Evolution of Flowering Plants Flashcards
What key trait in non-seed plants predisposed the evolution of seed plants
Heterospory — micro- and megaspores → pollen (microgametophyte) & ovule (megagametophyte
When do angiosperm fossils first appear
Early Cretaceous (~120 mya) – mostly pollen (sporopollenin fossilises well)
What did the earliest flowers resemble
Magnolia-like (simple flowers, ~2mm in size)
What is Archaeanthus
First complete angiosperm fossil, ancestor of the tulip tree
What is Archaefructus
Oldest known herbaceous aquatic flowering plant, from Yixian Formation, China (~125 mya)
What is Lesqueria
Extinct mid-Cretaceous magnoliid with distinctive fruiting structures (helically arranged follicles)
What evidence exists for ancient plant pollinator relationships
Paleoclusia (Clusiaceae) may have rewarded stingless bees with resin
Stingless bees found in Upper Cretaceous amber
Were early gymnosperms insect-pollinated
Yes – scorpionflies had specialised nectar-feeding parts by ~170 mya, Middle Jurassic
List 5 essential angiosperm features not in gymnosperms
- Carpel enclosing ovules
- Double fertilisation
- Double integument
- Flowers with sepals/petals/stamens/carpel
- Vessels in xylem and phloem companion cells
What is a carpel
Ovule-enclosing organ composed of stigma, style, and ovary
Gymnosperm vs Angiosperm ovules
Gymnosperm: naked, 1 integument, archegonia, multicellular gametophyte
Angiosperm: enclosed, 2 integuments, no archegonia, reduced embryo sac (7-8 cells)
What happens during double fertilisation in angiosperms
One sperm + egg → diploid zygote
One sperm + polar nuclei → triploid endosperm
How do gymnosperms and angiosperms differ in food source allocation
Gymnosperms store food before fertilisation
Angiosperms store food after fertilisation → more efficient
What is a fruit in botanical terms
A structure formed from flower/inflorescence parts containing seeds
Why do fruits become fleshy
To attract animals for seed dispersal (e.g., durian uses smell)
What are monocolpate and tricolpate pollen types
Monocolpate: single furrow; found in monocots + basal dicots
Tricolpate: 3 furrows; found in eudicots
What defines a clade
A monophyletic group: common ancestor + all descendants
Define homoplasy vs synapomorphy
Homoplasy: Shared trait from independent evolution
Synapomorphy: Shared derived trait from common ancestor
What genes were analysed in 1999 to revise angiosperm phylogeny
lastid atpB, rbcL, and nuclear 18s rDNA
What are the basal angiosperm clades
Amborella
Nymphaeales (water lilies)
ITA clade (Illiciaceae, Trimeniaceae, Austrobaileyaceae, Schisandraceae)
What traits make Bennittitales and Glossopterids potential angiosperm relatives
Bennettitales: bisexual cones, abundant in Triassic
Glossopterids: net-veined leaves, dominant in Permian, but unisexual cones
What is the Anthophyte hypothesis
Suggests that gnetophytes, Bennettitales, and angiosperms form a clade based on shared floral-like traits
What traits support the Anthophyte hypothesis
Vessel elements in xylem
Flower-like strobili
Insect pollination
Embryo sac (reduced female gametophyte)
Gnetophyte double fertilisation (no endosperm)
