lecture 8 generalities Flashcards
What is a haplontic life cycle?
Plants with n instead of 2n
What are the unique features of green plant chloroplasts?
- true starch storage compound
- thylakoids stacked in grana
- chlorophyll b (chlorophyll a is ancestral)
The bulk of the primary cell wall of green plants is composed of what substance?
Cellulose
Is the cell wall synthesized inside or outside the plasma membrane?
synthesized by plasma membrane + forms around it
What are plasmodesmata?
- Pores in the primary cell wall through which membranes
traverse between cells - Allows transfer of compounds between cells
- More efficient/rapid transport of solutes, including regulatory
and growth-mediating compounds, such as hormones
What is an embryo?
immature sporophyte
What is oogamy?
preadaptation to survival on
land in the streptophyte lineage
- Type of sexual reproduction in
which one gamete, (egg),
becomes larger and
nonflagellate - the other gamete
is, by default, called a sperm cell
- found in all land
plants and independently
evolved in many other groups,
including many other algae
Name the major apomorphies of the land plants.
- archegonium
- antheridium
- parenchyma
- cuticle
- sporophyte/embryo (alternation of generations)
Draw and label the basic haplodiplontic life cycle (alternation of generations) of all land
plants, illustrating all structures, processes, and ploidy levels.
Haploid gametophyte phase- gametes are produced by archegonium and antheridium and are fertilized and form a zygote- becomes an embryo- diploid sporophyte- differentiated (thru mitosis?) into diploid sporangium and sporocyte- undergoes meiosis to become haploid gametophytes
What is a sporangium?
- A portion of the sporophyte that differentiates as the spore-producing region
Name the possible adaptive features of the sporophyte.
- Large increase in spore production:
- In the absence of a sporophyte, a
single zygote will produce four
spores. - Growth of the zygote into a
sporophyte and sporangium can
result in the production of millions
of spores
- In the absence of a sporophyte, a
- Another possible adaptive value of
the sporophyte is associated with
its diploid ploidy level - Two copies of each gene may give
the diploid phase an increased
fitness in either of two ways
1. by potentially preventing the
expression of recessive, deleterious
alleles
2. by permitting increased genetic
variability in the sporophyte
generation (via genetic
recombination from two parents )
upon which natural selection acts,
thus increasing the potential for
evolutionary change
What are cutin and cuticle and what are their adaptive significance?
- A cuticle is a protective layer that is secreted to the outside of the cells of the epidermis- consists of a thin, homogeneous, transparent layer of
cutin (polymer of fatty acids) - Mechanical protection of inner tissue and protection from water loss
The adaptive advantage of cutin and
the cuticle: - prevention of desiccation outside the
ancestral water medium - Plants that are adapted to very dry
environments will often have a
particularly thick cuticle to inhibit
water loss
Define apical growth
directional proliferative growth facilitated by the self-renewing activity of an undifferentiated meristematic cell or cells
parenchyma
directional proliferative growth facilitated by the self-renewing activity of an undifferentiated meristematic cell or cells
- Cells derived from the
apical meristem region
form the parenchyma: a
solid mass of tissue - Unspecialized,
undifferentiated cells of
actively dividing tissue - Elongate to isodiametric
- Have a primary (1°) cell
wall only (rarely a
secondary wall) - Living at maturity and
potentially capable of
continued cell divisions - Function in metabolic
activities such as
respiration, photosynthesis,
lateral transport, storage,
and regeneration/wound
healing - May further differentiate
into other specialized cell
types - Not clear if the evolution of
both apical growth and true
parenchyma is an
apomorphy for the land
plants alone
