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How Plants Colonized Land

Cyanobacteria likely existed on land ___ _______ years ago.

1.2 billion

Around ___ _______ _____ ago, small plants, fungi, and animals emerged on land

500 billion years

Since colonizing land, how many plant species have diversified?

roughly 290, 000

Land plants are defined by ...

having terrestrial ancestors, even though some now might be aquatic

they do not include photosynthetic protists (algae)

Plants supply ______ and are the ultimate source of most food eaten by land animals.


Land plants evolved from _____ _____.

green algae (charophyte)

4 traits land plants share with algae.

1) Alternation of generations and Multicellular, Dependent Embryos
2) Walled Spores produced in Sporangia
3) Multicellular Gametangia

Alteration of generations and multicellular, dependent embryos

life cycles of land plants occur in two generations of multicellular organisms : gametophytes and sporophytes.

each generation gives rise to the other

this occurs in most algae, but not charophytes

distinguished by the fact that the life cycle includes multi-cellular haploid organisms and multi-cellular diploid organisms

5 generalized steps of alternation of generations

1) the gametophyte produces haploid gametes by mitosis.
2) Two gametes unite (fertilization) and form a diploid zygote.
3) the zygote develops into a multicellular diploid sporophyte.
4) the sporophyte produces haploid spores by meiosis.
5) the spores develop into multicellular haploid gametophytes.

Walled Spores Produced in Sporangia

sporophytes have multiple organs called sporangia that produce spores.

prevents exposed zygotes from drying out

alos found in plant spore walls

charophyte algae lack multicellular sporangia and their flagellated, water-dispersed spores lack sporopollenin.

Multicellular Gametangia

the production of gametes within multicellular organs called gametangia

female gametangia called archegonia
male gametangia called antheridia

Apical Meristems

localized regions of cell division at the tips of roots and shoots.

cells produced by Apical Meristems differentiate into the outer epidermis, which protects the body, and various types of internal tissue

4 key traits land plants SHARE with charophytes

1) rings of cellulose-synthesizing complexes
2) peroxisome enzymes
3) structure of flagellated sperm
4) formation of phragmoplast

kingdom of plants


dependency of the embryo on the plant

How are nutrients transferred from plants to embryo?

placental transfer cells


produce eggs and are the site of fertilization

female gametangia


produce and release sperm

male gametangia


additional derived trait of plants
waxy covering of the epidermis
aids in waterproofing, helping prevent excessive water loss while aiding in protection from microbial plants.


additional derived trait of plants
symbiotic associations between fungi and land plants that may have helped plants without true roots to obtain nutrients

create SA, obtain nutrients

Secondary Compounds

additional derived trait of plants
deters herbivores and parasites

Fossil evidence indictates that plants were on land at least ___ _______ _____ ago.

475 million years

Fossilized spores and tissues have been extracted from ___ _______ ____-old rocks.

475 million year

land plants are grouped based on the

presence or absence of vascular tissue

nonvascular plants are called


clades of seedless vascular plants

lycophytes (club mosses and their relatives)
pterophytes (ferns and their relatives)

seeless vascular plants are paraphyletic - of the same biological organization, or grade


embryo and nutrients surrounded by a protective coat

gymnosperms and angiosperms


the "naked seed" plants, including the conifers


flowering plants

Mosses and other nonvascular plants have lifecycles dominated by .....


3 phyla of small, herbaceous (nonwoody) plants

Liverworts (Hepatophyta)
Hornworts (Anthocerophyta)
Mosses (Bryophyta)

in all three bryophyte phyla, ____________ are larger and longer living than ___________.

gametophytes, sporophytes

___________ are typically present only part of the time


A spore germinates into a gametophyte composed of a _________ and gamete-producing gametophore


one cell thick filaments with large SA that enhances absorption of water and minerals


The height of gametophytes is constrained by ____ __ ________ ______.

lack of vascular tissue

anchor gametophytes to substrate, not composed of tissues, do not play a role in mineral absorption


Mature gametophytes produce flagellated sperm in __________ and an egg in each ___________.

Sperm swim through a film of water to reach and fertilize the egg.

antheridia, archegonium

Bryophyte sporophytes grow out of __________, and are the smallet and simplest sporophytes of all extant plant groups.


a sporophyte consists of a ....

seta (stalk)
sporangium (capsule)


absorbs nutrients from gametophyte

seta (stalk)

conducts nutrients into the sporangium (capsule

sporangium (capsule)

produce spores by meiosi


discharge spores

open - dry
closed - moist

Hornwort and moss sporophytes have _______ for gas exchange; liverworts do not.


What do mosses help retain in the soil



"peat moss"
forms extensive deposits of partially decayed organic material known as peat.

peat can be used as a source of fuel
important global resoivoir of organic carbon

overharvesting spaghnum and/or a drop in water level in peatlands could release stored CO2 to the atmosphere.

_____ and other ________ ________ ______ were the first plants to grow tall.

Ferns, seedless vascular plants

What was the prevalent form of vegetation for the first 100 million years of plant evolution?

Bryophytes and bryophyte- like plants

When did Vascular plants begin to diversify during the ________ and _____________ periods

Devonian and Carboniferous

Why are seedless vascular plants usually restricted to moist environments?

they have flagellated sperm

How far back do fossils of the forerunners of vascular plants date back?

425 million years

living vascular plants were characterized by

life cycles with dominant sporophytes
vascular tissue called xylem and phloem
well-developed roots and leaves

in contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in ________ _____

familiar ferns

in seedless vascular plants, gametophytes grow

on or below the soil surface

What does xylem conduct?

water and minerals, including dead cells called traicheids

strengthened by lignin and provide structural support


consists of living cells and distributes sugars, AA, and other organic products

________ ______ allowed for increased height, which provided an evolutionary advantage

Vascular Tissue

_____ are organs that anchor vascular plants.

Roots, they enable vascular plants to absorb nutrients form the soil

may have evolved from subterranean stems

______ are organs that increase the SA of vascular plants, thereby capturing more solar energy that is used for photosynthesis.


2 categories of leaves

microphylls - single vein (evolved as outbranch of stems)
macrophylls - highly branched vascular system (may have evolved as webbing between flattened branches)

___________ are modified leaves with sporangia.


____ are clusters of sporangia on the underside of sporophylls.



cone-like structures formed from groups of sporophylls

most seedless vascular plants are ___________, producing one type of spore that develops into a bisexual gametophyte.


All seed plants and some seedless plants are



give rise to female gametophytes


give rise to male gametophytes

2 phyla of seedless vascular plants

lycophyta (club mosses, spike mosses, and quillworts)
pterophyta (ferns, horsetails, whisk ferns, and their relatives)

_____ _________ _____ survived for millions of years in moist swamps

giant lycophyta trees

surviving species are small herbaceous plants

club mosses and spike mosses have vascular tissues and are not true mosses.

_____ are the most diverse seedless vascular plants, with more than ____ species

Ferns, 12000

most diverse in tropics, but also in temperate forests.

__________ were diverse during the _____________ period, but are now restricted to the genus Equistum.

Horsetails, Carboniferous

Increased ______ ___ ______________ removed CO2 from the atmosphere and may have contributed to global cooling at the end of the Carboniferous period.

growth and photosynthesis

The decaying plants of these _____________ _______ eventually became ____.

Carboniferous forests, coal

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