Plant Diversity. Overview: The Greening of Earth Imagine all land without life. Completely barren

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


plants







plants




Angiosperms (flowering) }Vascular Plants



plants



Gymnosperms

Angiosperms }Seed Plants }Vascular Plants



plants



Gymnosperms

Angiosperms }Seed Plants }Vascular Plants


Table 29-1

Table 29-1

Table 29-1

Table 29-1

Table 29-1

*

*


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!


plants



Gymnosperms

Angiosperms

We just did:


plants



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


Fig. 29-15b

Selaginella apoda,a spike “moss”


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


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)


Sporangium


Sorus

Fiddlehead

Spore(n)

Younggametophyte

Maturegametophyte(n) Archegonium

Egg

Antheridium

Sperm

FERTILIZATION


Fig. 29-13-3

Key

Haploid (n)

Diploid (2n)


Sporangium


Sorus

Fiddlehead

Spore(n)

Younggametophyte


Egg

Antheridium

Sperm

FERTILIZATION

Newsporophyte

Gametophyte

Zygote(2n)


Fig. 29-13-3

Key

Haploid (n)

Diploid (2n)


Sporangium


Sorus

Fiddlehead

Spore(n)

Younggametophyte


Egg

Antheridium

Sperm

FERTILIZATION

Newsporophyte

Gametophyte

Zygote(2n)

Where’s the dominant sporophyte?

Fern

Fig. 29-13-3

Key

Haploid (n)

Diploid (2n)


Sporangium


Sorus

Fiddlehead

Spore(n)

Younggametophyte


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?


plants



Gymnosperms

Angiosperms } Seed Plants }Vascular 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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Plant Diversity. Overview: The Greening of Earth Imagine all land without life. Completely barren