Download Guide 17

Bio 100 - Study Guide 17
Plants and Fungi
Defining the Plant Kingdom
• Systematists
– Are currently debating the boundaries of the plant
kingdom
Viridiplantae
Streptophyta
Plantae
Red algae
Figure 29.4
Chlorophytes Charophyceans Embryophytes
Ancestral alga
An overview of land plant evolution
Land plants
Vascular plants
Figure 29.7
Angiosperms
Origin of seed plants
(about 360 mya)
Origin of vascular
plants (about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga
Seed plants
Gymnosperms
Pterophyte
(ferns, horsetails, whisk fern)
Seedless vascular plants
Lycophytes
(club mosses, spike mosses, quillworts)
Mosses
Hornworts
Liverworts
Charophyceans
Bryophytes
(nonvascular plants)
Morphological and Biochemical
Evidence
• Many characteristics of land plants also appear
in a variety of algal clades
• Multicellular, eukaryotic, photosynthetic
• Cell walls of cellulose
• Chloroplasts with chlorophylls a and b
()
Chara,
a pond
organism
10 mm
40 µm
Coleochaete orbicularis, a diskshaped charophycean (LM)
There are four key traits that land plants share only with
charophyceans
– Rose-shaped complexes for cellulose synthesis
– Peroxisome enzymes
• Minimize loss of organic compounds as a result of
photorespiration.
– Structure of flagellated sperm
• Resembles that of charophycean sperm
– Formation of a phragmoplast
• Alignment of the cytoskeletal elements and Golgi
derived vesicles across the midline of the dividing
cell.
• Comparisons of both nuclear and chloroplast genes
– Point to charophyceans as the closest living relatives
of land plants
Adaptations Enabling the Move to
Land
• In charophyceans
– A layer of a durable polymer called sporopollenin
prevents exposed zygotes from drying out
• The accumulation of traits that facilitated
survival on land
– May have opened the way to its colonization by
plants
• Land plants possess a set of derived terrestrial
adaptations
• Many adaptations
– Emerged after land plants diverged from their
charophycean relatives
Derived Traits of Plants
• Five key traits appear in nearly all land plants
but are absent in the charophyceans
– Apical meristems
– Alternation of generations
– Walled spores produced in sporangia
– Multicellular gametangia
– Multicellular dependent embryos
• Apical meristems and alternation of generations
APICAL MERISTEMS
Apical
meristem
of shoot
Developing
leaves
Apical meristems of plant shoots
and roots. The light micrographs
are longitudinal sections at the tips
of a shoot and root.
Apical meristem
of root
Shoot
Root
100 µm
100 µm
Haploid multicellular
organism (gametophyte)
Mitosis
Mitosis
n
n
n
ALTERNATION OF GENERATIONS
Spores
n
n
Gametes
MEIOSIS
FERTILIZATION
2n
Figure 29.5
2n
Zygote
Mitosis
Diploid multicellular
organism (sporophyte)
Alternation of generations: a generalized scheme
• Walled spores; multicellular gametangia; and
multicellular, dependent embryos
WALLED SPORES PRODUCED IN SPORANGIA
Spores
Sporangium
Sporophyte and sporangium
of Sphagnum (a moss)
Longitudinal section of
Sphagnum sporangium (LM)
Sporophyte
Gametophyte
MULTICELLULAR GAMETANGIA
Female gametophyte
Archegonium
with egg
Antheridium
with sperm
Archegonia and antheridia
of Marchantia (a liverwort)
Male
gametophyte
MULTICELLULAR, DEPENDENT EMBRYOS
Embryo and placental
transfer cell of Marchantia
Figure 29.5
Embryo
Maternal tissue
2 µm
10 µm
Wall ingrowths
Placental transfer cell
Additional derived units
– A cuticle evolved in many plant species that
provides a hydrophobic surface
http://academic.kellogg.edu/herbrandsonc/bio111/leaves.htm
http://en.wikipedia.org/wiki/Cuticle
The cuticle means that passage of
gases (CO2, H2O) in and out of the leaf
can be regulated
Bryophytes
• Cuticle and stomates, gametangia and
dependent embryos
• The life cycles of mosses and other bryophytes
are dominated by the gametophyte stage
• Bryophytes are represented today by three
phyla of small herbaceous (nonwoody) plants
– Liverworts, phylum Hepatophyta
– Hornworts, phylum Anthocerophyta
– Mosses, phylum Bryophyta
Bryophyte diversity
Gametophore of
female gametophyte
LIVERWORTS (PHYLUM HEPATOPHYTA)
Plagiochila
deltoidea,
a “leafy”
liverwort
Foot
Seta
Marchantia sporophyte (LM)
HORNWORTS (PHYLUM ANTHOCEROPHYTA)
An Anthoceros
hornwort species
Sporophyte
Sporangium
500 µm
Marchantia polymorpha,
a “thalloid” liverwort
MOSSES (PHYLUM BRYOPHYTA)
Polytrichum commune,
hairy-cap moss
Sporophyte
Gametophyte
Gametophyte
Figure 29.9
Bryophyte Life Cycle - Moss
http://www.tutorvista.com/topic/bryophyte-life-cycle-gametophyte
Ecological and Economic Importance of Mosses
• Sphagnum, or “peat moss”
– Forms extensive deposits of partially decayed organic
material known as peat
– Plays an important role in the Earth’s carbon cycle
(a) Peat being harvested from a peat bog
(b) Closeup of Sphagnum. Note the “leafy” gametophytes
and their offspring, the sporophytes.
