Animal
Architecture
Whither Deuterostomes?
Rotation at the Proto-Deutero Node
A. Some researchers consider the
deuterostomes an ancestral group
relative to the rest of the animal taxa.
a. Note that it IS possible to rotate the
phylogeny around the DeuterostomeProtostome node.
What It Means
The Bauplan
Concept
1. Refers to the structural and
functional "plan" of an organism
a. Doesn't mean that an architect
designed it, although there often is
that appearance
b. A simpler explanation lies in natural
selection acting on population
variation.
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This Results In:
1. Body coloration due to how well an
organism matches its surroundings.
2. Body shape determined by how well
certain appendages permit
locomotion, food capture, defense.
3. Body machinery determined by how
well materials are processed,
transported, excreted.
What It Means
All components of the "bauplan" must
work effectively as a whole.
a. And because natural selection works
primarily on the organisms,
1. The necessary functional
interrelationship of the systems and
structures interacts with the historical
component inherent in living systems.
Observed Phenotypes
1. Are the accumulation of successful
characteristics, passed on to
offspring.
a. Characters persist because they
allow their possessors to survive and
reproduce.
b. Also, due to influences of random
factors such as chance, physical
constraints, and evolutionary history.
What It Means
. 2. This produces certain patterns of
organization that persist over
evolutionary time.
3. Manifested as major phyla, classes,
orders of organisms.
Cellularity
What are the
components of
a "Baupläne?"
a. Whether or not the organism has
cells.
b. It may or may not be advantageous to
have them.
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Body Symmetry
Organ Systems
a. How is the body arranged around one
or more axes?
b. Certain shapes benefit feeding,
locomotion.
The mechanisms required to run
multicellular organisms.
Organ Systems
2. Energy acquisition
a. Means for capturing, processing and
utilizing energy sources from the
external enviroment.
Organ Systems
4. Materials transport
a. Means for moving materials within
the body.
b. Essential for multicellular organisms
1. Support and movement
a. System of supporting, protective,
mechanical elements that permit the
body to support itself and/or move.
Organ Systems
3. Osmoregulation and excretion
a. means for regulating flow of water
and wastes into and out of the body.
Organ Systems
4. Gas exchange
1. Obtain oxygen, remove CO2, other
gaseous wastes.
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Organ Systems
Organ Systems
5. Information processing
a. Nervous system for receiving,
processing, responding to internal and
external stimuli.
b. Hormonal control of internal
processes.
6. Reproduction
a. Repair of genetic, somatic structures.
b. Production of new individuals; as
clones or as gametes.
Why be Multicellular?
Why be Multicellular?
1. There are lots of advantages to
unicellularity.
2. Evidenced by the success of the
Protozoa:
a. rapid reproduction
b. exploitation of microhabitats
c. opportunities for dispersal, resistant
forms widespread.
3. But, there are also advantages to
being larger:
a. Large size, multicellularity permits:
1. predator escape
2. greater variety of foods
3. greater specialization
4. greater capacity to tolerate unstable
environment.
In Short,
1. Once situations existed that
permitted multicellularity,
a. Perhaps existence of oxygen
(produced by plants)
2. Multicellularity led to explosive
adaptive radiation (preCambrian
Explosion, >600 myr ago).
a. Result: Multicellular animals:
METAZOA.
What happens
when you
become larger
and more
complex?
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Certain Organisms Don't
Exist
Cellularity,
Revisited
1. There are no 800 lb amoebas.
a. There are no single-celled squid, sea
stars.
b. Why?
c. Because there are physical
constraints on life.
Physical Constraints on Life
Physical Constraints on Life
1. Most living systems involve ionic
chemistry; what molecules can do in
water
2. There are physical limits on size.
3. Phylogenetic limits exist a. genetic variation.
b. evolutionary history.
c. selection intensity.
Consider a Cube
1. With 1 cm sides:
a. Each side: 1x1 =
1cm2
1. Substances must enter and exit cells
through the cell membrane
a. Thus, the physical relationship
between surface area and volume
places a limit on cell size.
Consider
Another Cube
2. With 2 cm sides:
1. each side: 2x2 =
4cm2
b. Total surface area:
6(1) = 6 cm2
2. total surface area:
6(4) = 24 cm2
c. Volume: base area
x height = 1x1
= 1 cm3
3. volume: base area x
height = 4x2 = 8 c3
d. s.a./vol. ratio: 6/1 =
6
4. s.a./vol. ratio: 24/8
=3
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If You Get Larger:
What Does It
Mean?
