Animalia

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Animalia

• Animals are multicellular, heterotrophic
  eukaryotes.
• Except for sponges all animals have tissues which
  are specialized collections of cells separated
  from other tissues by membranes.
• Tissues are arranged together to produce organs
  and organs are organized into organ systems (e.g.
  digestive system).

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Animalia

• Most animals are bilaterally symmetrical and form
  a large clade called the Bilateria.
• Bilateral animals have a left and right side, top
  and bottom, as well as front and rear ends.
• A smaller number are radially symmetrical (e.g.
  jellyfish).

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Divisions of the Bilateria

• We belong to a division of the Bilateria called
  the deuterostomes (a group defined by how the
  embryo develops).
• It includes us and all chordates as well as the
  echinoderms e.g. starfish (which have secondarily
  evolved radial symmetry).

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Porifera

• The phylum Porifera (the sponges) includes about
  5000 species almost all of which are marine
  (there are about 150 freshwater species).
• Sponges occur worldwide at all latitudes from the
  intertidal zone to the deep sea.
• Range in size from a few millimeters to 2 meters
  across.
• Porifera means pore-bearing and refers to the
  numerous pores and channels that permeate a
  sponges body.

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Yellow tube sponge
Barrel sponge
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Porifera

• Sponges are the simplest multi-cellular
  organisms, but they lack the germ layers of more
  complex metazoans.
• They have a cellular level of organization
  lacking true tissues and organs.
• Body is a mass of cells imbedded in a gelatinous
  matrix which is supported by a framework of
  spicules.

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Glass sponge spicules
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Porifera feeding

• Sponges are sessile and depend on water movement
  to bring in food and oxygen and remove wastes.
• Sponges generate their own flow of water having a
  unique water current system.

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Porifera feeding

• Water enters through many small pores called
  ostia and exits through fewer, larger oscula.

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Oscula
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Porifera feeding

• Openings are connected by a series of canals,
  which are lined by choanocytes (flagellated
  collar cells) that maintain the current and
  filter out food particles.

Choanocytes
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Cnidaria
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Cnidaria

• The phylum Cnidaria includes over 9,000 species
  of aquatic, radially symmetrical animals which
  have specialized stinging organelles called
  nematocysts.
• They include the jellyfish, box jellyfish, sea
  anemones, fire corals, sea pens and hard corals.

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Cnidaria

• Cnidarians are the simplest animals equipped with
  nerve cells which are arranged into a nerve net,
  but there is no central nervous system.

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Cnidaria digestion

• Cnidarians have an internal body cavity, the
  gastrovascular cavity, but no one-way gut. Food
  enters and waste exits through the same opening,
  the oral cavity.
• Digestion takes place extracellularly within the
  gastrovascular cavity.

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Body forms

• Cnidaria have one of two basic body forms
• Polyp
• Medusa
• In some groups one or other body form is used
  exclusively, but in others the two forms are used
  in a single life cycle.

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Polyp and medusa

• The polyp or hydroid form is adapted to a sessile
  existence and the medusa form to a free-floating
  or pelagic life.
• In both cases radial symmetry is favored because
  stimuli and food are equally likely to come from
  all directions.
• Polyps and medusae may look quite different, but
  are basically inverted versions of each other.

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Fig. 7.2
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Giant Jellyfish Cyanea capillata
Fig 7.14
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Fig 7.19
Sea anemones
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Polyp and medusa

• Both polyps and medusa are equipped with
  tentacles around the oral cavity.
• The tentacles are equipped with cnidocytes that
  contain stinging nematocysts, which are used to
  kill prey.

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Figure 7.3
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Coral Reefs

• Coral reefs are found in shallow waters in the
  tropics.
• They are calcareous structures and what makes
  them unique as geological structures is that they
  are formed by some of the organisms that live on
  them, specifically reef-building corals and
  coralline algae.
• They are the largest living structures on the
  planet.

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Coral Reefs

• Reef-building corals contain symbiotic algae
  (zooxanthellae) that supply a significant part of
  the corals energy in exchange for protection and
  access to light.
• These algae require light for photosynthesis and
  so reef-building corals can live only in clear
  waters less than 100m deep (and most species
  occur in much shallower waters).

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Coral polyps
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Brain coral (Anthozoa)
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Shumann Island, Papua New Guinea (fringing reef).
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Bilateral Animals

• Unlike the radiate animals all of these organisms
  are mobile and have evolved cephalization with
  their sense organs concentrated at the head end.
  There is also the beginning of a ladder-type
  nervous system.
• In addition, they are bilaterally symmetrical.

