Transcript ch 29-30 plant diversity notes-2007

Phylogeny and Systematics
Ch. 25
Phylogeny
• Evolutionary history of a species or group
of related species
• Reconstructing phylogeny is part of the
scope of systematics
– Systematics—the study of biological diversity
in an evolutionary context
Phylogenetic Trees
• Diagrams that trace evolutionary relationships as
best as they can be determined
• Systematist use evidence from:
– Fossil record
• Phenotypic appearances
– Molecular biology
• Comparison of nucleic acid sequences/amino acid sequences
• DNA sequence analysis—identifying & comparing
homologous sequences
• Species diverge as changes (genetic mutations) occur
Taxonomy
• Branch of biology
concerned with
naming and
classifying the diverse
forms of life
• Scientific name of an
organism = binomial
system
• Genus / species
Phylogenetic trees reflect the
hierarchical classification
Cladistic Analysis
Cladogram
• Synonymous with
phylogenetic
systematics
• Clade=evolutionary
branch
• Classifying organisms
according to the order
in time that branches
arose along a
dichotomous tree
• Analyzing the taxonomic distribution of
homologies enables us to identify the sequence
in which derived characters evolved during
vertebrate phylogeny.
Fig. 25.11
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Kingdom: Plantae
Plant Diversity
Ch. 29 & 30
Land plants evolved from green algae
• Green algae called
charophyceans are the
closest relatives of land
plants
• Four key traits in
common:
– Rose-shaped complexes for
cellulose synthesis
– Peroxisome enzymes
– Structure of flagellated sperm
– Formation of a phragmoplast
• Supported by genetic
similarites in both their
nuclear and chloroplast
genes
Chara,
a pond
organism
(LM).
10 mm
40 µm
Coleochaete orbicularis, a disk-shaped
charophycean (LM).
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
• 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
Plant Characteristics
• Multicellular eukaryotes
• Photosynthetic autotrophs
• Chloroplasts with photosynthetic pigments
– chlorophyll, carotenoids
• Cell walls contain cellulose
• Excess glucose stored as starch in plastids
Life Cycles of Plants:
Alternation of Generations
• Gametophyte—
multicellular individual
with haploid cells
– Produce haploid cells
that fuse to form
zygotes
• Sporophyte—multicellular
individual with diploid
cells
– Develop from the
zygotes that are formed
Gametophyte
Phase
Dark round structures are
antheridia or archegonia of
the fern gametophyte (x12)
The fern sporophyte grows from a
fertilized egg in an archegonium
on the gametophyte. (x12)
Fern
Fiddleheads
Sporophyte Phase
Sori on Fern
Leaf
Fern Leaf with
Sori
Plant Phylogeny
1. Origin of plants from aquatic ancestors—
Ordovician period (475mya)
–
–
Cuticle formation and jacketed gametangia
Vascular tissue with conducting cells
2. Diversification of seedless vascular
plants—Devonian period (400mya)
Plant Phylogeny
3. Origin of the seed—Devonian period
(360mya)
–
–
Seed = plant embryo packaged with food
store and protective coat
Gymnosperms—early seed plants—naked
seeds
4. Emergence of flowering plants—
Cretaceous period (130mya)
–
Angiosperms—plants bear seeds inside
flower’s protective ovaries
Land plants
Vascular plants
Seed plants
Angiosperms
Gymnosperms
Pterophytes
Seedless vascular plants
Lycophytes
Mosses
Hornworts
Liverworts
Charophyceans
Bryophytes
Origin of seed plants
(about 360 mya)
Origin of vascular plants
(about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga
Classification of Plants I
•Nonvascular Plants (Bryophytes)
•Division Bryophyta (mosses)
•Division Hepatophyta (liverwarts)
•Division Anthocerophyta (hornwarts)
Characteristics:
•Small herbaceous plants (nonwoody)
•No vascular tissue, so relies on diffusion and capillary action to get
water
•Need water to reproduce
•Gametophytes—larger and longer-living than sporophytes
•Sporophytes—typically present only part of the time
•Gametangia protect developing gametes
•antheridium—produce flagellated sperm
•archegonium—produce single egg
Division Bryophyta
(mosses)
http://gallery.criticalmoss.net/cache/moss_Moss.png_400.jpg
•Spongy mat—can absorb and
retain water
•Grips substratum with rhizoids
(cellular filaments)
http://www.dkimages.com/discover/previews/998/35002390.JPG
http://www2.una.edu/pdavis/images/liverworts/rhizoidUlbasechipol10CM.jpg
www.davidlnelson.md/Cazadero/Mosses.htm
Bryophyta
http://www.davidlnelson.md/Cazadero/CazImages/Moss_sporangium2.jpg
• The green leafy structures are gametophytes.
