1. First 2 billion years on Earth: 1.2 billion years ago:
Chapter 26: The Colonization of Land by Plants and Fungi Overview: The Greening of Earth
First 2 billion years on Earth:
1.2 billion years ago:
Around 500 million years ago:
About 385 million years ago:
Plants and fungi colonized the land as partners before animals arrived
Importance of Plants?
Importance of Fungi? 1

2. Concept 26.1: Fossils show that plants colonized land more than 470 million years ago
The closest relatives of land plants=
Many characteristics of land plants also appear in some algae
What characteristics?
However, some distinctive traits of land plants are only shared with charophytes, including:
Rings of cellulose-synthesizing complexes
Structure of flagellated sperm 2

3. Adaptations Enabling the Move to Land
In charophytes, a layer of a durable polymer called sporopollenin:
Sporopollenin is also found in plant spore walls
The movement onto land by charophyte ancestors provided a different environment, which included:
Land presented challenges: 3

4. Derived Traits of Plants
Key traits that appear in nearly all land plants but are absent in the charophytes include
Alternation of generations
Multicellular, dependent embryos
Walled spores produced in sporangia
Apical meristems
Additional derived traits include:
Cuticle
Stomata 4

5. Alternation of generations
Figure 26.6a
Alternation of generations
Gametophyte
(n)
Gamete from
another plant
Mitosis
Mitosis n n n n
Spore
Gamete
MEIOSIS
FERTILIZATION
Zygote
Figure 26.6a Exploring alternation of generations (part 1: cycle) 2n
Key
Haploid (n)
Sporophyte
(2n)
Mitosis
Diploid (2n) 5

6. Sporangium Sporophyte Gametophyte Figure 26.7a
Figure 26.7a Sporophytes and sporangia of a moss (Sphagnum) (part 1: photo)
Gametophyte 6

7. Sporangia 25 m 2 cm Rhizoids Figure 26.9
Figure 26.9 Aglaophyton major, an early land plant
2 cm
Rhizoids 7

8. Concept 26.2: Fungi played an essential role in the colonization of land
Fungi may have colonized land before plants
Mycorrhizae are symbiotic associations between fungi and land plants that may have helped plants without roots (non vascular) to obtain nutrients
FUNGAL NUTRITION
Cell walls?
Multicellular filaments or single celled 8

9. Reproductive structure Hyphae Spore-producing structures 60 m
Figure 26.10
Reproductive
structure
Hyphae
Spore-producing
structures
Figure Structure of a multicellular fungus
60 m
Mycelium 9

10. Some fungi have specialized hyphae called haustoria that allow them to extract or exchange nutrients with plant hosts
Plant
cell
wall
Fungal hypha
Plant cell
Figure Haustoria of mycorrhizae
Plant cell
plasma
membrane
Haustorium 10

11. Mycorrhizae:
Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex
Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane 11

12. Figure 26.12-3: Fungi Asexual and Sexual Reproduction
Key
Haploid (n)
PLASMOGAMY
Heterokaryotic
Heterokaryotic
stage
Diploid (2n)
Spore-
producing
structures
KARYOGAMY
Spores
SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION
Mycelium
Zygote
Figure Generalized life cycle of fungi (step 3)
GERMINATION
MEIOSIS
GERMINATION
Spores 12

13. The Origin of Fungi
Fungi and animals are more closely related to each other than they are to plants or other eukaryotes
DNA evidence suggests that:
Fungi are most closely related to unicellular protists called nucleariids
Animals are most closely related to:
This suggests that ____________________arose separately in animals and fungi
The oldest undisputed fossils of fungi are only about 460 million years old 13

14. The Move to Land
Fungi were among the earliest colonizers of land and probably formed mutualistic relationships with early land plants
For example, 405-million-year-old fossils of Aglaophyton contain evidence of fossil hyphae penetrating plant cells 14

15. Diversification of Fungi
Molecular analyses have helped clarify evolutionary relationships among fungal groups, although areas of uncertainty remain
There are about 100,000 known species of fungi, but there are estimated to be as many as 1.5 million species 15

16. Zygomycetes (1,000 species)
Figure 26.15
Chytrids (1,000 species)
Hyphae
25 m
Zygomycetes (1,000 species)
Glomeromycetes (160 species)
2.5 m
Ascomycetes (65,000 species)
Figure Exploring fungal diversity
Basidiomycetes (30,000 species) 16

17. Concept 26.3: Early land plants radiated into a diverse set of lineages
Ancestral species gave rise to a vast diversity of modern plants 17

18. Figure 26.16
Liverworts
Origin of land plants
Nonvascular
plants
(bryophytes)
ANCESTRAL
GREEN
ALGA
Land plants 1
Mosses
Hornworts
Lycophytes (club
mosses, spike
mosses, quillworts)
Seedless
vascular
plants
Origin of vascular plants 2
Monilophytes (ferns,
horsetails, whisk ferns)
Vascular plants
Gymnosperms
Origin of extant seed
plants
Figure Highlights of plant evolution 3
Seed plants
Angiosperms
500
450
400
350
300 50
Millions of years ago (mya) 18

