1. Summary from last time
470 mya years ago- the first fossils of land plants.
DNA evidence suggests that the first land plants came from an algal scum ~1.2 BYA in form of filamentous green alga.
First land plants were the Bryophytes
4) Today, these plants are still restricted to moist conditions.
5) They still have swimming sperm and are dependent on water for fertilization but are assisted by animals in that process.
6) They evolved spores which allows them to survive dry conditions and they evolved ways to become dormant as mature plants in drought.

2. Land Plants Review Bryophytes= Mosses, Liverworts, Hornworts
Moist environments
Swimming sperm
Homosporous- Single gametophyte
Gametophyte (n) haploid stage is dominant
Embryo (2n) is parasitic on gametophyte
Lack xylem & phloem
Small plants

4. Now LAND PLANT EVOLUTION Monocot Eudicot Gymnosperms (Naked seeds)
Angiosperms
(Seeds in flowers and fruit)
Now
Non-seeds
Seeds
Bryophytes
(Non-vascular)
Tracheophytes
(Vascular)
Green Algae

5. Tracheophytes
Tracheophytes

6. Overview of Land Plants
Bryophytes
Tracheophytes

7. Advances of Tracheophytes over Bryophytes
xylem and phloem
lignin = wood
thick waxy cuticle
stomates
profuse branching
increased young tissues for photosynthesis
increased areas for sporangia (as opposed to only one sporangium per sporophyte in the Bryophytes)
highly differentiated plant tissues and organs

8. What characteristic would you expect Tracheophytes to lack?
Mitochondria
Swimming sperm
Embryos
Gametangia
Seeds
Pollen
None. They would have them all 1

11. All with swimming sperm
First Tracheophytes
Whisk Ferns
Horsetails
All with swimming sperm
Club Mosses
Ferns
All lack seeds

12. Land Plants Review Tracheophytes: Ferns as an example
Moist environments
Swimming sperm
Homosporous- Single gametophyte
Sporophyte (2n) stage is dominant
Embryo (2n) is parasitic on gametophyte
WIth xylem & phloem
Can be large plants

13. Sporophyte Dominant in Tracheophytes
e.g. Ferns

14. Fern Life Cycle
SORI

15. Fern Life Cycle

16. Diploid (Sporophyte
generation
is dominant
In tracheophytes

17. Characteristics of Plants
Alternation of generations In Bryophytes the haploid (n) generation is dominant In Tracheophytes the diploid (2n) generation

20. Female pine cones
Male pine cones

23. Where are the gametophyte (n) tissues?
Answer: They are the few cells that undergo meiosis to produce the gametes

24. Homosporous Life Cycle
e.g. Bryophytes and Ferns
One kind of spore
One kind of gametophyte

25. Heterosporous Life Cycle
Seed Plants
2 kinds of spores
2 kinds of gametophytes

26. Land Plants Review Tracheophytes: Seed Plants;
e.g. Conifers, & Flowering plants
Found in all types of environments
Sporophyte (2n) dominant
Heterosporous= seed plants have two types of spores; two gametophytes
Gametophytes (n) are tiny and are the few cells that produce the pollen and egg
Xylem & Phloem
Can be large plants

27. Land Plants Review Homosporous 1 gametophyte
Heterosporous gametophytes
One type of spore
Mosses & Ferns
Two types of spores
Gymnosperms & Angiosperms

29. Plant Adaptations to Land
Selective advantages to land
Less competition for light and nutrients
Less predation
Problems with new environment
Physical support
Water loss and availability
Reproduction
Temperature fluctuations

30. How Plants Deal with Problems
Problem: Physical support
Solution: Internal support
Roots: anchor plants in soil
& acquire nutrients & H2O

31. How Plants Deal with Problems
Problem: Physical support
Solution: Internal support
Stems:
Turgor pressure in cells with cell walls
Lignin = “wood”
Secondary growth—i.e. growth in width
(Rings of Xylem)

32. How Plants Deal with Problems
Problem: Water loss & availability
Solution: Conserve & acquire H20
Acquire H20
H20 from soil via root
Transport via xylem
Mutualism with
fungus (mycorrhizae)

33. Fungi in Soil

34. Plants are connected to underground fungi
in a mutualistic relationship

35. Carbohydrates
Plant
Fungus
H20 & minerals

36. Fungi form connections with many plants
Fungal superhighway

37. Plants exchange nutrients
Fungal Superhighway

38. When herbivores (e.g. aphids) eat plants, the plants start making distasteful and toxic chemicals to deter further destruction

39. When plants are attacked by herbivores they send signals the each other via the mycorrhizae.
Fungal Internet

41. AND
When plants are attacked they produce volitles (vapors) which affect other plants to produce defensive chemicals

42. When plants are attacked they produce volitle (vapors) which pass through the air to alert other plants

43. And these vapors will attract aphid predators and parasitoids
Wasp laying egg in aphid

44. How Plants Deal with Problems
Problem: Water loss & availability
Solution: Conserve & acquire H20
Conserving H20—Reduce leaf size and store water

45. How Plants Deal with Problems
Conserving H20—Require large surface area for photosynthesis (leaves)
Waxy cuticle on leaves

46. How Plants Deal with Problems
Conserving H20—Require large surface area for photosynthesis (leaves)
Waxy cuticle on leaves prevents water loss
But what about the need for CO2?

47. Water Loss in Plants Problem: Need C02 for photosynthesis
Holes in surface of leaf, but this means H20 loss
Stomates & guard cells controls water loss

48. How Plants Deal with Problems
Conserving H20—Require large surface area for photosynthesis (leaves)
Deciduous leaves prevent water loss during winter

49. How Plants Deal with Problems
Problem: Water & reproduction
Solutions:
Pollen= non-swimming sperm with tough water resistant coat
Carried by wind or animals

50. Seeds= embryo + endosperm + seed coat
Seeds evolved 365 MYA
in Gymnosperms
Seeds found in Siberian permafrost
32,000 years old have been germinated.

51. How Plants Deal with Problems Seed Dispersal
Wind
Large surface area to catch the breezes
Maple seeds
with wings

52. How Plants Deal with Problems Seed Dispersal
Wind
Large surface area to catch the breezes

53. How Plants Deal with Problems Seed Dispersal
Water
Seeds must float
Coconuts

54. How Plants Deal with Problems Seed Dispersal
Animals
Caught on fur or body
Cockleburs

55. How Plants Deal with Problems Seed Dispersal
Animals
Fruit eaten by animals
& the seeds dropped at a distance from the parent plant

56. How Plants Deal with Problems Seed Dispersal
“Anachronistic Fruits” =
Fruits whose seed dispersers are extinct.
Osage orange

57. Osage Orange
Mastodon

58. Why Are There Different Leaf Shapes?

59. Leaf Evolution & Adaptations
WHY?

60. Next Time