final animals Flashcards
1
Q
Animal key concepts
A
Animals are multicellular, heterotrophic, eukaryotes with tissues that develop from embryonic layers
2
Q
animals are very-
A
diverse
3
Q
Kingdom animalia
A
a monophyletic kingdom of multicellular organisms within the eukaryotes
4
Q
Characteristics of (typical) animals
A
Nutritional mode
Cell structure and Specialization
-Unique cell types
reproduction and development
5
Q
Animals Nutritional mode
A
– Heterotrophs
– Ingest food
6
Q
Cell structure and Specialization
A
Collagen is the main structural protein in animals
Unique cell types
– Nerve cells
– Muscle cells
– Usually surrounded by membranes
7
Q
Reproduction and development
A
Most animals reproduce sexually
- Diploid stage usually dominant
8
Q
Exceptions for reproduction and development
A
- Some animals can/must reproduce asexually
-animals where there is only females
In some animals, the haploid stage dominates:
9
Q
Do animals have cell walls?
A
no, so they have structural proteins instead, like collagen
10
Q
Early animal development
A
Sperm fertilizes egg
– Small, flagellated sperm and large, non-motile egg
- Zygote undergoes rapid cell division called cleavage
- Cleavage leads to formation of a blastula
- Blastula undergoes gastrulation, forming a
gastrula with different layers of embryonic tissues
11
Q
Embryonic tissue layers give rise to different tissues:
A
the Endoderm of the archenteron gives rise to the tissue lining the
digestive tract
12
Q
Gastrulation
A
process in which one end of the embryo folds inward, expands and fills blastocoel, producing a hole
13
Q
gametocytes
A
specific subclass of meiocyte cuz product produced is a gamete
14
Q
gametes
A
sperm and eggs
15
Q
normally diploid stage is-
A
dominant
16
Q
parthenogenesis
A
produces female colonial lineages
17
Q
Cephalization
A
movement of sensory organs to anterior
18
Q
What is the blastula?
A
a hollow ball of cells, produced by cleavage after zygote
19
Q
What does coel mean on blastcoel
A
empty room
20
Q
What are the holes on animals
A
1 hole = gastrovascular cavity
2 holes = mouth, and anus
21
Q
diploblastic animals
A
has 2 embryotic layers
-endoderm and ectoderm
-simplest animals with true tissues
-mainly jellyfish
22
Q
What are the three embryotic layers
A
ectoderm
endoderm
mesoderm
23
Q
Larval stage(s)
A
Many (most) animals have at least one larval
stage
completely different when adults - butterfly’s
24
Q
What defines a larval stage?
A
Sexually immature
Morphology
Nutrition
metamorphosis
25
What are the advantage with larval stages?
less competition from parents are larva for food since they eat different things
26
Hox genes
Almost all animals, and only animals, have Hox genes that regulate the development of body form
-cephalization
* Although the Hox family of genes has been highly
conserved, it produces a wide diversity of animal
morphology
27
What do plants and animals have in common?
multicellular
ukaryotic
28
Three lines of evidence that choanoflagellates are closely related to animals
.Cell morphology
Cell morphology unique to animal cells
DNA sequence homology
29
Plasmogamy can directly result in which of the following?
heterokaryotic and dikaryotic cells
30
spores are always-
haploid -fungi
31
animals are less suseptible to parasitic fungi than plants cuz-
-animals have an immune system
-we evolved to with stand it (natural selection)
-we can move around
32
ediacaran animals are-
injestive heterotrophs
33
“Cambrian Explosion”
* Unprecedented diversification of animals
* Most of the fossils from it are of bilaterians, organisms that have the following traits:
– Bilaterally symmetric form
– Complete digestive tract
– One-way digestive system
its where a huge amount of species evolved
34
Why did the Cambrian Explosion occur?
