Chapter 29: How plants colonized land Flashcards
what did plants evolve from
green algae
what do plants supply
oxygen, food sources, and habitat for many other terrestrial organisms
of known plant species
325,000
key traits of plants
Plants and some algae are multicellular, eukaryotic, photosynthetic autotrophs
– Algae, like plants, have cellulose in their cell walls and chloroplasts containing chlorophyll
a and b
what is close to plants
charopjytes
key traits plants share with charophytes
– Cellulose-synthesizing membrane proteins are arranged
in rings, rather than linear sets (Non-charophyte algae)
– Structure of flagellated sperm
– DNA sequence similarities in nuclear, chloroplast, and
mitochondrial D N A
what clade is of charophytes is the closest to plants
lade Zygnematophyceae are the closest living relatives
of plant
plants did not descend from …
modern charophytes,
but share a common ancestor with them
what coating do charophytes have
sporopollenin (a layer of
durable polymer)
– prevents exposed zygotes from drying out
sporopollenin
(pollen and spore grains) is also found in plant
spore walls
benefits and challenges of the move to land
– Benefits: direct/unfiltered sunlight, more plentiful CO2
(compared to in water), and nutrient-rich soil (water edge)
– Challenges: scarcity of water and lack of structural support
against gravity
how did plants thrive onn land
Plants diversified as adaptations evolved that enabled them to
thrive on land despite challenges
what is the kindgom plant defined as
as embryophytes, plants with embryo
Key traits distinguish plants from charophytes
– Alternation of generations ▪ Occurs in some algae (chlorophytes but not in charophytes) – Multicellular, dependent embryo – Walled spores produced in sporangia – Apical meristems
two generations of multicelluarl orgnaisms
gametophytes and
sporophytes
The multicellular haploid gametophyte
produces haploid gametes (sperm and eggs) by mitosis
the fusion of sperm and egg gives rise to
multicellular diploid sporophyte, which produces
haploid spores by meiosis
embryo developed from
the formed zygote
diploid embryo
retained and
protected within the tissue of the female
gametophyte
placental transfer cells
Nutrients (sugars, amino acids etc) are
transferred from parent to embryo
why are plants called embryophytes
because of this
dependency of the embryo on the paren
sporophyte produces spores in multicellular
organs called
sporangia
The polymer sporopollenin,
makes the cell walls
of these spores resistant to harsh environments,
enabling plant spores to be dispersed through
dry air without harm
apical meristems
Localized regions of cell division at
the tips of roots and shoots a
Cells produced by apical meristems
differentiate into
various tissues
The cuticle
a covering of the epidermis that reduces water loss
The stomata (pores)
support photosynthesis by allowing gas exchange
between the outside air and internal plant tissues (e.g., oxygen and CO2)
Early plants lacked…
true roots (and leaves) making absorption of nutrients from the soil challenging
what did 420 million year old fossils suggest about the symbiotic associations with fungi
helped plants obtain nutrients
Nonvascular plants
ack an extensive transport
system (commonly called bryophytes)
examples of nonvascular plants
liverworts, mosses, and
hornworts
Vascular plants
have vascular tissue,
cells joined into tubes for the transport of water and
nutrients
Seedless vascular plants can be divided into clades:
Lycophytes (club mosses and their relatives)
• Monilophytes (ferns and their relatives).
