Bio 184 Angiosperms Notes- Flowering Plants
Differences of angiosperms from gymnosperms and all previous plants:
1. Ovules inside ovary (gymnosperms are naked seeds)
2. Eggs behind multiple sporophytic barriers
- Megagametophyte (embryo sac) only 7 cells
- Have 2 female gametes:
1. Egg – fuse with sperm to make zygote
2. Two polar nuclei in central cell (fuse with sperm to make endosperm)
3. Forms endosperm (3n)
4. Has fruit – mature ovary holding seeds
Ancestral traits = came first, before derived
Derived traits – came later, after ancestral
4 Steps to Evolution of Flower:
Steps to evolution of flower Ancestral Derived
Reduction – less # parts and size Complex Simple
Fusion - to each other or parts Free parts Fused parts – less
of diff species differentiation of early cells (of
primordial tissues)
Symmetry Radial Bilateral
Ovary Position Superior (within flower) Inferior (below flower)
Lots of innovations:
A. Flower:
- most important innovation!
- parts are hierarchically arranged
- *advantage in reproduction – uses biological systems that can be deeply integrated
- Angiosperms classified based on flower structure
- Parts:
1. Carpel – structures that house ovules within ovary
Stigma – top
Style – stem
Ovary – cavity that houses numerous ovules
Ovule – chamber that holds female gametophyte, embryo develops here
Receptacle – base where carpel sits
2. Stamens – have filaments with anthers that release pollen
3. Petals
4. Sepals – the outermost layer
- Usually green
- Enclose flower bud
- Collectively called calyx
Differences of angiosperms from gymnosperms and all previous plants:
1. Ovules inside ovary (gymnosperms are naked seeds)
2. Eggs behind multiple sporophytic barriers
- Megagametophyte (embryo sac) only 7 cells
- Have 2 female gametes:
1. Egg – fuse with sperm to make zygote
2. Two polar nuclei in central cell (fuse with sperm to make endosperm)
3. Forms endosperm (3n)
4. Has fruit – mature ovary holding seeds
Ancestral traits = came first, before derived
Derived traits – came later, after ancestral
4 Steps to Evolution of Flower:
Steps to evolution of flower Ancestral Derived
Reduction – less # parts and size Complex Simple
Fusion - to each other or parts Free parts Fused parts – less
of diff species differentiation of early cells (of
primordial tissues)
Symmetry Radial Bilateral
Ovary Position Superior (within flower) Inferior (below flower)
Lots of innovations:
A. Flower:
- most important innovation!
- parts are hierarchically arranged
- *advantage in reproduction – uses biological systems that can be deeply integrated
- Angiosperms classified based on flower structure
- Parts:
1. Carpel – structures that house ovules within ovary
Stigma – top
Style – stem
Ovary – cavity that houses numerous ovules
Ovule – chamber that holds female gametophyte, embryo develops here
Receptacle – base where carpel sits
2. Stamens – have filaments with anthers that release pollen
3. Petals
4. Sepals – the outermost layer
- Usually green
- Enclose flower bud
- Collectively called calyx