Several hypotheses
– New predator-prey relationships
– A rise in atmospheric oxygen
– The evolution of the Hox gene complex
35
Ecdysozoa
one of the caldes within the insects
triplo bilatera
-coelom- could have none, false, or true
lophotrochoza, deuterostomia
ecdysozoa
36
Mesozoic
dinosaurs were the dominant terrestrial vertebrates
* Angiosperms and insects
37
cenozoic
Cenozoic era followed mass extinctions of both terrestrial and marine animals
* Includes large, non-flying dinosaurs, marine reptiles
* Modern mammal orders and insects diversified during the Cenozoic
* Global climate cooled
-animals became a major group, where we are right now
38
Body plan
a set of morphological and developmental traits
* Some body plans have been conserved (spongi)
-barely changed
while others (us) have changed multiple times over the course of evolution
39
symmetry
* Animals can be categorized according to
symmetry of their bodies, or lack of it
40
radial symmetry
no front and back, or left and right
41
bilateral symmetry
Two-sided symmetry
* Bilaterally symmetrical animals have:
-dorsal
ventral
anterior
posterior
42
tissues
body plans also vary according to the organization of the animal’s tissues
* Tissues are collections of specialized cells isolated from other tissues by membranous layers
* During development, three germ layers give
rise to tissues and organs of animal embryos
-ecto, endo, meso
Sponges and a few other groups lack true tissues
43
Ectoderm
the germ layer covering the
embryo’s surface
44
Endoderm
the innermost germ layer and lines the developing digestive tube, called archenteron
45
Diploblastic animals
have ectoderm and endoderm
– Includes cnidarians and a few other groups
46
Triploblastic animals
also have an intervening
mesoderm layer;
-these include all bilaterians
– Includes flatworms, arthropods, vertebrates, and others
47
Body Cavities
Most triploblastic animals possess a body cavity
* A true body cavity is called a coelom and is derived from mesoderm
48
Body cavities of triploblastic animals
Coelomates
Psedocoelom
Coelomates are animals that possess a true coelom
-cavity is completely lined with mesoderm
A pseudocoelom is a body cavity derived from mesoderm and endoderm
49
Triploblastic animals possessing a pseudocoelom called
pseudocoelomates
-false coelom
-not completely lined with mesoderm (nemotods and nemefers)
50
Triploblastic animals that lack a body cavity are called-
acoelomates
-absent cavity
-platyhemeth
51
homecoel
not the same as a coelom
52
Protostome and Deuterostome Development
animals either have a protostome development or deuterostome development
53
Cleavage
protosome or deuterostome
With indeterminate cleavage, each cell in the
early stages of cleavage retains the capacity to
develop into a complete embryo
* Indeterminate cleavage makes possible identical twins, and embryonic stem cells
54
In protostome development
cleavage spiral and determinate
55
In deuterostome development
cleavage radial and indeterminate
56
Coelom Formation in protostome development
splitting of solid masses of mesoderm forms the coelom
57
coelom formation in deuterostme development
mesoderm buds from the wall of the archenteron to form the coelom
58
Fate of the Blastopore in protostome development
the blastopore becomes the mouth
59
Fate of the Blastopore in deuterostome development
the blastopore becomes the anus
60
the Blastopore
forms during gastrulation and connects the archenteron to the exterior of the gastrula
61
There are 5 important
points about the relationships among living animals that are reflected in their phylogeny:
-All animals share a common ancestor
-Sponges are basal animals- metazoa
-Eumetazoa- not porifera, true tissues
-Most animal phyla belong to the clade Bilateria, and are called bilaterians - triplo
-There are 3 major clades of bilaterian animals, all of which are invertebrates, except Chordata, which are classified as vertebrates
-lopho, deutero, ecdyso
62
Invertebrates
animals lacking a backbone
95% of known animal species
* They occupy almost every habitat on Earth
* They are morphologically diverse
63
sponges are-
basal animals that are in metazoa
64
Sponges are basal animals that lack-
-true tissues
* phylum Porifera are sponges
* They are sedentary and live in marine waters or fresh water
65
Sponges
are suspension feeders
* Water is drawn through pores into a cavity called the spongocoel and out through an opening called the osculum
* Sponges lack true tissues and organs
-sessil = dont move much
66
suspension feeders
capturing food particles suspended in water passing through their body
67
Anatomy of a sponge
Generate current
Ingest suspended food
has a shell full of gell (mesohyl) and one hole (simple sponge)
spongin or spicules
choancytes - coller cells that help move around and maintain structure
-food bits trapped and goes into ameobocytes
can regenerate
68
Cnidarians
Phylum Cnidaria is one of oldest groups in eumetazoa
both sessile and motile forms including jellies, corals, and hydras
diploblastic, radial body plan
* The basic body plan is a sac with a central digestive compartment, the gastrovascular cavity
A single opening to the gastrovascular cavity functions as mouth and anus
2 major clades
69
what belongs to clade Eumetazoa?
