INVERTEBRATES

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INVERTEBRATES

• Diverse life on Earth

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Evolutionary Stages in Animals
STAGE MILESTONE
1 Multicellularity
2 Tissues
3 Bilateral symmetry
4 Body cavity
5 Coelom
6 Segmentation
7 Jointed appendages
8 Deuterstomes
9 Notochord
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General Invert Characteristics

• All invertebrates share the following
• characteristics
• Heterotrophic
• Most animals have to move from place to place to
  search for food
• All animals are multicellular.
• Invertebrates have cells that lack cell walls

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General Invert Characteristics

• Invert cells are organized into tissues
• They have specialized muscle cells that allow for
  complex movements
• Reproduce sexually
• 99 of all animals on Earth are invertebrates (
  have no backbone)

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General Invert Characteristics

• Body organization
• CELLS ? TISSUES ? ORGANS? ORGAN SYSTEMS

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SYMMETRY

• All animals, including invertebrates display one
  of three types of symmetry in their body plans
• ASYMMETRY
• BILATERAL SYMMETRY
• RADIAL SYMMETRY

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ASYMMETRY

• Asymmetrical animals do not display any
  particular form of symmetry
• Example sponges

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BILATERAL SYMMETRY

• Bilaterally symmetrical animals, if cut down the
  middle, would have two halves that mirror each
  other.
• Example dragonfly

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RADIAL SYMMETRY

• Animals that display radial symmetry have a
  central point from which the rest of the body
  radiates out of.
• Example sea star

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Development of Organ Systems

• The organ systems of all animals develop from 1
  of 3 embyonic tissue layers

Layer Organ Systems Formed
ECTODERM Skin, body coverings nervous system
MESODERM Skeleton, muscles circulatory system
ENDODERM Digestive system
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SPONGES Phylum Porifera
Barrel sponge
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SPONGES Phylum Porifera

• Sponges are the simplest of all animals
• Most live in saltwater

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SPONGES Phylum Porifera

• Asymmetrical
• Have cell recognition ability can recognize
  other cells their own without having a nervous
  system
• Sessile (do not move)

Sponge
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SPONGES Phylum Porifera

• Sponges are filter-feeders
• They suck water in through pores using cells
  called choanocytes with flagella and filter out
  food to eat

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CNIDARIANS Phylum Cnidaria
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CNIDARIANS Phylum Cnidaria

• The cnidarians were the first eumetazoans or true
  animals
• First to develop 3 distinct cell layers as
  embryos
• Includes animals like jellyfish, hydras, sea
  anemones corals

Sea anemone
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CNIDARIANS Phylum Cnidaria

• Radially symmetric
• Are carnivores that capture prey using tentacles
  located around their mouths
• Tentacles containing stinging cells (cnidocytes)
  used to spear prey

Jellyfish
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CNIDARIANS Phylum Cnidaria

• Cnidarians digest food externally, like fungi
• Cnidarian body types come in two forms
• Polyp (Ex. hydra)
• Medusa (Ex. jellyfish)

Medusa body form
Polyp body form
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Bilateral Symmetry Begins
One important evolutionary advancement shared by
more advanced animals is bilateral symmetry. In
bilaterally symmetric animals an imaginary line
drawn down the middle would produce mirror images
on each side of the organism.
Dorsal
Posterior
Anterior
Ventral
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FLATWORMS Phylum Platyhelminthes
Marine flatworm
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FLATWORMS Phylum Platyhelminthes

• Bilaterally symmetric
• This is the first phylum to display
  cephalization, or the evolution of a definite
  head that contains organs with which they monitor
  their environments
• Flatworms are the simplest animals that have
  organs.

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FLATWORMS Phylum Platyhelminthes

• Flatworms have an eyespot to detect light
• They are acoelomates, which means they do not
  have any body cavities except a gut.
• Most species are parasitic.

Fluke
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PHYLUM NEMATODA Round worms
Ascaris
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PHYLUM NEMATODA Round worms

• Display bilateral symmetry
• Are pseudocoelomates, which means they have an
  internal body cavity
• Presence of the body cavity is important because
  it allows for the following to be present -
  circulation
• - movement
• - complex organ functions

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PHYLUM NEMATODA Round worms

• Have a one-way gut through which food passes in
  the mouth and out the anus
• Most are free-living in soil, but many are
  parasitic

Hookworm
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PHYLUM NEMATODA Round worms

• The blister below is caused by a parasitic worm
• To the right is a guinea worm exiting a persons
  ankle.

