A/L 2013 Biology Flashcards
State some distinguishing characteristics of angiosperms?
- Presence of flowers
- Presence of vessel elements in xylem
- Presence of sieve tube elements and companion cells in phloem
- Formation of a pollen tube to transport male nuclei to embryo sac/ovum/ovule
- Double fertilization
- Production of seeds within a fruit.
State the corresponding structure for angiosperm flower for the given structures in gymnosperms: Megasporophyll Microsporophyll Megasporangium Seed coat Wall of ovary
Megasporophyll - Carpel Microsporophyll - Stamen Megasporangium - nucellus Seed coat - Integument Wall of ovary - fruit coat
What are the major characteristic features in the lifecycle of Selaginella?
- Exhibit heteromorphic alternation of generations
- Dominant sporophyte
- Sporophyte produces strobilus
- Heterosporous / Produce microspores and megaspores
- Unisexual / Dioecious gametophyte
- Flagellated male gametes are produced
- Gametes fuse to form a zygote which develops into the embro.
What is self pollination?
Deposition of pollen of a flower in the stigma of the same flower (Eg: Oryza)
What is cross pollination?
Deposition of pollen of a flower on the stigma of a different flower of the same plant or a different plant.
What are the adaptations seen in plants for cross pollination?
- Unisexuality - Stamen and carpel lie in separate flowers (Zea mays, Cocos)
- Self sterility - In certain flowers the pollen grains are unable to germinate on its own stigma (Passiflora)
- Dichogamy - In many bisexual flowers the anther and stigma mature at different times.
- Heterostyly - Presence of stamen and stigma at different levels.
- Herkogamy - Structural barriers present between floral parts which prevent self pollination.
What is a seed?
The dispersal unit of seed plants which
contains the embryo and
stored food
surrounded by the seed coat.
What features of seeds have enabled seed plants to colonize land?
Presence of • A seed coat • Stored food in the endosperm/cotyledons • a dormancy period • efficient dispersal mechanisms
What is parthenocarpy?
Development of fruit from ovary without fertilization. Parthenocarpic fruits do not develop (viable) seeds (seedless).
Examples where parthenocarpy occurs naturally?
Banana
Pineapple
Examples where parthenocarpy can be induced?
Can be induced by applying plant growth substances.
Grapes
Oranges
Natural role of DNA polymerase
Synthesis of new DNA strand
Natural role of DNA helicase
Breaking of hydrogen bonds between two strands
Natural role of Restriction endonuclease
Cleaving DNA at specific sites
Natural role of Ligase
Joining of DNA fragments