All animals except sponges
- animals with true tissues
70
What is a gastrovascular cavity
1 hole, mouth and anus
not a complete digestive system
71
polyp cnidaria
mouth, tenticle up
-mainly asexual
72
medusa cnidaria
mouth tenticle down
only 2 tissue layers
sexual reproduction
73
What is mesoglea
serves as a skeleton to support the organism
acellular goo in cnidarias
74
* Nematocysts
specialized organelles within cnidocytes that
eject a stinging
thread
(stingers)
75
Cnidaria two major clades
Medusozoa
-sea wasps, jellies
Anthozoa
-sea anemones, corals
76
Medusozoans
all cnidarians that produce a medusa:
– Scyphozoans (jellies)
– Cubozoans (box jellies)
– Hydrozoans
77
Hydrozoans
Most hydrozoans alternate between polyp and medusa
forms
* Hydra, a freshwater cnidarian, exists only in polyp form and reproduces asexually by budding
78
Scyphozoans and cubozoans
The medusa is the predominant stage in the life cycle of most scyphozoans and cubozoans
79
Cubozoans
the medusa is box-shaped
often have highly toxic cnidocytes (in stinger)
80
Anthozoans
The clade Anthozoa includes the corals and sea
anemones, and these cnidarians occur only as polyps
81
Exchange with the Environment
A single-celled protist living in water has sufficient surface area to service its entire volume of cytoplasm
Multicellular organisms with a saclike body plan have body walls that are only two cells thick
82
intro to bilateria
Bilaterian animals have bilateral symmetry and triploblastic development
* Most have a coelom and a digestive tract with two openings
83
Bilateria
The clade Bilateria contains Lophotrochozoa, Ecdysozoa, and Deuterostomia
84
Intro to Lophotrochozoa
morphological
* Some develop lophophore for feeding, others pass through a trochophore larval stage, and few have neither feature
all are invertebrates
85
Traits of Playhelminthes
Habitats
– Marine,
– freshwater, and
– Damp terrestrial
* Protostomes
* Triploblastic development
* Free-living and parasitic forms
86
flatworms are-
acoelomates
a convergence due to pressures from environment
87
Body plan of Platyhelminthes
- Acoelomates
* Flat
– Thus, cells are close to the surrounding water.
* Lack organs specialized for gas exchange and circulation
* Nitrogenous wastes are removed by diffusion, and simple ciliated flame cells (protonephridia) help maintain osmotic balance.
88
what are protonephridia
Network of tubules with ciliated structures called flame bulbs
* Flame bulbs cap the branches of each protonephridium
* Urine excreted has low solute concentration – maintenance of osmotic
uptake of water from environment
89
Flatworms are divided into
two lineages
– Catenulida, or “chain
worms,” reproduce
asexually by budding
– Rhabditophora are more diverse and include both free-living and parasitic species
90
Free-Living Species
The best-known rhabditophorans are planarians
* Planarians live in
fresh water and prey on smaller animals
a lot are hermaphroditic
91
How do planarians compare to cnidarians
they both have one hole
92
why can planarians do without respiratory and circulatory systems?
