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Plant Diversity
Overview: The Greening of Earth
• Imagine all land without life.Completely barren.
Overview: The Greening of Earth
• Land surface WAS lifeless for >3 billion years!
• Now there’re about 290,000 plant species on land. Seriously. Wow.
• Plants supply oxygen and are the ultimate source of most food eaten by land animals
Land plants evolved from green algae• Green algae called charophytes are the closest relatives of land plants
Green AlgaeMosses
Ferns
Conifers(Gymnosperms)Flowering Plants (Angiosperms)
*Some biologists think the plant kingdom should be expanded to include some or all green algae!
What do plants need to survive?
WaterCarbon DioxideSunlight Nutrients. . .
Not much!
The Move to Land. . . • Benefits of moving to land:
• unfiltered sun • more CO2 • nutrient-rich soil (yes!)
• few herbivores or pathogens
• Challenges: • scarcity of water • lack of structural support
Plant Traits Enabling the Move to Land• Roots – suck up water and minerals in soil, anchor
• Leaves – produce energy/sugar through photosynthesis
• Vascular tissue • Xylem – pumps water & minerals
from roots to rest of plant• Phloem – pumps sugar/food/energy
from leaves to rest of plant
• Cuticle • Water and gas-tight; reduces water loss• Stomata – pores in leaf cuticle; open to allow gas flow
and close to reduces water loss
Fig. 29-UN7
Green Algae vs. Plants: SIMILARITIESTraits of Green Algae
Eukaryotic – have a nucleus
Multicellular – more than one cell
sexual and asexual reproduction
Photosynthetic – autotrophs that use chlorophyll
Extra energy stored as starches
Cells have cell walls made of cellulose
Traits of Plants
Eukaryotic – have a nucleus
Multicellular – more than one cell
sexual and asexual reproduction
Photosynthetic – autotrophs that use chlorophyll
Extra energy stored as starches
Cells have cell walls made of cellulose
Green Algae vs. Plants: DIFFERENCES• Universal plant traits:
– 1) Alternation of generations– 2) Sporangia - make walled spores– 3) Gametangia (multicelled)– 4) Apical meristems
– Common plant traits: – Roots -Leaves/Fronds -Stems– Vascular tissue -Cuticles -Stomata. . .– Seeds -Flowers
Universal Plant Trait #1: Alternation of
Generations• Reproductive cycle: alternation of generations.
• Sporophytes (2n) produce spores (n).• Spores grow into gametophytes (n).• Gametophytes make gametes (n), which
fuse to become a fertilized zygote (2n).• Zygotes grow into sporophytes.
Fig. 29-5a
Gametophyte(n)
Gamete fromanother plant
n
n
Mitosis
Gamete
FERTILIZATIONMEIOSIS
Mitosis
Sporen
n
2n Zygote
Mitosis
Sporophyte(2n)
Universal Plant Traits #2 and #3:
3) Gametophytes use gametangia to make gametes.
• archegonia are female gametangia • Remember: archeEGGonia produce EGGS!
• antheridia are male gametangia• site of sperm production and release
2) Sporophytes use sporangia to make spores.
Fig. 29-5c
SporesSporangium
Sporophyte
Sphagnum sporangium (LM)
Gametophyte
Universal Plant Trait #4:
Apical Meristems
• at tips of roots and stems
• Cells from apical meristems can become almost ANY type of plant tissue! (exciting)
Fig. 29-5e
Apicalmeristemof shoot
Developingleaves
Apical meristems
Apical meristemof root Root100 µm 100 µmShoot
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms (conifers)
Angiosperms (flowering)
Classifying Land Plants
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms (conifers)
Angiosperms (flowering)
Classifying Land Plants
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms (conifers)
Angiosperms (flowering) }Vascular Plants
Classifying Land Plants
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms
Angiosperms }Seed Plants }Vascular Plants
Classifying Land Plants
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms
Angiosperms }Seed Plants }Vascular Plants
Classifying Land Plants
Table 29-1
Table 29-1
Table 29-1
Table 29-1
Table 29-1
*
*
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms (conifers)
Angiosperms (flowering)
Classifying Land Plants
Nonvascular plants (Mosses and
worts!) • Past: many GIANT mosses • Now: small herbaceous plants
• No vascular system• Absorb water all over• Dominant gametophyte, small dependent
sporophyte
Fig. 29-9b
Plagiochiladeltoidea,a “leafy”liverwort
Nonvascular plants
Fig. 29-9c
An Anthoceroshornwort species
Sporophyte
Gametophyte
Fig. 29-9d
Gametophyte
Sporophyte
Polytrichum commune,hairy-cap moss
Fig. 29-5c
SporesSporangium
Sporophyte
Longitudinal section ofSphagnum sporangium (LM)
Gametophyte
Sporophytes and sporangia of Sphagnum (a moss)
Fig. 29-8-3
Key
Haploid (n)
Diploid (2n) Protonemata(n)
“Bud”
“Bud”
Malegametophyte(n)
Femalegametophyte (n)
Gametophore
Rhizoid
Spores
Sporedispersal
Peristome
Sporangium
MEIOSIS SetaCapsule(sporangium)
Foot
Maturesporophytes
Capsule withperistome (SEM)
Femalegametophytes
2 m
m
Raindrop
Sperm
Antheridia
Egg
Archegonia
FERTILIZATION
(within archegonium)Zygote(2n)
Embryo
Archegonium
Youngsporophyte(2n)
•Sperm swim through a film of water to reach and fertilize the egg!
