1. 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 444 
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

2. Plants and algae share the following characteristics
-chlorophyllous
-store energy mainly as starch
-cellulose cell walls
-form cell plates during cell division
-primitive plants have flagellated sperm like algae

3. Plants have adaptations for life on land
Plants are multicellular photosynthetic eukaryotes
Plants have some specific adaptations that are not found in algae

4. Plant
Roots anchor plant; absorb water and minerals from the soil
Reproductive structures, as in flowers, contain spores and gametes
Cuticle covering leaves and stems reduces water loss; stomata in leaves allow gas exchange
Leaf performs photosynthesis
Surrounding water supports alga
Stem supports plant and may perform photosynthesis
Whole alga performs photosynthesis; absorbs water, CO2, and minerals from the water
Holdfast anchors alga
Alga
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

5. Plants have apical meristems
Are the growth-producing regions of a plant
Help maximize exposure to the resources in the soil at root tip and air at buds

6. Plants have vascular tissue
distributes nutrients throughout Pteridophytes, Gymnosperms, and Angiosperms
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

7. Plants have secondary cell walls
The secondary cell walls of some plant tissues provide support
are thickened and strengthened by lignin, a polymer of alcohols that is extremely strong forming secondary cell walls

8. Plants have a cuticle and stomates/lenticels
A waxy cuticle covers the stems and leaves of plants
And helps retain water
Stomata/lenticels
Are tiny pores in leaves that allow for gas exchange

9. Many living plants can reproduce on land
Produce gametes that are encased in protective structures called ovules and pollen grains
Most gymnosperms and all angiosperms have nonflagellated sperm

10. 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
Liverworts
Hornworts
Mosses
Lycophytes (club mosses and relatives)
Pterophytes (ferns and relatives)
Angiosperms
Gymnosperms
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

11. Bryophytes lack vascular tissue and include
The mosses, hornworts, and liverworts
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

12. Vascular plants
Have supportive vascular tissues such as xylem that carries water and minerals and phloem that conducts carbohydrates
Pteridophytes and most gymnosperms have xylem tracheids and most woody gymnosperms have softwood
Gymnosperms called gnetophytes and angiosperms have tracheids and thick-walled vessels and if woody are called hardwoods

13. Pteridophytes are seedless vascular plants With flagellated sperm
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

14. Seed plants
Have pollen grains that transport sperm
Protect their embryos in ovules that grow into seeds
Seeds are better adapted than single-celled spores having a coat, stored carbohydrate, and an embryo

15. Gymnosperms, such as pines Produce seeds in cones
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. The seeds of angiosperms Develop within protective ovaries
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

17. ALTERNATION OF GENERATIONS AND PLANT LIFE CYCLES
Haploid and diploid generations alternate in plant life cycles
The haploid gametophyte
Produces eggs and sperm by mitosis

18. The zygote develops into the diploid sporophyte
In which meiosis produces haploid spores
Spores grow into gametophytes

19. Alternation of generations
Sporophyte plant (2n)
Key
Fertilization
Gametophyte plant (n)
Haploid (n)
Diploid (2n)
Sperm
Egg
Mitosis
Zygote (2n)
Gametes (n)
Spores (n)
Meiosis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

20. Mosses have a dominant gametophyte
A mat of moss is mostly gametophytes
Which produce eggs and swimming sperm
The zygote develops on the gametophyte
Grows into the smaller sporophyte

21. Characteristics of Bryophytes or Nonvascular plants
-no vascular tissue absorbing water by capillarity and
transporting carbohydrates by diffusion
-no true roots, stems, or leaves as lack vascular tissue.
Rhizoids are root-like but are only used for anchorage.
-Alternation of generations and gametophyte dominates with
gametes formed inside multicellular gameteangia called
antheridia or archegonia
-biflagellate sperm that require water for successful fertilization

22. Division Bryophyta “moss plant” @12,000 sps.
-gametophytes have rhizoids, an erect stem-like body,
and leaf-like organs
-often found in damp or aquatic habitats
-reproduce asexually by fragmentation

23. Sexual reproduction:

24. Life cycle of a moss Gametophytes (n) Key Haploid (n) Male
Diploid (2n)
Spores (n)
Egg (n)
Sperm (n) (released from gametangium)
Sporophytes (growing from gametophytes)
Meiosis
Sporangium
Female
Gametophytes (n)
Fertilization
Stalk
Sporophyte (2n)
Male
Zygote (2n) 1 2
Mitosis and development 3 4 5
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

37. Division Hepatophyta “liver plant” @6500 sps.
-20% gametophytes have a flattened body called
thallus and 80% have erect growth like mosses but
the stalk of the sporophyte is translucent
to white; its capsule is typically black and egg-shaped.
When it matures, the capsule splits open into four
equal quarters, releasing the spores to the air.
-in medieval ( ) period, people believed in
Doctrine of Signatures and lobed thallus indicated
plants were treatment for liver disease
-often found in damp or aquatic habitats and are
primarily tropical in range

38. Liverwort on Colorado River
near Bend, Texas Photograph
by Brian Scoggins

39. Ex. Marchantia (after French botanist)
-reproduce asexually by gemmae cups that act as rain
splashcups dispersing tiny clones
Sexual reproduction is similar to mosses except gameteangia
and sporangia grow in umbrella-like structures called
_____ and _____ and spores have elaters that curl and
uncurl due to changes in humidity

41. Phylum Anthoceratophta “Flowering horn plants” 100spp.
-mostly tropical
-Reproduce asexually by fragmentation and sexually like
mosses except with green
horn-like sporangium
-rare in Texas wetlands.
One population of yellow
hornwort known from
Ottine Wetlands in
Gonzales County, Texas
near Palmetto State Park

42. Some human and ecological importance of bryophytes
Pioneer organisms
Sphagnum or peat moss
-used as fuel
-used as soil conditioner as can
-absorb about 25X weight in
water
-smoky peat fires used flavor
barley used in making Scotch
Whiskey
Many species are good
indicators of air and water pollution