Post on 24-Feb-2016
description
The Wonderful World of Green Plant Diversity and
Evolution
Biol 366Spring 2014
Tree of Life: The Big Picture
EukaryotesArchaeaBacteria
ca. 4 bya
now
>3.5 bya
>2 bya
membrane-boundnucleus, organelles, etc.
Fig. 1.1 from Simpson
Green plants share:• Chlorophylls a (ancestral) and b
• Starch storage
• Stellate flagellar structure
• Certain gene transfers from the chloroplast to the nucleus
• And other features (see Ch. 3)
Green plant diversity:• Ca. 350,000 species
• Two major groups: 1) chlorophytes (marine and other green algae) and 2) streptophytes [freshwater green algae and embryophytes (= land plants)]
• A major branch (clade) in the eukaryotic Tree of Life
Fig. 3.1 from Simpson
Some definitions• Clade = branch on an evolutionary tree,
a lineage, includes an ancestor and all its descendants. Ex.: Green plants, chlorophytes, land plants.
• Paraphyletic group = a group that includes an ancestor and some (but not all) of its descendants, indicated by double quotation marks. Ex.: “Green algae”
Chlorophytes
Fig. 3.1 from Simpson
Basal streptophytes
desmids
Spirogyra
CharaNitella
(Judd et al. 2008)
Conjugation inSpirogyra
Haplontic life cycle (haploid dominantor zygotic meiosis)
The only diploid cellIs the zygote
zygote (2n)
haploid body
biology.unm.edu
mason.gmu.edu
CharalesHaplontic but some havemulticellular gametangia(gamete-producing structures)
♀
♂
Generalized charophyte life cycle:Alternation of generations
XX
gametangia
gametophyte
Embryophytes (land plants) share:
• Cuticle• Alternation of generations (multicellular
sporophyte and multicellular gametophyte)• Multicellular gametangia (gamete-producing
structures)• Multicellular sporangium (spore-producing
structure)• Embryo (young sporophyte)• Parenchyma? (more likely ancestral)
Generalized embryophyte life cycle:Alternation of generations
Bryophytes• Hornworts, liverworts, mosses• Gametophyte-dominant• No vascular tissue (except conducting
cells in a few mosses)• Separate male and female
gametophytes• Sperm must swim to the egg, therefore
need water for fertilization and therefore must remain small
hornworts
liverwortsmosses
Plant Tree of Life: Embryophtes
Tracheophytes(vascular plants)HornwortsLiverworts
ca. 450 mya
now Mosses“Bryophytes”
Liverwort gametophyte
Liverwortthallus showing air pores
LiverwortMulticellular gametangia(male = antheridia)
LiverwortMulticellular gametangia (female = archegonia)OogamyRetention of zygote within the female gametophyteMulticellular embryo
Hornworts
G
S
Moss male gametangia(= antheridia)
Capsule = sporangium of the sporophyte
Generalized embryophyte life cycle:Alternation of generations
Tracheophytes (vascular plants)• Vascular tissue (tracheids) present• Include lycophytes (quillworts, clubmosses,
spikemosses), monilophytes (ferns, horsetails, whisk ferns), and spermatophytes (seed plants)
Fig. 4.1 from Simpson
Lycophytes & Monilophytes
• Quillworts, clubmosses & spikemosses (= lycophytes); ferns, whisk-ferns, & horsetails (= monilophytes);
• Independent gametophytes and sporophytes• Sperm must still swim to the egg• Most are homosporous; a few evolved
heterospory• Many homosporous ferns have means of
avoiding self-fertilization
Lycophytes
Selaginella (spikemoss)
Lycopodium and friends (clubmosses)
Isoetes (quillwort)
Whisk-fern (Psilotum)
Ferns (Leptosporangia)
Monilophytes (ferns, horsetails, whisk ferns)
horsetails
1n
2n
2n2n
2n
1n spores
gametophyte
sporophyte
Nutritionally independentsporophytes andgametophytes
Fern Life Cycle,Fig. 4.32, Simpson
Lignophytes (woody plants) & Spermatophytes (seed plants)
• Secondary xylem (wood) & bark, heterospory, seeds, eustele, pollen (also pollen tube, pollination droplet)
• Includes gymnosperms and angiosperms
Fig. 5.1 from Simpson
Gymnosperms• Conifers, gingko, cycads, Gnetales
• Molecular data support this group as having a single common ancestor
• No obvious defining character (see characters for Lignophytes & Spermatophytes)
Female cone with each scalebearing usually two ovules; directly exposed to pollen
Male cones with eachscale bearing two or more microsporangia
biology.ualberta.edupine pollen
pine microsporangia
male
female
Fig. 5.7 from Simpson
Angiosperms• “Dicotyledons”, monocotyledons• Heterosporous (ancestral)• Sporophyte-dominant (ancestral)• Pollen = male gametophyte (ancestral)• Archegonia lost; embryo sac = female
gametophyte; ovules enclosed in carpels (indirect pollination)
• Double fertilization produces zygote + primary endosperm nucleus
Flower = a short, determinate shoot bearing highlymodified leaves, some of which are fertile (i.e.,bearing either microsporangia or megasporangia),with the megasporangia in carpels
Animal pollination syndromes
Wind pollination
A wide range of fruit types…
Fig. 5.7 from Simpson
http://www.mun.ca/biology/scarr/Angiospermae.html
over 300,000 species of angiosperms
The wonderful world of land plant diversity