1. Plants, Fungi, and the Colonization of Land
Chapter 17
Plants, Fungi, and the Colonization of Land

2. Plants and Fungi—A Beneficial Partnership
Orange groves in Florida, Texas, and California
Rely on associations between plants and fungi

3. Mycorrhizae, mutually beneficial associations of plant roots and fungi
Are common, and may have enabled plants to colonize land
A mycorrhizal fungus enveloping roots of a red pine tree

4. PLANT EVOLUTION AND DIVERSITY
17.1 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 
Figure 17.1A, B

5. 17.2 Plants have adaptations for life on land
Plants are multicellular photosynthetic eukaryotes

6. Plants have some specific adaptations That are not found in algae
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
Figure 17.2A

7. 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

8. Plants have vascular tissue
Which helps distribute nutrients throughout the organism
Figure 17.2B

9. Supporting the Plant Body
The cell walls of some plant tissues
Are thickened and strengthened by lignin

10. 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

11. Reproducing on Land Many living plants
Produce gametes that are encased in protective structures

12. 17.3 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
Figure 17.3A

13. Bryophytes lack vascular tissue and include
The mosses, hornworts, and liverworts
Figure 17.3B

14. Vascular plants
Have supportive vascular tissues

15. Ferns are seedless vascular plants With flagellated sperm
Figure 17.3C

16. Seed plants
Have pollen grains that transport sperm
Protect their embryos in seeds

17. Gymnosperms, such as pines Produce seeds in cones
Figure 17.3D

18. The seeds of angiosperms Develop within protective ovaries
Figure 17.3E

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

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

21. 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
Figure 17.4

22. 17.5 Mosses have a dominant gametophyte
A mat of moss is mostly gametophytes
Which produce eggs and swimming sperm
The zygote develops on the gametophyte
Into the smaller sporophyte

23. Life cycle of a moss Figure 17.5 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
Figure 17.5

24. 17.6 Ferns, like most plants, have a dominant sporophyte
Sperm, produced by the gametophyte
Swim to the egg

25. Life cycle of a fern Figure 17.6 Key Haploid (n) Diploid (2n) Egg (n)
Zygote (2n)
Sperm (n) (released from male gametangium)
Gametophyte (n) (underside)
Fertilization
Clusters of sporangia
New sporophyte (2n) growing out of gametophyte
Mature sporophyte (independent of gametophyte)
Spores (n)
Meiosis
Female
gametangium (n) 1 2
Mitosis and development 3 4 5
Figure 17.6

26. 17.7 Seedless plants dominated vast “coal forests”
Ferns and other seedless plants
Once dominated ancient forests
Their remains formed coal
Figure 17.7

27. 17.8 A pine tree is a sporophyte with tiny gametophytes in its cones
A sperm from a pollen grain
Fertilizes an egg in the female gametophyte
The zygote develops into a sporophyte embryo
And the ovule becomes a seed, with stored food and a protective coat

28. Life cycle of a pine tree
Key
Haploid (n)
Diploid (2n)
Zygote (2n)
Fertilization
Mature sporophyte
Pollen grains (male gametophytes) (n)
Meiosis
Female gametophyte (n)
Eggs (n)
Sperm (n)
Male gametophyte (pollen grain)
Seed coat
Embryo (2n)
Food supply
Seed
Ovule
Scale
Sporangium (2n)
Spore mother cell (2n)
Integument
Female cone bears ovules. 1
Sporangia in male cone produce spores by meiosis; spores develop into pollen grains. 2
Pollination 3
A haploid spore cell in ovule develops into female gametophyte, which makes eggs. 4
Male gametophyte (pollen) grows tube to egg and makes and releases sperm. 5
Zygote develops into embryo, and ovule becomes seed. 6
Seed germinates, and embryo grows into seedling. 7
Figure 17.8

29. 17.9 The flower is the centerpiece of angiosperm reproduction
Flowers usually consist of
Sepals, petals, stamens (which produce pollen), and carpels (which produce eggs)
Anther
Filament
Stamen
Petal
Receptacle
Ovule
Sepal
Stigma
Style
Ovary
Carpel
Figure 17.9A, B

30. 17.10 The angiosperm plant is a sporophyte with gametophytes in its flowers
In the angiosperm life cycle
Ovules become seeds, and ovaries become flowers

