1. Chapter 19
Plant Diversity

2. 19.1 Land plants evolved from green algae
Origins of Plants from Algae
Charophytes
Modern charophytes found in shallow fresh water around edges of ponds and lakes
Adaptations to land ~475 m-y-a
plant: a multicellular autotroph in which the embryo develops within the female parent

3. Challenges of Life on Land
Obtaining resources
Staying upright
Maintaining moisture
Reproducing

4. Obtaining resources Algae - resources from water only
Plants - resources from soil and air
Roots and shoots
vascular tissue: system of tube-shaped cells that branches throughout the plant
Soil= water and minerals
Air = sunlight as energy, use CO2

5. Staying Upright Algae stay upright by buoyancy Plants need support
lignin: a chemical
that hardens the
plants’ cell walls

6. Maintaining Moisture Need to maintain water level within
cuticle: waxy coating of leaves and other parts to retain water
Cacti, apples
stomata: pores in leaf’s surface that allows gas exchange
Regulated by guard cells

7. Reproducing on Land
Water provides means of dispersal and prevents gametes from drying out
Plants produce gametes in a “jacket” of protective cells
Prevents dehydration
Most are carried in pollen grains
Eggs are fertilized and develops into an embryo in the female parent; dispersed as seeds in protective coats

8. Plant Diversity
Origin of plants from charophytes; aquatic algal ancestors
Bryophytes: mosses and relatives
No seeds or lignin
Pteridophytes: ferns
Ligin-hardened vascular tissue, no seeds
Gymnosperms: conifers
Seeds without protective coat
Angiosperms: flowering plants
Seeds in protective organs, ovaries

9. Alternation of generations
Alternation between haploid and diploid forms
gametophyte: haploid generation that produces gametes
sporophyte: diploid generation that produces spores
Spores - develop into new organism on its own
Some have tough coats to survive in harsh environments
Gamete - needs to fuse with another to form a zygote
Not adapted to harsh conditions

10. 19.2 Bryophytes Includes mosses and relatives
Described as nonvascular plants because they lack the lignin-hardened vascular tissue
Some do have tubular cells
Male and female gametes produced separate locations
Sperm fertilizes the egg and the zygote forms a stalk-like structure that produces spores

12. Mosses Many gametophyte plants in a tight pack Sporophytes are stalks
Spongy
Absorb water

13. Hornworts
Hornlike sporophytes

14. Liverworts

15. 19.3 Pteridophytes Ferns Lignin-hardened tissues
Vascular tissue for water and sugar transport
Dominated Carboniferous period
Organic compounds formed fossil fuels
Heat and pressure

16. Reproduction Sporophyte is dominant generation
Creates gametophytes
Gametophytes have sperm and eggs

18. Ferns Most diverse and widespread Large leaves Shady forests
12,000 species
Large leaves
Shady forests
Some in deserts

19. Club “Mosses” Looks like a little pine tree Common on forest floors
Carboniferous ~40m

20. Horsetails Marshy sandy areas Carboniferous ~15m Outer layer is silica
Used as scouring pad

21. 19.4 Gymnosperms Bear seeds that are not enclosed in an ovary
Adaptations
Smaller gametophyte
Pollen
Seeds
Succeeded when temperatures dropped; ferns began to disappear

22. Smaller Gametophytes Sporophyte is more highly developed
Pine tree is the sporophyte
Gametophytes live in cones

23. Pollen Small male gametophytes that develop into sperm
Carried from male to female cones by wind
Evolved to travel without water

24. Seed
Consists of a plant embryo packaged along with a food supply within a protective coat

25. Reproduction Cone contains spore sacs
Spores develop into pollen grains (male)
Ovules (female) hold and help gametophyte grow
Pollen blown by wind to female cone
Sperm mature and fertilize eggs
Develops into embryo; new plant

27. Pine Cone Growth
Male Cone
Female Cones

28. Ginkgos & Gnetophytes Ginkgo biloba: only species of ginkgophytes
Fleshy seeds that look like fruit
Tolerates air pollution
Gnetophytes
Mormon Tea; desert shrub

29. Cycads & Conifers Conifers (Coniferophyta) Cycads (Cycadophyta)
Most are evergreens
Spruce, pine, fir, juniper, cedar
Cycads
(Cycadophyta)
Large, palm-like leaves (not actual palms)
Form a cone

30. 19.5 Angiosperms Flowering plants
Gametophytes develop with the flowers of the sporophyte
Flower: specialized plant shoot for reproduction
Attract insects and animals to transfer pollen

31. Reproductive Structures
Male = stamens
anther - pollen grains
Female = carpels
Ovary at base
Embryo sacs develop within ovules
Stigma receives sperm

32. Reproduction Pollen lands on sticky stigma
Tube grows from each pollen grain down toward an ovule
Two sperm cells are released
One sperm fertilizes an egg cell
Produces zygote --> embryo
Second sperm fuses with nuclei which develops into the endosperm
Ovule develops into a seed
Ovary wall thickens and forms a fruit

34. Monocots & Dicots Monocots Dicots Parallel leaf veins
Petals in multiples of 3
Lilies, orchids, palms, grasses
Dicots
Branched leaf veins
Petals in multiples of 4 or 5
Poppies, roses, sunflowers, oaks

35. Amborella & Water Lilies
“living fossil”
Only surviving species of oldest branch
Only found in New Caledonia
Water Lillies
Evolved before monocots and dicots

36. Star Anise & Others Evolved before monocots and dicots
Fruit is called Chinese Star

37. Human Dependence Crops; corn, wheat, rice, and other grains
Fruits of grass species
Feed for cows and chickens
Harvested for furniture, medicines, perfumes, decorations, and clothing fiber (cotton)
Only 280,000 known plant species
5000 species investigated for potential medicine sources
Humans may be destroying plants that we could use for medicine

38. Cotton
Cotton-top Tamarin