Download Invertebrate Diversity

Invertebrates
What is an Invertebrate?
• An invertebrate is a member of a
phylum of the kingdom Animalia that
does not have a backbone.
• There is a great deal of diversity within
this phylum. And as far as animals go,
the invertebrates far out-number the
vertebrates on the Earth.
• There are a number of characteristics
that are used to help identify and
classify the various invertebrates. We
will look at these characteristics
before we begin to examine each of
the groups.
Characteristics - Symmetry
• Body symmetry can be defined as quality
of a body shape that can be cut into equal
pieces that match.
• There are three types of body symmetry –
radial, bilateral and asymmetrical.
• Bilateral – Able to be cut down the middle
into two equal halves.
• Radial – Able to be cut into many equal
pieces around a central axis. (Like a pie –
pieces are cut from the centre.)
• Asymmetrical – No clearly defined body
shape so it can’t be cut into equal pieces.
Body Symmetry
• Radial Symmetry
• Bilateral
Symmetry
• Asymmetrical
Characteristics – Cell Organization
• The cells of an organism may exist
independently of each other or they
may act together to form various
tissues and organs.
• The arrangement of the layers of the
body is another trait that can be used
to classify organisms. The body may be
arranged in a way that classes the
organism as an acoelomate,
pseudocoelomate or a coelomate.
Body Types
Porifera
• The members of the phylum porifera are the
sponges.
• They are aquatic and mainly marine
(saltwater).
• They are sessile and feed by moving water
through themselves using cilia and filtering
out food particles.
• Oscula are openings in the sponges that
expel water once it has been filtered.
• Sponges reproduce both sexually and
asexually.
– Sexually – they’re hermaphrodites that produce
both sperm and eggs. Sperm are released and swim
to the eggs of another individual.
– Asexually – they may reproduce by budding.
Porifera
Cnidaria
• Cnidarians include jelly fish, sea anemones and
corals.
• They show radial symmetry.
• They have specialized tissue – not seen in
poriferans (sponges).
• They are aquatic with most species being marine.
• They may live in colonies or live alone.
• All cnidarians have nematocysts that are used to
sting other organisms. These are found on the
ends of the tentacles.
• Gastrovascular cavity – sac with only one opening
– serves in digestion, circulation and/or gas
exchange.
• Life cycles often include both a sessile polyp stage
and a free-swimming medusa stage. Polyps use
asexual budding to reproduce while medusae use
gametes to reproduce sexually.
Cnidaria
Platyhelminthes
• These are the flatworms – planarians, flukes
and cestodes (tapeworms).
• They show bilateral symmetry in a very
compressed, flattened body.
• They also have a gastrovascular cavity.
• Planarians are often freshwater organisms
but may live in very humid, shaded areas.
They are active hunters for their food.
• Flukes and cestodes are parasites that have
highly developed mouth parts for attaching to
and feeding from their hosts. A thick cuticle
also helps them survive the digestive tract of
their host.
• Flatworms reproduce sexually as many of
them are hermaphrodites as adults.
Platyhelminthes
Nematoda
• Nematodes are the round worms.
• They are scavengers in aquatic
environments and some are parasitic –
living in plants and animals.
• They are pseudocoelomates and have
a tube system for digestion. (Food in
one end and waste out the other.)
• They have neither a circulatory system
nor do they have a respiratory system.
• Most nematodes are microscopic but
some species can grow up to one
metre in length.
Nematoda
Annelida
• The annelids are segmented worms. They
have an elongated body with clearly defined
segments.
• The are coelomates with the capacity to
grow and move that far exceeds any other
worm phylum.
• They have a circulatory system – other
worms do not.
• The worms may be hermaphrodites – like the
earthworm – or have separate sexes like the
sand worm.
• Some annelids are parasites such as leeches.
• All of the annelids require a moist
environment in which to live. Some may live
in moist soil while other live freely in the
water.
Annelida
Mollusca
• Members of the phylum mollusca are
invertebrates with a shell.
• The body of a mollusc has three basic
parts – the foot, mantle and visceral
mass.
• The foot is used for motion, the mantle
secretes the shell and the visceral
mass contains the internal organs.
• There are three main categories:
– Bivalva – Shell fish.
– Gastropoda – Snails.
– Cephalopoda – Octopi and squids.
More Mollusca
Bivalva
• Clams, oysters, mussels and scallops – all
sessile as adults.
• Two part shell that has a hinge.
• An aquatic habitat is a must as they are filter
feeders.
Gastropoda
• Snails, slugs and whelks all represent the
gastropods.
• Most gastropods use their foot to move slowly
across surfaces.
• Gastropods use a radula – stretch of tissue lined
with spines – to scrape algae off of surfaces for
food.
• Some of the gastropods have a simple lung to fit
their terrestrial lifestyle while the aquatic
gastropods have gills.
Even More Mollusca
Cephalopods
• Cephalopods include octopi and squids.
The shell of these molluscs are internal
and have been reduced to an internal rod.
• They are marine predators that hunt for
their food. They have tentacles and
suction cups to capture and kill their prey.
• They have complex eyes and a highly
developed senses around their head –
“cephalo” means head. (Pod is foot.)
• The have the ability to use their siphons
to propel themselves by filling it with
water and quickly expelling it.
Mollusca Pics
Echinodermata
• Echinodermata literally means “spiny
skin”. This phylum includes the sea
urchin and the starfish.
• All of the echinoderms are marine
species.
• They have an internal skeleton that
has spiny projections that protrude
through the skin.
• Calcium plates make the outer surface
very hard to the touch – along with the
spines!
• They are not cephalized and show
radial symmetry as adults.
Echinodermata
Arthropoda
• The arthropods are the dominant
phylum of animals on the planet if you
consider the number of species within
the group.
• They have segmented bodies but the
segments have become highly
specialized (unlike the worms).
• Arthropods have an exoskeleton,
jointed legs and a hemocoel (blood
cavity). The exoskeleton is made from
a polysaccharide called chitin.
What the Shell?!?!
Having an exoskeleton provided several
challenges for the arthropods to overcome.
• Movement – shell was heavy and bulky – jointed legs
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and associated muscles evolved.
Breathing – living on the land was tough for both
gills and gas exchange through a thick shell – tubes
with holes leading through the exoskeleton called
tracheae developed to supply oxygen to body cells.
Growth – Exoskeleton is a rigid outer layer that
impedes growth – moulting developed in which the
old exoskeleton is shed and is replaced by a new,
larger one.
The hemocoel is an important as it is a modified
method of delivering blood to the internal organs via
an open circulatory system.
Specialized sensory receptors such as eyes and
antennae are prevalent in the arthropods. This goes
along with a high degree of cephalization.
Arthropoda Classes
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Arachnida (2)
Crustacea (2)
Insecta (3)
Chilopoda (2)
Diplopoda (2)
That’s All I Got…