31. Life cycle of an angiosperm
Pollen grains (n)
Meiosis
Stigma
Pollen grain
Pollen tube
Egg (n)
Ovule
Fertilization
Embryo
(2n)
Food
supply
Seed
coat
Seeds
Key
Haploid (n)
Diploid (2n)
Sporophyte (2n)
Ovary
Anther 1
Haploid spores in anthers develop into pollen grains: male gametophytes. 2
Haploid spore in each ovule
develops into female gametophyte,
which produces egg. 3
Pollination and
growth of
pollen tube 4
Zygote 5 6
Fruit
(mature ovary) 7
Seed germinates,
and embryo
grows into
plant.
Sperm
Figure 17.10

32. 17.11 The structure of a fruit reflects its function in seed dispersal
Fruits are adaptations that disperse seeds
Figure 17.11A–C

33. 17.12 Agriculture is based almost entirely on angiosperms
CONNECTION
17.12 Agriculture is based almost entirely on angiosperms
Angiosperms provide most of our food
And other important commercial products

34. 17.13 Interactions with animals have profoundly influenced angiosperm evolution
Angiosperms
Are a major source of food for animals

35. Animals also aid plants in pollination
Figure 17.13A–C

36. 17.14 Plant diversity is a nonrenewable resource
CONNECTION
17.14 Plant diversity is a nonrenewable resource
Many types of forests
Are being destroyed worldwide
Figure 17.14

37. Some plants in these forests Can be used in medicinal ways
Table 17.14

38. 17.15 Fungi absorb food after digesting it outside their bodies
Fungi are heterotrophic eukaryotes
That digest their food externally and absorb the nutrients
Figure 17.15A

39. A fungus usually consists of a mass of threadlike hyphae
Called a mycelium
Hypha
Mycelium
Figure 17.15B, C

40. 17.16 Fungi produce spores in both asexual and sexual life cycles
In some fungi, fusion of haploid hyphae
Produces a heterokaryotic stage containing nuclei from two parents

41. Meiosis produces haploid spores
After the nuclei fuse
Meiosis produces haploid spores
Key
Haploid (n)
Heterokaryotic (n + n)
(unfused nuclei)
Diploid (2n)
Heterokaryotic
stage
Fusion of nuclei
Fusion of cytoplasm
Sexual
reproduction
Meiosis
Zygote
(2n)
Spore-producing
structures
Germination
Asexual
Spores
(n)
Mycelium
Spores (n)
Figure 17.16

42. 17.17 Fungi can be classified into five groups
Fungi evolved from an aquatic, flagellated ancestor

43. Fungal phylogeny Figure 17.17A Chytrids Zygomycetes (zygote fungi)
Glomeromycetes
(arbuscular mycorrhizal fungi)
Ascomycetes
(sac fungi)
Basidiomycetes
(club fungi)
Figure 17.17A

44. Fungal groups include
Chytrids

45. Zygomycetes
Glomeromycetes
SEM 6,500
Figure 17.17B, C

46. Ascomycetes
Figure 17.17D

47. Basidiomycetes
Figure 17.17E

48. 17.18 Fungal groups differ in their life cycles and reproductive structures
Fungal life cycles
Often include asexual and sexual stages
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
Fusion of
nuclei
Meiosis
Mycelia of
different
mating types
Cells fuse
Young
zygosporangium
(heterokaryotic)
Zygosporangium (n + n)
Sporangium
Spores
(n) 1 2 3 4
Figure 17.18A

49. Fungal groups have characteristic reproductive structures
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
Fusion of
nuclei
Meiosis
Basidia
Spores (n)
Mushroom 1
Fusion of two hyphae
of different mating types 2
Growth of
heterokaryotic mycelium 3
Diploid nuclei 4
Spores
released 5
Germination of spores
and growth of mycelia
Figure 17.18B

50. 17.19 Parasitic fungi harm plants and animals
CONNECTION
17.19 Parasitic fungi harm plants and animals
Parasitic fungi cause 80% of plant diseases
And some serious human mycoses
Figure 17.19A–C

51. 17.20 Lichens consist of fungi living mutualistically with photosynthetic organisms
Lichens consist of algae or cyanobacteria
Within a fungal network
Fungal
hyphae
Algal
cell
Colorized SEM 1,000 
Figure 17.20A, B

52. 17.21 Fungi also form mutualistic relationships with animals
Some animals
Benefit from the digestive abilities of lichens
Figure 17.21

53. 17.22 Fungi have enormous ecological benefits and practical uses
CONNECTION
17.22 Fungi have enormous ecological benefits and practical uses
Fungi are essential decomposers
And provide antibiotics and food
Staphylococcus
aureus
Penicillium
Zone of
inhibited
growth
Figure 17.22A, B