viruses and prokaryotes - msliutdsb.weebly.com
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Fungi
What are examples of fungi?
Diversity and Importance of Fungi
Fungi come in a variety of shapes and sizes.
For example, Ontario forests have a variety of
natural growing mushrooms. The part of the
mushroom above ground is just a small portion of
the entire organism.
The “fairy ring” mushroom may be 100 m in diameter
with some documented cases of more than 5.5 km.
Diversity and Importance of Fungi
Fungi can often be mistaken for plants, given that
they can be seen growing off logs or wet leaves on
the ground.
However, evolutionarily speaking, fungi are more
closely related to animals then they are to plants.
Characteristics of Fungi
Unlike plants, fungi cannot photosynthesize to make
their own food.
They are heterotrophic organisms that breakdown
organic matter in the environment into nutrients
using digestive enzymes.
These nutrients can then be absorbed by the fungi.
Fungi also take in oxygen from the environment for
cellular respiration.
Mushrooms, moulds, mildew, yeast, truffles, and rusts
are common representatives of the fungi kingdom.
Ecological Roles
Many fungi play an important ecological role as decomposers.
Fungi recycle nutrients such as nitrogen and carbon by breaking down organic material.
Common food sources of fungi include fallen logs, bodies of dead animals, or wastes of living organisms.
Fungi often live in a symbiotic relationship with plants in which they exchange nutrients
Fungi can also be parasites, absorbing nutrients from the cells or body fluids of living hosts.
Parasitic fungi can cause a variety of plant diseases including wheat rust, corn smut, rot, and blight
Parasitic fungi can also cause diseases in humans, such as ringworm and athlete’s foot.
Structure and Function
Yeast is an example of a unicellular fungus, though
most fungi are multicellular.
The general structure of most multicellular fungi
includes several structures: hyphae, mycelium, and
fruiting bodies.
Hyphae
Hyphae are threads of cytoplasm surrounded by a
plasma membrane and covered by a cell wall
composed of chitin.
Hyphae usually have cell walls called cross-walls or
septum which divide the long filaments into many
separate cells. However large pores allow
cytoplasm and organelles to flow from cell to cell.
This movement helps to redistribute nutrients from one
part of its body to another.
Mycelium
The branching of the hyphae forms an interwoven
mat known as the mycelium (plural is mycelia).
The mycelium forms a large underground mass,
forming the majority of the organism.
It functions as the feeding structure of the fungi. Its
fibrous structure increases surface area for
absorption of nutrients.
Fungi are not mobile but the mycelium can grow
and branch out to expand their network.
Mycorrhizae
The large underground networks of mycelia can
form mycorrhizae, which are fungi that form
mutualistic association with plant roots.
The fungus receives sugars, starches, proteins, and
lipids from the plant roots. In return, the fungus acts
as an extension of the plant roots and collects
nutrients and water for the plant.
Since hyphae are tiny in diameter, they can
penetrate places that plant roots cannot.
Fruiting Body
In larger mushrooms, the part that appears above
ground is known as the fruiting body.
This is the reproductive structure of the mushroom.
Reproduction
Fungi can reproduce both sexually and asexually.
Asexual reproduction
A fungi releases spores which can be dispersed by the
wind or other factors.
Spores are haploid cells with thick cell walls that can
withstand unfavourable conditions.
When conditions are favorable, the spores can
germinate to form mycelium.
Reproduction
Sexual reproduction
The two sexes of fungi are assigned the symbols “+” or
“-”.
The haploid hyphae of opposite sexes will grow
towards each other a fuse to form a diploid
zygospore.
The zygospore generates haploid spores that are
genetically unique, increasing genetic diversity.
Reproduction
Sexual reproduction in fungi with fruiting bodies
When the haploid hyphae fuse, they produce a
dikaryotic hyphae.
The dikaryotic hyphae has two nuclei per cell.
This grows into the fruiting body above ground.
When the nuclei eventually fuse to form a diploid
nucleus, the cell can then divide into haploid spores to
begin the cycle again.
Major Phyla of Fungi
Phylum Reproductive Structure Examples
Zygomycota
(common moulds)
Zygospores that contain sexual
spores which are resistant to
unfavorable conditions
Black bread mould,
‘hat thrower’
Basidiomycota
(club fungi)
Club-shaped cell that contains
sexual spores
Mushrooms, club fungi,
shelf fungi, puffballs,
rusts
Ascomycota
(sac fungi)
Asci sacs that contain sexual
sporesYeast, truffles, morels
Chytridomycota
(chytrids)
Only fungi type with flagellated
sporesChytrids