cuz they are flat
93
Parasitic Species
Parasitic rhabditophorans live in or on other animals
* Two important groups of parasitic rhabditophorans are
trematodes and tapeworms
94
Trematodes
Trematodes parasitize a wide
range of hosts
* Most have complex
life cycles with alternating sexual and asexual stages
95
Tapeworms
-Tapeworms are parasites of vertebrates
* They lack a digestive system
* Tapeworms absorb nutrients from the host’s intestine
* Fertilized eggs, produced by sexual reproduction, leave
host’s body in feces
96
Phylum rotifera
Rotifers are tiny animals that inhabit aquatic environments
* Smaller than many protists (remember Stentor?) but with
specialized tissues/organs/organ systems
97
Rotifers
alimentary canal,
a digestive tube with a
separate mouth and anus within a fluid-filled hemocoel
* Many rotifers reproduce by parthenogenesis
* Some species are unusual in that they lack males entirely
98
parthenogenesis
females produce offspring from unfertilized eggs
99
Lophophorates include two phyla:
Ectoprocta and Brachiopoda
100
Phylum Mollusca includes (but not limited to)
– snails
– slugs
– oysters
– clams
– octopuses
– squids
101
Traits of molluscs
Most marine
– Some fresh water
– Some terrestrial
* Molluscs are soft-bodied animals
– Most protected by hard shell
* Some of the most sophisticated invertebrates
102
Mollusc body plan
All molluscs have a similar body plan with three
main parts:
– Muscular foot
– Visceral mass
– Mantle
* Many molluscs have a water-filled mantle cavity
* Many molluscs feed using a rasp-like radula
103
Mollusc reproduction
Most molluscs have separate sexes with gonads located in the visceral mass
– Exception: most snails are hermaphrodites
* Most marine forms have broadcast spawning and
planktonic trochophore larvae
104
Clades (Classes) in Mollusca
We will cover four of them:
– Gastropods (slugs, snails)
– Chitons
– Bivalves (clams, oysters, mussels, & other bivalves)
– Cephalopods (squids, octopuses)
105
Traits of gastropods
Most gastropods are marine,
– Many are freshwater and terrestrial species
* Most have a single, spiraled shell
– Slugs lack a shell or have a reduced shell
* The most distinctive characteristic of gastropods is torsion
– Anus and mantle end up above its head
106
Feeding in gastropods
Typically ‘grazers’ via rasping radula
* Rarely, modifications of radula to support carnivory
* Digestion via complete gut
107
Circulation in gastropods
Circulation:
via open system of vessels
108
respiration in gastropods
Respiration:
– Marine: Via gills in mantle cavity
– Freshwater/terrestrial: mantle cavity forms ‘lung’
109
Reproduction in gastropods
Marine: Dioecous with complex life-cycle (trochophore larvae)
* Freshwater/terrestrial: Hermaphroditic with direct development
110
Phylum Mollusca, the Chitons
* Chitons are oval-shaped marine animals encased in an armor of eight dorsal plates
* The use their foot like a suction cup to grip rock, and their radula to scrape algae off rock surfaces
111
Phylum Mollusca, the Bivalves
Clams, oysters, mussels, scallops”
112
Traits of bivalves
Shell divided into two halves (valves)
Powerful adductor muscles close the shell for protection
* Powerful foot for digging or anchoring
* Highly modified gills for feeding, respiration, and reproduction
* Some have eyes and sensory tentacles along edge of their mantle
113
Feeding in bivalves
Most are sessile, suspension feeders
* Ciliated gills create water currents
* Gills trap fine food-particles in mucus coat
* Water flows into mantle cavity via the incurrent siphon, passes over the gills, and exits via the excurrent siphon.
