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Chapter 32 Notes
Introduction to Animal
Evolution
Concept 32.1
General characteristics of animals:
- multicellular, heterotrophic eukaryotes
- take in food by ingestion
- lack cell walls; have cell junctions
made of structural proteins that hold
cells and tissues together
Concept 32.1
- tissues of impulse conduction and
movement: nervous and muscle tissue
- reproduce sexually; zygote that
undergoes cleavage
-divides into smaller cells after
fertilization creating a multicellular
structure called a blastula
Concept 32.1
- following the blastula stage is
gastrulation
- rearrange the cells to form a 3
layered structure called a gastrula
Concept 32.1
Concept 32.1
Concept 32.1
Concept 32.1
- some develop directly into adults;
others develop into a larva stage
(sexually immature). Will undergo
metamorphosis.
- animals most likely developed from a
colonial, flat protist
Concept 32.1
Concept 32.1
Concept 32.3
Animals can be classified by their body
structure
Subkingdom Parazoa:
- ex. Sponges
- have only 2 layers of cells; lack true
organs
Concept 32.3
Subkingdom Eumetazoa:
- possess true tissues
- divided into 2 branches based on
symmetry: radial and bilateral
Concept 32.3
Concept 32.3
Radial Symmetry:
- phylum Cnidaria and Ctenophora
- has a top and a bottom
- adapted for sessile (not motile)
lifestyle
- develop two tissue layers: ectoderm
(outer covering) and endoderm
(digestive tube lining)
Concept 32.3
Bilateral Symmetry:
- phylum platyhelminthes through
chordata
- have a top (dorsal), bottom
(ventral), head (anterior), and tail
(posterior)
Concept 32.3
- have three germ (tissue) layers:
triploblastic
- ectoderm: forms epidermis of skin
and nervous system
- endoderm: lining of digestive
tract, liver, pancreas
- mesoderm: skeletal, muscle,
circulatory, and lympatic systems
Concept 32.3
Animals can also be grouped by the
development of a body cavity or
coelom
- separates the digestive tract from the
outer body wall
- triploblastic animals can be grouped
by the coelom development
Concept 32.3
Acoelomates:
- phylum platyhelminthes
- no body cavity between the digestive
tract and the outer wall
- have only one opening; only a
gastrovascular cavity
- no blood vascular system
Concept 32.3
Psuedocoelomates:
- phylum rotifera and nematoda
- have a fluid filled cavity that is
incompletely or partially lined with
mesoderm
-cavity develops between the
mesoderm and endoderm
Concept 32.3
Coelomates:
- everything else
- fluid filled cavity that is completely
lined with mesoderm
- the digestive tract is suspended in the
cavity and held in place with connective
tissue called mesentery
Concept 32.3
Concept 32.3
Coelomates are further divided according
to the pattern of development that their
zygote goes through
- divided into protosome and
deuterosome coelomates
Concept 32.3
Protosome coelomates:
- spiral cleavage: during early cell
divisions, the divisions are diagonal to
the vertical axis of the embryo
- cells end up lying between rather than
on top of other cells
- first opening becomes the mouth,
second becomes the anus
Concept 32.3
- determinate cleavage: casts the
developmental fate of each cell very
early
Concept 32.3
Deuterosome coelomates:
- radial cleavage: cells divide at right
angles so the cells are above or below
each other
- first opening becomes the anus, second
becomes the mouth
- indeterminate cleavage: cells retain
ability to develop into complete embryo
Concept 32.3