Kingdom Animalia What are animals? Animals eat to live: ‘ingestively’ heterotrophic...
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Transcript of Kingdom Animalia What are animals? Animals eat to live: ‘ingestively’ heterotrophic...
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.
Water current
Food particles
Choanoflagellate (a protist)
Sponge feeding cell
Water current into sponge
Interior of sponge
Water current out of sponge
Sponge (an animal)
Choanoflagellate cell
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
• Endodermdigestive tract, liver, lungs
• Mesodermcirculatory system, muscles
• Ectodermskin, 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
Multiple planes of symmetry
Radial symmetryAsymmetry
Po
ste
rio
r
Ventral
Dorsal
Single plane of symmetry
An
teri
orBilateral
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)
Eumetazoa
Diploblastic, radial symmetry
Triploblastic, bilateral symmetry
Radiata(Phylum Cnidaria & Ctenophora)
BilateriaAll 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.
When the muscles on one side contract, the fluid-filled chamber does not compress. Instead, the animal bends.
Muscles contracted
Muscles relaxed
Muscles contracted
Muscles relaxed
Coordinated muscle contractions result in locomotion
3. Bilateria animals either have no coelom, pseudocoelom, or a true coelom
Phylum Platyhelminthes
Bilateria
No coelom
PseudocoelomPhylum Rotifera
Coelomates: All other PhylaCoelom
Phylum Nematoda
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
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.
Odd group out
• Three phyla of Coelomates have charateristics of both protostomes and deuterstomes
• These are the Lophphorate Phyla
Bilateria
ProtostomiaPhylum MolluscaPhylum AnnelidaPhylum Arthropoda
Bilaterialophophore
LophophoratePhylum BryozoaPhylum PhoronidsPhylum Brachiopoda
Radial cleaveage, mouth second, etc.
Spiral cleavage, mouth first, etc.
DeuterostomiaPhylum EchinodermataPhylum 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
Molecular Systematics is moving some branches around on the phylogenetic tree of animals
• Differences:
• Protostomes divided into 2 groups
• Lophotrochozoaannelids,molluscs, lophophorates
• Ecdysozoanematodes, arthropods
Trochophore larvae of annelids and molluscs
The Ecdysozoa are defined by molting
Nematodes and arthropods shed their
exoskeleton as they grow, a process
called ecdysis