BIOL 1020U Lecture Notes - Lecture 44: Gastrovascular Cavity, Bilateria, Lophotrochozoa

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21 Jun 2018
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Animal Diversity (Part 2) Lecture
Textbook Reference: Chapter 44 in Biology How Life Works (2nd ed.)
Section 44.3; pp.956 to 963
Bilaterians
Most animals belong to this group
Based on embryo formation and molecular sequence data
Bilaterians form two major groups:
Protostomes
Deuterostomia
Bilaterian characteristics:
-Bilateral symmetry
-Complex organs that develop from a triploblastic (3 germ layer) embryo
-Anatomical complexity of bilaterian animals allows for types of locomotion, feeding, gas
exchange, behaviour and reproduction unknown in earlier branching groups
Protostome animals can be further divided into two groups (based on molecular
sequence data):
1. Lophotrochozoa
2. Ecodysozoa
Lophotrochozoans
Where does the name come from?
Lophophore
Ciliated crown of tentacles used for feeding – name
comes from different characteristics found in some
members of the group
Trochophore larva
Have a tuft of cilia on top and additional cilia bands
around middle. Some members of group have
neither of these characteristics – some members
have both
Lophotrochozoan diversity:
Phylum Description/Characteristics
Platyhelminthes -Live in marine, freshwater, and
damp terrestrial habitats
-Flattened dorsoventrally
-Gastrovascular cavity with one
opening – food comes in and goes
out of the same place – no anus
-Triploblastic
-Acoelomates
-No circulatory system – filled with
mesodermal tissue (no cavity) –
1
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some get big, but they are thin –
only some layers of cells/tissues –
tube that has side branches –
convoluted (can distribute food to
all tissues) – relies of diffusion for
oxygen
Parasitic
Platyhelminthes
-Are nearly all free-living and
mostly marine
-Some live as parasite in or on
other animals
-Parasitize wide range of hosts
-Often have complex life cycles
with alternating sexual and asexual
stages
-Some require intermediate hosts
_many have suckers for attachment
to host
_though covering protects these
parasites – protection against all
digestive/acidic liquids found in
stomach – and from digestion by
host
_reproductive organs nearly fill
interior of worms
Tape worms – parasitic and
lack digestive system
_adults live mostly in
vertebrates, including humans
_scolex (suckers, hooks)
anchor worm in digestive tract
of host
_long series of proglottids,
sacs of sex organs, lie
posterior to scolex
_absorb food particles from
host
_scolex – can be get up 20m
long – gets corrugated in
intestines – allows it to stick –
picks up broken down
nutrients from intestines – life
cycle continues – they get
eliminated in feces when
eggs are laid and reproduce
over and over
-example of how evolution
does not always come in
complex movement – comes
from ancestors more complex
than them – lost some
features – in order to become
more adapt to their
environment
More lophotrochozoan diversity:
Phylum Structure Description/Characteristics
2
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Document Summary

Textbook reference: chapter 44 in biology how life works (2nd ed. ) Bilaterians: most animals belong to this group, based on embryo formation and molecular sequence data, bilaterians form two major groups: Complex organs that develop from a triploblastic (3 germ layer) embryo. Anatomical complexity of bilaterian animals allows for types of locomotion, feeding, gas exchange, behaviour and reproduction unknown in earlier branching groups: protostome animals can be further divided into two groups (based on molecular sequence data), lophotrochozoa, ecodysozoa. Ciliated crown of tentacles used for feeding name comes from different characteristics found in some members of the group. Have a tuft of cilia on top and additional cilia bands around middle. Some members of group have neither of these characteristics some members have both. Live in marine, freshwater, and damp terrestrial habitats. Gastrovascular cavity with one opening food comes in and goes out of the same place no anus. No circulatory system filled with mesodermal tissue (no cavity) .

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