Lecture 5

download report

Transcript Lecture 5

Biology 103 - Main points/Questions
1. How do plants keep growing for their entire
lives?
2. How do animal cells differentiate?
3. What are tissues?
4. How do organisms support themselves?
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
Gastrula
Blastopore
Cross section
of blastula
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
Section 36.6 in your book – gastrulation video
Hierarchy of Biology:
• Tissues are groups of cells with similar
structures/functions
• In humans there are many different tissues
that work together to build organs
• Organs working together to perform a task
are called organ systems
Tissue of the Day
• Connective tissue
– Made up of cells surrounded by large extracellular matrix (ECM)
– Often (but not always) includes collagen
– Many types including:
– Loose connective
– Bone
– Cartilage
– Blood (liquid ECM)
Table 28.3
Cartilage
cartilage
cells
collagen
Cartilage
chondrocytes
collagen matrix
Bone
bone cells
central canal
concentric bone matrix
Support system terminology:
• Internal skeleton
• External skeleton
• Hydrostatic skeleton
• Primary vs. secondary cell wall
• Secondary growth in plants
Skeletal systems in Animals
• Hydrostatic skeleton
– Uses pressurized fluids support organisms
weight
– Lacks strength
– Common example:
• Earthworm
Skeletal systems in Animals
• Exoskeleton
– external rigid tissue protects and supports
– Gives a lot of protection but...
– Can be very heavy
– Can interfere with growth
– Examples
• Arthropods:
• Mollusks
Adult cicada
sheds its
exoskeleton as
it outgrows it,
forming a new
exoskeleton.
Skeletal systems in Animals
• Endoskeleton –
– Uses internal rigid tissue to support weight
– Offers less protection but...
– Lighter weight
– Growth is simpler
– Examples • Vertebrates
A cat skeleton is a nearly ideal
balance of high strength and low
weight. Cats are adept at surviving
long falls in part because of this
balance.
Heavy Organisms Require Large-Diameter
Support Structures - in part to support the
added weight of the skeleton itself
Axial skeleton
(blue)
skull
Appendicular skeleton
(beige)
mandible
clavicle
scapula
sternum
humerus
rib
pelvis
ulna
vertebral
column
radius
coccyx
(tail
bone)
carpals
metacarpals
phalanges
femur
patella
tibia
fibula
tarsals
metatarsals
phalanges
The skeletal system in
humans is divided into two
parts the axial (in blue here)
and the appendicular (in
tan) skeletons
Axial skeleton
(blue)
skull
Appendicular skeleton
(beige)
mandible
clavicle
scapula
sternum
humerus
rib
vertebral
column
pelvis
ulna
radius
coccyx
(tail
bone)
carpals
metacarpals
phalanges
femur
patella
tibia
fibula
tarsals
metatarsals
phalanges
How does the Vertebrate
Skeleton develop?
• Bone and cartilage develop from
mesodermal tissue
• Bone replaces cartilage during
development
bone
cartilage
In this human fetus
much of the
skeleton is still
cartilage - which will
be replaced by bone
as the fetus ages.
Connecting microscopic view to
macroscopic view
• Remember what bone tissue looks like where do you find tissue like this in your
body?
• What do bones look like?
(b)
osteon
compact
bone
osteocytes
(within
spaces)
capillary
central
canal
Fig. 28.5
• Notice that there
is blood flow in
living bone! (Its
alive!)
• This is crucial for
bone growth &
healing.
large blood
clot
compact
bone
spongy
bone
1
The Vertebrate Skeleton is alive!
• Notice several types of tissue are actually
present in a living bone
– Bone
– blood
– connective tissue and epithelial tissue building
membranes
new blood
vessels
callus of
cartilage and bone
replaces clot
2
bony callus
3
healed fracture
4
callus of
new blood cartilage
and bone
vessels
replaces clot
bony callus
healed fracture
periosteum
large blood
clot
compact
bone
spongy
bone
1
2
3
Bone healing is only one way that
your body modifies its skeleton
4