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Announcements
1. Homework #1 - finish your quizzes!
2. Thinking about a quiz in lab…
3. Test #1 April 20th – bring a 50 question scantron
Biology 103 - Main points/Questions
1. What do you remember about fungal life
cycles?
2. What is the difference between growth and
development?
3. How do plants keep growing for their entire
lives?
4. How do animal cells differentiate?
Quick quiz but first…
• How well do you understand the following
(scale of 1-5, 1= fully, 3=some, 5 = not at all)
– Fungal life cycles
– Reproduction in Ferns
– Early animal develop. (cleavage  gastrula)
Fungal life cycles main ideas:
1. Meiosis produces
2. These structures (from 1) divide (mitosis) to
become a “thread-like”
that
grow into a mat called a
.
Any cell can fuse with a cell of another mating
type (no specialized gametes!)
3. Cytoplasm joins when cells fuse but initially
not the nucleus creating a
cell!
4. These structures on the back of a fern frond are called
5. They produce
that grow into the
.
generation.
6. During
development
animals grow into a
hollow ball of cells
called a
.
Fungal life cycles main ideas:
1. Meiosis produces Spores
2. These structures (from 1) divide (mitosis) to
become a “thread-like” hyphae that grow into
a mat called a mycellium.
Any cell can fuse with a cell of another mating
type (no specialized gametes!)
3. Cytoplasm joins when cells fuse but initially
not the nucleus creating a Dikaryotic cell!
4. These structures on the back of a fern frond are called Sori.
5. They produce Spores that grow into the Gametophyte generation.
6. During
development
animals grow into a
hollow ball of cells
called a Blastula.
Using the quiz results
• Did you remember the information from last
time? From the time before?
• Did you confuse familiarity with more in depth
knowledge?
• How much will you remember on Tuesday for
the lab quiz? On April 19th for the 1st exam?
Growth & Development
• Both plants and animals start off their diploid
phase as a single fertilized egg
• During development genetically identical cells
differentiate as genes are turned on and off.
• This causes cells to develop into specialized
tissues, a group of cells of similar
appearance and function.
• Developmental patterns determine which type
of tissues develop in which region.
Plant
and Animal development patterns
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
To understand we need to look a
little more at plant reproduction
Plant growth and development
• Remember the life cycle of plants?
Look at these
moss plants.
Where are the
sporophytes? the
gametophytes?
Where are the two generations?
Plant growth and development
• In flowering plants the gametophyte
generation is very small and comes in male
and female versions
• The female, egg producing gametophyte, is
completely retained on the sporophyte.
• The male gametophyte is Pollen!
• Both are produced on flowers
Fig. 22.16
Ovary
Anther
Fig. 22.16
Female Gametophyte is inside here!
Called an embryo sac
Male Gametophyte is inside here!
It is a pollen grain
Pollen grains
Anthers with pollen
Pollination vs fertilization
• In flowering plants the entire male
gametophyte plant (pollen) is transferred to the
location of the female gametophyte (ovary)
• We call this pollination and it is different from
fertilization.
• After the pollen gets transferred it still must
grow to the female gametophyte and fertilize
the egg.
Fig. 22.17.a
Pollen must get
transferred here
(pollination)
But the egg is all
the way down
here
Ovary
Pollen grain
Pollen tube
2 sperm
Pollen grows down
to the egg.
Fertilization occurs
down here
Egg
Pollen grain
The egg develops
inside a structure
called an ovule
found in the ovary
Ovary
Ovule
Egg
Ovule
Egg
2 sperm
Fertilization is
tricky…
both sperm
fertilize things…
one fertilizes egg,
one fertilizes 2
nuclei
So we get diploid zygote and triploid
endosperm (it is used for nutrition later)
Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Zygote (2n)
(egg plus sperm)
Development in plants
• We have seen in flowering plants:
– Fertilization happens inside the ovule
• Now lets look at how the embryo develops
– In flowering plants we pack the embryo in a seed.
– Seeds contain the embryo & food supplies
– Seeds of flowering plants are found surrounded by
fruit
Development in plants
• Where do these structures come from?
• They develop from structures already present
in the flower!
– Ovary  fruit
– Ovule  seed coat
– Zygote  embryo
– Endosperm  nutritive tissue inside seed
Relationship between a pea flower and a fruit (pea pod)
In the peanut
• Where is tissue from the parent plant? Can
you see ovule? Ovary?
