botany: Plant Life cycles and evolution Flashcards
How does an animal life cycle differ from a plant life cycle?
Animals produce gametes (sperm and eggs) that fuse to make the next generation, while plants have an additional stage called alternation of generations.
What is meiosis?
Meiosis is a type of cell division that produces cells with half the DNA of the parent cell, essential for gamete formation.
What is the difference between diploid and haploid cells?
Diploid cells (2n) have two of each chromosome type, while haploid cells (n) have only one of each.
What is a sporophyte?
A diploid (2n) stage in plants that produces haploid spores through meiosis.
What is a gametophyte?
A haploid (n) stage in plants that grows from a spore and produces gametes.
What occurs during fertilization in plants?
Two gametes (n) fuse to form a diploid zygote (2n), starting a new sporophyte generation.
What does “sporophyte dominance” mean?
In most land plants, the sporophyte (2n) stage is dominant, except for Bryophyta, where the gametophyte (n) stage is dominant.
How does the gametophyte stage differ in Bryophyta compared to Gymnospermae and Angiospermae?
In Bryophyta, the gametophyte is dominant and free-living, while in Gymnosperms and Angiosperms, it is very reduced and located within cones or flowers.
Why do Bryophyta and Pteridophyta need water for fertilization?
Their male gametes (sperm) need to swim to the female gametes (eggs), requiring a film of water for fertilization.
How do Gymnosperms and Angiosperms reproduce without water?
They use pollen, which allows fertilization without free water, an advantage in dry environments.
What adaptations help the sporophyte survive on land?
A waxy cuticle to reduce water loss, vascular tissues for transport, stomata for gas exchange, and strengthening tissues for support.
What is the advantage of seed formation in Gymnosperms and Angiosperms?
Seeds protect the embryo, allow dormancy in unfavorable conditions, and enable dispersal.
What is a phylogenetic tree?
A diagram showing evolutionary relationships between species, from ancient ancestors to modern groups.
From what common ancestor did land plants evolve?
Green algae.
How do Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms differ in terms of evolution?
Bryophytes are non-vascular with a dominant gametophyte. Pteridophytes evolved with vascular systems and a dominant sporophyte. Gymnosperms and Angiosperms developed seeds, with Angiosperms also producing flowers and fruits.
