Ch. 32 Part 1: Animal Body Plans Flashcards
In Complex Multicellular Organisms, bulk flow
circumvents the limitations of diffusion
Complex multicellularity depends on
cell adhesion, communication, and a genetic program for development
Animals
- Multicellular
- Heterotrophic eukaryotes with tissues that develop from embryonic layers
- can be characterized by “body plans”
Views of animal phylogeny
continue to be shaped by new molecular and morphological data
3 types of body cavities
1) Coelomate
2) Pseudocoelomate
3) Acoelomate
Pseudocoelomate
exists between the endoderm and mesoderm
false
Acoelomate
no body cavity
Coelomate
(eu)coelomate
within mesoderm only
true
Unicellular
- cell is autonomous
- can do all functions by themselves
- all prokaryotes, many eukaryotes
Simple Multicellularity
Colonial
- Cell adhesion molecules maintain structural integrity (Cadherins)
- Little intercellular communication or nutrient transfer
- Very little differentiation; cells retain most/all functions
- Nearly all cells in direct contact with external environment
- Little cost to losing a cell
- Common in algae
Advantages to colonial vs. unicellular
1) Avoid being eaten: size can be a deterrent
2) Maintain position in water column
3) Flagellar currents and filter feeding (suspension)
Disadvantages to colonial vs. unicellular
Cells no longer act in a corporative manner
-susceptible to “cancer”
Complex Multicellularity
- Highly developed adhesion mechanisms
- Specialized structures for intercellular communication
- Complex patterns of tissue and organ development guided by regulatory gene networks
- 3- dimensional organization
- plants, fungi, animals
Complex Multicellularity features
1) Adhesion
2) Communication
3) Development
4) Key innovation in multicellularity
Adhesion types
a) cadherins: cell = cell
b) integoins: cell = extracellular matrix (ECM) (critical in animals - no walls)
c) ECM
d) pectins
e) gap junctions: animal: physical connection and intracellular communication (tubes)
f) plasmodesmata: plant: physical connection and intracellular communication (tubes)
Communication types
a) gap junctions
b) plasmodes
c) integral (plasma membrane) receptors
d) intracellular receptors
Development
molecular signals direct differential gene expression leads to cellular => tissue => organ differentiation
a) division of labor because of
b) different environments
Key innovation in multicellularity
ability to enable cells to differentiate in Space instead of Time
Biological Design Principles
2nd law of Thermodynamics
diffusion
2nd Law of Thermodynamics
- disorder is spontaneous in our Universe
- i.e. high concentration to low concentration
- disorder to order is not spontaneous, but can occur if work is done (input of energy)
Diffusion
particles spontaneously move from areas of high concentration to low concentration
has to go through the diffusion path: O2 => membrane (SA) => Cytosol (V) => mitochondria
Size limits on cells
SA = 4 * pi * r^2
V = (4/3) * pi * r^3
radius is the only thing varied
SA/V ratio decreases as radius increases
Fiele’s Law
Js = DA (∆c/∆x) => linear Js vs [C]
Js = diffusion rate of s (flux) D = diffusion coefficient (empirically determined) solubility (how fast) A = surface area ∆c = concentration gradient ∆x = path length
Field’s Law and diffusion
increase in D, A, or ∆c will increase Js
decrease in ∆x will increase Js
Multicellularity and size of organisms
1) Multicellularity (complex)
2) Size
3) Animal Body Design
4) Body Cavities
5)
Multicellularity (complex)
- exterior > interior
- exterior < interior
(i. e. O2 > ; < CO2) - nutrients/waste
- temperature, pH, light physical force gradients
- shape
Size
If small, then diffusion can work
If larger, then diffusion is insufficient (limiting); therefore, resorts to bulk flow
Bulk Flow
a means by which molecules move through organisms at rates beyond those possible by diffusion alone across a concentration gradient (moving faster)
3 types of Animal Body Designs (trends)
1) Symmetry
2) Body Cavities
3) Germ layers
3 types of Symmetry
1) Asymmetric
2) Radial
3) Bilateral
Asymmetric
no mirror image when cut
i.e. sponge
Radial Symmetry
- mirror image
- many possible planes
- i.e. circular
- probably started here
Bilateral Symmetry
- mid-sagittal plane (left and right)
- mirror image
- one possible plane
- i.e. humans
(frontal) coronal plane
dorsal/ventral
Traverse plane
anterior/posterior
Germ Layers
embryonic tissues (1st ones) diploblastic vs. triploblastic
Diplobastic
2 germ layers:
1) endoderm
2) ectoderm
Triploblastic
3 germ layers:
1) endoderm
2) mesoderm
3) ectoderm
If triploblastic, then
protostome vs deuterostome
Protostome
- Blastopore first opening: mouth
- Spiral cleavage
- Schizocoely = split mesoderm
Deuterostome
- Blastopore first opening: anus
- Blastopore seconde opening: mouth
- Radial cleavage
- Enterocoely = grows out of the mesoderm
