Download Chapter 29- Comparing Invertebrates

Chapter 29- Comparing
Invertebrates
I. Invertebrate Evolution
A. Origin of the Invertebrates
1. Invertebrates fossils have been
found to date between 610-570
million years ago.
2. Now molecular paleontology
studies the fossils DNA.
3. The Ediacaran
fossils include some
of the earliest and
most primitive
animals.
4. The Cambrian
period, 544 million
years ago has
many different
fossils.
5. Example: Burgess
Shale animals.
B. Invertebrate Phylogeny
1. Some features evolved over time also.
2. These features include tissues, and
organs, patters of early development,
body symmetry, cephalization,
segmentation and the formation of
three germ layers and a coelom.
C. Evolutionary Trends
1. Specialized cells, tissues and organs.
2. Body symmetry- Sponges lack
symmetry BUT all other invertebrates
have some type of body symmetry.
3. Cephalization-Invertebrates with
cephalization can respond to the
environment in more sophisticated ways
than can simpler invertebrates.
4. Segmentation
5. Coelom formation- most complex
animals have a true coelom that is
lined completely with tissue derived
from the mesoderm.
6. Embryological development- Some of
them are deuterostomes, meaning
they have an anus.
II. Form and function in
invertebrates
A. Feeding and Digestion
1. Intracellular and extracellular
digestion- the simplest animals break
down food primarily through
intracellular digestion, but more
complex animals use extracellular
digestion.
2. Extracellular digestion- Food is
broken down outside the cells in a
digestive cavity and then absorbed
into the body cavity.
B. Respiration
1. Respiratory organs have large
surface areas that are in contact with
the air or water. Also, for diffusion to
occur the respiratory surfaces must be
moist.
C. Circulation
1. Most complex animals move blood
through their bodies using one or
more hearts and either an open or
closed circulatory system.
2. Open circulatory- blood is only
partially contained within a system of
blood vessels.
3. Closed circulatory- a heart or
something like it forces blood through
vessels within the body.
D. Response-invertebrates show three
trends in the evolution of the nervous
system: centralization, cephalization
and specialization.
1. Cephalization- where if any sense
organs the animal has are located at
the front of the head.
2. Specialization- cells with particular
cells.
E. Movement and Support
1. Invertebrates have one of three
main kinds of skeletal systems:
hydrostatic skeleton, exoskeleton, or
endoskeleton.
2. Hydrostatic skeleton- muscles are
surrounded by a fluid filled body cavity.
3. Exoskeleton- External skeleton.
4. Endoskeleton- A structural support
located inside the body.
F. Sexual and Asexual Reproduction.
1. Most invertebrates reproduce
sexually during at least part of their
life cycle. Depending on
environmental conditions, many
invertebrates may also reproduce
asexually.
2. External fertilization- fertilization
outside of the body.
3. Internal fertilization- fertilization inside
of the body.
The End