Transcript 3.2 The Plants File

3.2 The Plants
Learning Goals:
• Adaptations of plant to life on land
• Describe the alternation of generation of
plant
• Describe the major distinguish features of
the 4 main groups of plants (bryophytes,
lycophytes & pteridophytes, gymnosperms,
and angiosperms)
• Phylogeny of major plant groups (which
plant groups are more closely related?)
General Characteristics
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Autotrophic (undergo photosynthesis)
Have cell walls with cellulose
Have both male and female reproductive parts
Store energy as starch
Multi-cellular
Mostly land-dwelling
Form cell plates during cell division
Develop from embryos protected by tissues of the
parent plant
• Plant life cycle consists of 2 alternating phases:
sporophyte (diploid) and gametophyte (haploid)
The Shift to Land
Evidence suggests that green algae and land
plants are related.
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Both contain chlorophyll
Both have cellulose-based cell walls.
Both store food as starch.
They have shown genetic similarities.
Adaptations to Life on Land
• Seeds – enable embryo to survive unfavorable
conditions.
Adaptations to Life on Land
• Roots “mine” the soil for water and minerals
to transport to the shoot.
Adaptations to Life on Land
• Stomates (pores) in leaf epidermis regulate
gas exchange to maximize CO2 uptake and
minimize water loss
Adaptations to Life on Land
• Resist drying out due to:
1. Having a cuticle (waxy
layer)
2. The evolution of
multicellular sex organs –
to help protect gametes
3. Having resistant coat on
spores
Adaptations to Life on Land
• STEMS, ROOTS and LEAVES
contain vascular tissues for
water and mineral transport.
Adaptations to Life on Land
• Pollen – allows for male sex cells to travel via
wind, water and organisms
Key Terms
Haploid cells
• Contain 1 set of chromosomes (n)
• i.e. gametes – egg and sperm (sex cells)
• Produced by meiosis
Key Terms
Diploid cells
• Contain 2 sets of chromosomes (2n)
• i.e. somatic cells (all other cells of the body)
• Produced by mitosis
Key Terms
Sporophyte
• A diploid organism that produces haploid
spores
Gametophyte
• A haploid organism that produces haploid sex
cells (gametes)
Alternation of Generations
The life cycle of plants consists of two generations,
which alternate between a haploid and a diploid
stage.
The diploid generation of a plant is called the
sporophyte.
Through the process of meiosis, sporophytes
produce haploid spores, which can develop
without fertilization.
Alternation of Generations
The haploid spore grows into a plant body called
the gametophyte.
Gametophytes produce male and female
gametes, which fuse at fertilization and develop
into another sporophyte.
The cycle then repeats itself.
Alternation of Generations
Although all plant life cycles include a sporophyte and
gametophyte generation, one stage or the other is
characteristically dominant in different plant groups.
In non-vascular plants the dominant state (the familiar
green plant) is the gametophyte.
In vascular groups the sporophyte is the more dominant
generation. In flowering plants, the gametophyte is
reduced to a small group of cells entirely dependent on
the sporophyte.
Kingdom Plantae Diversity
(to be written as a note)
Four major groupings or divisions:
(1) Bryophytes
• Mainly mosses, liverworts and hornworts
• Show aquatic and terrestrial adaptations:
amphibians of plant world (though some live in
arid conditions).
• Minimal differentiation into tissues & organs: no
vascular tissue; no true leaves, stems, roots.
• Small plants close to the ground. Why?
• Sperm (n) swim to egg (sexual reproduction)
• Spores (2n) are wind/water dispersed.
• Seedless.
(2) Seedless Vascular Plants
(Spore-Producing)
• Mainly ferns, club mosses and horsetails
• Complex vascular tissue (tracheids for water
movement), but no true leaves or roots.
• Instead they have fronds (leaves) and rhizones
(underground stems for anchoring).
• Sperm swim to egg (no pollen). Haploid (n)
spores are wind dispersed.
• No seeds.
(3) Gymnosperms
• Pines, conifers, cycads, etc
• Vascular plants with leaves, stems and roots.
• Produce pollen so sperm no longer swim to
egg.
• No flowers. Naked seeds dispersed by cones.
• Female cones = seed cones / Male cones =
pollen cones
(4) Angiosperms
• Flowering plants
• Complex vascular tissue (tracheids and vessels for
water movement).
• Leaves, stems, roots, flowers, pollen
• Seeds within a protective wall called fruit
• Fruit used for dispersal (animal, wind, in rare
cases water).
• Most adapted group to terrestrial environment.
• Most recent and successful group – most species
Homework
• Read pg. 85-95
• Phylogeny of Gymnosperms worksheet (in
pkg)
• Construct a venn diagram comparing plants
vs. fungi
• Pg. 95 #1, 2 and 6