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Plathyhelminthes

• Among the simplest bilateral animals but of
  significant economic importance is the phylum
  Platyhelminthes, which includes a variety of
  parasitic forms such as the flukes and tapeworms.

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Plathyhelminthes

• They have evolved organs and in some cases organ
  systems. The simplest excretory or
  osmoregulatory systems and circulatory systems
  are found in members of these groups.

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Phylum Platyhelminthes

• Members of the Platyhelminthes typically have
  dorsoventrally flattened bodies that are usually
  slender and leaflike or ribbonlike.
• There are four classes in the Platyhelminthes.
  The Turbellaria are free living whereas as
  members of the Monogenea, Trematoda and Cestoda
  are parasitic.

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Class Trematoda

• There are about 9000 species of trematodes
  (flukes) all of which are parasitic. Most
  parasitize vertebrates.
• Adaptations for parasitism include suckers and
  hooks for attachment, glands to produce cyst
  material and increased reproductive capacity.

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Sheep liver fluke
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Clonorchis liver fluke

• Clonorchis is the most important liver fluke to
  infect humans. Common in much of Asia (including
  China, Japan and southern Asia).
• Adult flukes live in the bile passages and
  shelled miricidia pass out in feces. The
  miricidia enter snails eventually leave the
  snails as cercariae and find a fish where they
  encyst.
• If fish is eaten raw or poorly cooked the person
  becomes infected

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Class Cestoda (tapeworms)

• Tapeworms are parasites of the vertebrate
  digestive tract and about 4000 species are known.
• Almost all tapeworms require at least two hosts
  with the definitive host being a vertebrate,
  although intermediate hosts can be invertebrates.

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Class Cestoda

• Members of the Class Cestoda (tapeworms) are
  quite different in appearance from the other
  members of the Platyhelminthes.
• They have long, flat, tape-like bodies composed
  of a scolex for attaching to their host and a
  chain of many reproductive units or proglottids
  called a strobila. New proglottids form behind
  the scolex and the strobila may become extremely
  long.

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Tapeworm scolex
Hooks
Suckers
The scolex is equipped with suckers and hooks
that enable it to grip onto its hosts intestines.
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Class Cestoda

• Tapeworms live in the intestines and because they
  are immersed in digested food lack a digestive
  system of their own. Instead they simply absorb
  food across their tegument.

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Human tapeworms

• Humans are definitive hosts to several tapeworms
  including the beef tapeworm Taenia saginata, pork
  tapeworm T. solium, and fish tapeworm
  Diphyllobothrium latum.

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Human tapeworms

• The lifecycles of these parasites are similar.
• Shelled larvae are shed into the environment.
• These are consumed by the intermediate host and
  the larvae hatch, bury into blood vessels and
  make their way to skeletal muscle where they
  encyst becoming so called bladder worms or
  cysticerci.

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Human tapeworms

• The encysted larva waits, perhaps for years, for
  its host to be eaten.
• If the meat is uncooked the cysticercus extends
  its scolex, attaches to the wall of the intestine
  and within 2-3 weeks matures and begins growing
  and producing eggs. A tapeworm may be many
  meters long and live for years.

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8.15
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Mollusca
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Mollusca

• The molluscs are a very diverse group with over
  100,000 living species including such familiar
  organisms as clams, mussels, limpets, snails,
  squids and octopi.

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Mollusca

• Many molluscs possess a hard shell and as a
  result there are many fossil molluscs (more than
  30,000 species have been described).
• Molluscs were abundant in the oceans of the
  Cambrian period and must have evolved in the
  pre-Cambrian over 570 million years ago.

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Molluscs

• Living molluscs range in size from small clams
  and snails to the giant and colossal squids which
  can weigh up to 1,000 lbs and measure 60 feet
  long with tentacles extended.
• The shells of giant clams may be 1.5 wide and
  weigh 225 kg, but most molluscs have shells less
  than 5cm across.

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Molluscs

• The word Mollusca is from the Latin molluscus
  meaning soft and describes the soft body, which
  is one of the key features of the group.
• Most molluscs live in the sea and range from
  tropical to Arctic waters. Others occur in
  freshwater and on land.
• There is a great range of life styles that
  includes bottom feeding, filter feeding, boring,
  burrowing and pelagic forms.

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Molluscs

• Molluscs have diversified into a great variety of
  body forms from the sessile, filter-feeding clam
  to the slow-moving grazing snail to the actively
  hunting, intelligent octopus.
• These different forms are all derived from a
  basic molluscan body plan.