Gametophyte
(c) Sphagnum “leaf” (LM). The combination of living photosynthetic
cells and dead water-storing cells gives the moss its spongy quality.
Figure 29.10 a–d
(d) “Tolland Man,” a bog mummy dating from 405–100 B.C.
The acidic, oxygen-poor conditions produced by
Sphagnum canpreserve human or other animal bodies for
thousands of years.
Sporangium at
tip of sporophyte
Living
photo- Dead watersynthetic storing cells
100 µm
cells
At the end of the Carboniferous
• Ferns and other seedless vascular plants formed
the first forests
• Bryophytes and bryophyte-like plants
– Were the prevalent vegetation during the first 100
million years of plant evolution
• Vascular plants
– Began to evolve during the Carboniferous period
Classification of Seedless Vascular Plants
• Seedless vascular plants form two phyla
– Lycophyta, including club mosses, spike mosses, and
quillworts
– Pterophyta, including ferns, horsetails, and whisk
ferns and their relatives
http://www.bio.miami.edu/dana/160/160S09_10.html
The Significance of Seedless Vascular Plants
• The ancestors of modern lycophytes, horsetails, and
ferns
– Grew to great heights during the Carboniferous,
forming the first forests
Figure 29.15
Whatever the age of the first land plants
Those ancestral species gave rise to a vast diversity of
modern plants
Table 29.1
The Spermatopsida - Seed Plants
Gymnosperms - The Naked Seed Plants
Cycadophyta - The Cycads ("sago palms")
Ginkgophyta - The Maidenhair Trees
Coniferophyta - The Conifers
Gnetophyta - The Gnetophytes
Cycadophyta - The Cycads ("sago palms")
Like the club mosses and horsetails, many seedless
vascular plants have their sporophylls arranged spirally around
a central stem into a structure called a strobilus, or "cone."
Cycads produce male and female cones on separate
plants, and are thus dioecious
Pine Life Cycle
http://www.mun.ca/biology/scarr/Gymnosperma.html
• A flower is a specialized shoot with modified leaves
–
–
–
–
Sepals, which enclose the flower
Petals, which are brightly colored and attract pollinators
Stamens, which produce pollen
Carpels, which produce ovules
Carpel
Stigma
Anther
Stamen
Style
Ovary
Filament
Petal
Sepal
Receptacle
Figure 30.7
Ovule
Nutrition and Fungal Lifestyles
• Fungi are heterotrophs
–But do not ingest their food
• Fungi secrete into their surroundings
exoenzymes that break down complex
molecules
–And then absorb the remaining
smaller compounds
• Fungi consist of
–Mycelia,
networks of
branched hyphae
adapted for
absorption
• Most fungi
–Have cell walls
made of chitin
• The generalized life cycle of fungi
Key
Heterokaryotic
stage
Haploid (n)
Heterokaryotic
(unfused nuclei from
different parents)
PLASMOGAMY
(fusion of cytoplasm)
Diploid (2n)
KARYOGAMY
(fusion of nuclei)
Spore-producing
structures
Spores
SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION
Zygote
Mycelium
MEIOSIS
GERMINATION
GERMINATION
Spore-producing
structures
Spores
Figure 31.5
The End