Download L7: Intro. to Animal Diversity

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Evolution of Animals
Introduction to Animal Diversity
Lecture 7
Winter 2014
Eukaryotes
Prokaryotes
Major differences
Prokaryotes
• No nucleus
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Eukaryotes
• Nucleus
– Nucleoid region
– (DNA in a membrane-bound
region)
• Simple
• No membrane bound
organelles
• Complex
• Membrane bound
organelles
• Smaller (1-5 nm)
• Evolutionarily older
• Larger (10-100 nm)
• Evolutionarily younger
– Organelle – a structure with a
specified function w/i a cell
The Origin of Eukaryotic Cells
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Evolution of the
endomembrane
system
• Remember
endomembrane
system?
See Fig. 25.9
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Endosymbiosis
Remember endosymbiosis?
Mitochondria
• Formed when early
anaerobic eukaryotic cell
engulfed an aerobic
bacterium
• Benefits?
Plastids
• Formed when early
eukaryotic cell
(w/mitochondria) engulfed
a photosynthetic
cyanobacterium
• Benefits?
Protist Diversity
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What is a protist?
• Eukaryote
• Unicellular (primarily)
– Colonial
– Multicellular (algae “seaweed”)
• Metabolically diverse
– Photoautotrophs
– Heterotrophs
– Mixotrophs – combine both
See Fig. 25.9
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Protist Diversity
Origin of Multicellular Organisms
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• Earliest multicellular
fossil ~1.2 bya
• Cells gather in colonies
• Cell specialization
occurs to divide
particular life functions
• Multicellularity evolved
several times
independently among
eukaryotes
• “Protista” is a
paraphyletic
grouping
Fig. 28.3
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What are animals?
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Eukaryotes
Multicellular
Heterotrophic
Sexual reproduction (most)
Embryonic stage – blastula & gastrula
Specialized cells, tissues, organs for capturing
food, avoiding predation
– Muscles, nerves, sensory organs
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Brief Animal History
• Common ancestor of living animals ~675-875
mya ???
Fig. 32.3
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Brief Animal History
Animal Phylogeny
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• 565-550 mya - First fossils
• 535-525 mya - Cambrian
explosion
– Large diversification of
animals
– A Wonderful Life by
Stephen Jay Gould
• 360 mya - Vertebrates
move to land
Fig. 32.5
Fig. 32.10
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Body Symmetry
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Body Symmetry
• Asymmetric (no true symmetry)
Bilateral symmetry
• A body form with a
central longitudinal plane
that divides the body into
two equal but opposite
halves
– e.g., sponges
• Radial symmetry
– Can be divided into equal but opposite halves by any
plane through its central axis
– Sessile or planktonic
Fig. 32.7
– Must cut on midline
• Cephalization
– Sensory organs
concentrated in anterior
region
• Benefits?
Fig. 32.7
Evolution of true body tissue
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Embryonic Development
• Blastula
Tissue:
• An integrated group of cells with a common
function, structure, or both
– Hollow ball of cells that marks the end of the cleavage stage
• Gastrulation
– Blastula folds inward, producing layers of embryonic tissue
– Separated by membranous layer
• Gastrula
• Sponges lack true tissues
• All other animals - embryo with layered tissue
– Stage encompassing the formation of the layers
• Germ layers
– Ectoderm
– Endoderm
– Mesoderm
Fig. 32.2
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Evolution of digestive cavity
Evolution of true body tissue
• Diploblasts
– Ectoderm & endoderm
• E.g., Cnidarians (jellies, corals)
• Triploblasts
– Ectoderm, mesoderm, endoderm
– Bilateral symmetry
– Mesoderm forms muscles & most organs
between digestive tract and outer covering
Digestive cavity
• Gastrovascular cavity
– Sac with single
opening
– Acts as both mouth &
anus
Fig. 33.5
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• Complete digestive
tract (alimentary canal)
– Two openings, a mouth
and an anus
Fig. 41.9
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Evolution of body cavity
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Body cavity (coelom)
• Fluid or air-filled space separating the digestive
tract from the outer body wall
• Functions:
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Evolution of body cavities
• Pseudocoelom
– Formed from mesoderm &
endoderm tissue
– Pseudocoelomates
– Cushions internal organs
– Organs can move independently of outer body wall
• No body cavity
– Acoelomates
• True coelom
– Formed from
mesoderm
tissue
– Coelomates
Fig. 32.8
Fig. 32.8
Segmentation & Tagmatization
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• Segmentation
Skeletal Systems
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Endoskeleton
• Hard supporting element
buried within the soft
tissue
• E.g., bones & cartilage
(mammals), skeletal fibers
of inorganic material or
proteins (sponges),
ossicles (sea stars)
– Divided into parts,
sections
• Tagmatization
– Groups of segments
become specialized to
form specific function for
whole body
• Tagmata (tagma, sing.)
Fig. 33.29
Skeletal Systems
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Animal Development
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Fig. 33.36
Exoskeleton
• Hard encasement deposited on
an animal’s surface
• E.g., shells (snails, clams),
cuticle (crabs, insects)
• Metamorphosis
– A dramatic change from the larval form to the
adult form of an animal
• Larva
– Sexually immature form of an animal that is
morphologically distinct from the adult
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Protostome Vs. Deuterostome Development
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Protostome Vs. Deuterostome Development
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Coelom formation
Cleavage
– Gastrula stage
• Spiral
• Protostome
– Cleavage planes diagonal to vertical axis of embryo
• Radial
– Coelom forms from splits in the mesoderm (schizocoelous)
– Cleavage planes parallel or perpendicular to vertical axis of embryo
• Deuterostome
• Tiers of cells aligned directly above the other
– Coelom forms from mesodermal outpocketing in archenteron
• Determinate
– Developmental fate of cells determined very early
• Indeterminate
– Each cell retains capacity to develop a complete embryo
Fig. 32.9
Protostome Vs. Deuterostome Development
Fig. 32.9
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Animal Phylogeny
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Fate of blastopore
• Blastopore
– Indentation that during gastrulation leads to the
formation of the archenteron
• Protostome = “first mouth”
• Deuterostome = “second mouth”
Fig. 32.9
Fig. 32.10
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