Download Learning Outcome G4 Phylum Mollusca, Arthropoda

Learning
Outcome G4
Phylum Mollusca,
Echinodermata &
Arthropoda
Learning Outcome G4
 Analyse
the increasing complexity of the Phylum
Mollusca, the Phylum Echinodermata, and the
Phylum Arthropoda
Students who have fully met this learning outcome will
be able to:
Examine members of the Phylum Mollusca and describe
their unifying characteristics
 Describe how molluscs carry out their life functions
 Examine members of the Phylum Echinodermata and
describe their unifying characteristics
 Describe how echinoderms carry out their life functions
 Examine members of the Phylum Arthropoda and
describe their unifying characteristics
 Describe how arthropods carry out their life functions
 Compare how molluscs, echinoderms, and arthropods
have evolved to adapt to different niches
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Animalia
 Phylum Mollusca
 Kingdom
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Class
Class
Class
Class
Polyplacophora
Cephalopoda
Gastropoda
Bivalvia
 An
important food source to both humans and
other animals
 Great variety between species
 There are 7 classes of molluscs; we are going
to examine the 4 major classes.
 All molluscs are protostomes, which means
that during embryological development the
first opening to develop is the anus.
 Have a free-swimming ciliated larva, which
uses a band of muscle to bring food towards
the mouth
 Largest invertebrate phylum
 Great
variation within this phylum, although they
have inherited a common body plan form their
ancestors.
1. Foot
 Muscular and function in locomotion
 In cephalopods the head has become a modified head and
tentacles
2. Mantle
 A folded tissue that folds down around some or all of the
body
3. Shell
 Made up of calcium carbonate
 Can be internal or external
4. Gills
◦ Specialized respiratory structure that arises from
outgrowths of the mantle wall
5. Visceral mass
◦ Internal organs consisting of the gut, kidney, heart
and reproductive organs.
6. Radula
◦ a unique rasping “tongue-like” organ with hard
teeth that are used to scrape up food
 Generally
free-living and inhabit all known
aquatic and terrestrial ecosystems.
 They are a food source for fish, starfish, birds,
humans and a variety of other mammals.
 Molluscs live as predators, herbivores, detritus
feeders, parasites and form other symbiotic
relationships with other organisms.
 Bivalves, such as mussels perform an important
ecological role of recycling huge amounts of
sediment back into the environment.
 Also
their empty shells often provide homes
for other invertebrates.
 Molluscs play a critical role in the food chain
 Drastically impacted by oil spills and
pollution because most molluscs are filter
feeders and these pollutants smother the
gills or enter the digestive tract causing
inflammation and a variety of digestive
problems.
 Oil can also fill the mantle causing tumors
and irritating muscle.
 Marine
animals that eat algae or small
animals growing on rocks near the shore or
in the deep ocean
 Most of their bottom surface is taken up by a
large muscular foot.
 The upper surface consists of 8 overlapping
shell valves, which provide protection.
 Make
up the biggest group of molluscs
 Generally have large coiled shell, and this
group includes snails and whelks.
 Their foot has a hard plate which fills the
opening of the shell when the foot is
withdrawn and protects the soft body.
 Includes
clams, mussels, oysters and scallops
 Important food supply for humans
 The body of bivalves is held between two
protective valves connected by a ligament that
holds them apart along one edge.
 Two strong muscles pull the valves together.
 Bivalves do not move due to their large, heavy
shells.
 Complex system for filter feeding; that
involves the use of gills
 These
gills are large and covered with cilia;
the water circulates between the valves and
carries many small particles of food into the
mollusc.
 This water passes across the gills, and the
food particles are filtered out and embedded
in the mucus.
 Strings of mucus and food are then moved
toward the mouth by the cilia.
 Digestion occurs in the stomach and
undigested material exits via the anus
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Most complex mollusks and includes squids,
nautiluses, and octopods.
Only the nautiluses have a complex external shell
Octopods have 8 equal appendages all equipped
with suckers and tentacles.
Squids have 10 appendages, two of which the
tentacles are longer and have tentacles on
expanded tips.
The tentacles trap and grasp prey, which are
drawn towards the mouth.
