Download Understanding Our Environment - McGraw Hill Higher Education

Evolution of Multicellular Life
Chapter 15
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Outline
•
•
•
•
•
•
Complex Multicellularity
Fungus vs. Plants
Fungal Reproduction and Nutrition
Fungi Ecology
Kinds of Fungi
 Zygomycetes
 Ascomycetes
 Basidomycetes
Lichens and Mycorrhizae
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Complex Multicellularity
•
Individuals are composed of many highly
specialized kinds of cells that coordinate their
activities. Three Kingdoms:
 Plants
 Animals
 Fungi
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Complex Multicellularity
•
Two key characteristics separate complex
multicellular organisms from simple
multicellular organisms.
 Cell Specialization
- Different cells using different genes
- Cell Development
 Intercell Coordination
- Cell activity adjusts based on response
to functions of other cells.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
A Fungus Is Not A Plant
•
Differences between fungi and plants:
 Fungi are heterotrophs.
 Fungi have filamentous bodies.
 Fungi have nonmotile sperm.
 Fungi have cell walls made of chitin.
 Fungi have nuclear mitosis.
Copyright © McGraw-Hill Companies
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Permission required for reproduction or display
A Fungus Is Not A Plant
•
Body of a Fungus
 Fungi exist mainly in the form of slender
filaments (hyphae).
- Walls (septa) divide cells in filament.
 Main body is network of hyphae (mycelium).
- All parts of body are metabolically active.
- Because of cytoplasmic streaming, many
nuclei may be connected by shared
cytoplasm.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Fungal Reproduction and Nutrition
•
Fungi reproduce both asexually and sexually.
 Sexual reproduction initiated when hyphae
of genetically different mating types come
in contact and fuse.
- Heterokaryon - nuclei derived from
genetically different individuals.
- Homokaryon - nuclei derived from
genetically similar individuals.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Fungal Reproduction and Nutrition
•
•
Three kinds of reproductive structures:
 Gametangia - Gametes form within
 Sporangia - Spores form within
 Conidia - Asexual spore
Fungi obtain food by secreting digestive
enzymes into their surroundings and absorb
organic molecules produced by external
digestion.
 Some act as active predators.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Fungi Ecology
•
Fungi and bacteria are principle decomposers
in biosphere.
 Fungi virtually only organism capable of
breaking down lignin.
 Often act as disease-causing organisms for
plants and animals.
 Multiple commercial products depend on
biochemical activities of fungi.
- Cheese, Penicillin
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Kinds of Fungi
•
•
Nearly 73,000 described species.
Three fungal phyla are distinguished from
one another primarily by mode of sexual
reproduction.
 Zygomycetes
 Ascomycetes
 Basidiomycetes
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Zygomycetes
•
Zygomycetes are unique among fungi
because fusion of hyphae does not produce
heterokaryon.
 Two nuclei fuse and form diploid nucleus.
 Make up only about 1% of named fungi.
 Reproduction typically asexual.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Life Cycle of Zygomycete
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Ascomycetes
•
Ascomycetes is largest of three phyla with
about 32,000 named species.
 Reproduction usually asexual.
 Hyphae possess septa that divide cells.
 Named for characteristic sexual
reproductive structure (ascus) which
differentiates within the ascocarp.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Life Cycle of Ascomycete
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Basidiomycetes
•
•
•
Basidiomycota contains most familiar fungi
(mushrooms, toadstools, rusts and smuts).
Life cycle starts with production of hypha
from a germinating spore.
In sexual reproduction, zygotes from when
two nuclei of dikaryotic cells fuse.
 Occurs within club-shaped reproductive
structure (basidium).
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Life Cycle of Basidiomycete
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Unicellular and Asexual Fungi
•
•
Yeasts
 Generic name given to unicellular fungi.
- About 250 named species.
 Most yeast reproduction is asexual and
takes place by cell fission or budding.
Imperfect Fungi
 Sexual reproduction never observed.
- Cannot formally be assigned to one of
sexually reproducing phyla.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Lichens
•
Symbiotic association between fungus and
photosynthetic partner.
 Most of visible body consists of fungus, with
interwoven cyanobacteria or green algae.
- Fungus transmits biochemical signals to
partner directing production of metabolic
substances.
 Key component of primary succession.
 Can resist drying or freezing.
 Pollution indicators.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Mycorrhizae
•
Mycorrhizae are associations between fungi
and plant roots.
 Fungus filaments act as efficient root hairs,
and aid in direct transfer of minerals while
plant supplies organic carbon to the
symbiotic fungus.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Mycorrhizae
•
•
Endomycorrhizae - Fungal hyphae of
mycelium penetrate outer cells of the plant
root, as well as far into the soil.
Ectomycorrhizae - Mycorrhizae surround but
do not physically penetrate plant root cells.
 Highly specialized relationships in which a
particular plant species has become
associated with particular fungus.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Review
•
•
•
•
•
•
Complex Multicellularity
Fungus vs. Plants
Fungal Reproduction and Nutrition
Fungi Ecology
Kinds of Fungi
 Zygomycetes
 Ascomycetes
 Basidomycetes
Lichens and Mycorrhizae
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies
Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies