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Plant Diversity (CH 29 & 30)
Transcript of Plant Diversity (CH 29 & 30)
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
: a layer of durable polymer that prevents dessication due to air exposure.
Life on Land: Pros and Cons
-bright sunlight unfiltered by water/plankton
-few herbivores and pathogens (to begin with)
-scarcity of water
-lack of structural support against gravity
what are we waiting for?!
Alteration of Generations
-life cycle in which
give rise to
, and vice versa
-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
-where the gametes are produced
(produce sperm with flagella that can swim through water to reach egg)
(pear-shaped, single nonmotile egg)
-localized regions of cell division at the tips of roots and shoots
-covers epidermis, consists of wax and other polymers
-waterproofs plant, prevents dessication and some microbial attack.
-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
Diversification of Plants
-vascular plants (93% of all plant species known)
: 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)
an embryo packaged with a supply of nutrients inside a protective coat
-seeds not enclosed in chambers
-seeds develop in ovaries, which originate in flowers and mature into fruits. (90% of all plants)
Mosses and other nonvascular plants:
dominant life cycle
-germinating spores produce a
, a one-cell-thick mass
in favorable conditions
-each bud has an apical meristem, produces a
-gametophyte is anchored by
- long tubular single cells.
Not composed of tissues, do not function in water and mineral absorption
absorbs nutrients from gametophyte
(stalk) conducts minerals to
(aka capsule), which produces
spores by the multi-million.
-spores discharged thru
which open up under dry conditions and close in wet conditions.
-specialized pores calld
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
water and minerals
from roots via tracheid tubes, lignified for strength
amino acids, other organic products
-organs that absorb water and nutrients, also anchor plant, thus allowing it to grow taller
-increase plant surface area, primary organ of photosynthesis
-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
-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
Part II: THE EVOLUTION OF
: 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
-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
Ovules and Egg Production
-integument envelops and protects the megasporangium
-integument + megasporangium + megaspore = ovule
Pollen and Sperm Production
develops into pollen grain, which is the
protects the grain as it is transported (pollination).
Sperm Advantage: can be carried
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
The Seed Advantage
-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?
plants with "naked" seeds not enclosed in ovaries, ex: pine cones
-large cones and palm-like leaves, thrived during the Mesozoic era.
-Ginkgo biloba is the only surviving member. Seed-producing trees smell terrible.
-includes Ephedra, Gnetum, and Welwitschia. Found in tropics/desert
-cone-bearers, mostly evergreens
-largest gymnosperm phyla, 600 species
-seed plants with flowers and fruits
-a specialized shoot with up to four rings of modified leaves specialized for reproduction
enclose petals before they blossom
attracts pollinators with color,
smell. In wind-dispersed seed plants,
usually lacks bright color
-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
-double-fertilization: one sperm fertilizes
the egg (2n), one fuses with 2 nuclei in cell to produce the endosperm
Monocots v Eudicots
Seed Plant Products and Human Welfare
(potatoes, rice, wheat, maize, cassava, sweet potatoes = 80% total human calorie consumption)
(tea leaves, coffee beans, fermented fruits)
(herbal and prescription drugs alike)
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.
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.