Lecture 11 Flashcards
1
Q
What is the third embryonic germ layer that arose after the origin of diploblastic animals?
A
The mesoderm (triploblastic)
2
Q
What are the two clades of triploblastic animals called?
A
Protostomes and deuterostomes
3
Q
Which of the two clades of triploblastic animals has more numbers of species and individuals?
A
Protostomes
4
Q
When is the trait of the formation of the blastopore not universally shared?
A
No blastopore forms during early development of insects
5
Q
What are the characteristics of protostomes?
A
Bilateral symmetry
Anterior brain that surrounds the entrance to the digestive tract
Ventral nervous system consisting of paired or fused longitudinal nerves
6
Q
What type of coelom is found in protostomes?
A
Acoelomate- flatworms
Pusedocoelomate and coelomate
7
Q
In what two clades has the coelom been secondarily modified?
A
- Arthropods
- Mollusks
8
Q
How has the coelom been secondarily modified in arthropods?
A
Lost their ancestral coelom, internal cavity has become a hemoceol (blood chamber) where open circulatory fluid bathes internal organs
9
Q
How has the coelom been secondarily modified in mollusks?
A
Open circulatory system
Have some hemocoel but have retained enclosed coelom around major organs
10
Q
What are the two major clades of protostomes?
A
Lophotrochozoans
Ecdysozoans
11
Q
What type of skeleton do lophotrochozoans have?
A
Internal skeletons
12
Q
What type of larvae do many lophotrochozoans have?
A
Trochophore- free living larvae
13
Q
How do many lophotochozoans move?
A
Cilia
14
Q
What do several, distantly related groups of lophotrochozoans have?
A
A lophopore
15
Q
What is a lophopore?
A
A circular or U shaped ridge around the mouth that bears one or two rows of ciliated, hollow tentacles
16
Q
What is the purpose of a lophopore?
A
Food collection and gas exchange
17
Q
How has the lophopore evolved?
A
Independently, at least twice, or else it was ancestral and has been lost
18
Q
What is a characteristic of most individuals with a lophopore?
A
Sessile as adults
19
Q
What do some lophotrochozoans, including flatworms, ribbon worms, annelids and mollusks, exhibit?
A
A form of radial cleavage known as spiral cleavage- these are a nonmonophyletic group called spiralians
20
Q
What are members of several groups with radial cleavage like?
A
Worm-like
21
Q
What is the purpose of a worm-like body?
A
To be able to burrow efficiently in muddy and sandy marine sediment or soil
Except mollusks
22
Q
What do ecdysozoans have?
A
An exoskeleton
23
Q
What is the external skeleton of ecdysozoans?
A
Non-living covering secreted by underlying epidermis
24
Q
What does an exoskeleton provide?
A
Protection and support
25
How do ecdysozoans grow?
By shedding or moulting the exokeleton and replacing it with a new one
26
What recent evidence showed that molting evolved 500 million years ago?
Discovery of cambrian period soft-bodied arthropod
27
What evidence suggests that ecdysozoans have a common ancestor?
Molecular and genetic evidence, including a set of shared hox genes
28
What happens when an ecdysozoan molts?
The new exoskeleton has not yet hardened, the animal is vulnerable- slow moving and soft
29
What name is given to the exoskeleton of wormlike ecdysozoans that are thin and flexible?
Cuticle
30
What does a cuticle allow?
Some protection, little body support, gas, mineral and water exchange
31
What does a cuticle restrict?
Animals to a moist habitat
32
Where do most animals with a cuticle live?
Marine sediment
33
How do marine sediment worm-like cuticle covered ecdysozoans capture larger prey?
Using a toothed pharynx
34
What is a pharynx?
A muscular organ at the anterior end of the digestive tract
35
What type of eaters are many wormlike ecdysozoans?
Predators- eating protists and small animals
36
How is the exoskeleton of other ecdysozoans thickened?
Layers of protein and polysaccharide chitin
37
What does chitin do?
Impedes passage of oxygen and nutrients into the animal
38
How do animals with hard exoskeletons move rapidly?
Apendages- extensions of the body that can be manipulated by mucles
39
What did evolution of apendages during late precambrian period lead to?
Arthropod clade
40
What triploblastic animal was difficult to classify as protostome or deuterstome and why?
Arrow worms because they retained features that are ancestral to diploblastic animals
41
What is the body plan of arrow worms?
