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Plant Diversity (CH 29 & 30)

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greta moore

on 25 July 2014

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Transcript of Plant Diversity (CH 29 & 30)

Plant Diversity
I & II

I: How Plants Colonized Land
Land Plants Evolved From Green Algae
4 pieces of Evidence
1. Rings of Cellulose-synthesizing proteins
in the plasma membrane.
2. Peroxisome Enzymes
which help minimize the loss of organic products due to photorespiration.
4. Formation of a phragmoplast,
a group of microtubules that forms between the daughter nuclei of a dividing cell.
3. Structure of flagellated sperm
Adaptations Allowing the move to Land
Sporopollenin
: a layer of durable polymer that prevents dessication due to air exposure.
Life on Land: Pros and Cons
Pros Cons
-bright sunlight unfiltered by water/plankton
-plentiful CO2
-mineral-rich soil
-few herbivores and pathogens (to begin with)
-scarcity of water
-lack of structural support against gravity
what are we waiting for?!
Derived Traits
Alteration of Generations
-life cycle in which
gametophytes
give rise to
sporophytes
, and vice versa
Ploidy level
Haploid (n)
Diploid (2n)
Gametophyte




Sporophyte
-haploid (n), gives rise to sperm and eggs (gametes) by mitosis.
- diploid (2n), produces haploid
spores by meiosis.
Walled Spores Produced in Sporangia
sporocytes (2n) undergo mitosis to produce haploid spores inside the
Sporangia
Multicellular Gametangia
-where the gametes are produced


Male:
Antheridia
(produce sperm with flagella that can swim through water to reach egg)
female:
Archegonia
(pear-shaped, single nonmotile egg)
Apical Meristems
-localized regions of cell division at the tips of roots and shoots
Cuticle
-covers epidermis, consists of wax and other polymers
-waterproofs plant, prevents dessication and some microbial attack.
Secondary Compounds
-alkaloids, terpenes, tannins, flavanoids....
-bitter taste/strong odor/toxic
-used to defend against herbivores and parasites
C A F F E I N E
T E T R A H Y D R O C A N N A B I N O L
N I C O T I N E
M E N T H O L
M O R P H I N E
Camellia sinensis
Cannabis sativa

Nicotiana tabacum
Mentha species
Papaver somniferum
Diversification of Plants
BRYOPHYTES
-vascular plants (93% of all plant species known)
Vascular Tissue
: cells joined into tubes that transport water and nutrients throughout the plant body.
SEEDLESS VASCULAR PLANTS
-lycophytes (club mosses and family)
-pterophytes (ferns and family)
Seed:
an embryo packaged with a supply of nutrients inside a protective coat
Gymnosperm
Angiosperm
-seeds not enclosed in chambers
-seeds develop in ovaries, which originate in flowers and mature into fruits. (90% of all plants)
(nonvascular plants)
Mosses and other nonvascular plants:
Gametophyte
dominant life cycle
-Liverworts
-Hornworts
-Mosses
-germinating spores produce a
protonema
, a one-cell-thick mass

-protonema produces
buds
in favorable conditions

-each bud has an apical meristem, produces a
gametophore

-gametophyte is anchored by
rhizoids
- long tubular single cells.

Unlike roots:
Not composed of tissues, do not function in water and mineral absorption
bryophyte gametophyte
bryophyte sporophyte
-
foot
absorbs nutrients from gametophyte
-
seta
(stalk) conducts minerals to
sporangium
(aka capsule), which produces
spores by the multi-million.
-spores discharged thru
peristome
(teeth-like)
which open up under dry conditions and close in wet conditions.

-specialized pores calld
stomata
allow gas exchange, close in hot dry conditions to minimize water loss.
mosses retain nitrogen, some species harbor N-fixing cyanobacteria as well.

can survive the loss of most H20
and then rehydrate when water becomes available.
Ferns and other seedless vascular plants:the first to grow tall
TRANSPORT
XYLEM


PHLOEM
-conducts
water and minerals

up
from roots via tracheid tubes, lignified for strength
-tubes distribute
sugars,
amino acids, other organic products
where needed
ROOTS
-organs that absorb water and nutrients, also anchor plant, thus allowing it to grow taller
LEAVES
-increase plant surface area, primary organ of photosynthesis
microphylls
megaphylls
SPOROPHYLLS
-modified leaves that bear spores, ex: pine cone
-most seedless vasculars are homosporous: one type of sporangium, one type of spore, grows into bisexual gametophyte
-all seed plants are heterosporous: megasporangia and microsporangia which develop into female and male gametophytes respectively.
Classifying Seedless Vasculars
Lycophyta



