Land plants are defined by ...
having terrestrial ancestors, even though some now might be aquatic
they do not include photosynthetic protists (algae)
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.
the production of gametes within multicellular organs called gametangia
female gametangia called archegonia
male gametangia called antheridia
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
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
Fossil evidence indictates that plants were on land at least ___ _______ _____ ago.
475 million years
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
3 phyla of small, herbaceous (nonwoody) plants
in all three bryophyte phyla, ____________ are larger and longer living than ___________.
A spore germinates into a gametophyte composed of a _________ and gamete-producing gametophore
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.
Bryophyte sporophytes grow out of __________, and are the smallet and simplest sporophytes of all extant plant groups.
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
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 ________ _____
What does xylem conduct?
water and minerals, including dead cells called traicheids
strengthened by lignin and provide structural support
________ ______ allowed for increased height, which provided an evolutionary advantage
_____ 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)
most seedless vascular plants are ___________, producing one type of spore that develops into a bisexual gametophyte.
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
most diverse in tropics, but also in temperate forests.
__________ were diverse during the _____________ period, but are now restricted to the genus Equistum.
Increased ______ ___ ______________ removed CO2 from the atmosphere and may have contributed to global cooling at the end of the Carboniferous period.
growth and photosynthesis