Photosynthesis

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Animals

• What makes an animal?
• How can you tell if something is an animal or
  not?
• What are some examples of animals?

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Evolution of Animals (intro)

• All animals are multicellular heterotrophic
  organisms that must take in preformed food.
• mulitcellular made of more than one cell
• heterotrophic take in preformed food from other
  organisms
• food complex organic molecules often glucose
  related compounds

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Outline

• Criteria for the Evolution of Animals
• 1. Multicellularity
• 2. True Tissues
• 3. Bilateral Symmetry
• 4. Body Cavities
• 5. The Coelom
• 6. Segmentation
• 7. Development

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Evolution of Animals (intro)

• All animals are multicellular heterotrophic
  organisms that must take in preformed food
• Classification Criteria
• Level of organization
• Cellular, tissue, organ
• Body Plan
• Sac, tube-within-a-tube
• Segmentation
• Segmentation leads to specialization

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Evolution of Animals (intro)

• Classification Criteria, cont
• Symmetry
• Radial - Two identical halves
• Bilateral - Definite right and left halves
• Type of Coelom
• Acoelomate
• Pseudocoelom
• Coelom
• Early Developmental Pattern
• Protostome - First embryonic opening becomes the
  mouth
• Dueterostome - Second embryonic opening becomes
  the mouth

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AnimalsHow does this picture demonstrate that
an animal is involved?
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Traditional Phylogenetic Tree of Animals
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Animal?

• In order to be considered an animal, what must be
  true about this organism?

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Multicellularity

• Sponges
• Only level of animal to have cellular
  organization
• Saclike bodies perforated by many pores
• Beating of flagella produces water currents that
  flow through pores into central cavity and out
  osculum
• Sessile filter feeders
• Asexual reproduction by fragmentation or budding

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Simple Sponge Anatomy
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Porifera in the Animal Cladogram

• Sponges
• sitting at the bottom of the animal phylogeny
• simplest of the existing animals and possibly
  one of the simplest of all time

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True Tissue Layers Ctenophora Cnidarians

• Many animals have a total of three possible germ
  layers
• Ectoderm outside layer skin or outer covering
  , brain and peripheral nerves
• Endoderm inside layer gut track and some
  digestive tissues
• Mesoderm inner layer muscles
• phlya Ctenophora and Cnidaria develop only
  ectoderm and endoderm
• Diploblasts animals derived from only 2
  embryonic layers
• Radially symmetrical

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True Tissue Layers

• phlya Ctenophora and Cnidaria develop only
  ectoderm and endoderm
• So what is in the middle if these organisms (the
  first with true tissue layers) ?
• What are Ctenophora called again?

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Types of Symmetry
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Comb Jellies - Ctenophora

• Characteristics
• Small, transparent, and often luminescent
• Most of body composed of mesoglea
• Largest animals propelled by beating of cilia
• Capture prey with tentacles

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Comb Jelly Compared to Cnidarian
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Cnidarians

• Tubular animals that most often reside in shallow
  marine waters
• Polyp and medusa body forms
• Specialized stinging cells (cnidocytes)
• Fluid-filled capsule, nematocyst
• Two-layered body sac
• Outer layer - Protective epidermis
• Inner layer - Gastrovascular cavity
• Nerve net found throughout body

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Cnidarian Diversity
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Hydra

• Freshwater cnidarian
• Small tubular poly body about one-quarter inch in
  length
• Gastrovascular cavity is central cavity
• Tentacles can respond to stimuli
• Can reproduce sexually and asexually

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Anatomy of Hydra
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Obelia

• A colony of polyps enclosed by a hard, chitinous
  covering. Chitin?
• Feeding polyps
• Extend beyond covering
• Have nematocyst-bearing tentacles
• Reproductive polyps
• Budding of new polyps
• Also has sexual reproduction (medusae) stage

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Obelia Life Cycle
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Ctenophora and Cnidarians

• Where are we now?
• How are cnidarians and ctenophora different from
  sponges?
• What new feature do they posses that sponges
  did not have?
• http//www.youtube.com/watch?vbcmLxsJ5SAgfeature
  related

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Bilateral Symmetry

• New Characteristics
• Bilateral Symmetry
• animals have a left and right
• one plane of symmetry
• Cephalization
• identifiable or obvious head end of the animal
• having mouth and/or sensory organs at one end

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Bilateral Symmetry

• Pseudocoelomates
• Both phyla today will be considered
  pseudocoelomates
• What is the difference between acoelomates,
  pseudocoelomates and coelomates (or
  eucoelomates?)

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Bilateral Symmetry

• Coelomates (also known as eucoelomates "true
  coelom") have a fluid filled body cavity called
  a coelom with a complete lining called peritoneum
  derived from mesoderm (one of the three primary
  tissue layers).
• Pseudocoelomate  have a pseudocoel (literally
  false cavity), which is a fully functional body
  cavity. Tissue derived from mesoderm only partly
  lines the fluid filled body cavity of these
  animals. Thus, although organs are held in place
  loosely, they are not as well organized as in a
  coelomate.
• Acoelomate animals, like flatworms, have no body
  cavity at all. Organs have direct contact with
  the epithelium. Semi-solid mesodermal tissues
  between the gut and body wall hold their organs
  in place.