Great predators due to efficient respiratory and
circulatory systems
Have a muscular mantle which is well designed
for water flow.
The squid’s body is stream-lined and maintains its
shape, with the aid of a pen.
 An octopod has no shell and the body is incredibly
flexible.
 A pen is the internal remnants of a shell.
 Both the squid and octopus use water jets that are
powered by contractions of the mantle for fast
swimming.
 Nautiloids swim with the aid of their numerous arms
 Both squids and octopods have digestion occur in
their stomach, which is aided by enzymes secreted by
the digestive glands.
 Nutrients are absorbed in the stomach and some
additional absorption occurs in the starting of the
small, coiled intestine.
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 Undigested
material is excreted into the mantle
cavity
 The circulatory system of a cephalopod is closed
and capable of maintaining a high flow rate and
blood pressure.
 The large, extensively folded gills have a separate
“gill heart” to pump blood back to the “systemic
heart” which pumps it out of the body.
 The cephalopods nervous system is also highly
developed with a large brain that contains several
ganglia.
 In the octopus the brain has 10 lobes, and the
animals are good learners.
 Octopods have been trained to solve simple
problems and have the ability to remember
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Squids and octopods have image forming eyes, which
are very close to the eyes of vertebrates but have a
different embryonic origin (convergent evolution).
Complex eyes are crucial to the survival of these
predatory animals which depend of vision to find their
prey.
Cephalopods are dieoccius and fertilization is internal.
In squid the fertilized eggs are deposited in a
gelatinous capsule and both the male and female die
after mating.
In octopods, the fertilized eggs are attached to the roof
of the cave or crevice in which the female live and she
guards and cleans them for several months until they
hatch.
During this time the female eats little or nothing
Animalia
 Phylum Echinodermata
 Kingdom
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Class
Class
Class
Class
Class
Asteroidea
Ophiroidea
Echinoidea
Holothuroidea
Crinoidea
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Generally large and live on the bottom of
large bodies of water
Usually marine
Have spiny skin, which is a key characteristic
of this group
Have radial symmetry and many have 5
similar body segments around a central core.
The larval sate is bilaterally symmetrical
The development of echinoderm eggs is
similar to the development of chordate eggs.
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Deutrostomes
Have a endoskeleton that is made up of
calcified plates covered by an epidermis
These plates may be a single plate
Example – starfish have a single flexible plate
or a fused solid shell has in sea urchins.
Has a complicated water vascular system.
The coelom is separated into two parts:
◦ the perivisceral coelom which plays a role in
circulation and excretion
◦ The hydrocoel which function in locomotion and
feeding
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Bottom dwellers of all ocean
May live in large numbers
Recycle nutrients in ecosystems by feeding on
dead and decaying materials
Starfish are important marine carnivores that
control the population of other animals
However large population ofechinoderms can be
troublesome, they can wipe out whole populations
of molluscs.
They can also cause severe damage to coral reefs
Sea urchins are essential to the control and
distribution of algae
Non parasitic but are home to many parasites.
 1800
species
 Have tube feet which help in movement and
feeding.
 Tube feet are part of the water vascular system
 At the end of each arm, starfish have a
microscopic eyes that can only see light and dark.
 The mouth is located on the underside of the
stomach
 Able to regenerate
 Feed on mussels and other molluscs.
 Wide diversity in body plan and feeding
 Pentaradial symmetry
 Bodies made of calcium carbonate which form
ossicles.
 Closely
related to sea stars
 5 long slender whip-like arms
 Arms can be up to 60 cm
 Spiny
globular animals
 Move via tube feet
 Vary in color
 Food source for sea otters and seals
 Sea urchin eggs are a human delicacy
 Elongated
both with leathery skin
 Sends hormones through the water to attract a
mate
 Body contains collagen, so the body can
looses and tighten at will which allows this
organism to move through small spaces.
 Can expose it’s intestines to predators when
feeling threatened, this is known as
eviceration.
 Form large herds and can form symbiotic
relationships
 Live
in shallow and deep water
 Mouth is on the surface surrounded by
feeding arms
 Generally attached to substrate but can be
unattached.