• What part is the embryo?
– Can you see specialized regions of the embryo?
– Look for a root tip and leaves
• Endosperm in the peanut is gone –
consumed to fuel development of the peanut.
Development in plants
From: http://waynesword.palomar.edu/ecoph8b.htm
Peanut flower but…
http://en.wikipedia.org/wiki/Peanut
Peanuts harvested from underground…
http://en.wikipedia.org/wiki/Peanut
Development in plants
From: http://waynesword.palomar.edu/ecoph8b.htm
Development in plants
• As the zygote undergoes mitosis it
specializes different tissues
• Unlike the animals plants maintain regions of
undifferentiated tissues (called meristems)
– This tissue is capable of dividing and forming any
other plant tissue
– Plants have meristem at the tips of all growing
shoots and roots
– This pattern is set up inside the seed.
• When the zygote divides the cells recognize
their position in the ovule. They use this
information to alter gene expression.
• Cells near the base start to divided differently
becoming the embryonic root
Development into a seed
•• But
Cells
remember
“higher” up
thatwill start to
some
become
cells
theremain
embryonic shoot &
undifferentiated
leaves
(they
haven’t committed to
develop a certain way)
Development into a seed
• Meristem tissue ready
for when the seed
germinates
Fig. 22.12.b
Seed development can be
modified as in the peanut…
Fig. 22.12.a
Development in plants
• While the seed is developing the rest of the
flower also changes
• Ovary tissue develops into the fruit that
surrounds the seed(s)
Fig. 24.5.a
Fig. 24.5.b
So what do animals do?
Fig. 21.2
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
All animals start out
as a fertilized egg
that undergoes
mitosis.
In deuterostomes (?)
cells divide at right
angles while in
protostomes (?)
they divide in a
spiral pattern
(a) Fertilized egg
Animal Development
• We will focus on two basic strategies for
development seen in two major groups
– Protostomes include arthropods and mollusks
– Deuterostomes include all the chordates
• These groups have several differences in
their development we focus on 3
– Cleavage pattern
– Timing of cell specialization
– Fate of blastopore
Protostome development
(examples: molluscs, arthropods)
Eight-cell stage
Spiral and determinate
Deuterostome development
(example: chordates)
Eight-cell stage
Radial and indeterminate
In mammals these cells
can be separated and
each will produce a
separate identical
embryo – deuterostome
development
(b) Four-cell stage
Other organisms
(protostomes - like
arthropods and
mollusks) specialize
each cell as it is made.
Pull one off and the
embryo will not develop.
In many animals
in both groups
the cells divide
and produce a
hollow ball of
cells called a
blastula.
(c) Early blastula
Specific cells on the
outside of this ball
then “crawl” up
inside the hollow
space in a
process called
gastrulation
(d) Later blastula
• During gastrulation cells further specialize
into three embryonic tissues
– Endoderm – the innermost cells
– Mesoderm – cells in the middle
– Ectoderm – cells that remain on the outside
• This process also creates an opening into
the ball called a blastopore
Video: Sea Urchin Embryonic Development
Cleavage
Zygote
Eight-cell stage
Cleavage
Zygote
Cleavage Blastula
Eight-cell stage
Blastocoel
Cross section
of blastula
Blastocoel
Cleavage
Endoderm
Cleavage Blastula
Ectoderm
Zygote
Eight-cell stage
Gastrulation
Blastocoel
Cross section
of blastula
Gastrula
Blastopore
Archenteron
Protostomes and Deuterostomes
• We have seen:
– Cleavage pattern differences, spiral vs. radial
– Timing of cell specialization differences
• The last difference we look at is the fate of
the blastopore.
– As the embryo develops the open space inside
the gastrula will be the digestive tract – the
blastopore will be one of the openings – either
the mouth or the anus.
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
Anus
Mouth
(c) Fate of the blastopore
Key
Digestive tube
Ectoderm
Mesoderm
Endoderm
Anus
Mouth
Mouth develops from blastopore. Anus develops from blastopore.
• As embryos continue to develop tissues
continue to specialize
• Each of these 3 embryonic tissues will give
rise to numerous tissues/organs in the adult