what can form a clade and can be divided into
further clades
seed plants
seed
embryo packaged with a supply of
nutrients inside a protective coat
gymnosperms
produce seeds that are not enclosed in
chambers (naked seeds)
angiosperms
produce seeds that develop inside
chambers that originate within flowers
what dominates the life cycles of mosses and nonvascular plants
gametophytes
bryophytes
3 phyla
- phylum hepaophyta
- phylum brophyta
- phylum anthocerophyta
which gametophytes are larger and longer living than sporophytes
Haploid gametophytes are dominant
byrophte gametophytes
Gametophytes can produce multiple gametangia,
structures that produce gametes
anrchegonia
female gametangia, produce a single nonmotile egg
antheridia
male gametangia, produce many motile
sperm (swims to reach egg through a film of water in
response to chemical attractants)
bryophyte sporophyte consists of three major
parts
The foot absorbs nutrients from the gametophyte
– The seta (stalk) conducts nutrients to the sporangium
– The capsule (sporangium) produces spores by meiosis
A peristome (tooth like structure)
op of the
capsule disperses spores when conditions are dry
Moss and hornwort sporophytes are
– larger and more complex than liverworts
– Have stomata (which liverworts lack)
Mosses are common in moist
forests and
wetlands
Many mosses are able to live in extremely cold,
hot, and dry environments because they can
survive the loss of moist of their body, then
rehydrating after when moisture is available
Some mosses that colonize bare, sandy soil help
to
reduce nitrogen loss from the soil
some moss harbors nitrogen fixing cyanobacteria
that increase the availability of nitrogen (northern
coniferous forest
Wetland moss Sphagnum, or “peat moss ,” forms
extensive deposits of
decayed organic material
creating peat formation
The low temperature, pH, and oxygen level of peatlands
stop decay of moss
Peat can be used as a source of
fuel
Peatlands cover
r 3% of Earth’s land surface and contain
roughly one-third of the world’s soil carbon (organic)
Overharvesting of Sphagnum for the use of peat fuel
contributes to
global warming by releasing stored CO2
to the atmosphere
first plants to grow tall
Ferns and other seedless vascular plants
what tissue allowed plants to grow much taller
• Vascular tissue
Like bryophytes, seedless vascular plants have
flagellated sperm and are usually restricted to
moist environments
• In contrast with bryophytes, sporophytes of
seedless vascular plants
the larger, more
complex alternative generation life cycle
Living vascular plants are characterized by
Life cycles with dominant sporophytes – Transport in vascular tissues called xylem and phloem – Well-developed roots and leaves – Spore-bearing leaves called sporophylls
Rhizoids
anchor gametophytes to substrate
examples of sporophytes
leafy plants
example of gametophytes
tiny plants growing
on or below the soil surface
what are the 2 types of vascular tissue in vascular plants
xylem and phloem
Xylem
conducts most of the water and minerals
tracheids
- tube shaped cells
- carry water and minerals up from the roots
Water-conducting cells of the xylem are strengthened by
a polymer lignin and provide structural
support
taller plants vs smaller plants for sunlight
-taller able to compete better
Phloem tissue are arranged
tubes for transport of organic materials (sugar, amino acids etc
roots
organs that anchor vascular plants into
ground
what do leaves do
increase the surface area for the light capture and conduct most of the photosynthesis in plants
leaves are categorized by two types
- microphylls
- megaphylls
microphylls
small, often spine-shaped leaves with
a single vein, are found only in lycophytes
megaphylls
larger leaves with a highly branched
vascular system, are found in all other plant groups
sporophylls are modified leaves with what
sporangia
sori
clusters of sporangia on the undersides of fern
sporophylls
many lycophytes and most gymnosperms have
strobili
strobili
clumps of sporophylls in cone-like structures
The sporophylls of angiosperms are called
carpels and stamens
Most seedless vascular plants are
homosporous
bisexual gametophyte
male and female gametes
heterosporous
All seed plants and some seedless vascular
megaspores
give rise to female gametophytes,
microscpores
give rise to male gametophytes
two clades of seedless vascular
plants
– Phylum Lycophyta includes club mosses, spike
mosses, and quillworts
– Phylum Monilophyta includes ferns, horsetails, and
whisk ferns and their relatives
Lycophytes grow in
diverse habitats
Some gametophytes are
photosynthetic; others form below ground symbioses with fungi
Sporophytes have both
leaf-forming upright
stems, and ground-hugging root-forming stems
Spikemosses and quillworts are all heterosporous
clubmosses and homosporou
spikemosses and clubmosses have strobili
sporophylls clustered into club-shaped cones
what is the most widespread seedless vascular plants, with more than 12,000 species
ferns
ferns are most diverse in the tropics but also thrive in
temperate forests
Horsetails sporophytes have jointed…
stems with rings of small leaves branches
horestails are
homosporous (cone releasing spores)
whisk ferns resemble
ancestral vascular plants but are closely related to modern ferns
– All are homosporous