Coelom divided into three compartments: head, trunk, tail
42
Where are most arrow worms found?
Swimming in the open sea, some on sea floor
43
How do arrow worms exchange gas and waste?
Diffusion through body surface (due to size between 3mm and 12cm)
44
What type of circulatory system do arrow worms have?
None- waste/nutrients are moved by coelomic fluid propelled by cilia lining the coelom
45
What type of development do arrow worms have?
Direct development
46
How are arrow worm eggs fertilized?
Internally following elaborate courtship between two hermaphroditic individuals
47
How are arrow worms stabalised in water?
By two pairs of lateral fins and a tail
48
What do arrow worms eat?
They are predators of planktonic organisms in the open ocean
49
How do arrow worms capture prey?
They are motionless, movement signals approach of prey, they dart forward and grasp prey with stiff spines adjacent to mouth
50
How many species of ectoprocts are there?
4500
51
What do ectoprocts live in?
colonies in a house made of material secreted by the external body wall
52
Where do all ectoprocts live?
Marine- a few in fresh or brackish water
53
What is the structure of an ectoproct colony?
Small individuals connected by strands of tissue along which nutrients can be moved.
54
How are ectoproct colonies founded?
Asexual reproduction of founding member- 2 million individuals
55
Where can ectoprocts be found?
Rocks in coastal regions in many parts of the world
56
How do individual ectoprocts increase their contact with prey?
By oscillating and rotating their lophophore which can also be retracted
57
How are eggs fertilized in ectoprocts?
Internally, developing embryos are brooded before exit as larvae
58
What diverse group is found below ectoprocts?
Flatworms, rotifers and ribbon worms
59
What type of coelom do flatworms, rotifers and ribbon worms have?
Flatworms- acoelomate
Rotifers- Psuedocoelomate
Ribbon worms- coelomate
60
How do flatworms keep each cell near their body surface for gas exchange?
Dorsoventrally flattened body form
61
What type of gut does a flatworm have:
A mouth opening into a blind sac
62
What is the structure of a flatworms blind sac?
Highly branched
63
What are some free-living flat worms
Cephalized- head bears chemoreceptor organs, two eyes and a brain
64
How do free-living flatworms move?
Glide over surfaces powered by broad bands of cilia
65
What type of feeding do flatworms have?
Most are internal parasites
Other feed externally on living or dead animal tissues
Some are free-living
66
What are the two groups of most species of living flatworm?
Tapeworm and flukes- internal parasites particularly of vertebrates
67
What disease do some tapeworms and flukes cause in humans?
Schistosomiasis
68
What group of flatworms are external parasites of fishes and other aquatic vertebrates?
Monogeneans
69
What group includes most free-living species of flatworm?
Turbellarians
70
How big are rotifers?
50-500 micrometers long
71
What type of gut do rotifers have?
A complete gut as well as specialized internal organs
72
What type of body cavity do rotifers have?
A psuedooel
73
What is the function of the psuedocoel in rotifers?
Hydrostatic skeleton
74
How do rotifers move?
Rapdily beating cilia
75
What is the most distinctive organ of rotifers?
Ciliated corona (surmounts head)
76
Coordinated beating of cilia sweep particles of organic matter down through the mouth into what complicated structure?
The mastax- which grinds food
77
What species of rotifers has only females?
bdelloid rotifers
78
Where do most rotifers live?
Freshwater
79
Where do some other rotifers live?
Surfaces of mosses or lichens in a desiccated, inactive state until it trains
80
What are ribbon worms also called?
Nemerteans
81
What type of excretory system do ribbon worms have?
Simple nervous and excretory systems
| Complete digestive tract
82
How do ribbon worms move?
Small by beating cilia
| Large by using waves of muscle contraction to move over or burrow into sediment
83
What is the fluid filled cavity of ribbon worms?
Rhynchocoel
84
What lies within the fluid filled rhynchocoel?
Hollow, muscular proboscis (feeding organ)
85
How does the proboscis work?
Contraction of muscles around rhynchocoel cause proboscis to exit explosively through anterior pore
86
What might line the proboscis?
Sharp stylets that pierce prey and discharge paralysis causing toxins
87
Where do ribbon worms live?
Largely marine, some live in freshwater or on land
88
What other groups of animals use a lophophore to feed?
