Download Chapter 32 - Workforce Solutions

Chapter 32
Overview of Animal Diversity
General features of Animals
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Animals are heterotrophs and multicellular
Muscle and nervous system (high mobility)
Diverse in form and habitat
Sexual reproduction
Characteristic pattern of embryonic
development
Five key transitions in animal
evolution
• Evolution of tissues allowed specialization
• Evolution of different forms of symmetry
(radial or bilateral)
• Evolution of body cavity
• Evolution of different patterns of development
• Evolution of segmentation or repeated units in
body
Tissues evolved allowing specialized
functions
• Parazoa – lack definite symmetry and lack
tissues and organs. Example-sponges can
differentiate and dedifferentiate
• Eumetazoa – have well-defined symmetry and
well defined tissues and differentiation is
irreversible
Radial or Bilateral Symmetry
Symmetry - arrangement of body parts
Kinds of symmetry:
• Radial symmetry (Parts of body arranged around a central
axis and any plane passing through axis can divide the
organism to form mirror images). Phylum Cnidaria
• Bilateral symmetry
 have dorsal and ventral surfaces
 have anterior and posterior ends
 show cephalization - concentration of nervous tissue
at the anterior end of an organism
 Phylum Chordata
Three germ layers (except sponges)
• In most animals – ectoderm, mesoderm and
endoderm
• Outer ectoderm develops into body coverings
and nervous system
• Middle mesoderm develops into skeleton and
muscles
• Inner mesoderm develops into digestive organs
and intestines
Kinds of body cavities
Acoelomates – no body
cavity and cells and organic
material fill the space
between mesoderm and
endoderm
Pseudocoelomates have
pseudocoels located between
mesoderm and endoderm
Coelomates have coelom
formed from mesoderm
What led to development of circulatory
systems?
• Development of a coelom created problems with
circulation of nutrients and removal of wastes.
Coelomates developed Circulatory systems
• Open circulatory systems – the blood passes from
vessels into sinuses where it mixes with body fluids
before it returns to the vessels
• Closed circulatory systems – blood flow is
continuous through vessels separated by body fluids
Basic pattern of development in bilaterians
Embryonic development of Protostomes and
Deuterostomes
• Protostomes
• Embryonic cells cleave
in spiral pattern
• Exhibit determinate
development
• Blastospore becomes
animal’s mouth
• Coelom originates from
mesodermal split
• Deuterostomes
• Embryonic cells cleave
in radial pattern
• Exhibit indeterminate
development
• Blastospore becomes
animal’s anus
• Coelom originates from
invagination of
archenteron
Segmentation
• Segmentation is convergent
• Allows redundant organ systems
• Allows for more efficient and flexible
movement
• Found in annelids, arthropods and chordates
but now segmentation is common in many
other animals.
Taxonomy: Kingdom Animalia
• contains well over 30 phyla
• basic categories:
invertebrates - animals without a backbone
vertebrates - animals with a backbone
Role of Molecular Biology in
evolution of animals
• Molecular Biology is helping scientists
understand the origins of animal clades
• Rapid diversification (due to evolution of Hox
genes) of animals started in beginning of
Cambrian period – Cambrian explosion
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