114
Circulation and respiration in bivalves
Somewhat similar to gastropods:
– Open circulation
– Gill in mantle cavity
115
Reproduction in bivalves
Marine - mostly dioecous with complex lifecycles and trochophore larvae
* Freshwater - mostly hermaphroditic with direct development
– However, some have glochidia (larvae)
116
Phylum Mollusca, Cephalopods
“Squids, Octopuses, Cuttlefish, Nautiluses”
117
Traits of cephalopods
* Class Cephalopoda includes squids and octopuses, carnivores with beak-like jaws surrounded by tentacles of their modified foot
* Well-developed sense organs and complex brain
Squids use their siphon to fire a jet of water, which allows
them to swim very quickly
* One small group of shelled cephalopods, the nautiluses,
survives today
118
Cephalopod eye
Highly acute vision in many cases
* In some respects appears to be a “better design” than the vertebrate eye
119
Feeding in cephalopods
Most octopuses creep along the sea floor in search of prey
* Squids use their siphon to fire a jet of water, which allows them to swim very quickly
120
Circulation in cephalopods
Unlike other molluscs, cephalopods have a closed circulatory system
121
Reproduction in cephalopods
* Diocecious
* Direct development
* Many are semelparous
* Often sophisticated courtship rituals
* Transfer of spermatophore
122
Protecting Freshwater and
Terrestrial Molluscs
Molluscs are the animal group with the largest number of recent extinctions
* Most threatened groups are
– Freshwater bivalves, including pearl mussels
– Terrestrial gastropods, including Pacific island land snails
* These molluscs threatened by habitat loss, pollution, and non-native species
123
Annelida means “little rings”
Annelids are segmented worms
– Body resembles a series of fused rings
* Habitats
– Marine
– Aquatic
– Terrestrial (damp soils)
124
Traits of annelids
All annelids have segmented bodies
* Development
– Protostomous
– Bilateral
– Triploblastic
– Coelomate
* Complete gut with mouth and anus
* Sophisticated nervous, circulatory, reproductive and excretory systems
125
Reproduction in annelids
Sexual reproduction via hermaphroditism
Sexual reproduction via dioecy
– Most undergo external fertilization (broadcast spawning)
– Ciliated larvae (trochophore) that is planktonic
126
The phylum Annelida was traditionally divided into three classes:
– Oligochaeta (earthworms and their relatives)
– Polychaeta (polychaetes)
– Hirudinea (leeches)
127
Recent molecular analyses indicate that the annelids can be divided into two major clades:
* Errantia
* Sedentaria
128
Errantians
Most are mobile, marine organisms
* Many have parapodia on each body segment
* Each parapodium has numerous chaetae, bristles made of chitin
* Parapodia are not unique to this clade
have jaws and eyespots
129
what are parapodium
fleshy feet that helps with locomotion and respiration
130
131
Sedentarians
tend to be less mobile than errantians (not as moveable)
* Some species burrow into the substrate, while others live in protective tubes
* Tube-dwelling sedentarians
often have elaborate gills or
tentacles used for filter feeding
* The clade also includes
leeches and earthworms
132
Earthworm movement
Muscles work against non-compressible coelomic fluid, which acts as hydostatic skeleton
chaetae provide traction
133
Earthworm reproduction
Earthworms eat through soil, extracting nutrients as the soil moves through the alimentary canal
* Earthworms are hermaphrodites but crossfertilize
* Some reproduce asexually by fragmentation
Hermaphrodites that crossfertilize
mucus secreted by the ciltellum forms an egg case, which slips off worm
134
metanepridium
filters out fluid out body, pees as they go
135
Sedentarians - leeches
* Most species of leeches live in fresh water; some are marine or terrestrial
* Leeches include predators of invertebrates, and parasites that suck blood
Leeches secrete a chemical called hirudin to prevent blood from coagulating
136
leaches
Flattened body
Reduced coelom
Chaetae typically absent
Suckers at anterior and posterior
137
Traits of ecdysozoans
defined by molecular evidence
* Covered by a tough coat called a cuticle
* The cuticle is shed or molted through a process called ecdysis
nematodes and arthropods
138
Species diversity in the Ecdysozoans
The Ecdysozoa is a dominant animal group
– Niche proliferation
– Abundance
– Species richness
* This unparalleled success is predominantly due to arthropods
– And, to a lesser extent, nematodes
139
Nematoda
Roundworms”
140
Traits of nematodes
Do not have segmented bodies OR circular muscles
– Contrast with annelids
Nematodes have an alimentary canal, but lack a circulatory system
141
Reproduction in nematodes
usually sexual, by internal fertilization
* Most species have separate males and females
* Females may deposit >100,000 fertilized eggs per day
– These zygotes are often resistant to severe environmental conditions
142
Ecdysis
Body covered in tough cuticle
* To facilitate growth, nematodes periodically shed their old cuticle and secrete a larger one
143
cuticle
is an exoskeleton constructed from layers of protein and chitin
144
Habitats of nematodes
Habitats
– Aquatic
– Soil
(free-living)
– Moist tissues of plants
– Body fluids and tissues of animals (parasites)
* Includes some of the most common and devastating
parasites of humans
145
roles of nematodes
Important in decomposition and nutrient cycling
* Little is known about most species
* Most animals and plants have nematode parasites
146
Why are nematodes so good at parasitism?
