1. Kingdoms Protista & Fungi Ch. 17

2. The Origin of Eukaryotic Cells
Eukaryotic cells appeared first around 1.7 billion years ago
eukaryotic cells possess an internal structure called a nucleus

3. The Origin of Eukaryotic Cells
The endosymbiotic theory is a widely accepted explanation for the origin of mitochondria and chloroplasts in eukaryotes from bacteria
present-day mitochondria and chloroplasts still contain their own DNA
this DNA is remarkably similar in size and character to the DNA of bacteria

4. The theory of Endosymbiosis

5. The Evolution of Sex
A profound difference between prokaryotes and eukaryotes is that eukaryotes have the capacity for sexual reproduction
sexual reproduction involves two parents contributing gametes to form the offspring
gametes are usually formed by meiosis and are haploid
the resulting offspring are diploid
But sexual reproduction is not the only way that eukaryotes can reproduce
many eukaryotes reproduce by asexual reproduction, which is reproduction without forming gametes
the offspring of asexual reproduction are genetically identical to the parents
many eukaryotes reproduce mainly by asexual reproduction, switching to sexual reproduction only during environmental stress

6. The Evolution of Sex
A different asexual strategy in eukaryotes is parthenogenesis, the development of an adult from an unfertilized egg
Many plants and marine fishes undergo a form of sexual reproduction that does not involve partners
this is called self-fertilization and involves one individual providing both male and female gametes

8. The Evolution of Sex
Sexual reproduction is one of the most important evolutionary innovations of eukaryotes
it provides a means of shuffling genes, creating genetic diversity
genetic diversity is the raw material of evolution
the greater the genetic diversity, the more rapid the evolutionary pace

9. General Biology of Protists, the Most Ancient Eukaryotes
Protists are eukaryotes united on the basis of a single negative characteristic
they are not fungi, plants, or animals
in all other respects, they are highly variable with no uniting features

10. Figure 20.5 A unicellular protist

11. Figure 20.8 The major protist clades

12. A Diverse Kingdom Euglenozoa: Euglenoids
Euglena is a representative euglenoid
two flagella
contractile vacuole to help regulate the osmotic pressure within the organism
a light-sensitive stigma which helps this photosynthetic form find light
asexual reproduction
Figure Euglena

13. A Diverse Kingdom Stramenopila: Brown algae (phylum Phaeophyta)
are the longest, fastest-growing, and most photosynthetically productive living things
all are multicellular and most are marine
their life cycle has alternating generations
Figure 20.11(a) Brown algae

14. A Diverse Kingdom Stramenopila: Diatoms (phylum Chrysophyta)
photosynthetic
encased by unique double wall of silica
abundant in both oceans and freshwater habitats
Figure 20.11b Diatoms
Fossilized deposits of diatom shells are mined as “diatomaceous earth.”

15. A Diverse Kingdom Alveolata: Ciliates (phylum Ciliophora)
Complex and unicellular
possess large numbers of cilia
have a defined cell shape and two nuclei per cell
the pellicle is a proteinaceous scaffold, found inside the plasma membrane, that confers flexible support
asexual reproduction is by fission while sexual reproduction is by conjugation
Figure A ciliate

16. A Diverse Kingdom Alveolata: Dinoflagellates (phylum Pyrrhophyta)
photosynthetic unicellular protists
usually bear two flagella of unequal length
a stiff outer coating of cellulose and silica, giving them unique shapes

17. Dinoflagellates

18. A Diverse Kingdom Alveolata: Dinoflagellates (continued…)
some dinoflagellates produce bioluminescence or powerful toxins that cause “red tides”
“red tides” are population explosions of these kinds of dinoflagellates
Figure Red tide

19. A Sporozoan Life cycle Plasmodium : malaria

20. Chapter 21
Fungi Invade the Land

21. A Fungus is Not a Plant
The fungi are a distinct kingdom of organisms, comprising about 74,000 species
mycologists are scientists who study fungi
There are many significant differences between fungi and plants, including
fungi are heterotrophs
fungi have filamentous bodies
fungi have nonmotile sperm
fungi have cell walls made of chitin
fungi have nuclear mitosis

22. A Fungus Is Not a Plant
fungi exist mainly in the form of slender filaments called hyphae (singular, hypha)
each hypha is basically a long string of cells
different hypha can associate with each other to form much larger structures
a mass of hyphae is called a mycelium
the main body of a fungus is not a mushroom but the extensive network of fine hyphae that penetrate the soil, wood, or flesh in which the fungus is growing
the mycelium may contain many meters of hyphae

23. Masses of hyphae form mycelia
The dense interwoven mat you see here growing through leaves on a forest floor is a mycelium made up of microscopic hyphae.