If You Get More Complex:
1. Increased cell numbers, increased
size = increased complexity.
a. Individual cells are limited in their
ability to do different things.
b. But: increased cell numbers permits
cellular specialization.
c. Increased efficiency is obtained by
increased specialization.
1. Increasing volume->increasing
cellular activity ->increased
nutritional requirements, increased
waste production.
2. Thus, by dividing organism into
smaller parts, increased efficiency at
materials transport.
a. Sponges absorb better than paper
towels.
Venus Williams vs. the
Arizona Cardinals
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If You Get More Complex:
2. Greater specialization, however,
necessitates maintenance
mechanisms.
a. nerve cells aren't very good at
catching their own food.
b. Required systems: the ones
mentioned above.
Cellular Associations
Tissue
Organization
Porifera
1. Multicellular animals may consist of
loosely organized groups of cells
a. little specialization
b. little integration among functional
groups of cells
2. Examples:
a. Sponges
b. Mesozoa - linearly arranged clusters
of cells.
True Tissues
Mesozoa
1. Cells arranged as functional units.
a. Specialization of structure and
function.
b. Usually arranged in systems and
organs.
2. Arrangement is often laid down early
in development.
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Diploblastic Arrangement
Aurelia aurita
1. Epidermis - outer layer
2. Gasterodermis - inner, digestive layer
3. Mesenchyme - middle layer of cells,
but no true mesoderm
b. Examples:
1. cnidarians, ctenophores
Pleurobrachia sp.
Triploblastic Arrangement
1. Epidermis - outer layer, derived
from embryonic ectoderm.
2. Endodermis - digestive layer,
derived from endoderm
3. Mesodermis - inner muscle, organ
layers, derived from mesoderm
Notoplana acticola
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Body
Symmetry
Spherical
1. Cody of the organism is arranged so
that any plane can cut it into equal
parts
2. Relatively few examples in metazoa
except early in development
3. Protozoa
a. radialaria
b. multicellular algae: Volvox
Astrolithium sp.
How ARE
Organisms
Arranged?
Pandorina sp.
Irregular
1. Body of organism is arranged so that
no plane cuts it into equal parts.
2. Examples:
a. amoebae
b. sponges
3. Neither spherically nor irregularly
symmetrical organisms have polarity
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Mayorella sp.
Mycale loveni
Haliplanella luciae
Isodictya sp.
Radial
1. Body is arranged along a longitudinal
axis (varying in length).
a. Often with oral, aboral ends
b. Polarity is established
2. Planes drawn parallel to the
longitudinal axis divide the animal
into equal halves.
3. Often associated with sessile feeding.
Pachycerianthus fimbriatus
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Biradial
1. Similar to radial symmetry except
that only two planes will cut the
animal into equal halves.
a. Usually some secondary
specialization on feeding arrangement
2. There can be more involved versions
of this.
a. triradial, pentaradial, etc.
Fungia scutaria
Chaetonotus sp.
Metridium senile
Bilateral
1. A single plane divides the body into
equal halves.
2. often with other functional surfaces.
a. dorsal, ventral, lateral.
b. anterior, posterior.
3. Usually locomotory specialization
4. Often associated with cephalization
(association of nervous tissue in
anterior end).
Urechis caupo
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Apis mellifera
Body Cavity
Arrangement
Acoelomates
1. Possess no body cavity
2. Instead, parenchyma tissue and
muscles.
3. Examples:
a. Platyhelminthes
b. Nemerteans
Opisthorchis sinensis
Bipalium kewense
An Antarctic
nemertean
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Pseudocoelomates
1. Possess a body cavity,
2. Fluid filled pseudocoel; organs
supported by hydrostatic pressure.
3. Lack mesenteries
4. Examples:
a. Blastocoelomate (Ascelminth) phyla
A horsehair worm
Eucoelomates
1. Possess a body cavity
2. Not fluid filled or under pressure
3. Organs supported by mesenteries
4. Examples:
a. all other phyla
Corynosoma sp.
Pycnophyes greenlandicus
Opisthopus transversus
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Florometra serratissima
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