Transcript Plants and Fungi

Plants and Fungi
By the end of this class you should understand:
• The differences between algae, plants and
fungi, and between groups of plants
• The role of vascular structures in organisms
• The reproductive cycles of different plants and
fungi
• The functions of major structures and
materials unique to each group
Algae, Plants, and Fungi
• Algae, plants, and fungi are
all different groups of living
things
– Easy to lump together
because they are all
immobile
• Commonality: Cell walls!
• Major differences exist
between the three groups
Structure and Lifestyle
• Algae: Photosynthetic and have
cell walls but their cells are not
organized into tissues and organs
– Also can’t live on land
• Fungi: Have cell walls but are not
photosynthetic
– Fungi must grow on their food
• Plants are photosynthetic and
have tissues/organs
Apparent Tangent:
• If you want to build a
building with bathrooms on
every floor but you don’t
have good pipes, how tall
can you make the building?
• If you have good pipes,
how tall can you make the
building?
Plant Structures
• A major development that
separates most plants from
algae is being vascular
– A vascular plant has xylem and
phloem
• Vascular structures help bring
water from roots up to the
leaves, and sugar from leaves
to the roots
– Xylem brings water up
– Phloem brings sugar down
Algae, Mosses and Ferns
• There are clearly more
advanced structures in each of
these groups
– Algae are completely nonvascular
and live in water
– Bryophytes (including mosses)
are plants that can live on land
but are restricted in height
because they are not vascular
– Ferns are vascular plants
• Date back to before the dinosaurs
Moss & Fern Life Cycle
• Mosses and ferns are clearly
related because they have
similar life cycles
• Rather than produce gametes
that immediately fertilize to
make new plants, their
gametes undergo mitosis and
grow into a gametophyte
• Gametophytes produce
gametes through mitosis that
fertilize to make a sporophyte
Behold the Multistage Life Cycle!
Additional Note on Plant Sex
• Some plants are divided into
male plants and female plants
– One plant produces male
gametes or pollen, another plant
produces female gametes
• Other plants are
hermaphrodites, and each plant
can make both male and female
gametes
– Some of these hermaphrodites
can self-pollinate, others are
restricted from doing so
Plant-Only Structures
• Plants grow their sturdy
structures (including xylem and
phloem) using carbohydrates
– Made from photosynthesis!
• Sugars linked into a mesh called
lignin are super-durable
– Wood is made with lignin
• Cell walls are usually made of
another carbohydrate
compound called cellulose
Additional Plant Structures
• Unlike algae, plants can
grow on land
– Use lignin to stand up
straight
– Use vascular structures to
bring water into plant
• Plants have different
organs to adapt to living
on land
– Roots
– Stems
– Leaves
Plant Groups
• Bryophytes
– Mosses
• Seedless vascular plants
– Ferns
• Seed plants
– Gymnosperms
• Plants with pinecones (pine,
redwood, etc)
– Angiosperms
• Flowering and fruiting plants
Bryophytes
• Mosses and similar small plants
such as liverworts
• The large part of the plant is
usually the gametophyte
(haploid)
– Produces small sporophytes that
produce new spores through
meiosis
• No xylem/phloem, allow
nutrients and water to diffuse
across its surface
– Thus limited in size
Seedless Vascular Plants
• Ferns are the most common
example of seedless vascular
plants
– Seedless: sporophyte/gametophyte
stages
– Vascular: have xylem/phloem so can
get tall
• The sporophyte is the main plant
– Gametophytes are produced by the
small structures on the underside of
the leaves
– Produce spores that grow into new
ferns
Seed Plants
• Seeds are a more recent
invention of plants
– First gymnosperms appeared
around 300 million years ago
• Seeds are useful because they are
durable and can wait for the right
moment to start growing
– As opposed to new sporophytes
which don’t have a protective
covering at any point
• Divided into gymnosperms and
angiosperms
Seed Structure
• Seeds are formed from the
fertilization of a microspore
(pollen) and megaspore (ovule)