24. A Fungus Is Not a Plant
Fungal cells can intercommunicate because fungal cells are separated by incomplete septa (singular, septum)
cytoplasm can flow freely among the cells of the hypha
many nuclei may be connected together by the shared cytoplasm
proteins synthesized throughout the hyphae can be carried to hyphal tips
all parts of the fungal body are metabolically active

25. Figure 21.3 Septum and pore between cells in a hypha

26. Reproduction and Nutrition of Fungi
Fungi reproduce both asexually and sexually
all fungal nuclei, except for the zygote, are haploid
often in sexual reproduction of fungi, different “mating types” must participate
when two hyphae of different mating types come into contact, the hyphae fuse

27. Reproduction and Nutrition of Fungi
Spores are a common means of reproduction among the fungi
Spores are well suited to the needs of an organism anchored to one place
Spores are small and light and remain suspended in the air for long periods of time and may be carried great distances
When a spore lands in a suitable environment, it germinates and begins to divide, forming a new fungal hypha

28. Many fungi produce spores

29. Reproduction and Nutrition of Fungi
All fungi perform external digestion
they secrete digestive enzymes into their surroundings and then absorb back into their bodies any organic molecules
many fungi are able to break down the cellulose in wood
some fungi are carnivores
for example, the oyster fungus attracts nematode worms and then feeds upon them

30. Figure 21.5 The oyster mushroom

31. Table Fungi

32. Ecological Roles of Fungi
Fungi, together with bacteria, are the principal decomposers in the biosphere
Fungi are virtually the only organisms capable of breaking down lignin in wood
Fungi, by breaking down substances, release critical building blocks from the bodies of dead organisms and make them available to other organisms

33. Fungi as Parasites Cause series plant and animal diseases
Examples:
Corn smut
Mildew
Wheat rust
Cordyceps
Cause some human disease
Athletes foot
Ringworm
Thrush

34. Ecological Roles of Fungi
Fungi often act as disease-causing organisms for both plants and animals

35. Ecological Roles of Fungi
Fungi have many important commercial uses
the manufacture of bread, beer, wine, cheese and soy sauce all depend on fungi
many antibiotics are derived from fungi
some fungi can be used to clean up toxic substances from the environment

36. Ecological Roles of Fungi
Some fungi are edible, others contain poisonous toxins

37. Ecological Roles of Fungi
Fungi are involved in a variety of intimate symbiotic associations with algae and plants
the fungus contributes the ability to absorb minerals and other nutrients from the environment
the photosynthesizer contributes the ability to use sunlight to power the building of organic molecules

38. Ecological Roles of Fungi
Two kinds of mutualistic associations between fungi and autotrophic organisms are ecologically important
mycorrhizae are symbiotic associations between fungi and the roots of plants
lichens are symbiotic associations between fungi and either green algae or cyanobacteria

39. Ecological Roles of Fungi
In most mycorrhizae, the fungal hyphae actually penetrate the outer cells of the plant root and extend far out into the soil
these are called endomycorrhizae
In some mycorrhizae, the fungal cells grow between but do not penetrate the roots
these are called ectomycorrhizae

40. Figure 21.16 Endomycorrhizae and ectomycorrhizae

41. Ecological Roles of Fungi
A lichen is a symbiotic association between a fungus and a photosynthetic partner
most of the visible body of the lichen consists of its fungus, but interwoven between hyphal layers are cyanobacteria, green algae, or both
lichens can invade harsh habitats but are sensitive to pollutants

42. Lichens growing on a rock