Evolutions of land plants - Week 15 Flashcards
What is archaeplastida
monophyletic group that descended from the ancient protists that engulfed a cyanobacteria
(primary endosymbiosis)
What are embryophyes?
Land plants
Land plants closest relatives
Chara, coleochaeta
What type of life cycle do land plants have?
haplo-diplontic lifecycles
Sexual life cycle of embryophytes?
See diagram
Sexual life cycle of embryophytes?
See diagram
What are 3 sexual life cycles?
Diplontic - animals/ some fungi - exists as multicellular diploid most of the time, but gametes are haploid
Haplontic - chara/ coleochaete - Haploid being, but zygote divides by meiosis with no multicellular diploid growth
Haplo-diplontic - all living land plants - both hap and diploid within generation, zygote undergoes mitotic division
Reproduction in chara, what are 3 structures and what do they do?
Oogamous - small motile sperm, large immotile egg
Megagametangia - egg cells born in
Microgametangia - sperm cells born in
Needs for Invading the land/ air
- Avoiding desiccation (drying up)
- access to water (vascular system)
- Avoiding drying up, but allowing gas exchange
- evolutions of stomata
- waxy cuticle and sporopollenin
Reproduction in embryophyes, 3 structures
Note: sporophyte becomes intercalated into life cycle: delay is meiosis until after mitosis
Archegonia (specialised megagametangium) - produces egg
Antheridium - producing sperm
transfer cell - transfers nutrients to developing embryo (like placental cell)
Embryophytes - Bryophytes contain what?
Liverworts, mosses, hornworts
Characteristics of mosses
Diagram in book
Advanced mosses (polytrichum) have rudimentary transport systems
- Hydrom = water/ xylem
- leptom = photosynthate/ phloem
- Gametophyte shoot grows from apical meristem
Characteristics of liverworts
Diagram in book
Most primative embryophytes
- parenchymatous body
- very thin cuticle- no root, true leaves, vascular system
Characterists of hornworts
- antheridia and archegonia buried in gametophyte thallus
- cell have just one chloroplast
- symbiotic with cyanobacteria
Adaptive features of embryophytes
- archegonia
- thin cuticle
- stomata (not liverworts)
- vasscular tissue = xylem and phloem
All extant land plants have what type of generations?
Heteromorphic alternations
Tracheophytes are what?
Vascular plants
What represents a possible intermediate between bryophytes and tracheophtes?
Cooksonia (late silurian - 428 mya)
What is a tracheid?
In all tracheophytes - vascular plants
water conducting cells
thickened with lignin
Evolution of sporophyte branching, 3 types
Dichotomus (smallest)
Pseudomonopodial (unequal)
Monopodial (biggest, even)
What is the stele composed of ?
xylem and phloem
Evolutionary trend in early tracheophytes
increased branching in sporophytes increased size of sporo reduction in size of gametophyte increased complexity of vascular system evo of leaves and roots
Evolutions of leaves
microphylls
megaphylls
single vascular strand no stem
branched vascular strands attached to main stem
Selective force for the evolution of leaves
Reduction in CO2
When did the first forests start?
359.2 mya carboniferous period
