Topic 2 - What are flowering plants - key features of angiosperms (BIOL 2242)

angiospermae

clade of flowering plants

“angio” =

vessel

“sperm” =

seed

“angiosperm” =

enclosed seed

angiosperms are sometimes called ________

Anthophyta

synapomorphies

shared, derived characteristics

• form the basis for inferring evolutionary relationships

land plants form the clade ________

Embryophytes

• time of divergence ~ 450 mya

ancestrally, what generation is dominant

gametophyte

challenges of living on land (vs. aquatic)

• reproductive challenges - aquatic serves as a medium for gamete dispersal

• gravity

• susceptible to predation - have to develop features to discourage feeding

• susceptible to desiccation - water scarcity

• initially lack of gametes/seed dispersal mechanisms (no animals present at first)

opportunities of living on land (vs. aquatic)

• easier gas exchange - CO2/O2

• easier access to sunlight/nutrients - soil

• create CO2 - transformed life on earth

Lignophyta

woody plants

spermatophyta

seed plants (gymno and angio)

synapomorphies of seed plants (Lignophyta/Spermatophyta)

• megahyllous leaves

• seeds with multicellular embryos

• heterosporous (spores of different sexes are different)

heterosporous

• microspore = pollen

• megaspore = embryo sac (develops inside the megasporangium = ovule)

synapomorphies of flowering plants (angiosperm/anthophyta)

• can be considered Division Magnoliophyta

• ovules enclosed within carpel (maternal tissue)

• stigma (female part) formed of carpellary tissue (receives pollen)

• 2-4 microsporangia (anthers) per microsporophyll (anthers + filament)

• double fertilization - second sperm fuses with polar nuclei of embryo sac (produces endosperm - typically polyploid 3N)

microsporophyll

leaf that includes the male parts

endosperm

nourishes the growing embryo and polyploid (3N)