bio ch. 26: phylogenetic distribution of molecular organisms

diveristy unit

simple multicellular characteristics

cells show little differnence, cells remain in contact with environment, adhesion molecules hold cells together, can survive loss of individual cells with minimal impact

aggregative multicellularity

free living eukaryotes come together during one stage in life, temporary, likely result of environment (ex. slime molds)

cenocytic organization

nuclei divide repeatedly, cytoplasm does not divide, onr large multinuclear cell

advantages of simple multicellularity

colonies too large to be eaten, anchoring (seaweed), enhanced feeding

complex multicellularity features

strong cell adhesion, cell-to-cell communication, complex gene regualtion networks, control cell differentiation and development

complex multicellulairty characteristics

specialized tissues and organs, only some cells reproduce, loss of key tissues can be lethal, 3d body organization

3d body organization

interior cells lack direct environmental access, requires internal transport of nutrients, oxygen, and molecular signals

evolution of complex multicellularity

animals, fungai, green algae, red algae, brown algae

diffusion

net movement of molecules from high to low concentrations during to random motion, effective over short distances

constraints with diffusion

cell size, cell shape, tissue thickness, can’t transport far distances

sponges use diffusion

cells remain close to circulating seawater, body filled with porse and canals, large size achieves without isolating cells from environment

sea jellies use diffusion

thin layers, composed mainly of water, oxygen passes directly through

bulk flow

movement of fluid driven by pressure differences, moves substances faster and further distances

bulk flow enables

ozygen transport, nutrient distribution, hormone signaling

bulk flow in vertebraes

oxygen diffuses in lungs, binds hemoglobin to red blood cells, heart pumbs blood through vessels

bulk flow in plants

xylem transports minerals from roots to leaves and phleom transports sugra from leaves to roots

bulk flow in fungai

use osmosis, transport nutrients through filament network

requirments for multicellular organisms

adhesion, communication, genetic regulatory network

cedherins

cell-cell adhesion

intergrins

attach cells to extracellular matrix

adhesion in plants

pectins

cell communication in animals

endocrine, paracrine, autocrine, contact dependent

endocrine signaling

long distance travel of hormones

autocrine signaling

A cell signals itself by releasing a ligand that binds to receptors on its own surface

contact dependent signaling

physical contact between adjacent cells required for communication

paracrine signaling

nearby

plant evolutionary consequences

cells cannot engulf particles, cells can’t absorb orgnanic molecules, depend mainly on photosynthesis, lack pseudopodia, no flagella, cells can’t migrate

blastula

hollow, single-layered ball of cells formed during pre-embryo

grastula

blastula develops into differentiating germ layers, embryo

oxygen began

2.4 BYA

intergrins

transmembrane receptors that bridge the extracellular matrix ot the intracellular actin cytoskeleton