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Kingdom Animalia (Diploblasts and Porifera)
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Lecture notes on kingdom animalia, diploblasts, and porifera.
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Lecture 1: Introduction to Animalia kingdomKingdom Animalia key characteristics:
Mode of nutrition
Cell structure
Development
Animals and fungi are more closely related to each other than they are to plants. They form a group
called opisthakonts.
Mode of nutrition
Plants - autotrophs - photosynthesis
Fungi - heterotrophs - growing on th resource
Animals - heterotrophs - resource is digested
Cell structure
Plants - cell wall - cellulose
Fungi - cell wall - chitin
Animals - no cell wall - cells and tissues held together by extra cellular matrix (structural proteins
such as collagen)
Development
The body plans are patterned by conserved Hox genes. Hox genes control development of all
animals. The evolution of Hox genes was thought to drive evolution of body plans. Hox genes lie in a
chromosome in the order they're expressed. They show spatial and temporal colinearity.
Vertebrates have 4 copies of Hox genes found in a fruitfly. Hox genes switch on and regulate genes
further down. A change in Hox expression results in a change in your body plan. Regions of the body
are identified using Hox genes.
Evolutionary history of animals
Neoproterozoic Era (1b - 542m years ago)
Cryogenian period (850 - 635mya) - no fossil evidence but sponge-like metazoans existed
, Ediacaran period (635 - 542mya) - earliest fossil evidence
Paleozoic era (542 - 251mya)
Emergence of predator prey relationship, improved hunters and improved defences
Increase in o2 levels
Evolution of Hox gene and other genetic changes that allowed more developmental flexibility and
diversity
Vertebrates made the transition to land 365mya
Cambrain explosion: 542-525mya
Mesozoic era (251 - 65.5mya)
Began with permian-triassic mass extinction
Dominated by reptiles
First small mammals
Cenozoic era (65.5mya - present)
Mass extinction event
Dominated by mammals
Rise and diversification of mammals
Animals can be classified by:
Body plan symmetry
Tissue layers
Body cavities
Protostome vs deuterostome development
Body plan symmetry
No symmetry (porifera)
Radial symmetry (cnidaria, ctenophora)
Bilateral symmetry (most animals)
Tissue layers
Gastrulation generates 2 layers: ectoderm and endoderm. A third layer can emerge later called the
mesoderm. Mesoderm allows the development of true organs. Primitive animals (cnidaria,
ctenophora) are diploblasts; majority of animals are triploblasts.
Body cavities
Body cavities are where the organs are kept.
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