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Presentation on theme: "Fungi."— Presentation transcript:

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

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