“Molecular warfare”
– Redirect their hosts’ cellular functions
– Evade detection by immune systems
147
Arthropod origins
Two Hox genes (linked to segmentation) likely went through extensive re arrangement and sophistication
-(all but sponges)
148
Traits of arthropods – the “winning plan”
Developmental:
– Protostomous, bilateral, coelomate
* Additional:
– Body segmentation, a hard exoskeleton, jointed and paired appendages, sensory organs
hemocoal= open circulatory system
149
Segmentation
permits specialization of
functions, thus efficient division of labour among regions
150
* Well-developed, anterior, sense organs (cephalization)
– Eyes
– Olfactory receptors
– Antennae
151
Other traits for anthropods
Open circulatory system
* True coelom much reduced
* Gas exchange
– gills
- feathery extensions
– Terrestrial arthropods
- internal surfaces specialized for gas exchange.
152
three major lineages that diverged early in phylum’s evolution
Chelicerates
–Myriapods
–Pancrustaceans
153
The Chelicerates
clade Chelicerata
named for clawlike feeding appendages called chelicerae
* They have an anterior cephalothorax and a posterior abdomen
* Extant groups:
– Horseshoe crabs
– Spiders
– Scorpions
– Ticks
– Mites
154
The earliest cheliceriforms were-
-eurypterids
(water scorpions - extinct)
155
Most modern cheliceriforms are-
-arachnids,
which include:
spiders, scorpions, ticks,
and mites
156
Traits of arachnids
Arachnids have an abdomen and a cephalothorax, which has six pairs of appendages, the most anterior of which are the chelicerae
* Gas exchange in spiders occurs in respiratory organs called book lungs
* Many spiders produce silk, a liquid protein, from specialized abdominal glands
157
What are gonopores in antropods
the exit for eggs
158
Myriapods
* Millipedes and centipedes
– Terrestrial
– Pair of antennae
– Jaw-like mandibles
159
Millipedes
Don’t really have 1000 legs
* Each legged-segment has two pairs of legs
Eat decaying plant matter
160
Centipedes
* Don’t really have 100 legs
* Each legged-segment has one pair of legs
Carnivores
161
Pancrustaceans
terrestrial insects are more closely related to crustaceans than myriapods
* Some crustaceans are more
closely related to insects than other crustaceans (crustaceans are paraphyletic!)
* Together, insects and crustaceans form the clade Pancrustaceans
162
Whats in phylum pancrustaceans?
all anthropods thats not chelicerates or myriapods
163
Pancrustaceans - Crustaceans
Crustaceans live in marine and freshwater
* Many crustaceans have highly specialized appendages for feeding and locomotion
* Small crustaceans exchange gases through the cuticle; larger crustaceans have gills
Open circulatory system
* Most crustaceans go through 1+ swimming larval stages
* Most crustaceans have separate males and females
164
Isopods
include terrestrial, freshwater, and marine species
–Pill bugs are a well known group of terrestrial isopods
165
Decapods
all relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp
166
Planktonic crustaceans include many species of-
branchiopods
* Branchiopoda is a class of crustaceans.
-fairy shrimp, clam shrimp
mostly small, freshwater animals that feed on plankton and detritus
167
Maxillopods
* Barnacles
mostly sessile crustaceans
* They have a cuticle that is hardened into a shell of CaCO3
168
Pancrustaceans - Hexapods
Aerial, terrestrial, aquatic (but few marine)
* The internal anatomy of an insect includes several complex organ systems
169
hexapod Reproduction
Typically sexual,
separate males & females
170
hexapod importance
Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops
171
Traits of the Deuterostomia
* Deuterostome development
* Bilaterians, although not all are bilaterally symmetrical as adults
* Defined mainly by DNA
– Not by morphology
172
Main clades of the Deuterostomia
Echinodermata
Chordata
173
Intro to phylum Echinodermata
Echinoderms = “spiny-skinned animals”
* Sand dollars, sea stars, sea urchins, sea cucumbers, etc.
