Lecture 22 - Growth Flashcards
Growth
- increase in cell mass
- irreversible increase in biomass
describe unicellular, animal, and plant growth
Unicellular
- > grow then divide
Animals
- > grow throughout body often restricted in time
Plants
- > grow throughout lifetime, restricted in space
Development
- change in form
- change from simple to complex/specialized form
describe animal and plant development
Animal
- > well established body plan
Plants
- > minimal body plan
Phenotype depends on ___________
environment, not just genome
- > how we develop, how we grow is not dependant strictly on our genome
describe the growth of unicellular organisms (on the cellular level)
- > division (usually) results in two daughter cells in the same size as the original
- > growth occurs before division
- > “growth” usually refers to colony growth
describe the growth of multicellular organisms
Animals
- > growth fastest when embryo, often stops when juvenile (determinant growth and structure)
Plants
- > growth rates decline, but don’t stop until death (indeterminate growth and structure)
Growth curves
- > typically signmoid growth pattern is very common
- > the first derivative of the curve = rate of growth
* lag phase: slow growth
* Exponential/log phase: rapid growth
* stationary phase: slow/no growth
deveopment in multicellular organisms
development of animals
- > cleavage of the zygote produces hollow blastula
- > cell fold/move/rearrange, producing a two-or three-layed gastrula (morphogenesis)
- > cells and tissue types produced according to cell layer (ecto,endo,mesoderm)
- > zygote = totipotent (can develop into new organism)
radial vs bilateral symmetry
- > radially symmetric animals are diploblastic (no mesoderm)
- > bilaterally symmetric animals are triploblastic (organogenesis follows gastrulation)
what happens to deteriorating animals cells
deteriorating cells need replacement
- > stem cells divide producing a stem cell and another cell that specializes (precursor cell)
how are embryonic and adult stem cells different
embryonic
- > pluripotent and widely distributed
adult SC
- > multipotent
- > needed for production of cells that continuously turn-over (blood,hair,etc.)
- > spacially (brain, bone marrow, etc.)
development in plants
- > embryogenesis establishes primary growth axis, first leaves, and regions of cell dividion
- > organogenesis in plants occurs after germination
- > growth restricted in space
primary vs secondary growth of plants
Primary growth
- > occurs in apical meristems
- > cell division and elongation
- > increases length
Secondary growth
- > occurs in lateral meristems
- > cell division
- > increases width
phenotypic plasticity
Phenotypic plasticity is the ability of one genotype to produce more than one phenotype when exposed to different environments
i.e. desert locus can be green or yellow-black, this adaptation is caused by contact with con-specifics
