An Overview of Animal Diversity Chapter 32, Bio 11 Exam 3

Professor Palmtag

Animal

= multicellular heterotroph that

ingests its food

Description of animals

-Multicellular

-Nutritional mode

-Ingest food and digest it internally with enzymes 

Animal Tissues (except sponges and other

parazoans)

• Lack cell walls (this includes sponges)

• Abundance of extracellular structural

protein (collagen), connective tissue

• Muscle and nervous system

(coordinated movement)

No alternation of generation…

although in some animals haploid life

stages occur through parthenogenisis

Animal Reproduction

All capable of sexual

reproduction:

- Some also capable of

asexual reproduction

- Sperm and egg produced

directly from meiosis

- Embryonic development

-Genetic developmental regulation

Animals are not..

Protists 

Choanoflagellates

-Protist/Unicellular/free living/colonial

-Suspension feeders

-Like organisms was probably the ancestor to animals more than 700 mya

-This and animals share similar cell signaling and cell adhesion genes

-This is nearly identical to some sponge cells

Fertilized egg

= zygote, totipotent

stem cell

Choanoflagellates are the most closely related protists to

…animals

Cell adhesion genes

genes that make proteins

Primitive animals

do not have tissues

Cell divides up but does not lose…

volume

Cleavage

(cell matures into a
multicellular embryo)

Blastula

a hollow ball of cells that forms during early embryonic development after the morula stage

Blastocoel 

The hallow/cavity part of the ball usually fluid or air filled space 

Gastrula/Gastrulation

Indent in the blastula

Archenteron

the internal cavity that forms the primitive gut

Blastopore

is the opening that connects the archenteron to the outside of the embryo

becomes mouth or anus

Pluripotent stem cells

cells that have the ability to develop into any type of cell in the body, except for the cells that support the development of the embryo

Ectoderm

outside

Endoderm

inside

Mesoderm

middle/inner 

Egg polarity genes or maternal affect genes (not unique to animals)

-expressed to totipotent stem cells, produce transcription factors that select:

Genes associated with body plan formation

Head

anterior

Tail

Posterior 

Homeobox Genes

Master Regulatory Genes

(not unique to animals)

-When expressed, produce transcription factors that select:

Genes associated with establishing pluriptency

Ectodermal, mesodermal, and

endodermal tissues are each

Pluripotent

Hox Genes (unique to animals)

-When expressed, produce transcription factors that select:

-Genes that establish segmentation 

-Locations of legs, wings, atennae, forelimbs, rear limbs, etc. 

Transcription factors

are proteins used to trigger the expression (use) or silencing (nonuse) of a gene

Digestive system, liver, and lungs

Endoderm

Integumentary system and nervous system

Ectoderm

Mesoderm 

Musculoskeletal system and all other organs 

Homeobox Genes ???

Master regulatory Genes

Established endo-meso-ectodermal germ layers

Stimulate production of transcription factors

Establish pluripotency

Hox Genes ???

Establish pattern of late embryonic development

Stimulate production of transcription factors

Establish location of appendages, wings, forelimbs, hind limbs, antennae, etc.

Maternal Affect Genes ???

Egg polarity genes 

Gene expressed in totipotent stem cells 

Stimulate production of transcription factors 

Establish body plan, head/tail  

Hox genes (late embryonic development, unique to animals except sponges)

Produce transcription factors that organize late

embryonic body plan

Body plan

Set of morphological and developmental traits

Radial symmetry

(Jellyfish) Pizza cut not exactly even

Bilateral symmetry

(Humans/Most animals) exact math perfect symmetry down middle of animal

Dorsal

Back

Ventral

Belly

Anterior

Head region

Posterior

Rear region

Post embryonic development 

Larva/nymph 

Metamorphosis to juvenile/adult  

Animals differ in a variety of developmental traits

Differences may be used to characterize diversity among
animals

Number of pluripotent stem cell (germ) tissues

(diploblastic or triploblastic)

Body cavities

coelomate, acoelomate, or pseudocoelomate (different than cavities involved in embryotic development)

Animal differences 

-Pluripotent (diploblastic or triploblastic)

-Body cavities (coelomate, acoelomate, or

pseudocoelomate)

-Symmetry (no symmetry, radial, or bilateral)

-Embryonic development

-Protostome or deuterostome

-Cleavage (pattern of cells on early embryo)
-Body cavity formation
-Fate of blastopo

Fate of blastopore 

either becomes the mouth or the anus

Number of pluripotent stem cell (germ) tissues

• A. None, Parazoans (sponges) do not have tissues

• B. Diploblastic, Cnidarians and Ctenophores (radial symmetry)

Radial symmetry germ layers

• Ectoderm,

• Outer covering of organism and nervous system (in some species)

• Endoderm,

• Digestive system

Bilateral symmetry germ layers 

C. Triploblastic, all organisms with bilateral symmetry

• Ectoderm

- Outer covering of organism

- Central nervous system (in most species)

• Endoderm

-Digestive tract, liver, and lungs

• Mesoderm

-Muscles and all other organs

Sponges no layers

cause they have no tissues

Jellyfish cnidarian

are diploblastic

Chimpanzees and humans

triploblastic

Most triploblastic organisms have

a coelom (some don’t)

Coelom

= body cavity

Coelom

• Fluid or air-filled sac

• Cushions suspended organs

• Skeletal like function (non-compressible) in some

organisms, earthworms

• Allows for internal growth and movement

• Dampens vibrations

• Coelom type is not monophyletic, does not

indicate evolutionary relationships

Coelomates “true coelom”

• Derived from mesoderm

• Forms structures to suspend internal organs

Pseudocoelomates

“false coelom” (nothing false

about it)

• Exists between endoderm and mesoderm

Acoelomates

“no coelom”

Asymmetric…

no tissues

Radial…

all diploblastic 

Bilateral

all triploblastic

Spiral cleavage

protostome

Radial cleavage

deuterostome

Cleavage potency

First eight cells are a mixture of

pluripotent cells

protostome

Determinate cleavage

deuterostome

Indeterminate cleavage

First eight cells are

totipotent cells

The diversification of animals

• All animals share a common ancestor

• Sponges are basal taxon, parazoans

• Eumetazoans have tissues (parazoans do not)

• Most animals are triploblastic bilaterians

Three major clades of bilaterians

• 1) Deuterostomia

• 2) Lophotrochozoans

• Mostly protostomes, NOTE: Ectoproctids

and Priapulids have deuterostome

development

• Lophophore or

• Trochophore larvae

• 3) Ecdysozoans

• Exoskeleton

Pattern of cleavage

Deuterostome Protostome

Radial Spiral

Potency of eight cell stage

Deuterostome Protostome

Indeterminate (totipotent) Determinate (pluripotent)

Coelom formation/ mesoderm

development

Deuterostome                        Protostome

Archenteron outpocketings Mesodermal splits

Fate of the blastopore

Deuterostome                       Protostome

Anus                                         Mouth

Coelom forms from splits in

mesoderm, around base of

archenteron

protostome

Coelom forms within mesodermal

outpocketings at the top of the

archenteron

deuterostome

Fate of blastopore…etc

-Mouth forms from the blastopore,

protostome

-Anus forms from the blastopore,

deuterostome