Bulk Flow and Circulation

Bulk Flow

movement of air/water/blood and the substances in it, driven by pressure differences between 2 regions; moves large volumes quickly along long distances

What “large” organisms can function via diffusion?

fungi, algae (green, red, brown), early land plants (mosses, bladderworts, etc)

Fungi are

heterotrophic absorbers so their body plan maximizes SA for absorption from the environment, little need for transportation

What does fungi have to allow transport via diffusion between cells?

hyphae connected by pits or are single multi-nucleate cells

Marine/Aquatic Algae

body surrounded by O₂ and nutrients, diffuse across body wall, no need for transport

Photosynthetic Algae

entire body can produce energy

Early Land Plants via diffusion

leaves low to the ground so O₂ and nutrients diffuse across body wall; no need for transport; photosynthetic (entire body can produce energy); similar to green algae

Early Vascular Plants Characteristics

no vascular tissue, small sizes, damp environments, no roots (hold-fast to anchor), support weight via hydrostatic systems

Vascular Land Plants Characteristics

roots maximize SA for absorption; vascular tissues; bulk flow through vascular tissues

Xylem

tubes of dead cells

Phloem

tubes of living cells

Xylem bulk flow

water, minerals, hormones; cohesion-tension mechanism; water potential; fluids passively pulled up by transpiration

Phloem bulk flow

sugar; fluids actively pushed from source to sinks by translocation

Cohesion-Tension Mechanism

water molecules are polar so they bind together as they travel from area of high water pressure (in roots) to lower water pressure (leaves & veins in apoplast of mesophyll cells)

cohesion

strong bonds between water molecules

adhesion

strong bonds between water molecules and other polar materials

Water Potential

combination of osmotic gradient and pressure gradient; water moves from high to lower

Air Water Potential/Pressure

lowest water potential; very low water pressure

Ground water potential

highest; logs of dissolved salts → strong osmotic gradient

Source

tissue with lots of sucrose

Sink

tissue where sugars can be stored or used

Translocation

sucrose actively pumped into phloem at source; osmotic gradient causes influx of water from xylem into phloem; positive water pressure pushed fluid down to the sink where sucrose is actively pumped out of phloem, osmotic gradient pulls water back into xylem

Symplast

fluid just inside cell membrane; connected via plasmodesmata; requires crossing cell membrane (selects what moves)

Apoplast

fluid of extracellular space in cell wall and middle lamella

Plasmodesmatas

openings between cells

Transpiration

plants lose water through tiny pores in their leaves (stomata)

Circulatory Systems are tied to what?

body plans

Sponges

no symmetry; no differentiated guts as cells engulf food particle and diffuse nutrients; rely on diffusion

Cnidaria

radial symmetry; blind gut for bulk flow; fluid movement is non-directed and generated by muscles in body wall and cilia in gut cavity; larger size, increasing complexity of gut cavity increase SA for diffusion

Blind Gut

cavity with same entrance and exit for nutrients/water/fluid

What use gut as bulk flow system and lack additional body cavities?

ctenophora, platyhelminthes, cnidaria

ctenophora

biradial symmetry; gut for bulk flow; fluid movement is non-directed and generated by muscles in body wall and cilia in gut cavity; larger size, increasing complexity of gut cavity increase SA for diffusion

Platyhelminthes

bilateral symmetry; use gut for bulk flow; fluid movement is non-directed and generated by muscles in body wall and cilia in gut cavity; larger size, increasing complexity of gut cavity increase SA for diffusion

Radial Symmetry

multiple planes of symmetry around a central axis

Bilateral symmetry

only one plane divides the body into left/right

biradial symmetry

only two planes of symmetry exist due to paired structures even though the body is mostly radial

Pentaradial

5 planes of symmetry around central axis

Pesudocoelomate

only outer surface lined with mesoderm

Coelomate

inner and outer surfaces lined with mesoderm

Coelom

fluid filled internal spaces between digestive tract and body wall

What cavities serve as bulk flow system in animals?

fluid-filled that surround organs and the gut

Fluid movement in Animal body cavities?

non-directed and generated by muscles in the body wall and cilia

Animal Body Cavities in larger animals

portions of the cavity can specialize to form dedicated circulatory systems

Animal Vascular Systems

carry fluid from loading to unloading sites; bulk flow is directed; fluid movement by pump, vessels, valves

Fluid movement in Animal Vascular Systems

generated by a pump (heart), organized and directed by vessels, direction of flow is managed by valves

Open Vascular system

connective fluid moves through defined vessels, but exchange occurs in open sinuses

Hemolymph

circulating fluid in invertebrates

Closed Vascular Systems

convective fluid (blood) moves through defined vessels and exchange occurs across walls of small vessels called capillaries

What invertebrates have open circulatory systems?

anthropods

What invertebrates have closed circulatory systems?

cephalopods (squids, octopuses)

Fish in water circulatory system

vertebrate ancestral condition; blood oxygenated at gills; closed circulatory system with 2-chambered heart and single circulatory circuit

Fish breathing air circulatory system

boney fish ancestral condition; blood oxygenated at lungs; 2 circuits from heart

Pulmonary circuit

heart to lungs to heart

Systemic Circuit

heart to muscle/body to heart