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PHYLUM NEMATODA Round worms

• Nematodes have muscles that extend the length of
  their bodies which enable their wiggling movement

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-END-Invertebrate Notes - Part One

• Study for QUIZ over
• Invertebrate Notes (Part 1) at the beginning of
  next class!!

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PHYLUM MOLLUSCA Mollusks
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PHYLUM MOLLUSCA Mollusks

• Coelomates
• Display bilateral symmetry
• Mollusks are the only advanced coelomate that do
  not have a segmented body

Snail
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PHYLUM MOLLUSCA Mollusks

• Mollusks have body plans with 3 distinct regions
  
• 1. Visceral mass
• 2. Mantle
• 3. Foot
• They use gills, skin or simple lungs to breathe.

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PHYLUM MOLLUSCA Mollusks

• There are 3 main classes in Phylum Mollusca to
  include
• Gastropods
• Bivalves
• Cephalopods

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PHYLUM MOLLUSCA Mollusks

• Gastropods include snails and slugs
• They have a muscular foot, a radula for feeding
  and a shell (except slugs)

Banana slug
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PHYLUM MOLLUSCA Mollusks

• Bivalves include organisms like clams, oysters
  and scallops
• They have a two- part shell held together by a
  hinge
• Filter-feeders

Scallop
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PHYLUM MOLLUSCA Mollusks

• Bivalve body structure

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PHYLUM MOLLUSCA Mollusks

• Cephalopods are organisms like octopuses squids
• Their name means head foot because most of
  their body consists of their heads

Octopus
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PHYLUM MOLLUSCA Mollusks

• Cephalopods are considered the most intelligent
  animals of all invertebrates
• They have a well-developed brain and a complex
  nervous system

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PHYLUM ANNELIDA Segmented Worms
Polychaete
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PHYLUM ANNELIDA Segmented Worms

• This phylum includes organisms such as
  earthworms, polychaetes and leeches.
• Bilaterally symmetric

Leech
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PHYLUM ANNELIDA Segmented Worms

• Are coelomates, which means they have a true body
  cavity which allows for specialized tissues to
  form.
• Have repeated, specialized internal external
  body segments

Earthworm
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PHYLUM ANNELIDA Segmented Worms

• Have an advanced circulatory system
• Annelids breathe through their skin, thus they
  must live in moist environments
• Earthworms are important soil dwellers as they
  function to aerate soil.

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PHYLUM ARTHROPODA Arthropods
Scorpion
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PHYLUM ARTHROPODA Arthropods

• This is an extremely diverse phylum
• Includes insects, crustaceans and arachnids
• These are the first animals with jointed
  appendages
• Arthropod jointed foot

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PHYLUM ARTHROPODA Arthropods

• Class Insecta includes all insects like bees,
  butterflies, ants, centipedes roaches to name
  a few.
• 6 legs
• This the most successful group of all the animals

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PHYLUM ARTHROPODA Arthropods

• Class Crustacea are mostly marine animals
• This class includes such animals as crabs,
  lobsters, shrimp, crawfish and horseshoe crabs

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PHYLUM ARTHROPODA Arthropods

• Class Arachnida includes such animals as spiders,
  mites, scorpions and pseudo- scorpions
• 8 legs

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PHYLUM ARTHROPODA Arthropods

• Arthropods use spiracles to breathe spiracles
  are openings to tubes that transmit oxygen to the
  arthropod
• They have compound eyes, which are made up of a
  bunch of individual visual units that come
  together to form an image.
• Arthropods comprise more than ½ of all life on
  Earth (insects mostly)

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PHYLUM ARTHROPODA Arthropods

• Arthropods have a hard exoskeleton made of chitin
  that serves to protect them.
• For many their exoskeleton must molt in order
  for them to grow

Cockroach
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PHYLUM ECHINODERMATAEchinoderms
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PHYLUM ECHINODERMATAEchinoderms

• This phylum includes such organisms as sea stars,
  brittle stars, sea cucumbers, sea urchins and
  sand dollars.
• They display radial symmetry.

Sea cucumber
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PHYLUM ECHINODERMATAEchinoderms

• Echinodermata refers to the spiny skin that
  most organisms of this phylum have.
• Most echinoderms have an endoskeleton made of
  ossicles.

Sea star
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PHYLUM ECHINODERMATAEchinoderms

• Echinoderms are unique because they have a water
  vascular system, which is essentially a series of
  canals tube feet that they use for movement.

Sea urchin
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PHYLUM ECHINODERMATAEchinoderms

• Echinoderms do not have a head or brain, but they
  do have a nervous system.
• Their nervous system consists of a ring of nerves
  that branch into each arm.

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THE END

• Study for Invertebrate Note Quiz (part 2) at the
  beginning of next class!!