Lectures 16-24 Flashcards
What are the chlorophyta?
the green algae
- start of terrestrial green line
Why do we know land plants are monophyletic?
genetic sequencing
- evolved from within a particular group of freshwater green algae = CHAROPHYTA
What charophyta is thought to be the most closely related to land plants?
Zygnema
What is gametic meiosis?
gametes produced directly by meiosis and fuse immediately without mitosis
- most lifecycle = diploid (animals)
What is zygotic meiosis?
when meiosis occure immediately after diploid zygote formation
- lifecycle mainly in haploid form
- fungi
What is sporic meiosis?
mitosis occurs in both haploid and diploid phase and so 2 multicellular phases - all land plants
= alternation of generations
What is the haploid multicellular phase of plants life cycle called?
gametophyte
What is the diploid multicellular phase of plant lifecycle called?
sporophyte
Stages of plant life cycle?
x 6
1) Diploid multicellular stage
2) Meiosis to produce haploid spores
3) Mitosis of spores to haploid multicellular
4) Produce gametes by mitosis
5) Fertilisation of gametes = diploid
6) Mitosis to produce multicellular
What is a clade?
Monophyletic group
- group of organisms containing all decendants of an ancestor
What is a grade?
a group of organisms that share similarities but are not monophyletic
What are the bryophytes?
Liverworts, hornworts and mosses - GRADE
- 470 millions years ago to present
- most closely related to charophyte algae
- haploid dominant
- small diploid sporophyte is parasitic to haploid
What are the liverworts?
bryophytes which are most likely the earliest evolving land plant group
- more or less amphibious thin plants
- patches of cuticle and air pores
- film of water over surface for reproduction as sperm need to swim
What are hornworts?
bryophytes
- resemble liverworts but have a full water-repellent surface cuticle
- has 2 celled stomata in diploid
- very few species
What are mosses?
Bryophytes
- fundamental to worlds carbon balance
- have rudimentary cellular water transport systems —> not xylem
- ~9,000 species
- green spongy = haploid
- extensions are diploid
- need water on surface to reproduce as sperm swim
What are the vascular plants?
clade
- 420 million years ago to present
- all but bryophytes
- vertical water transport by xylem and also tough, rigid body
- diploid sporophytes mainly
- spore-producing bodies held high for long spore distribution
split
1) Non-seed producers = spore producers
2) seed plants
What are the two main groups of living spore-producers?
1) lycophytes
2) ferns and horsetails
- both still rely on water for reproduction
What are lycophytes?
spore producers
- called clubmosses but not mosses
- few species remain
- first plants to have leaves with vascular supply
- thickened stems which gave first trees (though not small)
- phloem
What are horsetails?
- ring of vascular tissue around hollow stem
- strength
- small
What are ferns?
spore producers
- large megaphylls (leaves) which produce spores
- still water-dependent
What are the seed plants?
1) gymnosperms
2) flowering plants = angiosperms
- when gametophyte generation, egg and then next sporophyte generation within sporophyte tissue
- when world dried out = dominant
What are the three types of gymnosperms?
1) Cycads
2) Ginkgo
3) Conifers
What are cycads?
Gymnosperms
- abundant 260-180 mya
- single unbranched stems with mass of tough, highly divided leaves
What is the maidenhair tree? Ginkgo?
only remaining ginkgo species left
- gymnosperm
- changed very little in past 150 mya