Transcript Protists and Fungi - T.R. Robinson High School

Protists and Fungi
Chapter 17.1, 18.1, & 18.3
Kingdom Protista: the most
diverse of all eukaryotes
Ch 17.1
Protists
Protists: eukaryotes that are not
animals, plants, or fungi
Most protists are unicellular and free-living
(not parasitic)
Protists have the typical eukaryotic cell
structure, including internal membranes, a
nucleus surrounded by a nuclear envelope,
and organelles such as mitochondria and
chloroplasts (in some species)
Protist Complexity
Being mostly unicellular, protists are
considered the simplest form of eukaryotic
organism
Most human cells are highly specialized,
carrying out only certain tasks
The protist's one cell must consume and
process food, respond to stimuli, excrete
wastes, and reproduce
Protists can justifiably be considered the
most complex of eukaryotic cells, since
each cell must carry out all of an
organism's life functions.
Protist nutrition used for classifying
Scientists group protists by lifestyle:
animal-like, fungus-like, and plant-like
protists
Protozoans: Animal-like;
heterotrophs that ingest (eat) food
Algae: Plant-like; autotrophic
making food through
photosynthesis
Fungi
Ch 18.1 & 18.3
Structure & Function of Fungi
Hypha: a thread of
cytoplasm; many
hyphae together make
up the body of a
fungus
Mycelium: interwoven
mat of hyphae that
functions as the
feeding structure of a
fungus
functions as the feeding
structure of a fungus
fungal mycelium can grow
as much as a kilometer of
hyphae each day as it
branches within its food
What’s the world’s largest
organism?
Scientists have discovered one enormous
mycelium in Oregon that measures 5.5
kilometers across and spreads through
almost 9 square kilometers of forest (larger
than 1,600 football fields)
Scientists also estimate that this fungus is
at least 2,400 years old
Qualifies as one of Earth's oldest and
largest living organisms
Mycelium
The branching mycelium enables the
fungus to obtain food by absorptive
nutrition
Absorptive nutrition: method by which
fungi absorb small organic molecules
from their surroundings
First, the fungus digests food outside its
mycelium by secreting powerful enzymes into
its surroundings
These enzymes break down complex
molecules into smaller molecules the mycelium
can absorb
Fungi’s role
Many fungi play an important role as
decomposers
Fungi recycle nutrients such as nitrogen
and carbon by breaking down organic
material
Common food sources for fungi are fallen
logs, bodies of dead animals, or the wastes
of living organisms
Parasitic fungi absorb nutrients from the
cells or body fluids of living hosts
Parasitic fungi cause about 80 percent of
all plant diseases
Reproduction of Fungi
Fungi reproduce by releasing large
numbers of microscopic spores
Spores: haploid single cell with a thick
wall that functions in the dispersal
stage in fungal reproduction
spread by the wind and can withstand
unfavorable conditions for long periods of time
Most fungi produce spores asexually by mitosis
at the tips of specialized hyphae
Many fungi also produce spores sexually
Haploid hyphae from different mycelia fuse together
and combine their genetic material
Fungi have a major impact on
other life
Ch 18.3
Lichens
Lichens: mutualistic pairing of a
fungus and an alga
The photosynthetic algae feed the
fungus
The fungal mycelium provides a suitable
habitat for the algae, helping to absorb
and retain water and minerals
Lichen actually consists of millions of
tiny algal cells within a mesh of fungal
hyphae
Lichens
One benefit of symbiosis is that lichens are able to
live in environments where neither fungi nor algae
could live alone
Lichens are important pioneer organisms on newly
cleared rock and soil surfaces, such as burned
forests and volcanic flows
In the arctic tundra, caribou graze on lichens at
times of the year when other foods are unavailable
As tough as lichens are, however, many do not
tolerate air pollution
Their absorption of minerals from rain and moist air
makes them particularly sensitive to chemicals such as
sulfur dioxide
The death of sensitive lichens in an area can be an early
warning of poor air quality.
Micorrhizae
Micorrhizae: symbiotic relationships
between fungal hyphae and plant roots
The fungi absorb water and essential minerals
from the soil and provide these materials to the
plant
The fungal mycelium greatly increases the
surface area of the root in contact with the soil,
which increases the plant's absorption of water
and minerals
The sugars produced by the plant nourish the
fungi
Disease causing fungi
Of the 100,000 known species of fungi about 30
percent are parasites, mostly on or in plants
Dutch elm disease- has eliminated most elm trees
in North America
The fungus was accidentally introduced into the United
States on logs sent from Europe after World War I
Only about 50 species of fungus are known to be
parasitic in humans and other animals
Among these are yeast infections of the lungs, some of
which can be fatal
Other fungal parasites produce a skin disease called
ringworm, so named because it appears as circular red
areas on the skin
Some fungi attack the feet and cause intense itching and
sometimes blisters- known as athlete's foot, is highly
contagious, but it can be treated with various fungicides
Athlete’s Foot
Ring Worm
Commercial use of fungi
The distinctive flavors of certain kinds of
cheeses come from the fungi used to
"ripen" them
Yeasts are particularly important in baking,
brewing, and winemaking
Used in making of antibiotics
In addition to edible mushrooms, other
edible fungi include truffles
In nature, truffles release strong odors that
attract mammals and insects that dig up the
fungi and disperse their spores
Role of fungi in chemical cycling
Fungi and bacteria are the principal
decomposers that supply ecosystems with
the nutrients essential for plant growth
The air is so loaded with fungal spores that
as soon as a leaf falls or an insect dies, it is
covered with spores that quickly grow into
fungal hyphae
Without decomposers, elements such as
carbon and nitrogen would accumulate in
organic matter
Plants and the animals they feed would
starve because elements taken from the
soil would not be returned
Questions?
1.
Which of the following is a symbiotic
relationship?
1.
2.
3.
4.
2.
3.
Penicellium
Bread mold
Yeast
lichen
What do fungi produce that allows them to
break down dead organisms?
How do humans use fungi?
1.
2.
3.
4.
To flavor certain foods
As a source of antibiotics
As ingredients in baking and brewing
All of the above
Questions?
4. What is an important role of fungi in
an ecosystem?
5. What is the cause of the human
disease ring worm?