Angiosperm Embryology Flashcards
What is a genetic lifecycle?
Diploid multicellular individuals undergo meiosis to create haploid gametes. Male and female haploid gametes fuse during fertilization to produce a diploid zygote. The zygote then undergoes mitosis.
Who has a gametic lifecycle?
Animals, some protists, algae
What is a zygotic lifecycle?
A diploid zygote undergoes meiosis to produce haploid daughter cells. The haploid daughter cells undergo mitosis to produce many haploid cells. A female and male haploid daughter cells come together during fertilization to create a diploid zygote.
What has a zygotic lifecycle?
Fungi, some algae
What is a sporic lifecycle?
A diploid individual called a sporophyte undergoes meiosis to produce haploid spores. The spores undergo mitosis creating many haploid gametophytes. Male and female gametophytes come together during fertilization to produce a diploid zygote. The zygote undergoes mitosis to produce multiple diploid sporophytes.
What has a sporic lifecycle?
Plants and many algae
What is a sporic lifecycle also called?
Alternation of generations
What is alternation of generations?
The alternation between a multicellular haploid (gametophyte) and a diploid (sporophyte) stage.
What is a gametophyte?
The haploid stage where the organism produces gametes (sperm and egg) through mitosis.
What is a sporophyte?
The diploid stage where the organism produces spores through meiosis.
In what populations are mutations fixed faster? (Fixed = goes to 100% in population)
Haploid populations
What is a tapetum?
A lipid layer that coats the surface of a pollen grain
Explain the female angiosperm lifecycle up to fertilization.
The diploid ovule in the megasporocyte undergoes meiosis producing 4 haploid megaspores.
3 of the haploid megaspores dissentigrate.
The haploid megaspores under goes 3 rounds of mitosis creating haploid a 7 celled 8 nucleate embryo sac called the megagametophyte.
What is inside the haploid embryo sac of angiosperms?
1 egg
2 synergids
1 polar nuclei
3 antipodals
Explain the male angiosperm lifecycle up to fertilization
In the pollen sac, diploid microsporocytes divide via meiosis creating tetrads of haploid microspores. Each tetrad contains 4 microspores. A haploid spore undergoes mitosis creating 1 tube cell and 1 generative cell. The generative cell undergoes mitosis again and becomes 2 sperm cells. The 2 sperm cells and 1 tube cell are in a singular pollen grain. The pollen grain is then transferred to the stigma via pollination and the pollen tube grows down the style to the ovule and enters the embryo sac where sperm cells are discharged.
Explain what happens after angiosperm fertilization.
One sperm fuses with the egg to create a diploid zygote, the other sperm fuses with the polar nuclei to create a triploid primary endosperm nucleus.
What are the stages of embryo development
- Globular stage
- Heart stage (dicots)
- Torpedo stage
What is the globular stage?
Primary endosperm nuclei repeatedly divides forming free floating nuclei, zygote starts to divide and forms a basal cell which develops into a suspensor to elevate the embryo in the sac and transport nutrients. An apical cell divides to form a globular mass of cells.
What is the heart stage?
Walls develop around the free fendosperm nuclei to for a cellular endosperm that provides nutrients for embryo. The embryo becomes heart shaped with the formation of cotyledon primordia.
What is the torpedo stage?
The embryo elongates and the vascular system for the roots and shoot are formed.
What are the integuments?
They are the sheath around the embryo sac that decides to let the pollen in. They develop into the seed coat.
Explain carpel evolution
Sporangia are on the edges of the leaf originally, but the leaf the. Rolled in on itself and the carpel fused creating an ovary.
What is the role of the suspensor?
It provides embryo nutrients and regulates growth. Eventually undergoes programmed death so it is not present in mature embryos.
What is epigeous germination?
The cotyledons are above ground. Most dicots.
Roots in ground → hypocotyl hook shape above ground → seed coat and cotyledons below ground → cotyledons pull up and are above ground.