19. Land plants informally grouped based on:
Most plants have vascular tissue for the transport of water and nutrients; these constitute the vascular plants
Nonvascular plants are commonly called 19

20. Bryophytes: A Collection of Early Diverging Plant Lineages
Bryophytes are represented today by three clades of small herbaceous (nonwoody) plants
Liverworts
Mosses
Hornworts
Moss Life Cycle: 20

21. FERN LIFE CYCLE

22. MOSS http://bcs.whfreeman.com/thelifewire/content/chp29/29020.html
LIFE
CYCLE

23. (a) Plagiochila deltoidea, a liverwort Gametophyte
Figure 26.17
Sporophyte
(a) Plagiochila deltoidea, a
liverwort
Gametophyte
(c) Anthoceros sp., a hornwort
Sporophyte
(a sturdy
plant that
takes months
to grow)
Capsule
Figure Bryophytes (nonvascular plants)
Seta
Gametophyte
(b) Polytrichum commune, a moss 23

24. Seedless Vascular Plants: The First Plants to Grow Tall
Bryophytes were the prevalent vegetation during the first 100 million years of plant evolution
The earliest vascular plants date to 425–420 million years ago
Vascular tissue allowed these plants to grow tall
Early vascular plants lacked ___________
Seedless vascular plants can be divided into clades
Lycophytes (club mosses and their relatives)
Monilophytes (ferns and their relatives) 24

25. (a) Diphasiastrum tristachyum, a lycophyte
Figure 26.18
2.5 cm
2.5 cm
Strobili
(conelike
structures
in which
spores are
produced)
Figure Lycophytes and monilophytes (seedless vascular plants)
(a) Diphasiastrum tristachyum, a
lycophyte
(b) Athyrium filix-femina, a
monilophyte 25

26. Life Cycles with Dominant Sporophytes
In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in familiar ferns
The gametophytes are:
Flagellated sperm must: 26

27. Figure 26.19
PLANT GROUP
Ferns and other
seedless
vascular plants
Mosses and other
nonvascular plants
Seed plants (gymnosperms and angiosperms)
Reduced, independent
(photosynthetic and
free-living)
Reduced (usually microscopic), dependent on
surrounding sporophyte tissue for nutrition
Gametophyte
Dominant
Reduced, dependent
on gametophyte for
nutrition
Sporophyte
Dominant
Dominant
Gymnosperm
Angiosperm
Sporophyte
(2n)
Microscopic female
gametophytes (n) inside
ovulate cone
Microscopic female
gametophytes
(n) inside these parts
of flowers
Sporophyte
(2n)
Gametophyte
(n)
Microscopic
male
gametophytes
(n) inside
these parts
of flowers
Example
Figure Gametophyte-sporophyte relationships in different plant groups
Microscopic
male
gametophytes (n)
inside pollen
cone
Sporophyte (2n)
Sporophyte (2n)
Gametophyte
(n) 27

28. Transport in Xylem and Phloem https://highered. mcgraw-hill
IMPORTANCE?
XYLEM
PHLOEM 28

29. Evolution of Roots and Leaves29

30. Concept 26.4: Seeds and pollen grains are key adaptations for life on land
Seed plants originated about 360 million years ago
An adaptation called the seed allowed them to expand into diverse terrestrial habitats
A seed consists of:
Mature seeds are dispersed by: 30

31. Extant seed plants are divided into two clades
Gymnosperms:
Angiosperms:

32. Terrestrial Adaptations in Seed Plants
In addition to seeds, the following are common to all seed plants:
Reduced gametophytes
Ovules
Pollen 32

33. (a) Unfertilized ovule (b) Fertilized ovule (c) Gymnosperm seed
Figure
Immature
ovulate cone
Integument (2n)
Female
gametophyte (n)
Seed coat
Megaspore (n)
Spore
wall
Spore wall
Egg nucleus
(n)
Food
supply
(n)
Discharged
sperm nucleus
(n)
Megasporangium
(2n)
Figure From ovule to seed in a gymnosperm (step 3)
Pollen
grain (n)
Male
gametophyte
Pollen tube
Embryo (2n)
Micropyle
(a) Unfertilized ovule
(b) Fertilized ovule
(c) Gymnosperm seed 33

34. The Evolutionary Advantage of Seeds
A seed develops from the whole ovule
A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat
ADVANTAGE over spores?
IMPORTANCE? 34

35. Early Seed Plants and the Rise of Gymnosperms
Fossil evidence reveals that by the late Devonian period, some plants had begun to acquire features found in seed plants but did not bear seeds
Gymnosperms appeared in the fossil record about 305 million years ago
Gymnosperms largely replaced nonvascular plants as the climate became drier toward the end of the Carboniferous period 35

