Plant Diversity
Chapter 29-30
Evolution
Green algae ancestorCharophytes (green algae)Closest plant relativeOver 470 million years ago
Evolution
Similarities (algae-plants)AutotrophsMulticellular eukaryotesCellulose in cell wallsChlorophyll a & b
Fig. 29-4
ANCESTRALALGA
Red algae
Chlorophytes
Charophytes
Embryophytes
Virid
iplan
taeStrep
top
hyta
Plan
tae
Evolution
Traits derived by plants1. EmbryophytesEmbryos develop in maternal tissues2. SporangiaWalled spores3. Multicellular gametangia4. Apical meristems
Evolution
Move to land-less waterCuticle:Waxy substance - protects water lossStomata (stoma-singular):Opening in leafGas exchange
Evolution
Leaves – Greater photosynthesis surface
Dominant diploid phase Shorter haploid stageStructural support of vascular tissue
Fig. 29-6
(a) Fossilized spores
(b) Fossilized sporophyte tissue
Fig. 29-5a
Gametophyte(n)
Gamete fromanother plant
n
n
Mitosis
Gamete
FERTILIZATIONMEIOSIS
Mitosis
Sporen
n
2n Zygote
Mitosis
Sporophyte(2n)
Alternation of generations
Fig. 29-5e
Apicalmeristemof shoot
Developingleaves
Apical meristems
Apical meristemof root Root100 µm 100 µmShoot
Life cycles
Alteration of generationsMulticellular haploid & diploid Brown, green & red algae have similar life cycle
Life cycle
Gametophyte:“gamete plant”Haploid generationProduce haploid gametes by mitosisFuse during fertilization (zygote)
Life cycle
Sporophyte:”spore plant” Diploid generationMeiosis produces haploid sporesLeads to multicellular haploid gametophyte
Life cycle
SporangiaOrgan where meiosis takes placeDiploid produces 4 haploid sporesMulticellular haploid gametophyteGametangia:Organ where gametes are produced
Fig. 29-5a
Gametophyte(n)
Gamete fromanother plant
n
n
Mitosis
Gamete
FERTILIZATIONMEIOSIS
Mitosis
Sporen
n
2n Zygote
Mitosis
Sporophyte(2n)
Alternation of generations
Life cycle
Seed plants Gametophyte nutritionally dependent on sporophytesGametophyte generation gets smallerMore specialized for land
Plant diversity
Nonvascular plants:Lack vascular tissueVascular plants:Contain water-conducting xylemFood-conducting phloemStems, leaves & roots
Groups
1. Nonvascular land plants– Mosses, liverworts, hornworts
2. Seedless vascular plants– Club mosses– Ferns
3. Gymnosperms (naked seed)4. Angiosperms (flowering plants)
Fig. 29-7
Origin of land plants (about 475 mya)1
2
3
1
2
3
Origin of vascular plants (about 420 mya)
Origin of extant seed plants (about 305 mya)
ANCES-TRALGREENALGA
Liverworts
Hornworts
Mosses
Lycophytes (club mosses,spike mosses, quillworts)
Pterophytes (ferns,horsetails, whisk ferns)
Gymnosperms
Angiosperms
Seed
plan
tsS
eedless
vascular
plan
ts
No
nvascu
larp
lants
(bryo
ph
ytes)
Lan
d p
lants
Vascu
lar plan
ts
Millions of years ago (mya)
500 450 400 350 300 50 0
Table 29-1
Liverworts, hornworts
Seedless vascular plants
Gymnosperms
Angiosperms
Nonvascular land plants
SmallLack vascular tissue Found in damp, shady habitatsNeed water to reproduce sexuallyGametophytes are photosyntheticMore visible (green)Sporophytes attached to gametophytes
Nonvascular land plants
Mosses (Bryophytes)Rhizoids: “roots” Cells to absorb water“leaves” Green, haploid, single cell layer thickMost abundance in the tropicsVery sensitive to air pollution
Moss
Seedless vascular plants
Earliest form of vascular plantsExternal water for fertilizationNo seedsSporophyte more complexSporophyte & gametophyte are photosyntheticLive independently
Ferns
Seed plants
425 million years agoSeeds gives the plant advantages1. Protection of embryo by sporophyte2. Easier to disperse3. Dormant stage
Seed plants
2 kinds of gametophytesMale (pollen grains)Female (ovule)No need for external water Sperm move to egg in a pollen tube
Gymnosperms
Gymnos Greek for “naked”Sperma “with seed”Lack flowers & fruitOvules are naked at time of pollinationPines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods.
Angiosperms
Flowering plantsOvules are closed by diploid tissues at time of fertilizationAngeion means “vessel” in GreekSperma “seed”
Flower structure
Receptacle:Where flower parts are attachedSepals:Green leaf likeProtect the immature flower
Flower structure
Petals:Colored, attract pollinatorsStamens (male gametophytes)– Anther: Pollen producing – Filament: a stalk
Carpels (female gametophytes)Ovule(base), ovary, stigma & style (connects the stigma to the ovary)
Flower structure
Life cycle
PollinationPollen transfers to the stigmaSelf-pollination or from another plantProduce a germinating seed Young sporophyte (diploid)
Life cycle
Benefits
FoodRice, wheat, potatoesCoffee, tea, cocoaMedicinesDigitalis (heart med)Morphine (pain relief)Fuel Wood
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