Pterophyta
-club mosses, spike mosses, quillworts
-Carboniferous period saw giant lycophyte trees 40 m tall
-ferns, horsetails, whisk ferns
Seedless Vascular Plants: Who cares?
-vascular tissue = increased rate of photosynthesis = increased removal of CO2, leading to global cooling and glacier formation

-formed the first forests, we now happily harvest their skeletons to keep the lights on in this room
I want to feel
the sand between
my toes!
Part II: THE EVOLUTION OF
SEED PLANTS

: an embryo and its food supply,
surrounded by a protective coat.

"a mobile version of a pregnant
woman's uterus" -your textbook
Seeds and Pollen Grains: Key Adaptations for land
Reduced Gametophytes

-develop from spores inside sporangia, protecting gametophyte from UV radiation, dessication, other environmental stress, allowing them to obtain nutrients from the sporophyte

-much easier than free-living gametophytes, the SU v ESF student analogy
Heterospory
Mega
sporangia
Micro
sporangia
Ovules and Egg Production

-integument envelops and protects the megasporangium
-integument + megasporangium + megaspore = ovule
Pollen and Sperm Production
-
microspore
develops into pollen grain, which is the
gametophyte
+
pollen wall.
-wall of
sporopollenin
protects the grain as it is transported (pollination).
Sperm Advantage: can be carried
long distance
by pollen grain, whereas previous free-living gametophyte could only swim through a film of water.
Free Living Gametophyte
i'm so fast!
Sperm inside a pollen grain
sucker.
The Seed Advantage
-protective layer
-food supply
-ability to travel great distance
-can remain dormant for significant time
seedless plants v seeded: transporting an ice cube across the ocean in a canoe vs flying across in a plane with a refridgerator What?
GYMNOSPERMS
plants with "naked" seeds not enclosed in ovaries, ex: pine cones
-Four Phyla
Cycadophyta
-large cones and palm-like leaves, thrived during the Mesozoic era.
Ginkgophyta
-Ginkgo biloba is the only surviving member. Seed-producing trees smell terrible.
Gnetophyta
-includes Ephedra, Gnetum, and Welwitschia. Found in tropics/desert
EPHEDRINE
Coniferophyta
-cone-bearers, mostly evergreens
-largest gymnosperm phyla, 600 species
ANGIOSPERMS
-seed plants with flowers and fruits
FLOWERS
-a specialized shoot with up to four rings of modified leaves specialized for reproduction
enclose petals before they blossom
produces microspores
produces megaspores
attracts pollinators with color,
smell. In wind-dispersed seed plants,
usually lacks bright color
FRUIT
-a mature ovary
-protects seed and aids in their dispersal
-can be fleshy (tomatoes, apples, grapes)
or dry (beans, nuts, rice)
Adaptations help disperse seeds
Aid in Wind Dispersal
Hitchhike on Animals
Appeal as Food Source
-bright, sweet-tasting and nutritious
fruit is dispersed miles from origin with a ready-made supply of natural fertilizer
Angiosperm Life Cycle
-Cross-pollination increases genetic
variation
-double-fertilization: one sperm fertilizes
the egg (2n), one fuses with 2 nuclei in cell to produce the endosperm
(3n)

Monocots v Eudicots
Seed Plant Products and Human Welfare
-
food
(potatoes, rice, wheat, maize, cassava, sweet potatoes = 80% total human calorie consumption)
-
drink
(tea leaves, coffee beans, fermented fruits)
-
livestock feed
(meat consumption)
-
paper production
-
building construction
-
fuel
-
durable fibers
(clothing, textiles)
-
medicines
(herbal and prescription drugs alike)

Key Concepts:
1. Land plants evolved from green algae
2. Mosses and other nonvascular plants have life cycles dominated by gametophytes
3. Ferns and other seedless vascular plants were the first plants to grow tall
These compounds help plants defend themselves from herbivores and other pests.
Key Concepts:
Key Concepts:
1. Seeds and pollen grains are key adaptaions for life on land
2. Gymnosperms bear "naked" seeds, typically on cones
3. The reproductve adaptations of angiosperms include flowers and fruit
4. Human welfare depends greatly on seed plants.
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