24: Angiosperm

What are angiosperms?

Flowering/fruiting plants

Angio = container

Sperma = seed

(gymno = naked)

Global dispersion of angiosperms vs gymnosperms

Gymnosperms in pacific and NW region (cooler regions)

Angiosperms taken over everything else

What is a flower?

Determinate structure (its future is planned out)

Arranged in a sequential order in whorls (arrangement of similar anatomical parts in a circle around a point on an axis)

What parts make up a flower?

Carpel

Stamen

Petal

Sepal

Sepals

modified leaves that offer protection to the bud

usually green

the leaves on the bottom of flowers

Petals

often bright, large and attractive to lure in pollinators (if pollinated by animals)

Stamen

Male part of the flower

Contains the microsporangia

Made up of anther (fuzzy tip) and the filament (stick)

Carpel

Female flower part

Stigma = tip/apex, sticky surface where pollen lands and pollen tube germinates

style = from stigma down to ovary

Ovary= contains the ovule

Do gymnosperms have ovules?

NONONONONONONONO, they have the megasporangium that’s just hanging out

Sporophyll

spore-producing leaf-like organ

sporo = spore-producing

phyll = leaf-like organ

Megaphyll

big leaf for photosynthesis

What are the origins of flower whorls?

Carpel & Stamen: modified sporophylls

Petals & Sepals: modified megaphylls

What are all the layers inside an ovule?

Integument, megasporangium, female gametophyte, archegonium, egg

Where are gymnosperm ovules?

Exposed on cone scales

What are fruits developed from?

Ovaries can develop into fruits after fertilization

What lead to the angiosperms taking over?

Flowers increase precision/frequency of pollen transfer

• Specialization to local conditions, coevolution with pollinators and dispersers

Environment change and disturbance created habitats where angiosperms could diversify

How do angiosperms have increased rates of transpiration and photosynthesis?

Their lineages underwent rapid genome downsizing, which meant they could pack their leaves with smaller, more abundant stomata and dense vein networks

Endosperm

Nutrient-rich tissue that is food supply during seedling establishment

Endosperm in Monocot vs Eudicot Seeds

Monocots: Endosperm is liquid, develops into starchy solid

Eudicots: Endosperm is liquid, develops into two cotyledons

Cotyledons in eudicots vs monocots

Monocot has 1, eudicot has 2

cotyledon: first seed leaf

Pericarp

the fleshy part of fruit (everything else besides actual seed inside)

What develops into the pericarp?

The mature ovary wall

How do fruits help with dispersal

Wind: small/dry fruits can open, cling, or ride the wind

Water: thick shell can prevent water damaging the seed, buoyancy

Animal - internal: fleshy fruits can be brightly colored, seeds tough and undamaged if eaten, young fruits are green to hide them among leaves to prevent the fragile seeds inside from being hurt. unripe fruit also bitter/sour to discourage animals, also cling on tightly to parent plant

Animal - external: catch on hair of animals