• The brown structures are sporophyte stalks and
spore capsules.
Raindrop
Key
Male
gametophyte
Life Cycle of Moss
Haploid (n)
Diploid (2n)
Sperm
“Bud”
Spores develop into
threadlike protonemata.
A sperm swims
through a film of
moisture to an
archegonium and
fertilizes the egg.
Antheridia
The haploid
protonemata
produce “buds”
that grow into
gametophytes.
Protonemata
Most mosses have separate
male and female gametophytes,
with antheridia and archegonia,
respectively.
“Bud”
Egg
Gametophore
Spores
Female
Archegonia
gametophyte
Meiosis occurs and haploid
spores develop in the sporangium
of the sporophyte. When the
sporangium lid pops off, the
peristome “teeth” regulate gradual
release of the spores.
Peristome
The sporophyte grows a
long stalk, or seta, that emerges
from the archegonium.
Sporangium
MEIOSIS
Mature
sporophytes
Rhizoid
Seta
Calyptra
Capsule
(sporangium)
Foot
FERTILIZATION
(within archegonium)
Zygote
Embryo
Archegonium
Young
sporophyte
Capsule with
peristome (SEM)
Female
gametophytes
Attached by its foot, the
sporophyte remains nutritionally
dependent on the gametophyte.
The diploid zygote
develops into a
sporophyte embryo within
the archegonium.
Division Hepatophyta
(liverworts)
http://www.kingsnake.com/westindian/hepaticopsida5.JPG
•Sporangia have coilshaped cells that spring
out and disperse spores
LIVERWORT
SPOROPHYTE
•Sporophytes are horn-shaped,
elongated capsules that grow
from the mat like gametophyte
•Photosynthetic cells have only
one large chloroplast
sporophyte
www.botany.hawaii.edu/.../Cyanobacteria.htm
Division Anthocerophyta
(hornworts)
gametophyte
http://taggart.glg.msu.edu/bot335/Hornw.jpg
hornwort Phaeoceros
Classification of Plants
•Vascular Plants
Seedless Vascular Plants
•Division Lycophyta (lycophytes)
•Division Sphenophyta (horsetails)
•Division Pterophyta (ferns)
•Characteristics:
•Sporophytes are the larger generation
•Gametophytes are tiny plants that grow on or below the
soil surface
•Terrestrial Adaptations:
•Roots-transport water
•Cellulose (structure support)
•Vascular tissue-xylem (water) and phloem (food)
•Pollen-eliminates need for water in reproduction
•Increased dominance of diploid sporophyte
Division Lycophyta
(lycophytes)
Lycopodium
annotinum
Order Isoetales
Quillworts
•Low-growing plants with
rhizomes and true leaves
•Some are epiphytes (use
another organism as a
substratum
Rhizome: stem like part of
the plant from which the
leaves grow
sporangia
http://hcs.osu.edu/hcs300/svp1.htm
http://hcs.osu.edu/hcs300/svp1.htm
Division Sphenophyta
(horsetails)
Sphenophytes consist of only one genus, Equisetum, with about thirty
living species known worldwide
Homosporous-bisexual gametophyte produces egg and sperm
Division Pterophyta (ferns)
• Most diverse seedless
vascular plants
• Fronds-compound leaves
• Homosporous
• Sporangia borne on
underside of specialized
sporophylls
• Water necessary for
fertilization
• Sporophyte develops
within archegonium
http://en.wikipedia.org/wiki/Fern
http://en.wikipedia.org/wiki/Image:Sa-fern.jpg
3 Variations on Alternation of Generations in Plants
Evolution of Roots
