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Plants, Fungi, and the Colonization of Land

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Presentation on theme: "Plants, Fungi, and the Colonization of Land"— Presentation transcript:

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

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

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

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