Transcript Nerve activates contraction - University of Indianapolis

Kingdom Animalia
What are animals?
• Animals eat to live:
‘ingestively’
heterotrophic
• Multicellular
• lack a cell wall
Origins and Early Diversification of Animals
• Sponges are the oldest known animals in the fossil record
and are similar to protistan choanoflagellates.
Choanoflagellate (a protist)
Sponge (an animal)
Water current
out of sponge
Choanoflagellate
cell
Food
particles
Water
current
Sponge
feeding
cell
Interior
of sponge
Water current
into sponge
Origins and Early Diversification of Animals
• There are about 35 Phyla in Kingdom Animalia
• We’ll review approximately 14 of these
• Four basic features vary in different animal body
plans, and are the basis for grouping animals
into different phyla:
1. Embryonic tissues
2. Body symmetry
3. Presence of a body cavity
4. Details of early development
1. Tissues
• Tissue= highly organized and functionally
integrated group of cells
• All animals but sponges have tissues
arranged in layers in their embryos
No tissues
Tissues present
Parazoa
(Phylum Porifera)
Eumetazoa
(all other phyla)
1. Tissues
• In animals with embryonic tissues, the tissues are
arranged in layers
• Endodermdigestive tract, liver, lungs
• Mesodermcirculatory system, muscles
• Ectodermskin, nervous tissue
• There may be 2 or 3 layers:
• Diploblastic endo & ecto only
• Triploblastic all 3
2. Symmetry
• An animal’s body plan may have no symmetry (sponges),
or show radial or bilateral symmetry
Asymmetry
Radial symmetry
Bilateral
symmetry
Single plane of
symmetry
Anterior
Posterior
Multiple
planes of
symmetry
(1. And 2.) Tissues and Symmetry
• Animals that are diploblastic show radial symmetry
• Animals that are triplobastic show bilateral symmetry
No tissues
Tissues
present
Parazoa
(Phylum Porifera)
Diploblastic,
radial symmetry
Eumetazoa
Triploblastic,
bilateral symmetry
Radiata
(Phylum Cnidaria
& Ctenophora)
Bilateria
All other Phyla
Significance of
Tissues and Symmetry
• Animals with bilateral symmetry are capable of
unidirectional movement
• Mesoderm made musculature possible
• Together: directed movement and hunting
3. Fluid-filled body cavities
• A coelom (body cavity) develops within mesoderm tissue
in most triploblasts.
• The coelom provides space in which organs can develop
and acts as a hydrostatic skeleton in soft-bodied animals.
• Some triploblasts have a pseudocoelom, which develops
between mesoderm and endoderm and functions just as a
coelom does.
Body plans of the bilateria
Hydrostatic skeleton of a nematode
Muscle
Gut
Fluid-filled
pseudocoelom
Body wall
Coordinated muscle contractions result in locomotion
Muscles relaxed
Muscles
contracted
Muscles
contracted
When the muscles
on one side contract,
the fluid-filled chamber
does not compress.
Instead, the animal bends.
Muscles
relaxed
3. Bilateria animals either have no coelom,
pseudocoelom, or a true coelom
No coelom
Bilateria
Pseudocoelom
Phylum
Platyhelminthes
Phylum
Rotifera
Phylum
Nematoda
Coelom
Coelomates: All other Phyla
4. Early events in embryogenesis
• The last feature used to categorize animal body
plans deals with details of the early development of
animals
• Animals develop from a single-celled zygote through
a process called gastrulation
Figure 32.1 Early embryonic development (Layer 1)
Figure 32.1 Early embryonic development (Layer 2)
Figure 32.1 Early embryonic development (Layer 3)
Early events in embryogenesis
• Among coelomates, there are 2 groups:
• Protostomes: spiral cleavage, mouth develops first,
coelom develops within blocks of mesoderm.
• Deuterostomes: radial cleavage, mouth develops
second, coelom develops from mesoderm cells that bud
off the endoderm.
Figure 32.7 A comparison of early development in protostomes and deuterostomes
Odd group out
• Three phyla of Coelomates have charateristics
of both protostomes and deuterstomes
• These are the Lophphorate Phyla
Bilateria
Spiral cleavage,
mouth first, etc.
lophophore
Bilateria
Radial cleaveage,
mouth second, etc.
Protostomia
Phylum Mollusca
Phylum Annelida
Phylum Arthropoda
Lophophorate
Phylum Bryozoa
Phylum Phoronids
Phylum Brachiopoda
Deuterostomia
Phylum Echinodermata
Phylum Chordata
Molecular Systematics is moving some branches
around on the phylogenetic tree of animals
• Data based on nucleotide sequence of the
small subunit ribosomal RNA (SSU-rRNA)
• Early branches still the same
• Deuterostomes still the same
Animal phylogeny based on sequencing of SSU-rRNA
Molecular Systematics is moving some branches
around on the phylogenetic tree of animals
• Differences:
• Protostomes divided into 2 groups
• Lophotrochozoaannelids,molluscs, lophophorates
Trochophore larvae of
annelids and molluscs
• Ecdysozoanematodes, arthropods
The Ecdysozoa are defined by molting
Nematodes and
arthropods shed their
exoskeleton as they
grow, a process
called ecdysis
Animal phylogeny based on sequencing of SSU-rRNA