Animalia
 Phylum Arthropoda
 Kingdom
 Divided into 4 subphyla
1. Trilobitomophas
 Trilobites are currently extinct but are
extremely important part of the fossil record
2. Myriapods
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Include centipedes and millipedes
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Many legs and strongly segmented
3. Chelicerata – includes spiders
4. Crustacea – crustaceans such as crayfish
5. Uniramia – insects
 Most
numerous and diverse group of animals
 Live in all habitats including arctic ice,
deserts, the deep ocean, the mountains,
prairie lands and the skies.
 Their ability to live in such a diverse range of
habitat and to adapt to changing
environments, ensures that this phylum will
be around for a long time.
 Live
closely with humans in symbiotic
relationships
 Example – tiny mites living in hair follicles
 May
eat and destroy plant/crops
 Primary pollinator of plants
 Utilize many food sources, as well as are the
source of food for many different animals
 Many parasitic forms control the number of
other arthropods.
 Evolved
from a segmented ancestor, who
either lost their segments or the segments
have become fused together.
 Have a well developed head with jointed
appendages that may be used for locomotion
or adapted for prey manipulation.
 Posterior to the head is a thorax, which may
bear walking appendages.
 The head and thorax are fused together to
form a cephalothorax.
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Skeletons may be either inside or outside the body
An exoskeleton is present in crustaceans such as crabs,
lobsters, spiders and insects
The exoskeleton is composed of chitin, which is a non-living
material that may be thick and heavy.
An exoskeleton is a strong protective covering on the exterior
of the body
The exoskeleton protects the arthropod but is very heavy
Arthropods shed their exoskeleton as they grow become it
does not grow with them.
This process is known as molting.
In molting the inner layer of the cuticle dissolves and is
recycled to make a new larger cuticle beneath the old one.
This new cuticle is initially flexible and has many
folds
 The animals take in water or air causing the
exoskeleton to swell up.
 This pressure created by the swelling splits the
remaining old cuticle and expands the new cuticle.
 Once it has stretched, the new cuticle begins to
harden.
 An arthropod is very vulnerable during molting, as
it lacks the protection of its cuticle and may not
have enough ridigity in its body to escape
predators.
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Due to having an exoskeleton arthropods are not quick
movers.
Once the cuticle hardens the excess water or air that has
caused the body to swell is expelled.
Endoskeletons are present in chordates such as fish, frogs,
reptiles and mammals.
The skeletons of some kinds of fish are composed of flexible
cartilage while other fish and most chordates have
exoskeletons composed mainly of living bone.
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Many terrestrial arthropods have specialized excretory
organs called malphigian tubules.
This organ lies in blood-filled spaces and secretes fluid
into the hind gut where reabsorption of fluids and
dissolved materials occurs.
The nervous system of primitive arthropods resemble that
of annelids.
More complex forms especially those with complex social
behaviors show an increase in brain size and complexity
and an increase in sensory abilities.
The eyes of arthropods may be simple and consist of only
a few photoreceptors or they may have thousands of
receptors and be capable of forming a crude image.
Have attenae
Have primitive ears composed of a flexible membrane
stretched across an opening in the cuticle.
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The circulatory system of arthropods is open, with blood
bathing tissues in spaces called sinuses.
This system of open spaces replaces the coelom as the major
body cavity.
This is known as a homocoel.
The coelom exists but is reduced
A heart and arteries deliver blood to the body and sinuses.
The blood may be oxygenated by gills in aquatic forms or by
book lungs in terrestrial forms.
The blood serves a secondary role in delivering oxygen to the
cells and removing carbon dioxide.
This groups has a tracheal system, consisting of open tubes
connecting to the outside by spiracles, which are openings in
the cuticle.
The branched and cuticle-lined tracheal system reaches
through the body and connects directly to the atmosphere.
Most arthropods have internal fertilization and
separate sexes.
 The eggs of many species hatch directly into a form
which resembles the adult with no larval stage.
 In other the first free living stage after the egg is
similar to the adult but different in some way.
 A series of molts is required before the adult form is
attained.
 Many arthropods have a larval stage the resembles
the adult only superficially or not at all this is known
as metamorphosis.
 Pheromones are hormones that attract the opposite
sex
 Parthenogenesis is a type of asexual reproduction
where unfertilized eggs develop into offspring.
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