* Approximately 7,000 species
* Marine
* Benthic
* Sessile or slow-moving
174
Echinoderm body plan
A thin epidermis covers an endoskeleton of hard calcareous plates
* Unique water vascular system
175
water vascular system
– Network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange
176
Symmetry in echinoderms
Adults of most echinoderms are radially symmetrical
– Often with five arms
– Not perfect radial symmetry
177
Reproduction in echinoderms
Typically separate males and females
* Broadcast spawning
– Release gametes into water column
178
Living echinoderms are divided into five clades
Asteroidea
(sea stars and sea daisies)
– Ophiuroidea
(brittle stars)
– Echinoidea
(sea urchins and sand dollars)
– Crinoidea
(sea lilies and feather stars)
– Holothuroidea
(sea cucumbers)
179
Self-defence in sea cucumbers
When threatened, some sea cucumbers expel sticky threats or even their intestines out of their anus
* Fortunately, they regenerate
180
Traits of the chordates
* Bilaterians
* Deuterostomes
* Various clades
– Cephalochordata
– Urochordata
– Vertebrata
(invertabrates)
All chordates share a set of derived characters
* Some species have some of these traits only during embryonic development
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Four key characters of chordates:
– Notochord
– Dorsal, hollow nerve cord
– Pharyngeal slits or clefts
– Muscular, post-anal tail
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Notochord
Longitudinal, flexible rod between digestive tube and nerve cord
* Skeletal support
* Muscular support
* In most vertebrates, only remnants remain at adulthood
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Dorsal, hollow nerve chord
* Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord
* Develops into central nervous system
– Brain
– Spinal cord
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Pharyngeal slits
Functions of pharyngeal slits:
– Suspension-feeding structures in invert chordates
– Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods)
– Develop into parts of ear, head & neck in tetrapods
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Pharyngeal clefts
develop into slits that open to
the outside of the body
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Muscular, post-anal tail
Chordates have a tail posterior to the anus
* In many species, the tail is greatly reduced during embryonic development
* Contains skeletal elements and muscles
* Provides propelling force in many aquatic species
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Cephalochordata
“Lancelets”
* Named for blade-like shape
* Marine suspension feeders
* Retain characteristics of the chordate body plan as adults
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Urochordata
“Tunicates”
* More closely related to other chordates than are
lancelets
* They are marine suspension feeders
– Most sessile; some planktonic
– Some solitary; others colonial
– Hermaphroditic, broadcast spawning
* As an adult, a tunicate draws in water through an
incurrent siphon, filtering food particles
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what has the fewest Hox genes than other vertebrates
Tunicates with 9
others have 13
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Vertebrates are chordates that have a backbone
A skeletal system and complex nervous system have allowed vertebrates to become more efficient at two essential tasks:
– Capturing food
– Evading predators
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Derived Characters of Vertebrates
Vertebrates have two or more sets of Hox genes;
-lancelets and tunicates have only one cluster
* Vertebrates have the following derived characters:
– Vertebrae enclosing a spinal chord
– An elaborate skull
– Fin rays, in the aquatic forms
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What is in Group metazoa?
All animals
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What is in group eumetazoa?
All except porifera
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what is in group bilateria
acoela
all deuterstomia
all lophotrochozoa
all ecdysozoa
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What is in group deuterstomia?
Hemichordata
echinodermata
chordata
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What is in group lophotrochozoa
Platyhelminthes
rotifera
ectoprocta
brachiopoda
mollusca
annelida
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What is in group ecdysozoa
nematoda
arthopoda
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What does cleavage form?
the blastula
-a hollow ball
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after the balstula stage -
gastrulation happens
-the layers of embryonic tissues that develop into adult body parts are produced
the developmental stage is called a gastrula
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What is metamorphosis?
a developmental transformation that turns the animal into a juvenile that resembles an adult but not yet sexually mature
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Homeoboxes
-most animals share a unique homeobox-containing family genes, known as hox genes
hox genes play an imaportant role in the development of animal embryos controlling the expression of dozens or even hundreds of other genes that infulence animal morphology
-sponges lack hox genes
hox genes regulate the formation of anterior-posterior axis, as well as other aspects of developoment
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cephalization
bilaterally symmetrical body plan animals have sensory eqipment cooncentrated at their anterior end, including the central nervous system in the head (the brain)
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many radial symmetric animals are
sessile (attached to a substrate)
planktonic (drifting or weakly swimming like jellies)
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Bilateral symmetic animals are typically more-
active and move from place to place