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Bilateral Symmetry

• Flatworms (phylum Platyhelminthes)
• Majority are parasitic
• Organ-level organization
• No specialized circulatory or respiratory
  structures
• Have undergone cephalization
• Ladder-type nervous system
• Ribbon worms (phylum Nemertea)
• Have distinctive proboscis
• Have a complete gut track

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Flatworms

• Belong to the phylum platyhelminthes. (Plat
  flat)
• There are three classes
• Turbellaria
• Trematoda
• Cestoda

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Characteristics of Flatworms

• They are acoelomates (they dont have body
  cavities)
• They have bilateral symmetry
• Show cephalization
• Respiration through skin
• Single opening to digestive tract (pharynx)

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Free-living Flatworms

• Planarians (genus Dugesia)
• Live in freshwater habitats
• Head is bluntly arrow shaped
• Auricles function as sense organs
• Two light-sensitive eye spots
• Three kinds of muscle layers
• Outer circular layer
• Inner longitudinal layer
• Diagonal layer

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Planarian Anatomy
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Planarians

• Planarians, cont.
• Excretory organ functions in osmotic regulation
  and water excretion
• Can reproduce asexually
• Hermaphroditic
• Practice cross-fertilization

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Parasitic Flatworms

• Parasitic flatworms are flukes (trematodes) and
  tapeworms (cestodes)
• Well-developed nerves and gastrovascular cavity
  are unnecessary
• Flukes
• Reproductive system well developed
• Usually hermaphroditic

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Life Cycle of Schistosomiasis
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Parasitic Flatworms

• Tapeworms
• Have anterior region with modifications for
  attachment to intestinal wall of host
• Behind head region, scolex, a long series of
  proglottids are found
• Segments each containing a full set of both male
  and female sex organs
• Complicated life cycles

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Life Cycle of a Tapeworm, Taenia
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Class Trematoda

• Are parasitic flukes
• Have suckers on both ends of the body
• Can live inside or outside of host
• Not much cephalization

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Class Trematoda

• Nervous and excretory systems like turbellarians
• Hermaphrodites
• Have complex life cycles

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Class Cestoda

• Parasitic
• Tapeworms
• Long, ribbon-like bodies
• Absorbs nutrients from host
• Hermaphrodites

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Tapeworm Anatomy
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Ribbon Worm, Lineus
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Phylum Nemertea (Rhynchocoela) Ribbonworms

• The nemerteans (ribbon worms) are long, marine
  predatory worms and there are about 1000 species
  known.
• Unlike members of the Platyhelminthes nemerteans
  have a complete gut with a mouth and anus and a
  true circulatory system

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Phylum Nemertea (Rhynchocoela) Ribbonworms

• Prey is captured using a long muscular proboscis
  armed with a barb called a stylet..
• The proboscis lies in an interior cavity called
  the rhynchocoel and muscular pressure on fluid in
  the rhynchocoel causes the proboscis to be
  quickly everted.
• The prey is wrapped in the sticky, slime-covered,
  proboscis and stabbed repeatedly with the stylet.
  Neurotoxins in the slime incapacitate the prey.

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Internal structure of female ribbon
worm (left). Nemertean with proboscis extended
(below)
8.18
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8.19
Baseodiscus mexicanus a nemertean from the
Galapagos Islands
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Pseudocoelom

• What is different about the animals we discussed
  today?
• How are flatworms (Platyhelminthes) different
  from cnidarians?
• How are nemertea (ribbon worms) different from
  flatworms?

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Pseudocoelom

• Pseudocoelom
• A false body cavity that is incompletely lined
  by mesoderm
• Provides a space for internal organs and can
  serve as hydrostatic skeleton
• Both phyla today are animals with a complete body
  gut track and pseudo coelom
• phylum Nematoda and Rotifera

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Types of Body Cavities

• 3 types of body cavities

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Types of Body Cavities

• acoelomate

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Types of Body Cavities

• pseudocoelomate

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Types of Body Cavities

• Coelomates not
• there yet

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Pseudocoelom
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• Roundworms (phylum Nematoda)
• Non-segmented, generally colorless worms
• Several parasitic roundworms infect humans

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Roundworm Anatomy
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Parasitic Roundworms

• Ascaris Intestinal roundworm
• Trachinella - Trichinosis
• Dirofilaria - Heartworms
• Wuchereria - Elephantiasis

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Filarial Worm
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Rotifers

• Rotifers (phylum Rotifera)
• Named for crown of cilia resembling a rotating
  wheel
• Serves as both as an organ of locomotion and aids
  direction of food to mouth
• Important base of many ecosystems
• Planktonic
• Transparent organisms
• Can survive dessication

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Rotifer
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Rotifers on youtube.com
25X Magnification
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Pseudocoelomates

• How are nematoda and rotifera different from
  platyhelminthes and nemertea (flatworms and
  ribbon worms?)