Ch 17 Plants Colonization of Land
PLANT EVOLUTION AND DIVERSITY
•Plants evolved from green algae – Molecular, physical, and chemical evidence
• Indicates that green algae called charophyceans are the closest living relatives of plants
LM 4
44
Figure 17.1A, B
Coleochate Chara
•Plants have adaptations for life on land– Plants are: multicellular photosynthetic
eukaryotes
– Plants have some specific adaptations • That are not found in algae
Plant
Rootsanchor plant;absorb water andminerals fromthe soil
Reproductive structures, as in flowers,contain spores and gametes
Cuticle covering leaves and stemsreduces water loss; stomata inleaves allow gas exchange
Leaf performs photosynthesis
Surrounding watersupports alga
Stem supports plant and mayperform photosynthesis
Whole algaperformsphotosynthesis;absorbs water,CO2, andminerals fromthe waterHoldfastanchors alga
Alga
Figure 17.2A
•Obtaining Resources from Two Locations– Apical meristems
• Are the growth-producing regions of a plant• Help maximize exposure to the resources in the
soil and air
• Maintaining Moisture– A waxy cuticle covers the stems and leaves of
plants• And helps retain water
– Stomata• Are tiny pores in leaves that allow for gas exchange
– Plants have vascular tissue• Which helps distribute nutrients throughout the
organism
Figure 17.2BXylem Phloem
• Reproducing on Land– Many living plants
• Produce gametes that are encased in protective structures
“Gametangia”
• Plant diversity reflects the evolutionary history of the plant kingdom– Some highlights of plant evolution
Origin of vascular plants(about 420 mya)
Origin of seed plants(about 360 mya)
Origin of land plants(about 475 mya)
Seed plants
Land plants
Bryophytes(nonvascular plants)
Vascular plants
Seedless vascular plants
Live
rwor
ts
Hor
nwor
ts
Mos
ses
Lyco
phyt
es(c
lub
mos
ses
and
rela
tives
)
Pte
roph
ytes
(fer
ns a
nd r
elat
ives
)
Ang
iosp
erm
s
Gym
nosp
erm
s
Figure 17.3A
– Bryophytes lack vascular tissue and include• The mosses, hornworts, and liverworts
Figure 17.3B
– Ferns are seedless vascular plants • With flagellated sperm
Figure 17.3C
•Seedless plants dominated vast “coal forests”
– Ferns and other seedless plants • Once dominated ancient forests
– Their remains formed coal
Figure 17.7
Strip Mining in SE Kansas
– Seed plants• Have pollen grains that transport sperm • Protect their embryos in seeds
– Gymnosperms, such as pines • Produce seeds in cones
Figure 17.3D
– The seeds of angiosperms• Develop within protective ovaries
Figure 17.3E
•The structure of a fruit reflects its function in seed dispersal
– Fruits are adaptations that disperse seeds
Figure 17.11A–C
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