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Fungi.  Heterotrophs that secrete digestive enzymes on organic matter and absorb released nutrients Saprobes feed on organic remains (major decomposers.

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Presentation on theme: "Fungi.  Heterotrophs that secrete digestive enzymes on organic matter and absorb released nutrients Saprobes feed on organic remains (major decomposers."— Presentation transcript:

1 Fungi

2  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 thallus (leaflike part) close-up of gemmae male gametophyte

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

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

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 ginkgo other genera gymnosperms ferns cycads angiosperms (flowering plants)

40 Evolution of Flowering Plants

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

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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