Protosomes
• Lophotrochozoa

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Introduction I

• Segmented animals
• Have paired, jointed appendages
• Specialized for walking, feeding, sensory
  reception, sex and defense
• Exoskeleton of protein and chitin
• Thick spots are armor
• Molting is necessary for arthropods to grow
• Evolutionary Connection
• Moved out of water following plants and the fungi

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Introduction II

• Open circulatory system with a dorsal hear that
  pumps hemolymph.
• Evolution Connection
• System evolved convergently in the mollusks and
  arthropods
• Aquatic forms have gills
• Terrestrial forms have either tracheae or book
  lungs

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Introduction III

• Trilobites
• Extinct maring arthropods covered by a hard
  segmented shell
• No connection to the theory of evolution right
  nowRB

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Subphylum Myriapoda

• Have unbranced appendages
• Single pair of antennae
• Class Chilopoda
• Centipedes
• Class Diplopoda
• Millipedes

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Subphylum Chelicerata

• Body consists of a cephalothorax and abdomen
• No antennae or mandibles
• There are six pairs of jointed appendages
• Appendages are for manipulation of food,
  locomotion, defense or copulation.
• Four pairs serve as legs
• First pair
• Chelicerae
• 2nd Pair
• Pedipalps

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Subphylum Crustacea

• Lobsters, crabs, shrimp, pillbugs and barnacles
• Body consists of a cephalothorax and abdomen
• Typically have five pairs of walking legs
• Have two pairs of antennae
• Sense taste and touch
• Third appendages are mandibles
• Used for chewing
• Two pairs of maxillae, posterior to the mandibles
• Manipulate and hold food

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Subphylum Hexapoda

• Includes class Insecta
• Considered to be an articulated, tracheated
  hexapod
• Body consist of head, thoarax and abdomen
• Have tracheae for gas exchange
• Have Malpighian tubules for excretion
• Have unbranched appendages
• Single pair of antennae

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Hexapods II

• Live in almost every terrestrial habitat and in
  freshwater
• Rarely found in a marine environment
• Success is associated with the ability to fly
• Can escape predators
• Find food and mates
• Disperse to new habitats faster
• May also help, from an evolutionary
  perspective, explain the diversity of insects and
  angiosperms

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Hexapods III

• Body is divided into three parts
• Head
• Thorax
• Abdomen
• Antennae are present
• Mouth parts are modified for chewing, sucking and
  lapping
• Have three pairs of legs
• Internal anatomy has complex organ systems.
• Waste removed from hemolymph via malphigian
  tubules
• Tracheal system lined with chitin carries O2
• Nervous system consists of ventral nerve cords
  with several segmental ganglia
• Metamorphosis is central to insect development
• Most insects only mate once
• Females lay eggs on a food source for next
  generation

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Insect Diversity
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Insect Diversity II
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Evolution Connection

• Wings
• First evolved as extensions of the cuticle that
  helped the insect absorb heat and were later
  modified for flight
• Not true appendages
• May have served as gills in aquatic insects
• Wings functioned for swimming
• Allowed animals to glide from the vegetation to
  the ground

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Deuterostomia (Second Mouth)the Deuterostomes
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Introduction I

• Radial cleavage
• Indeterminate cleavage
• Anus develops from blastopore
• Two phyla
• Enchinodermata
• Chordata

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Phylum Enchindermata (Spiny Skin)

• Deuterosomes

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Introduction I

• Over 6000 marine animals with spiny skin, water
  vascular system (network of canals that branch
  off into tube feet), tube feet and endoskeleton.
• Sessile or slow moving animals
• Larvae have bilateral symmetry
• Most adults exhibit penta-radial symmetry
  (secondary radial symmetry)
• Body parts radiate from the center as five spokes.

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The Classes of Enchindernata

• Class Crinoidea
• Sea lilies feather stars
• Attach themselves to their substrate by a stalk
• Crawl using long flexible arms
• Class Asteroidea
• Sea stars
• Central disk with five or more arms
• Use tube feet for locomotion
• Attach themselves tightly to a substrate or creep
  slowly along the sea floor
• Can regenerate lost body parts

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Classes of Enchinodermata II

• Class Ophiuroidea
• Brittle stars
• Move by lashing their arms
• Some species are predators while others are
  scavengers
• Class Echinoidea
• Sea urchins and sand dollars
• Lack arms
• Have solid shell and are covered with spines
• 5 rows of tube feet, and muscles that pivot long
  spines, used for locomotion

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Classes of Enchinodermata III

• Class Holothuroidea
• Sea cucumbers
• Animals with elongated flexible bodies
• Mouth surrounded by circle of five rows of tube
  feet that serve as tentacles.
• Class Concentriclyloidea
• Newly discovered
• Armless bodies are disk shaped with five-fold
  symmetry
• Live on waterlogged wood in deep seas.

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Phylum Chordata

• Invertebrates
• Deuterosomes

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Subphylum Urochordata

• Tunicates
• Suspension feeding, marine animals with tunics
• Larvae have typical chordate characteristics
• Free swimming
• Adults of most groups are sessile suspension
  feeders

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Subphylum Cephalochordata

• Lancelets
• Small segmented, fishlike animals that exhibit
  chordate characteristics

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Evolution Connection

• Tunicates were probably the first chordates to
  evolve.
• Subphyla Cephalochordata and Vertebrata may be
  sister taxa
• Groups that diverged from a recent common ancestor

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