What is an Animal?
Characteristics of Animals
• All animals have several characteristics in
common. What are the four common
characteristics of animals?
– Eukaryotic
– Multicellular
– Heterotrophic
– No cell wall
What Do Animals Do to Survive?
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Feeding
Respiration
Circulation
Excretion
Response
Movement
Reproduction
Trends in Animal Evolution
• Your survey of the
animal kingdom will
begin with simple
forms and move
through more
complicated ones.
Phylogenetic relationships: Trends in
Animal Evolution
Cell Specialization and Levels of
Organization
• Groups of
specialized cells
that work together
form tissues.
• Tissues join
together to form
organs.
• Group of organs
work together to
form organ systems
– EX: Circulatory
system
Cephalization
• Concentration of sense organs and nerve cells
at the front end or head of the body.
Animal Body Plans
• What is symmetry?
Asymmetry
Radial Symmetry
Bilateral
Symmetry
Animal Body Plans
• Acoelom
– Without a body cavity
Animal Body Plans
• Pseudocoelom
– Fluid-filled internal
space that is in
direct contact with
the wall of the
digestive tract.
Animal Body Plans
• Coelom
– Fluid-filled body
cavity completely
lined by a layer of
mesoderm cells
Animal Body Plans
How do these body plans
develop?
Early Development
Development of Animal Body Plans
• Cell Division
– The zygote divides by mitosis and cell division to
form two cells in a process called cleavage.
– How important is this first cell division?
Zygote
Development of Animals: Gastrulation
(a process of forming cell layers)
• The zygote undergoes a series of divisions to
form a blastula, which is a hollow ball of cells.
Demo
Phylums Porifera and Cnidaria only have two layers
Protostome vs. deuterostome
Mouth is formed from the blastopore
Anus is formed from the blastopore
Formation of a Coelom (body cavity):
Neurulation
• Body cavity – a fluid-filled space that lies
between the digestive tract and the body wall.
Gastrula
Embryo Development