ANIMAL KINGDOM • DIGITAL STUDY NOTES
ANIMAL KINGDOM
BASIS OF CLASSIFICATION
Kingdom Animalia / Metazoa
• Multicellular
• Heterotrophic — dependent on other organisms for food
• Holozoic mode of nutrition: first ingestion, then digestion
METAZOA / KINGDOM ANIMALIA
Subkingdom Parazoa: primitive metazoans → Phylum Porifera
Subkingdom Eumetazoa: true tissues; includes the more advanced animal phyla.
Major phyla listed in the notes
• Porifera
• Coelenterata / Cnidaria
• Ctenophora
• Platyhelminthes
• Aschelminthes / Nematoda
• Annelida
• Arthropoda
• Mollusca
• Echinodermata
• Hemichordata
• Chordata
LEVEL OF ORGANISATION
• Cellular — only cells are present; e.g. Porifera.
• Tissue — groups of similar cells perform a specific function; e.g. Coelenterata and Ctenophora.
• Organ — tissues organise to form an organ; Platyhelminthes up to Chordata.
• Organ system — from Aschelminthes up to Chordata.
EXAM FOCUS
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,ANIMAL KINGDOM • DIGITAL STUDY NOTES
SYMMETRY & BODY PLAN
SYMMETRY
• Asymmetrical — body cannot be divided into equal halves through any plane; mostly Porifera.
• Radial — body can be divided into equal halves through any plane; e.g. Coelenterata and Ctenophora; Echinodermata
is noted as radial in the adult.
• Bilateral — body can be divided into equal halves through only one plane; Platyhelminthes up to Chordata.
BODY PLAN
BODY PLAN
Blind sac Tube within tube
one opening mouth → anus
• Cellular aggregation — only cells are differentiated; e.g. Porifera.
• Blind sac — one opening acts as both mouth and anus; e.g. Coelenterata, Ctenophora, Platyhelminthes.
• Tube within tube — separate openings act as mouth and anus; e.g. Aschelminthes up to Chordata.
GERM-LAYER FORMATION
Ovum + sperm → zygote → divisions → gastrula → germ layers
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, ANIMAL KINGDOM • DIGITAL STUDY NOTES
GERM LAYERS & COELOM
GERM LAYERS
ectoderm ectoderm
endoderm endoderm
mesoderm
Diploblastic Triploblastic
• Diploblastic — two germ layers: ectoderm and endoderm. A non-cellular mesoglea is present between them. Examples
in the notes: Coelenterata and Ctenophora.
• Triploblastic — three germ layers: ectoderm, mesoderm and endoderm. Example: Platyhelminthes up to Chordata.
COELOM
Acoelomate Pseudocoelomate Eucoelomate
• Acoelomate — absence of coelom; examples listed: Porifera, Coelenterata, Ctenophora and Platyhelminthes.
• Pseudocoelomate — example: Aschelminthes.
• Eucoelomate — true coelom; examples listed from Annelida up to Chordata.
True coelom: body cavity lined by mesoderm on both sides. The notes state that coelom is formed by splitting of
mesoderm.
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ANIMAL KINGDOM
BASIS OF CLASSIFICATION
Kingdom Animalia / Metazoa
• Multicellular
• Heterotrophic — dependent on other organisms for food
• Holozoic mode of nutrition: first ingestion, then digestion
METAZOA / KINGDOM ANIMALIA
Subkingdom Parazoa: primitive metazoans → Phylum Porifera
Subkingdom Eumetazoa: true tissues; includes the more advanced animal phyla.
Major phyla listed in the notes
• Porifera
• Coelenterata / Cnidaria
• Ctenophora
• Platyhelminthes
• Aschelminthes / Nematoda
• Annelida
• Arthropoda
• Mollusca
• Echinodermata
• Hemichordata
• Chordata
LEVEL OF ORGANISATION
• Cellular — only cells are present; e.g. Porifera.
• Tissue — groups of similar cells perform a specific function; e.g. Coelenterata and Ctenophora.
• Organ — tissues organise to form an organ; Platyhelminthes up to Chordata.
• Organ system — from Aschelminthes up to Chordata.
EXAM FOCUS
Page 1
,ANIMAL KINGDOM • DIGITAL STUDY NOTES
SYMMETRY & BODY PLAN
SYMMETRY
• Asymmetrical — body cannot be divided into equal halves through any plane; mostly Porifera.
• Radial — body can be divided into equal halves through any plane; e.g. Coelenterata and Ctenophora; Echinodermata
is noted as radial in the adult.
• Bilateral — body can be divided into equal halves through only one plane; Platyhelminthes up to Chordata.
BODY PLAN
BODY PLAN
Blind sac Tube within tube
one opening mouth → anus
• Cellular aggregation — only cells are differentiated; e.g. Porifera.
• Blind sac — one opening acts as both mouth and anus; e.g. Coelenterata, Ctenophora, Platyhelminthes.
• Tube within tube — separate openings act as mouth and anus; e.g. Aschelminthes up to Chordata.
GERM-LAYER FORMATION
Ovum + sperm → zygote → divisions → gastrula → germ layers
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, ANIMAL KINGDOM • DIGITAL STUDY NOTES
GERM LAYERS & COELOM
GERM LAYERS
ectoderm ectoderm
endoderm endoderm
mesoderm
Diploblastic Triploblastic
• Diploblastic — two germ layers: ectoderm and endoderm. A non-cellular mesoglea is present between them. Examples
in the notes: Coelenterata and Ctenophora.
• Triploblastic — three germ layers: ectoderm, mesoderm and endoderm. Example: Platyhelminthes up to Chordata.
COELOM
Acoelomate Pseudocoelomate Eucoelomate
• Acoelomate — absence of coelom; examples listed: Porifera, Coelenterata, Ctenophora and Platyhelminthes.
• Pseudocoelomate — example: Aschelminthes.
• Eucoelomate — true coelom; examples listed from Annelida up to Chordata.
True coelom: body cavity lined by mesoderm on both sides. The notes state that coelom is formed by splitting of
mesoderm.
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