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Molluscan body plan

• At its simplest the molluscan body consists of a
  head-foot and a visceral mass.
• The head-foot contains the locomotory, feeding,
  cephalic, and sensory organs.
• The visceral mass includes the digestive,
  circulatory, respiratory and reproductive organs.

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Molluscan body plan Head-foot

• Many molluscs have a well developed head that
  contains a mouth, often tentacles, and some
  specialized sensory organs.
• Many possess eyes that range from very simple
  light sensing structures to the highly developed
  eyes of cephalopods.

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Bay scallop (note the blue eyes).
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Cuttlefish
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Incurrent and excurrent siphons of Northwest
ugly clam
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Mating snails.
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Cone shell
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Phylum Annelida

• The annelids (L. annelus a little ring) are the
  segmented worms.
• The annelid body is metameric being composed of
  serially repeated segments or metameres.
• Each segment is separate from the next segments
  being divided by partitions or septa.

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Segmentation

• Within each segment are components of most organ
  systems such as the circulatory, nervous and
  excretory systems.
• Thus, there is a degree of redundancy in annelids
  so that if a segment is damaged it need not be
  fatal.

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Segmentation

• The evolution of segmentation is the great
  evolutionary innovation of the annelids.
• Because the coelom is divided by septa the force
  of muscle contraction in a segment is not
  transmitted throughout the body, but instead is
  confined to the single segment.
• Thus, one segment may elongate while the adjacent
  one contracts and this allows the animal to make
  fine, controlled movements

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Annelids

• Annelids occur worldwide being found in the sea,
  freshwater, and in the soil.
• They feed on organic matter in the mud or soil,
  by filtering suspended particles from the water,
  act as predators, or suck blood.

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11.3B
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Worlds largest leech Haementeria ghilianii
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Phylum Arthropoda

• The Arthropoda (from the Greek Arthron, joint and
  podus, foot) are the largest group of organisms
  and they occur in all environments on earth.
• The group includes spiders, ticks, mites,
  centipedes, millipedes, crustaceans, insects and
  others.

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Characteristics of the Arthropoda

• Bilaterally symmetrical with a segmented
  (metameric) body divided into head, thorax and
  abdomen cephalothorax and abdomen or fused head
  and trunk.

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Characteristics of the Arthropoda

• Jointed appendages. Primitively one pair per
  segment, but number often reduced.
• Appendages often greatly modified for specialized
  tasks.

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Characteristics of the Arthropoda

• Exoskeleton of cuticle.
• Exoskelton secreted by underlying epidermis. Made
  of chitin, protein, lipid and often calcium
  carbonate.
• Exoskeleton is shed periodically (ecdysis) as the
  organism grows.

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Classification of Phylum Arthropoda

• Subphylum Chelicerata horseshoe crabs, spiders,
  tick, mites, scorpions,
• Subphylum Crustacea crabs, lobsters, copepods,
  barnacles, pill bugs
• Subphylum Myriapoda millipedes and centipedes
• Subphylum Hexapoda springtails, insects

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Hobo spider
Brown recluse spider
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Female Black Widow spider with egg sac
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12.10 a
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Dust mite
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Wood tick
Wood tick
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12.32B
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12.16A
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Phylum Echinodermata

• The echinoderms (hedgehog skin) are a very
  unusual group that includes about 7000 living
  species.
• Members include starfish, brittle stars, sea
  urchins, sea cucumbers, and sea lilies or feather
  stars.
• They are deuterostomes (as are chordates), but
  have secondarily evolved radial symmetry from
  bilateral symmetry (they still have bilaterally
  symmetrical larvae).

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Characteristics of the Echinodermata

• Exclusively a marine group. They cannot
  osmoregulate so rarely occur even in brackish
  water.
• The body is not segmented, but shows pentaradial
  symmetry.
• There is no head or brain and the nervous system
  is relatively simple.

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Characteristics of the Echinodermata

• They possess an endoskeleton of dermal calcareous
  ossicles, which are connected together by
  connective tissue.
• Possess a unique water vascular system that
  consists of a series of canals that extend from
  the body surface as tube feet.
• These tube feet are tentacle-like and enable the
  animal to move. In some species movement of the
  arms or spines contributes to locomotion too.

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Classes of Echinoderms

• There are a total of five classes of echinoderms
  and about 7300 species.
• Class Asteroidea sea stars or starfishes
• Class Ophiuroidea Brittle stars
• Class Echinoidea Sea Urchins, Sand dollars
• Class Holothuroidea Sea cucumbers
• Class Crinoidea Sea Lilies and Feather stars.

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Cushion seastar (Asteroidea)
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Brittle star (Ophiuroidea)
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Sea urchins
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Sea cucumber
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Feather star