• Roots are organs that anchor vascular plants
• They enable vascular plants to absorb water
and nutrients from the soil
• Roots may have evolved from subterranean
stems
Evolution of Leaves
• Leaves are organs that increase the surface area of
vascular plants, thereby capturing more solar
energy that is used for photosynthesis
• Leaves are categorized by two types:
– Microphylls, leaves with a single vein
– Megaphylls, leaves with a highly branched
vascular system
• According to one model of evolution, microphylls
evolved first, as outgrowths of stems
Classification of Plants II
• Vascular Plants
• Seed Plants
• Gymnosperms
–
–
–
–
Division Coniferophyta (conifers)
Division Cycadophyta (cycads)
Division Ginkgophyta (ginkgo)
Division Gnetophyta (Gnetae)
Seeds Replace Spores
• Relatively harsh terrestrial environment led to
development of resistant structures for the
dispersal of offspring
• Seeds more hardy because of multicellular nature
• Seed = sporophyte embryo + food supply
surrounded by protective coat
• Seed plants are heterosporous
– Megasporangia produce megaspores  female
gametophyte
– Microsporangia produce microspores  male
gametophyte
• Seed plants evolved from
plants with
megasporangia, which
produce megaspores that
give rise to female
gametophytes
• Seed plants evolved from
plants with
microsporangia, which
produce microspores that
give rise to male
gametophytes
cavehill.uwi.edu/FPAS/bcs/bl14apl/pter3.htm
Heterospory: The Rule Among
Seed Plants
Micrograph of Selaginella
Ovules and Production of Eggs
• An ovule consists of a megasporangium, megaspore, and
one or more protective integuments
• Gymnosperm megaspores have one integument
• Angiosperm megaspores usually have two integuments
Integument
Female
gametophyte (n)
Seed coat
(derived from
integument)
Spore wall
Egg nucleus (n)
Megasporangium
(2n)
Megaspore (n)
Unfertilized ovule
Male gametophyte
(within germinating
pollen grain) (n)
Micropyle
Fertilized ovule
Discharged
sperm nucleus (n)
Pollen grain (n)
Food supply
(female
gametophyte
tissue) (n)
Embryo (2n)
(new sporophyte)
Gymnosperm seed
http://www.wildliferanger.com/users/www.wildliferanger.com/upload/Th
e%20Pollinator%20515.JPG
Pollen and Production of Sperm
• Microspores develop into
pollen grains, which contain
the male gametophytes
• Pollination—transfer of
pollen to the part of a seed
plant containing the ovules
• Dispersal by air or animals
• If a pollen grain germinates,
it gives rise to a pollen tube
that discharges two sperm
into the female gametophyte
within the ovule
The Evolutionary Advantage of
Seeds
• A seed develops from the whole ovule
• A seed is a sporophyte embryo, along with its food
supply, packaged in a protective coat
commons.wikimedia.org/wiki/Image:Avocado_seed...
Division Coniferophyta (conifers)
Araucaria cunninghamii. The hoop pine. Lake Tinaroo Falls Dam,
Queensland, Australia.
•Largest division of Gymnosperms
-most are evergreens: pines, spruces, firs, larches, yews, junipers,
cedars, cypresses, and redwoods
Sequioadendron giganteum.
The Giant Sequoia.
Yosemite National Park,
Mariposa County,
California.
