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