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Biology 103 - Main points/Questions
1. Remember how plants and animals reproduce?
2. What else makes plants special
3. What is different about the fungi?
4. Are growth and development the same thing?
Remember Animal life cycles:
• Meiosis produces
• Gametes fertilize to make a
• This
produce a
undergoes
to
.
• Few animals have asexual reproduction
exclusively
Remember Animal life cycles:
• Meiosis produces gametes (haploid)
• Gametes fertilize to make a diploid zygote
• Zygote undergoes mitosis to produce a
multicellular diploid organism.
• Few animals have asexual reproduction
exclusively
Fig. 10.3.b
Remember plant life cycles:
• Meiosis produces
• Haploid
divide (mitosis) to make
haploid a(n) _____
plant
• This
produces
–
specialized haploid sex cells (like animals)
• These
make a
fuse (called
) to
(grows into an embryo)
Remember plant life cycles:
• Meiosis produces spores
• Haploid spores divide (mitosis) to make
haploid a “gametophyte” plant
• Gametophytes produce gametes –
specialized haploid sex cells (like animals)
• These gametes fuse (fertilization) to make a
zygote (grows into an embryo)
What is a Plant?
Some characteristics:
(1) Plants are multicellular eukaryotes.
(2) Plants are autotrophic
(3) Plants alternate multicellular haploid and
multicellular diploid generations
•
What does that mean?
Plants:
1. Alternate haploid
and diploid stages
2. Each is
multicellular
3. Different groups
have different
stages that are
most common.
More Plant characteristics
(4) Plants have embryos that are dependent on
a mature plant for nutrition
(5) Plant cells have cellulose cell walls that
provide structural support.
More Plant characteristics
(6) Special adaptations for life on land
•
•
•
Most have special transport tissues/structures
(roots, vascular tissue…)
Can team up with fungi to absorb nutrients
(mycorrhizae)
Waxy cuticle (slows water loss) & Stomata
(allows gas exchange)
Fig. 22.2.b
More Plant characteristics
Subcategories of Plants:
• The plant kingdom has many subdivisions
we will talk mostly about four:
– Mosses – some of the most primitive land plants, lack
vascular tissue, dominant gametophyte
– Ferns – seedless
vascular plants
• More subcategories
– Conifers/gymnosperms – plants with seeds but
without flowers and fruit
– Flowering plants (angiosperms) – plants with
flowers and fruit for reproduction
Last Kingdom to focus on is Fungus
• Lots of different types we will focus on one
– the group that includes the gilled
mushrooms you are most familiar with
• Like other groups most fungi use sexual
reproduction at least some of the time.
What is an Fungus?
Four criteria describe the Fungi.
(1) Fungal cells have a cell wall of chitin (of
course still have membrane!)
(2) Fungi are heterotrophic eukaryotes
– Fungi secrete exo-enzymes that digest
macromolecules outside their bodies. They
then absorb the smaller subunits - causing
them to be called absorptive heterotrophs.
(3) Fungal cells are usually form long threadlike filaments called hyphae
– The body of a majority of fungi is a complex mat
of these hyphae called a mycellium
– Mushrooms are only a small part of the body of
a fungus
• Mass of hyphae –
called a mycelium
– the mycelium is
the main “body”
of the organism
– the mycelium
usually contains
several meters of
hyphae
• Individual hypha
– each hypha is
basically a long
string of cells
– Mitosis generates
new cells
• cells communicate
through gaps in wall
called septa
(singular, septum)
cell wall
cytoplasm
pore
septum
two haploid
nuclei
– cytoplasm can flow
freely among the
cells of the hypha
– 2 haploid nuclei
often in a single cell
(= dikaryotic)
Septum and pore between cells
(4) Fungal life cycles are dominated by a
haploid phase that grows from a haploid
spore by mitosis.
– Most fungi reproduce both sexually and
asexually
– Fungal life cycles are distinctly different from
plants an animals
Fungal Life Cycle Terminology:
• Haploid v. Diploid
• Dikaryotic
• Spore
• Mating type
Sexual reproduction in Fungi
Haploid Spore
Mitosis
Meiosis
Cells Fuse
Mitosis
Dikaryotic Cell
Fungal life cycles main ideas:
• Meiosis produces spores
• Haploid spores divide (mitosis) to make
haploid mycelium
• Any cell can fuse with a cell of another mating
type (no specialized gametes!)
