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

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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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