1. Fungi

2. Fungi
Heterotrophs that secrete digestive enzymes on organic matter and absorb released nutrients
Saprobes feed on organic remains (major decomposers in ecosystems)
Symbionts, harmless or beneficial
Parasites
Include single-celled yeasts and large multicelled species

3. A Fungal Symbiont: Lichen

4. Fungal Groups Three major groups
Zygote fungi, sac fungi, and club fungi

5. Fungal Life Cycles Sexual and asexual spore production
In multicelled species
Spores germinate, give rise to filaments (hyphae)
Filaments grow into extensive mesh (mycelium)
Sexual reproduction
Hyphae form short-lived, spore-producing reproductive structures (mushrooms)

6. Fungal Spore-Producing Structures

7. Zygomycetes: Zygote Fungi
Include molds that grow on foods (fruits, breads)
A few species are dangerous pathogens
Hyphae: Continuous tubes with no cross-walls

8. Ascomycetes: Sac Fungi
The most diverse group
Single-celled yeasts and multicelled species

9. Predatory Sac Fungus

10. Basidiomycetes: Club Fungi
Multicelled club fungi also have hyphae with cross-walls and can produce complex reproductive structures (mushrooms)
Many club fungi are major decomposers in forest habitats

11. Life Cycle: Club Fungi

12. Lichen
A composite organism that consists of a fungal symbiont and one or more photoautotrophs (green algae or cyanobacteria)
The fungus makes up most of the lichen, and obtains nutrients from its photosynthetic partner

13. Lichens

14. Mycorrhizae (Fungus-Roots)
Symbiotic interaction between fungus and plant
Fungal hyphae surround or penetrate roots and supplement their absorptive surface area
Fungus shares some absorbed mineral ions with the plant, gets some carbohydrates back

15. A Mycorrhiza

16. Fungal Infections
A number of pathogenic fungi can destroy crops, spoil food, and cause diseases in humans
Examples: Athlete’s foot, apple scab, ergot

17. Poisonous Mushrooms

18. Plant Evolution

19. Plant Adaptations to Land
Most groups are adapted to dry and often cold habitats through structural modifications
Stomata across epidermal surfaces
Waterproof cuticle
Xylem and phloem (vascular tissues)

20. Alternation of Generations
Land plants alternate between gametophyte (haploid) and sporophyte (diploid) generations

21. From Haploid to Diploid Dominance
Dominant stages
Haploid body (algae and nonvascular plants)
Diploid body (most modern plants)
Complex sporophytes retain, nourish, and protect new generations through seasons
Production of two spore types allows evolution of pollen grains and seeds in two lineages

22. Evolutionary Trends in Plant Life Cycles

23. Fig. 21.3, p.335

24. Bryophytes Mosses, liverworts, and hornworts
Nonvascular (no xylem or phloem)

25. Life Cycle: Bryophytes
Sperm swim through water droplets or film of water to eggs
Sporophytes stay attached to larger gametophytes
Spores that give rise to gametophytes are wind-dispersed

26. Life Cycle: Bryophytes

27. female gametophytes
male gametophyte
thallus (leaflike part)
close-up of gemmae

28. Peat Bogs: Sphagnum

29. Seedless Vascular Plants
Lycophytes, horsetails, whisk ferns, true ferns

30. Life Cycle: Seedless Vascular Plants
Dominated by the sporophyte
Spore-bearing structures
Sori of ferns
Sperm swim through water to reach eggs

31. The sporophyte
(still attached to
the gametophyte)
grows, develops.
zygote
rhizome
sorus
Diploid Stage
fertilization
meiosis
Haploid Stage
Spores are
released.
Spores develop.
egg-producing
structure
egg
mature
gametophyte
(underside)
sperm-producing
structure
A spore
germinates,
grows into a
gametophyte.
sperm

32. Fern Diversity

33. Seed-Bearing Vascular Plants
Gymnosperms and flowering plants (angiosperms)

34. Life Cycle: Seed Plants
Microspores become pollen grains in which sperm-producing male gametophytes develop
Megaspores give rise to female gametophytes (with eggs) inside ovules
Seed: A mature ovule
Part of ovule forms nutritive tissue and seed coat (protects embryo sporophyte)

35. Gymnosperms: Naked Seeds
Conifers, cycads, ginkgos, and gnetophytes
Many are well adapted to dry climates
Life cycle: No ovaries
Ovules form on exposed surfaces of strobili or (in conifers) female cones

36. Gymnosperms

37. section through one
ovule (the red “cut”
in the diagram
to the left)
surface view of a
female cone scale
(houses two ovules)
ovule
section through
a pollen sac
(red cut)
surface view of a
scale of a male
strobilus (houses
two pollen sacs)
mature
sporophyte
seed
coat
embryo
nutritive
tissue
zygote
seedling
seed formation
Diploid Stage
fertilization
meiosis
meiosis
pollen tube
Haploid Stage
sperm-producing cell
(view inside
an ovule)
pollination
(wind deposits
pollen grain
near ovule)
Microspores
form, develop
into pollen
grains.
Megaspores
form; one
develops into
the female
gametophyte.
Germinating pollen grain (the
male gametophyte). Sperm
nuclei form as the pollen tube
grows toward the egg.
eggs
female gametophyte

38. Angiosperms: Flowering Plants
Only angiosperms have flowers
Many coevolved with birds, bees, bats, and other animal pollinators
Most widely distributed and diverse plant group
Two largest classes: Dicots and monocots

39. angiosperms
(flowering
plants)
cycads
ferns
gymnosperms
ginkgo
other genera

40. Evolution of Flowering Plants

41. petal
stamen
(microspores
form here)
sepal
carpel
(megaspores
form here)
ovule
in an
ovary

42. Life Cycle: Flowering Plants
Monocot life cycle: An example of sexual reproduction in flowering plants
Formation of pollen and eggs
Double fertilization produces an embryo sporophyte and nutritive tissue that supports it
Protective seeds form in ovaries
Outer ovary tissues later develop into fruits

43. Monocot Life Cycle: Lily

44. Summary: Plant Evolutionary Trends