Topic 17 Flashcards
Angiosperm Life Cycle Characteristics
- Sporophyte is the dominant generation, large plant we see
- Gametophytes are microscopic and depend on sporophyte
- The Three F’s (flowers, double fertilization, and fruits)
Generative Cell
One cell in the two-cell male gametophytes in angiosperms that develop sperm nuclei
Tube Cell
One of the two cells in the two-celled male gametophyte of angiosperms that forms the pollen tube necessary for fertilization
Double Fertilization
Occurs in angiosperms when the pollen tube discharges two sperm nuclei into the female gametophyte within an ovule, resulting in a triploid cell
Two Functions of Fruits
Protect seeds and assist in seed dispersal
Adaptive Advantages of Angiosperm Fertilization
- Nutrient stores in endosperm after double fertilization
- Fruit development usually initiated by fertilization
- Female gametophytes undergo significant size reduction
- Rapid development of the small female gametophyte
Angiosperm Abiotic Pollination
Pollination through water pollination or wind pollination
Angiosperm Biotic Pollination
About 80% of angiosperm species rely on animals for pollination, and about 65% of flowering plants are pollinated by insects
Coevolution and Example
The simultaneous evolution of interacting species in response to the selection pressures exerted by each other.
Ex) flowering plants have evolved alongside specific pollinators.
Ex) Darwin’s Orchid: a moth-pollinated plant with nectar spurs marching the length of the hawk-moth tongue
Self-fertilization
An advantageous trait for plants in isolated environments or where pollinators are rare.
Angiosperms AVOID self-fertilization
Mechanisms Preventing Self-fertilization in Angiosperms
- Self-incompatibility
- Floral structure of incomplete flowers that are either monoecious or dioecious
- Temporal and spatial separation where stamens and carpels on a plant mature at different times
Monoecious
Incomplete flowers with both male and female flowers growing on the same plant
Dioecious
Incomplete flowers with male and female flowers on different plants
Angiosperm Evolution
Angiosperms formed through adaptive radiations coinciding with the decline of gymnosperm groups during the Cretaceous period due to developing modified xylem cells, rabid speciation with co-evolution, and rapid reproductions
Monophyletic v. Paraphyletic Angiosperms
Monocots are monophyletic and dicts are paraphyletic
Eudicot Seeds v. Monocot Seeds
Eudicot seeds contain an embryo with an embryonic acis attached to two cotyledons (seed leaves), while Monocot seeds have one cotyledon and a large endosperm
