frst 210 midterm 2

seed cone

megagametophytes developed
each ovuliferous cone scale develops two megagametophytes
each of these can become a seed if fertilized

compound buds

contain bud primordia for vegetative, pollen, and seed development

somatic embryogenesis

the production of plant embryos from body (somatic) cells
tissue cultures of partial embryo and megametophyte containing an embryo
callus tissue becomes embryonic

zygotic meiosis

zygote undergoes meiosis immediately after it is formed, all individuals that are produced are haploid until the next zygote is formed.
most fungi, some green algae, many protozoa

sporic meiosis

an alternation of haploid and diploid generations (plants, many algae)
sporophyte- microgametophyte (pollen grain) megagametophyte- ovule (8 cell nuceli, 7 cells, 2 polar nuclei)

fern life cycle

gametophytes (N) and sporophytes (2N) of ferns are both photosynthetic and self supporting
mature sporophyte (fern) -> produce spores
germinate as a gametophyte -> sperm and egg fertilize to become a zygote
embryo develops from the gametophyte -> grows into a mature sporophyte

gymnosperm bud characteristics

can be vegetative, male (pollen cone) or female (seed cone)

pollen cone

microspores:
pollen mother cell produces four microspores
each microspore will divide to become a pollen grain (microgametophyte)

fertilization in douglas-fir

megagametophyte fully develops 3 wks after pollination
each ovule has one megagametophyte with 4-7 archegonia each containing one egg cell
several egg cells can be fertilized but only one develops into a mature embryo

gametic meiosis

animals, some fungi and brown algae
individuals spend most of their lifecycle in the diploid phase (sporophyte)
gamete is the only haploid cell produced

double fertilization in angiosperms

one sperm will fertilize the egg to produce a 2N zygote
the other sperm will fuse with the 2 polar nuclei to produce the 3N endosperm (nutritional reserve)

white pine blister rust

effects white bark pine
along with mountain pine beetle decimating populations
genetic solutions may be effective due to genetic variation making some individuals resistant to the fungus

determining genetic resistance

separate genetic from environmental effects
go into heavily infected pop and locate trees with no infection
cross res x res, sus x sus, and res x sus

evolutionary forces acting on populations

mutation
genetic drift
selection
mating system
gene flow

mutation

ultimate source of all genetic variation necessary for evolution by natural selection
can occur during meiosis, mitosis, or due to DNA damaging agents (UV radiation)
mutations are very rare

selection

requires
- variation for traits
- inheritance of traits from parents to offspring
- probability of surviving and reproducing caries or increases with the characteristics of the trait inherited
changing selective pressures in the anthropocene
artificial selection

genetic drift

random changes in allele frequency from generation to generation resulting in genetic changes over time and loss of genetic variation
increases the risk of deleterious alleles
occurs most in small pops

effective population size

Ne
estimate of the genetic population size that is inversely proportional to the rate of loss of variation due to genetic drift
smaller Ne causes loss of genetic diversity as well as greater inbreeeding
non-linear relationship- gen div loss accelerates as Ne declines (very rapid in small pops)
10-50% of the census number of individuals in a pop, depending on how much the number of offspring varies among individuals and how related individuals are

gene flow

the movement of individuals or gametes between different populations
(seed dispersal)
introduces new genetic diversity

mating system

inbreeding vs outcrossing
inbreeding often reduces seed viability, growth rate, and overall fitness -> inbreeding depression
inbreeding is avoided in trees by having separate male and female reproductive structures (one above other, different times, genetic incompatibility mech, separate trees for sexes)