Bio Exam 2 updated

Fungi

Kingdom composed of eukaryotic heterotrophs; many obtain energy and nutrients from dead organic matter

Have cell wall made of chitin

Store excess food as glycogen

Produce pigments (but not chlorophyll)

Evolved during Precambrian time

Classified according to differences in life cycles and types of sporangia

fungi absorption

Fungi get carbon from organic sources, the hyphen tips release enzymes, those enzymes breakdown a substrate, products diffuse back into hyphae

Osmotrophy

Cells release digestive enzymes and then absorb resultant nutrient molecules

saprotrophic decomposers

Recycle dead plants and animals into chemical nutrients like carbon and nitrogen that are released back into the soil, air and water

Mycelium (roots)

Body of most fungi is multicellular mycelium

a vast network of thread-like hyphae

Haploid

Hyphae

each of the branching filaments that make up the mycelium of a fungus.

Job: secrete enzymes that help break down the rotting wood, leaves, and other organic debris, creating nutrients that are not readily accessible to other life forms

Gives mycelium larger SA/V ratio so it can reach farther distances

Grow from tip (osmosis, cytoplasmic streaming)

septate hyphae

contain cross-walls (septa)

aseptate hyphae

no cross walls

multinucleated

cytoplasmic streaming

The motion of cytoplasm in a cell that results in a coordinated movement of the cell's contents.

Occurs in multicellular fungal hyphae where pores at the center of the septum permit cytoplasm, organelles, and in some cases nuclei, to flow directionally from cell to cell

fungal sexual reproduction

Way that fungi reproduce which involves four different stages: haploid hyphae, dikaryotic stage, diploid zygote, spores

Produces nonmotile spores

1. Mycelium of two fungi keep dividing until they are touching

2. Two haploid cells (one from each mycelium) fuse together making one giant cell with two nuclei (Dikaryotic stage) \-- this doesn't have to happen immediately, could be a long time

3. Zygote is created because two nuclei fuse together making a cell with one nuclei that is 2n (diploid zygote)

4. Zygote grows and divides to create a fruiting body- a part of the fruiting body undergoes meiosis producing spores that are unicellular and haploid which then fall to the ground creating more mycelium

fungal asexual reproduction

Produce nonmotile spore

-budding: A bud which is formed detaches to develop into a new organism (ex. yeast)

-fragmentation: occurs when a fungal mycelium separates into pieces with each component growing into a separate mycelium

-Production of spores (conidia) by single mycelium:

Mycelium use mitosis (since already haploid structures) to produce unicellular spores which do mitosis to make more mycelium that is genetically the same

zygospore fungi

Mainly saprotrophs decomposing animal and plant remains, bakery goods in pantry

Some parasites of soil protists, worms and insects

Bread Mold \= rhizopus spp.

Sporangium- enclosure where spores are formed

Zygospore- a thick-walled spore of some algae and fungi that is formed by union of two similar sexual cells, usually serves as a resting spore

Sac Fungi (Ascomycetes)

Most are saprotrophs that digest resistant materials containing cellulose, lignin, or collagen

Most contain septate hyphae

Morels and Truffles (type of sac fungi)- gourmet delicacies sniffed out by dogs and pigs

Causes plant diseases- Powdery mildews; leaf curl fungi; ergot of rye; chestnut blight and Dutch elm disease

Examples of Sac Fungi: Yeast, Penicillium, Cordiceps (parasite of insects)

Sac Fungi: asexual reproduction

Yeasts usually reproduce by budding

Small bulge forms on side of cell

Receives a nucleus and gets pinched off and becomes full size

The other ascomycetes produce spores called conidia or conidiospores

--Vary in size and shape and may be multicellular

--Conidia usually develop at the tips of conidiophores

--Conidiophores differ in appearance and are diagnostic

--Conidia are windblow

--Conidia of cladosporium causes allergies

Sac Fungi: sexual reproduction

Ascus-fingerlike sac that develops during sexual reproduction

Asci usually surrounded and protected by sterile hypha (fruiting body) within an ascocarp (the fruiting body)

--In cup fungi, ascocarps are cup shaped

--In morels they are stalked and pitted

Haploid hyphae fuse to make diploid nucleus

Mitosis and meiosis produce 8 ascospores

Spores are wind blows

Sac Fungi - Yeasts

Term "yeasts" is loosely applied to unicellular fungi, many of which are ascomycetes

Budding is common form of asexual reproduction

Sexual reproduction results in the formation of asci and ascospores

When some yeasts ferment,they produce ethanol and carbon dioxide (do this if there is no oxygen)

Yeast essential ingredient in making bread,beer,wine

Ex. Aspergillus and Candida which cause serious human infections

Evolutionary History of Plants

1. Nonvascular plants: nourishment of multicellular embryo within female plant

2. seedless vascular plants: vascular tissue

3. gymnosperms and angiosperms: produce seeds

4. flowering plants: attract pollinators that give rise to fruits

Alternation of Generations

• Sporophyte

• Gametophyte

• Zygote

• Spore

• Gametes

Sporophyte

2n so in diploid state

Gametophyte

includes n so in haploid state

Zygote

a diploid cell that will become the sporophyte

Spore

a haploid cell that will become the gametophyte

Gametes

fuse in fertilization to form zygote

Nonvascular plants (bryophytes)

hornworts, liverworts, mosses

Characteristics of Nonvascular plants

• Lack specialized means of transporting water and organic nutrients

• Do not have true roots, stems, and leaves

• Each forms a monophyletic phylum

• Share a common structural, reproductive, and ecological features

• Models of earliest terrestrial plants

• Gametophyte is dominant generation

--produces eggs in archegonia

--Produces flagellated sperm in antheridia

--sperm swim to egg in film of water to make zygote

• Small in size, harsh environments

Hornworts and Liverworts

‣ hornworts have small sporophytes that carry on photosynthesis (100 spp)

‣ resemble tiny green broom handles

‣ closest to vascular plants

‣ liverworts have either flattened thallus or leafy appearance (6,500 spp)

Mosses

‣ usually have a leafy shoot, some are secondarily flattened

‣ can reproduce asexually by fragmentation

‣ dominant gametophyte (larger, longer-lived)

‣ dependent sporophyte consists of foot, stalk, and sporangium

‣ 12,000 spp. Arctic to America

‣ damp shady locations, desert bogs or streams