Brachiopods and phoronids
89
How did the lophophore evolve?
Independently, or was lost in other groups
90
When were brachiopods most abundant?
Paleozoic and mesozoic eras
91
How big are the 20 known species of phoronids?
5-25cm
92
What are characteristics of phoronids?
Sessile worms living in muddy or sandy sediments or attached to rock substrate
93
Where are phoronids found?
Marine waters, from intertidal zone to about 400 m deep
94
What do phoronids secrete?
Tubes of chitin in which they live
95
How do phoronids capture food?
Cilia drive water on top of the lophophore tentacles, water moves through, particles are caught and transported to mouth by ciliary action
96
How do phoronids reproduce?
Eggs are released into water to be fertilized, but some eggs are retained in certain species to be brooded until hatching
97
What are brachiopods?
Solitary marine animals with a rigid shell dividing them into two parts connected by a ligament
98
What do brachiopods superficially resemble?
Bivalve mollusks- shells evolved independently
99
How are brachipods shells different to mollusk shells?
Brachiopod shells are dorsal and ventral- bivalves have lateral shells.
100
Where are brachiopods lophophores located?
Within their shells
101
How big are brachiopods?
4-6cm long, up to 9
102
How do brachiopods live?
Attached by short, flexible stalk to solid substratum or embedded in soft sediment
103
How are gasses exchanged in brachiopods?
Across body surfaces
104
How are annelids and mollusks related?
They are sister groups
105
How are annelids different to other worm groups?
They are clearly segmented
106
What is the name given to the unique body plan of mollusks?
Tripartite body plan
107
What were the earliest segmented worms?
Preserved in fossils from the late cambrian, they were burrowing marine worms
108
In most annelids, how is the coelom arranged?
Each coelom in a segment is isolated from the other segments
109
What is the name given to the nerve centre that controls the coelom of each segment of an annelid?
Ganglion
110
How are ganglions function coordinated?
Nerve cords connect ganglion
111
What is the surface of most annelids?
A thin, permeable body wall for gas exchange- thus most are restricted to moist environments
112
Where do annelids live?
Marine, freshwater, moist terrestrial environments
113
What are two major groups of annelids?
Polychaetes
| Clitellates
114
Where do most polychaetes live?
Marine, burrowing in soft sediments
115
How many eyes do polychaetes have?
One or more pairs
116
How many tentacles do polycheates have?
One or more pairs
117
Where are polychaetes tentacles and what do they do?
At the anterior end
| Filter prey from surrounding water
118
In polychaetes, how are segments arranged?
Body wall of most segments extends laterally in a series of thin outgrowths called parapodia
119
What are parapodia in polychaetes?
Paired bristle appendages used for locomotion, sensation or respiration
120
What protrudes from parapodia?
Setae- stiff bristles
121
What do setae do on polychaetes parapodia?
Form temporary attachments to the substratum
122
What is the name of the clade of polycheates that lost their digestive tract?
pogonophorans
123
What are pogonophorans?
Burrowing animals with a crown of tentacles through which gas exchange occurs
124
What do pogonophorans live in?
A tube of chitin and other substances which they secreted
125
What does the pogonophoran coelom consist of?
An anterior compartment into which tentacles can be withdrawn and a long, subdivided cavity the length of most of the body
126
What end of the pogonophoran body is segmented?
The posterior end
127
What do pogonophorans eat?
Dissolved organic matter in the sediment in which they live or surrounding water
128
How is uptake of nutrients by pogonophorans facilitated by? In which organ does this occur?
Endosymbiotic bacteria
| Trophosome
129
Where do most clitellates live?
Freshwater or terrestial environments
130
What are the two major groups of clitellates?
Leeches and oligochaetes
131
What are some characteristics of oligochaetes?
No parapodia, no eyes, no anterior tentacles, few setae.
132
What is a familiar oligochaete?
Earth worms
133
What is a common feature of all oligochaetes?
They are hermaphroditic (each individual is born male and female)
134
How is egg and sperm exchanged between oligochaetes?
Simultaneously between two copulating individuals
135
What do oligochaetes do with their eggs?
Lay them in a cocoon outside of the adults body
136
What happens to the eggs laid in a cocoon by oligochaetes?
The cocoon is shed when development is complete and miniature, independent worms emerge
137
What are some features of leeches?
