Week 11
Animals I
Reading Modules in Principles of Biology:
101. Diversity in Animals
• Characteristics of Animals
• Classification of Animals
• Molecular Data and the Animal Tree of Life
102. Invertebrates
• Invertebrate Form and Function
• Describing Invertebrates
Reminder: e questions you encounter embedded within the reading or after it are there to give you feedback on
your understanding of the text. Answering those questions is optional (but encouraged), and your answers to those
questions are not visible to me or recorded by me.
This Week’s Schedule
Course Related
Other
SUN
MON
TUE
†
Lecture: Week 11 Reading Quiz (8:00–8:05)
Basic Animal Structure
Begin Animal Phylogeny
Lab: Multicellularity and Development
Prelab Activity due in MasteringBiology by 8 a.m.
WED
THU Lecture:
Continue with Animal Phylogeny
FRI
SAT Week 11 Homework due in MasteringBiology by 10 p.m.
†
†Indicates
an assignment due date.
Lecture art and a variety of other materials are available online. Log into Canvas, navigate to
the current week, and open the resource folder to see what is available.
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Learning Outcomes for Week 11
Summarize the major ways that animals differ from other organisms, such as
their life cycles, feeding, and body structures.
✓
Compare the different body plans exhibited by animals and describe how
scientists use them to classify animals.
✓ ✓ ✓
Identify major groupings within the animal tree of life.
✓ ✓
Explain how the animal tree of life differs depending on whether it is based on
morphological or molecular data.
✓ ✓
✓
is is important and we’ll spend some time on this in class. In a nutshell:
•
Morphologists use developmental patterns to group most animals into either a
protostome clade (Protostomia) or a deuterostome clade (Deuterostomia).
•
When molecular biologists first began to apply DNA sequence analysis to these
animals, they discovered the following:
First, the DNA data confirmed that the deuterostomes do in fact appear to
group together.
Members of the protostome clade, on the other hand, were not always closely
related to other protostomes. (Some were as equally related to deuterostomes
as they were to fellow protostomes.)
•
e molecular biologists determined that the protostomes should not be grouped
together based on developmental patterns but rather by DNA sequence
similarity. ey proposed breaking Protostomia into two groups: the
Lophotrochozoa and the Ecdysozoa.
•
erefore, the molecular phylogeny recognizes three groups of bilaterians:
lophotrochozoans, ecdysozoans, and deuterostomes. e morphological
phylogeny recognizes protostomes and deuterostomes.
Describe the basic features and constraints of invertebrate form and function.
✓ ✓ ✓
Describe the relationship between presence or absence of a coelom and
complexity of organ systems.
✓
•
In particular, keep in mind that many invertebrates use fluid in their coelom as a
way to move. By squeezing on this fluid, they can propel their bodies forward.
is is referred to as a hydrostatic skeleton.
✓
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Describe the relationship among the following groupings: invertebrates,
protostomes, bilateria.
✓ ✓ ✓
is is not as explicitly spelled-out in the text, so here is my synopsis for you:
•
Among the animals that have true tissues (i.e., everyone except the sponges),
there are two body plans based on symmetry: radial symmetry vs. bilateral
symmetry.
•
While there is some debate on the origins of radial symmetry, it is well-accepted
that bilateral symmetry evolved once in the animal lineage and that all bilateral
animals share a common ancestor. e term Bilateria is used as the name for this
monophyletic group.
•
Among the bilaterians, two developmental “plans” can be observed. Protostomes
are animals whose bodies are formed when their blastopore (a very early
embryonic structure) forms their mouth, while the blastopore of deuterostomes
forms their anus.
–Stome means mouth. Proto– means first and deutero– means second.
Deuterostomes form their anus first and their mouths second.
•
e term invertebrate is a convenient (but informal) term that describes any
animal that lacks a backbone. We generally think of invertebrates as soft-bodied
organisms, but that’s too simplistic. (A horseshoe crab is definitely not softbodied.)
•
e term vertebrate is a true taxonomic name for animals with a vertebral
column (backbone). e Vertebrata is a subgrouping of the Phylum Chordata.
Humans, fish, amphibians, reptiles, and all other mammals belong to this group.
Differentiate between deuterostome and protostome patterns of development.
•
✓ ✓ ✓
See above. We’ll spend time on this in class as well.
Terms, Titles, and People You Should Know
body plan
lophotrochozoans
radial vs. bilateral symmetry
ecdysozoans
Cambrian explosion
invertebrate vs. vertebrate
determinate vs. indeterminate cleavage
notochord
radial vs. spiral cleavage
sessile
blastopore
filter feeding
gastrulation
coelom
endoderm
pseudocoelom
mesoderm
ectoderm
coelomate vs. pseudocoelomate vs.
acoelomate
protostome vs. deuterostome
cephalization
diploblastic vs. triploblastic