Nonvascular plants(mosses)
From nonvascular to vascular. . .
• NONVASCULAR PLANTS owned Earth for 100 million years!
• BUT they needed moist environments:• No vascular system to take water up from soil!• Sperm have to SWIM to egg
• So later, VASCULAR PLANTS took over!• Vascular tissue pumped water up from soil AND allowed
them to grow TALL!
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms
Angiosperms
We just did:
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms
Angiosperms }Vascular Plants
Moving on to:
Traits of Vascular Plants
• Dominant sporophyte generation• Vascular tissues• True roots and leaves• Can grow TALL!
• So. . .they can live farther from water!
Dominant Gametophyte or Sporophyte?• In non-vascular
plants, the gametophyte dominates
Sporophyte
• In vascular plants, the sporophyte dominates
Sporophyte
GametophyteGametophyte
Ferns (seedless vasc. plants)
• vascular tissue• spores, not seeds
• spores are sexual and haploid: not yet fertilized!
• Dominant sporophyte or gametophyte? • Diverse - more than 12,000 species of
ferns!• Mostly tropical, some temperate
Fig. 29-15a
Ferns (seedless vasc. plants)
Fig. 29-15b
Selaginella apoda,a spike “moss”
Ferns (seedless vasc. plants)
Fig. 29-15c
Isoetesgunnii, a quillwort
Seedless vascular plants
Fig. 29-15d
a club “moss”
Seedless vascular plants
Fig. 29-15f
Athyriumfilix-femina,lady fern
25 c
m
Ferns (seedless vasc. plants)
Fig. 29-13-1
Key
Haploid (n)
Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
FERN Alternation of Generations
Fig. 29-13-2
Key
Haploid (n)
Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
Spore(n)
Younggametophyte
Maturegametophyte(n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATION
FERN Alternation of Generations
Fig. 29-13-3
Key
Haploid (n)
Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
Spore(n)
Younggametophyte
Maturegametophyte(n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATION
Newsporophyte
Gametophyte
Zygote(2n)
FERN Alternation of Generations
Fig. 29-13-3
Key
Haploid (n)
Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
Spore(n)
Younggametophyte
Maturegametophyte(n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATION
Newsporophyte
Gametophyte
Zygote(2n)
Where’s the dominant sporophyte?
Fern
Fig. 29-13-3
Key
Haploid (n)
Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
Spore(n)
Younggametophyte
Maturegametophyte(n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATION
Newsporophyte
Gametophyte
Zygote(2n)
DOMINANT sporophyte
Review: Dominant Gametophyte or Sporophyte?• In non-vascular plants, the gametophyte dominates
Sporophyte
• In vascular plants, the sporophyte dominates
Sporophyte
GametophyteGametophyte
You should now be able to:Tell whether the gametophyte generation or the sporophyte generation is dominant in each of the following major groups of plants:
1. In non-vascular plants?
2. In seedless vascular plants?
3. In seed plants?
• Most plants have vascular tissue; they’re vascular plants• Mosses have no vascular tissue; they’re nonvascular
plants
Nonvascular plants (mosses)
Seedless vascular plants (ferns)
Gymnosperms
Angiosperms } Seed Plants }Vascular Plants
Classifying Land Plants
And finally, seed plants!• A seed is an embryo and nutrients surrounded by a protective coat
• Seed plants form a clade and can be divided into further clades:– Gymnosperms, the “naked seed” plants, including
the conifers– Angiosperms, the flowering plants
Parts of a Seed Cotyledon – “seed leaf”
Purpose: reproduction - protects embryo, provides nutrients, may aid in dispersal
Gymnosperms (mostly conifers) Basics: have vascular tissue, seeds,
dominant sporophytes
Gymnosperm - means “naked seed” Conifer - cone-bearing trees: pine, fir, spruce Cone - scaly structure produced by some
seed plants; support either male or female reproductive structures; site of seed-production
Table 29-1
!
!
Angiosperms (flowering plants) WAY most common Produce flowers Seeds are enclosed in fruits
Either monocots or dicots (1 seed leaf or 2) May be annuals, biennials, or perennials
Annuals – only live one year, seeds survive winter Biennials – complex 2-year life cycle Perennials – “hibernate” through winter, come back
year after year
Parts of a Flower? Parts of a flower!
-Pistil
New terms (will be on next vocabulary sheet)
Gymnosperm
Conifer Cone Angiosperm Flower Cotyledon Monocot Dicot
Annual Biennial Perennial Petal Sepal Stamen Pistil
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