They lack parapodia and tentacles, undivided coelom, filled with undifferentiated tissue
138
What are groups of segments at each end of a leeches body modified into?
Suckers, used for temporary anchoring to aid movement
139
How does a leech move along the substratum?
The posterior sucker attaches, the leech extends its body by contracting circular muscles, leech shortens by contracting longitudinal muscles, etc.
140
Where do leeches live?
Freshwater or terrestrial habitats
141
How do leeches suck blood?
Makes an incision in the host.
| Secretes an anticoagulant to keep blood flowing
142
What is the name of the medicinal leech?
Hirudo medicinalis
143
What is Hirudo medicinalis used for?
Reduce fluid pressure and prevent blood clotting in damaged tissues, to eliminate pools of coagulated blood and to prevent scaring
144
What are the anticoagulants of other leeches being studied for possible medical uses for?
contain anesthetics and blood vessel dilators
145
What were the probable features of the ancestors of modern mollusks?
Unsegmented, wormlike animals
146
What have mollusks undergone?
A dramatic evolutionary radiation
147
The evolution of what feature set the stage for the dramatic animal evolutionary evolution of mollusks?
Tripartite (three parts) body organization
148
What are the three major components of the mollusk body plan?
A foot, visceral mass, mantle
149
What is the foot of a mollusk?
A large, muscular structure
150
What was the mollusk foot originally used for?
Locomotion and support of internal organs
151
What happened to the mollusk foot in squids and octopuses?
It was modified to form arms and tentacles
152
What is the foot used for in clams?
A burrowing organ
153
What is the visceral mass of mollusks?
Where the heart, digestive tract, excretory and reproductive organs are concentrated
154
What is the mantle of mollusks?
A fold of tissue that covers the organs of the visceral mass, secretes a hard calcareous shell typical of many mollusks
155
What happens with the mantle in most mollusks?
It extends beyond the visceral mass to form a mantle cavity
156
What is within the mantle cavity in mollusks?
vascularized gills for gas exchange
157
How is a current of water generated to move over mollusks gills?
Cilia beat
158
How do mollusks feed?
Gills can be used as a filter feeder,
| Others used a rasping structure called a radula to scrape algae from rocks
159
Where has the radula been modified and what into?
Marine cone snails
| Into a drill or poison dart
160
What circulatory system do mollusks have?
Not a closed system
| Fluid empties into large hemocoel
161
What are 5 major groups of mollusks?
```
Monoplacophorans
Chitons
Bivalves
Gastropods
Cephalopods
```
162
How are monoplacophorans different to all other living mollusks?
Gas exchange organs, muscles and excretory pores are repeated over the length of the body
163
What characterizes chitons?
Multiple gills and shell plates, bilateral symmetry, simple internal organs
164
What do most marine chitons eat?
They are marine herbivores
| Scrape algae from rocks with radulae
165
How do chitons move?
Slowly by rippling waves of muscular contraction in the foot
166
Where does fertilization of chitons take place?
In the water
| Sometimes internally and then brooded
167
What are some familiar examples of bivalves?
Clams, oysters, scallops, mussels
168
Where are bivalves found?
Marine and freshwater
169
What is the body plan of bivalves?
Small heads, hinged two-part shells
170
What do most bivalves use their foot for?
To burrow into mud and sand
171
How do bivalves feed?
By taking water in through an incurrent siphon and filtering out food using their gills
172
How does water and gametes exit bivalves?
Through their excurrent siphon
173
Where does fertilization of bivalves take place?
In open water
174
Give some examples of gastropods.
Snails, whelks, limpets, slugs, naudibranchs, abalones
175
How do gastopods move?
Gliding on their muscular foot,
| Swimming using foot (sea butterflies, heteropods)
176
What are two features of naudibranchs?
Lost their protective shell
| Aposematic or camouflaged coloring
177
How many parts make up the shell of shelled gastropods?
one
178
In terrestrial species of mollusks (gastropods only) what is the mantle tissue modified into?
Highly vascularized lung
179
Name some cephalopods.
Squids, octopuses, nautiluses
180
How is the excurrent siphon modified in cephalopods?
To allow the animal to control water content in mantle cavity- move by jet propulsion
181
What did jet propulsion of cephalopods allow
Them to become major predators
182
How do cephalopods capture and subdue prey/
With their tentacles
183
What cephalopods still have chambered shells to control their buoyancy?
Nautiloids