36. Gymnosperms are an important part of Earth’s flora
Gymnosperms were better suited than nonvascular plants to drier conditions due to adaptations including
Seeds and pollen
Thick cuticles
Leaves with small surface area
Gymnosperms are an important part of Earth’s flora
For example, vast regions in northern latitudes are covered by forests of cone-bearing gymnosperms called conifers 36

37. (a) Sago palm (Cycas revoluta) (b) Douglas fir (Pseudotsuga menziesii)
Figure 26.21
(a) Sago palm (Cycas revoluta)
(b) Douglas fir (Pseudotsuga
menziesii)
Figure Examples of gymnosperms
(c) Creeping juniper (Juniperus
horizontalis) 37

38. The Origin and Diversification of Angiosperms
Angiosperms seed plants with reproductive structures
They are the most widespread and diverse of all plants
WHAT IS THE FLOWER? 38

39. Stigma Carpel Stamen Anther Style Filament Ovary Petal Sepal Ovule
Figure 26.22
Stigma
Carpel
Stamen
Anther
Style
Filament
Ovary
Petal
Figure The structure of an idealized flower
Sepal
Ovule 39

40. Angiosperm Evolution
Darwin called the origin of angiosperms an “abominable mystery”
Fossil evidence and phylogenetic analysis have led to progress in solving the mystery, but we still do not fully understand the evolution of angiosperms 40

41. Fossil evidence: Angiosperms originated at least 140 million years ago and dominated the landscape by the end of the Cretaceous period, 65 million years ago
Chinese fossils of 125-million-year-old angiosperms help us to infer traits of the angiosperm common ancestor
Archaefructus sinensis, for example, was herbaceous and may have been aquatic 41

42. (a) Archaefructus sinensis, a 125-million-year-old fossil
Figure 26.23
Carpel
Stamen
5 cm
(a) Archaefructus sinensis, a
125-million-year-old fossil
Figure An early flowering plant
(b) Artist’s reconstruction of
Archaefructus sinensis 42

43. Angiosperm phylogeny: The ancestors of angiosperms and gymnosperms diverged about 305 million years ago
Angiosperms may be closely related to Bennettitales, extinct seed plants with flowerlike structures 43

44. Microsporangia (contain microspores) Ovules Figure 26.24
Figure A close relative of the angiosperms? 44

45. Most recent common ancestor of all living angiosperms Amborella
Figure 26.25
Most recent common ancestor
of all living angiosperms
Amborella
Water lilies
Amborella
Water lilies
Star anise
and relatives
Magnoliids
Star anise
Monocots
Eudicots
150
125
100 25
Millions of years ago
Eudicots
Figure Exploring angiosperm phylogeny
Magnoliids
Monocots 45

46. Concept 26.5: Land plants and fungi fundamentally changed chemical cycling and biotic interactions
The colonization of land by plants and fungi altered the physical environment and the organisms that live there
What is a LICHEN? 46

47. A foliose (leaflike) lichen
Figure 26.26
A foliose (leaflike) lichen
Crustose
(encrusting) lichens
(a) Two common lichen growth forms
50 m
Figure Lichens
Fungal hyphae
Algal cell
(b) Anatomy of a lichen involving an ascomycete fungus
and an alga 47

48. Plants affect the formation of soil
Role of the roots?
Role of leaf litter/decaying plant parts?
Plants have also altered Earth’s atmosphere by releasing oxygen to the air through photosynthesis 48

49. Plants and fungi affect the cycling of chemicals in ecosystems
Plants absorb nutrients:
Decomposers, including fungi and bacteria:
Plants and the Carbon cycle: 49

50. Biotic Interactions What are biotic interactions?
How did plants and fungi effect species interactions? 50

51. Fungi as Mutualists and Pathogens51

52. (b) Tar spot fungus on maple leaves (a) Corn smut on corn
Figure 26.29
Figure Examples of fungal diseases of plants
(b) Tar spot
fungus
on maple
leaves
(a) Corn smut on corn
(c) Ergots on rye 52

53. Plant-Animal Interactions
Animals influence the evolution of plants, and vice versa
For example, animal herbivory selects for plant defenses
For example, interactions between pollinators and flowering plants select for mutually beneficial adaptations 53

54. Bilateral symmetry Radial symmetry Time since divergence
Figure 26.UN06
Bilateral symmetry
Radial symmetry
Time since divergence
from common ancestor
Common
ancestor
Figure 26.UN06 In-text figure, flower shape hypothesis, p. 524
“Bilateral” clade
Compare
numbers
of species
“Radial” clade 54

55. (a) A satellite image from 2000 shows clear-cut
Figure 26.30
(a) A satellite image from
2000 shows clear-cut
areas in Brazil (brown)
surrounded by dense
tropical forest (green).
(b) By 2009, much more
of this same tropical
forest had been cut
down.
Figure Clear-cutting of tropical forests
4 km 55