Transcript The Wonderful World of Animals!

The Wonderful World of
Animals!
What is true about ALL animals?
• They are eukaryotic
• They are multicellular
• They are heterotrophs (If they make their own
food, they are not animals)
• They lack cell walls
• They possess nervous tissue and muscle (at
least myosin and actin in some form)
• Generally, they reproduce sexually
How do we begin to classify animals?
• 1. How many “layers” do they have?
• Uniblastic
• Diploblastic: only an endoderm and ectoderm
• Triploblastic: endoderm, mesoderm,
ectoderm
– Vast majority of animal phyla are triploblastic
How do we begin to classify animals?
• 2. What type of “symmetry” do they have?
• Radial symmetry: best for animals that don’t
have to move much…
How do we begin to classify animals?
• Bilateral symmetry: great for animals that
need to move fast
• With bilateral symmetry came “cephalization”
– The movement of sensory organs and nervous
tissues in a head at the anterior of the animal
– Good to have this all up front…it’s what
encounters a new environment 1st
How do we begin to classify animals?
• With bilateral symmetry also came
“segmentation”
• Developing a series of ‘body units’ (like an
earthworm)
• Allowed animals to develop specialized
parts…legs, wings, antennae
How do we begin to classify animals?
• 3. What do their body cavities look like?
• Coelom: “body cavity”
• A. Acoelomate: no body cavity; everything
between body wall and internal organs is filled
with mesenchyme
Flatworm
Body Cavities
• B. Pseudocoelomate: mesoderm lines the
inside of the body wall but NOT the internal
organs
Ascaris: A Parasitic Roundworm
Body Cavities
• C. Coelomate: Both inside body wall and
internal organs are lined by mesoderm
• “peritoneum”
Phylum Porifera
• Sponges!
– Uniblastic
– If any symmetry at all, it is radial
– Sessile
Phylum Cnideria
• Usually radial symmetry
• Diploblastic: Has 2 cell layers: endoderm and
ectoderm
• Blind gut: mouth and anus are the same opening
• All are carnivores; possess nematocysts
• Jellyfish, sea anemones, corals
Ctenophores (Comb Jellies)
• Complete guts (separate mouth and anus)
• Usually radial symmetry
• Diploblastic: Has 2 cell layers: endoderm and
ectoderm
• Sticky tentacles, not nematocysts
Protostomes vs. Deuterostomes
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•
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Stome: Mouth
Proto: First
Deutero: Second
Protostome: Mouth forms 1st from
blastopore
• Deuterostome: Anus forms 1st from
blastopore, mouth arises elsewhere 2nd
What is a blastopore anyway?
• Spot in the embryo where vegetal pole folds
inward
This is a sea urchin embryo…Is it a
protosome or a deuterostome?
Comparison/Contrast
Protostomes
Deuterostomes
• Triploblastic
• Bilateral symmetry
• Cephalized (anterior
brain)
• Blastopore becomes
the MOUTH
• VENTRAL nervous
system
• Triploblastic
• Bilateral symmetry
• Cephalized (anterior
brain)
• Blastopore becomes
the ANUS
• DORSAL nervous
system
Protostomes (many phyla)
Lophotrochozoans
• Grow by adding size
• Flatworms
(Platyhelminthes)
• Rotifera
• Annelids
(Segmented worms)
• Mollusks
Ecdysozoans
• Grow by molting
• Nematodes (cuticles)
• Arthropods
(segmented external
skeleton)
– Crustaceans
– Insects
– Arachnids
Those who grow by adding size
• Platyhelminths (flatworms)
Those who grow by adding size
• Rotifers
Those who grow by adding size
• Annelids (includes the earthworm)
Circulatory System of an Annelid
• The circulatory system is CLOSED
Blood is enclosed within
vessels and does not
mix with other body
fluids
As you might expect, this
is also characteristic of all
vertebrates
Those who grow by adding size
• Mollusks
• From snails to clams to octopus to giant squid
Body plan of a mollusk
• Visceral mass, mantle, & foot
Circulatory System of a Mollusk
• The circulatory system is OPEN
Arthropods
will be like
this too.
Blood mixes
with other body
fluids
Those who grow by molting
• These animals have an “exoskeleton”
• Nematodes (Roundworms)
– External cuticle: flexible but unsegmented
• Arthropods: Segmented external skeleton
– “Jointed foot”
Arthropods
• Crustaceans
• Insects
• Arachnids
Crustaceans
• Marine animals
• 3 body segments
• Head, thorax, and abdomen
Insects
1.4 MILLION species
Arachnids
• Scorpions and spiders
On to Deuterostomes
• Two major classifications
• 1. Echinoderms
• 2. Chordates
– Characterized by dorsal notochord which becomes
the vertebrae in Vertebrates
Echinoderms
• Starfish, sand dollars, sea urchines
Chordates
• Features at some point during development
– Pharyngeal slits
– A dorsal hollow nerve cord
– A dorsal supporting rod (notochord)
– A tail extending past the anus
– A ventral heart
Relationship of Chordates
• We’ll draw a picture here!
How the Circulatory Systems
Differ Among the Chordates
Fish
Lungfish
Amphibians
Crocodile
Reptiles
Birds and Mammals