embryo development Flashcards
describe alternation of generations in angiosperms and it’s 3 derived traits
3 derived traits = flowers, double fert, production of fruit
describe gametophyte development
-most reduced gametophytes are in angiosperms
-dependent on sporophyte for nutrients (enclosed in sporophyte tissues)
what are the first 3 steps in female gametophyte formation?
1) carpel develops
2) 1 or more ovules form in ovary
3) embryo sac develops in ovule
what happens to the megasporocyte in the production of female gametophytes?
megasporocyte enlarges and undergoes meiosis
what happens to the one megaspore that survives?
it undergoes mitosis 3 times w/o cytokinesis to give rise to one cell with 8 haploid nuclei
what happens to the cell with 8 haploid nuclei?
the cell divides and forms the embryo sac (synergids help guide pollen to sac)
how are microsporangia produced?
stamens grow and each anther produces 4 microsporangia
what do the sporangia contain?
microsporocytes that undergo meiosis to form haploid microspores
what do the microspores undergo?
mitosis to produce pollen grain with 1 generative cell and 1 tube cell
what makes up the pollen grain?
tube/generative cells + sporopollin protective wall
how does pollination occur in angiosperms? (3)
- microsporangia release pollen which sticks to the stigma of another flower
- pollen grain absorbs water and germinates
- releases tube nucleus that divides into two sperm cells
why is double fertilization beneficial?
ensures the endosperm develops only in ovules where the egg has been fertilized
how does the seed carry out development?
stockpiles proteins, oils, and starch allowing embryo to develop into a new sporophyte
how does the endosperm develop?
- triploid nucleus divides to form a supercell
- cytokinesis forms membranes to produce cell walls
- endosperm becomes solid
what are suspensors?
thread of cells that transfer nutrients to the embryo
what are cotyledons?
part of the seed embryo which may become the 1st leaf
what is the first organ to emerge in the seed?
radicule which develops into the primary root
what is a developmental switch?
switch from vegetative structures to flowers (reproductive structures)
how is the transition into a floral meristem triggered?
external cues and internal signals
when and why is sexual reproduction good?
-in unstable environments
-seeds have longer dispersals
-seeds can be dormant (but fragile and nutrient draining)
-increase in variation
when and why is asexual reproduction good?
-no need for pollinator
-pass genetic legacy
-good in stable conditions
