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Biology 102
Chapter 32
Animal Diversity
Concept 1: Animals are (multicellular, heterotrophic, eukaryotes).
Nutrition: Animals can’t produce their food, instead they ingest organic
molecules then use their Enzymes to digest them.
Cell structure and specialization: animals do not have cell walls, instead they
have proteins external to cell membrane ( outside the cell ) which gives
structural support to the cell. (the most abundant is of these is collagen).
Cells of most animals organize into tissues (group of similar cells that act as a
functional unit ) such as muscle and nervous tissues (these tissues are not
found in plants or fungi).
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Biology 102
Chapter 32
Animal Diversity
Reproduction and development : a flagellated sperm fertilizes a no motile
egg to form a zygote, which undergoes cleavage(a succession of mitotic
divisions without cell growth) , then the cleavage leads to a stage called
blastula then to gastrulation which forms a stage called gastrula . see the
figure
Most animals go to a larval stage ( ‫ (مرحلة اليرقة‬a larva is a sexually immature
animal, which undergoes metamorphosis that turns the animal into a
sexually immature adult
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Biology 102
Chapter 32
Animal Diversity
Homeoboxes : genes that regulate development and most animals share a
unique homeobox called hox genes which play a role in embryonic
development and morphology . ( sponges do not have hox genes )
Hox genes regulate the formation of anterior and posterior axis ( see later in
concept 3)
Concept 2 ‫مش مطلوب‬
Concept 3: animals can be characterized by body plans :
Symmetry : animals have types of symmetry
1-no symmetry like sponges
2- Radial symmetry like sea anemones ( top and bottom sides )
3- bilateral symmetry ( which have two axis ) front anterior to back posterior
sides , top dorsal and bottom ventral sides , right and left sides.
The symmetrical body fits the lifestyle of animals, eg: radial animals are
sessile (attached to substrates ‫ )ال تتحرك‬or planktonic (slowly swimming).
By contrast bilateral animals have a brain or central nervous system and
move actively.
Tissues: true tissues are isolated from other tissues by membranous layers
(sponges and some few animals lack true tissues).
During gastrulation the embryo is divided into two or three layers( called
germ layers ) which form the body tissues:
1- Endoderm: turns into the digestive tract and organs like liver and lungs.
2- Ectoderm: turns into the outer covering of an animal and the central
nervous system.
3- Mesoderm: forms the muscles and organs between the digestive tract and
the outer covering.
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Biology 102
Chapter 32
Animal Diversity
Animals are divided into two groups based on these layers :
1- Triploblastic: they have all three layers.
2- Diploblastic: they have the endoderm and the ectoderm but lack the
mesoderm.
Body cavities : triploblastic animals divide into three groups based on
their body cavity ( a coelom is a body cavity between the digestive tract
and the outer body )
1- Coelomates: have a true coelom.
2- Pseudo coelomates: have a pseudocoelome.
3- Acoelomates: do not have a coelom …. See the figure
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Biology 102
Chapter 32
Animal Diversity
A body cavity has many functions
1- It cousins the organs.
2- Earthworms have a coelom that contains a noncompresible fluid.
3- The cavity allows the organs to grow independently of the outer body
wall.
A grade : animals that share key biological features
A clade : a group which shares an ancestor
Protostome and Deutereostome development : see table 
Type
Cleavage
Coelom formation
Fate of Blastopore
Protostome
1-Spiral/diagonal
2-determinate
3-a 4 cell stage cant form
an animal
Deutereostome
1-Radial/parallel or
perpendicular
2-indeterminate
3-can form identical twins
from the 4 cell stage
Solid masses of
Mesoderm buds along with
mesoderm split and form the archenteron cavity
the coelom
become the coelom
Mouth from blastopore
Anus from blastopore
See figure 
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Biology 102
Chapter 32
Animal Diversity
Concept 4: views of animal phylogeny …
Three dozen phyla of extant (exist) animals are recognized ( ‫ قبيلة من‬63
‫)الحيوانات معروفة اللى االن‬
Analyzing genomes , morphological traits , rRNA , hox genes ,
mitochonderional genes , protein coding nuclear genes
are ways of organizing animal phyla .
All animals share a common ancestor (monophyletic) and form a clade called
metazoa.
Sponges are basal animals. ch33
Eumetozoa is a clade of animals with true tissues
Most animals are bilaterian
Clade bilateria is diversified into three lineages ( invertebrates except phyla
chordata which includes both vertebrates and invertebrates )
1- Deutereostomia
2- Lophotrochozoa
3- Ecdysozoa ….
( you will study this deeply in chapter 33)
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