• Cytoplasm joins but not nucleus at first
(dikaryotic cell!)
Fig. 21.8.a
Some fungi have very long-lived
dikaryotic mycelia
• These are reproductive
structures of mycelium
that may be huge
• Some spread over 3.4
square miles and may
be 2500 years old.
Fig. 21.12
• Fairy Rings
– A ring of mushrooms may appear overnight.
– These are the reproductive structures of an
underground mycelium (grown from a spore)
– As the mycelium grows
out, it decomposes the
organic matter in the
soil and mushrooms
form just behind this
advancing edge.
Growth vs. Development
• These fairy rings help illustrate the difference
between growth and development
• What do you think is the difference?
• The mycellium is growing through the soil but
it is only when conditions are right that the
fungus triggers the development of
mushrooms.
Growth vs. Development
• Growth occurs as
– Cells divide
– Cells increase in size
• Development occurs as cells alter gene
expression (cell differentiation)
• Plants and Animals use different strategies
Plant
and Animal development patterns
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Plant Growth & Development
• In flowering plants we still see haploid
(gametophyte) and diploid (sporophyte)
stages.
• Main plant is sporophyte
– Gametophyte is retained by sporophyte
• Looking at the development of embryo
– First look at flowers
Fig. 22.17.a
Fig. 22.17.a
Stamen
is both
filament
sepal
petal
stigma
anthers
style
Plant Growth & Development
• In flowers the sporophyte generation gives
rise to the gametophyte in two different
places
• Male gametophyte produced in Anthers
• Female gametophyte is produced in Ovule
• Lets see how…
• Male gametophytes are produced in
the anther…
• Meiosis occurs and produces
microspores
• These undergo mitosis to produce
pollen (the male gametophyte)
• Female gametophytes are produced in
the ovule (inside an ovary)…
• Meiosis occurs and produces a
megaspore
• The megaspore undergoes meiosis to
produce an embryo sac (the female
gametophyte)
mature pollen
sperm cells (n)
tube cell
nucleus
stigma
sperm
style
tube cell
nucleus
ovary
integuments
egg (n)
polar nuclei
within central
cell
Development into an embryo
What about animal embryos – do
we all have shelled eggs?
• Reproduction & Development
• In most, a small flagellated sperm fertilizes a larger,
nonmotile egg to make a zygote
• The zygote undergoes cleavage (mitosis), forming a
hollow ball of cells called the blastula.
• Some cells of the blastula then “crawl” inside
(gastrulation)
• This forms a gastrula with 2 tissue layers and
an opening (the blastopore!)
• Gastrulation
produces three
tissue layers
• Occurs after
implantation in
humans (and other
placental mammals)
• The placenta provides
continuous nutrition
during development
instead of stored yolk
• Three tissues are:
– Ectoderm (outside)
– Mesoderm (middle)
– Endoderm (inside)
• Tissues specialize to
become...
• Three tissues are:
– Ectoderm (outside)
– Mesoderm (middle)
– Endoderm (inside)
• Tissues specialize to
become...
Protostomes and Deuterostomes
• there are two major kinds of animals
representing two distinct evolutionary lines
– protostomes
• the mouth develops from or near the blastopore
– deuterostomes
• the anus forms from or near the blastopore; the
mouth forms on another part of the blastula
Figure 25.34 Embryonic
development in protostomes and
deuterostomes.
Protostomes and Deuterostomes
• deuterostomes also differ from protostomes
in three other fundamental ways
– the pattern of cleavage
• protostomes have spiral cleavage while
deuterostomes have radial cleavage
– fating of cells
• it occurs later in deuterostome cleavage than in
protostome cleavage
– origin of the coelom
Biology 103 - Main points/Questions
1. Remember how humans reproduce?
2. What makes an organism an animal & how do
we subdivide the animal kingdom?
3. What are some other animal reproductive
strategies?
4. What is different about the fungi?