– This occurs at the flower
• A seed always has a protective
coating around the new embryo,
stored food for the embryo, and
usually a delivery system for
getting it away from the parent
plant
– In angiosperms this delivery system
is called a fruit (not always
delicious)
Gymnosperm
• Gymnos refers to nudity
– The gymnasium is so called
because the Greeks always
exercised naked
• Gymnosperms have “naked
seeds” with no fruit
– Does have a protective armor
around the seeds
– These are what we think of as
pinecones
• Pines, redwoods, conifers
Angiosperm
• Angiosperms have flowers for
improved fertilization
– All other plants must depend on
wind fertilization only, and
some angiosperms do as well
• Angiosperms all produce fruits
for their seeds
– The fruit serves as a delivery
system for separating the
offspring from parents (seed
dispersal)
– Reduces competition
Examples of Seeds and Fruits
Flower Anatomy
• Flowers vary wildly in structure (of course) but all
have certain features in common:
– Petals (often to attract pollinators)
– Stamen (produce pollen)
– Carpel (holds ovule and allows fertilization)
• Flowers often have some method of attracting
animals to bring the pollen from one flower to
another
– Edible pollen
– Nectar
– Structures that resemble female insects
Generic Flower
Fungi
• Fungi diverged from protists
around the time of the Cambrian
Explosion (500+ mya)
• Fungi are actually more closely
related to animals than to plants
– Their cell walls are made of chitin,
the same material in an insect
exoskeleton
• Mushrooms, molds, and yeasts
are all fungi
Fungal Anatomy
• All fungi live as tiny interconnected
threads that grow inside their
environment such as the soil
– Each thread is called a hypha (plural
hyphae)
– A cluster of hyphae is called a
mycelium
• The large cap that grows out of the
ground is the reproductive fruiting
body of the fungus which remains
buried underneath
Fungus Food
• Fungi grow on their food and digest it externally
– No internal digestive system
• By secreting enzymes on their food, they break it
down, then absorb the nutrients through their cell
walls
– Nutrients can diffuse from one cell to the next, but they
have no vascular system and so are limited in height
Giant Fungi?
• Since fungi have no vascular
system they cannot grow very
tall
– They can, however, grow sideways
a very large distance
• The largest known organism on
earth is a fungus that covers at
least 4 square miles (over 2000
acres) in Oregon
– WTF
Hyphae in Action
• Many fungi do not produce any
fruiting body and are entirely
made of hyphae
– These are called molds or yeasts
• The hyphae are actually haploid
and only fertilize to make a
zygote during mating season
– The zygote immediately undergoes
meiosis to make more hyphae
Mushroom Anatomy
• In mushroom species, the stalk and cap are formed by
the hyphae after they have undergone cytoplasmic
fusion
– This means that two haploid cells have fused their cytoplasm
but not their nuclei
– This is written as the cells being n+n instead of 2n
• In the mushroom cap, the nuclei fuse, a zygote is
formed, and then it undergoes meiosis to make more
new spores for hyphae
Fungus Environments
• Fungi grow on their food since they
can’t chase after it
– Fungal spores are spread by the wind
and land on all sorts of things that are
edible
• Many fungi grow in soil eating dead
things
• Some fungi grow on our food
(bread molds)
• Some fungi grow on our flesh!
Fungal Infections
• Fungi that grow on a living thing
are using a parasitic feeding
strategy
• In humans and other animals,
fungal infections can be a source
of disease (athlete’s foot, yeast
infections, ringworm)
• Many fungi can grow on specific
plants and kill them for food
(often called rusts)
– The famous potato blight in
Ireland was a protist similar in
structure to a fungus
Fungi as Partners
• Some fungi live in a symbiotic
relationship (mutually beneficial)
with other organisms
• Lichen are a composite organism
with algae or cyanobacteria living
inside the cell walls of fungi
– How does each side benefit?
• Some fungi grow on roots of
plants, call mycorrhizae (singular:
mycorrhiza)
– How does each side benefit?
See you in lab!