Division Coniferophyta (conifers)
Needle-shaped conifer leaves are adapted to dry conditions
•thick cuticle covers the leaf
•stomata are in pits, reducing water loss
Division Coniferophyta (conifers)
Mature ovulate cones and seeds
Heterosporous- both male
and female gametophytes
develop from different
types of spores on
separate cones
http://www.seinangu.ac.jp/~djohnson/natural/campusplants/023pine.cone3.JPG
http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/Male
_stroboli.jpg
Division Coniferophyta (conifers)
Cedrus deodora. Near Placerville
http://upload.wikimedia.org/wikipedia/commons/3/3b/Cycas_inflo
rescence.jpg
Division Cycadophyta
(cycads)
Leaves and male cone of
Cycas revoluta
• Living fossils—
Jurassic Period is
sometimes called the
"Age of Cycads"
http://a.abcnews.com/images/Technology/nc_cycads_071004_ms.jpg
http://www.hort.wisc.edu/mastergardener/Features/botgardens/lotusl
Division Cycadophyta
(cycads)
Cycas revoluta
http://z.about.com/d/forestry/1/7/l/i/Ginkgo_biloba_st
ueber.jpg
www.science.siu.edu/.../ginkgophyta.html
Ginkgo biloba
Division
Ginkgophyta
(ginkgo)
www.science.siu.edu/.../ginkgophyta.html
Ephedra andina.
http://wc.pima.edu/~bfiero/tucsonecology/plants/images/s
w_ephe01.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Ephedra_
andina_1.jpg/581px-Ephedra_andina_1.jpg
Division Gnetophyta
(Gnetae)
Mormon tea
Classification of Plants II
•Vascular Plants
Seed Plants
Angiosperms
Division Anthophyta (flowering plants)
Reproductive adaptations of
angiosperms include flowers and fruits
• Angiosperms are flowering plants
• These seed plants have reproductive structures
called flowers and fruits
• They are the most widespread and diverse of all
plants
Stigma
Stamen
Anther
Carpel
Style
Filament
Ovary
California Poppy
Petal
Sepal
Sunflower
Ovule
Receptacle
Division Anthophyta
(flowering plants)
Indian Paintbrush
in Grand Canyon.
Fruit develop from the ovary
http://www-plb.ucdavis.edu/labs/rost/Tomato/Reproductive/stages2aa.gif
Fruits
• A fruit typically
consists of a mature
ovary but can also
include other flower
parts
• Fruits protect seeds
and aid in their
dispersal
• Mature fruits can be
either fleshy or dry
Tomato, a fleshy fruit with soft
outer and inner layers of pericarp
Ruby grapefruit, a fleshy fruit
with a hard outer layer and soft
inner layer of pericarp
Nectarine, a fleshy
fruit with a soft outer
layer and hard inner
layer (pit) of pericarp
Milkweed, a dry fruit that splits
open at maturity
Walnut, a dry fruit that remains
closed at maturity
Fruits
• Various fruit
adaptations help
disperse seeds
• Seeds can be carried
by wind, water, or
animals to new
locations
Wings enable maple
fruits to be easily
carried by the wind.
Seeds within berries
and other edible fruits
are often dispersed in
animal feces.
The barbs of cockleburs
facilitate seed dispersal
by allowing these fruits to
hitchhike on animals.
The Angiosperm Life Cycle
• In the angiosperm life cycle, double fertilization
occurs when a pollen tube discharges two sperm
into the female gametophyte within an ovule
• One sperm fertilizes the egg, while the other
combines with two nuclei in the central cell of
the female gametophyte and initiates
development of food-storing endosperm
• The endosperm nourishes the developing
embryo
Key
The
Angiosperm
Life Cycle
Haploid (n)
Diploid (2n)
Microsporangium
Microsporocytes (2n)
Anther
Mature flower on
sporophyte plant
(2n)
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n) Male
gametophyte
(in pollen
grain)
Generative cell
Ovary
Germinating
seed
Pollen
grains
MEIOSIS
Stigma
Pollen
Megasporangium tube
(n)
Sperm
Surviving
megaspore
(n)
Embryo (2n)
Endosperm
(food
supply) (3n)
Seed
Pollen
tube
Seed coat (2n)
Style
Antipodal cells
Female gametophyte
Polar
nuclei
(embryo sac)
Synergids
Eggs (n)
Pollen
tube
Sperm
(n)
Zygote (2n)
Nucleus of
developing
endosperm
(3n)
Eggs
nucleus (n)
FERTILIZATION
Discharged
sperm nuclei (n)
Tube cell