Invertebrate Animals Flashcards
(98 cards)
1
Q
Animal 7 characteristics
A
Eukaryotic
Heterotrophic
Multicellularity
No cell wall
Motile at some life stage
Somatic cells are diploid
Diplontic life cycle
2
Q
Eukaryotic
A
True nucleus
Membrane-bound organelles
Compartmentalized cytoplasm
3
Q
Heterotrophic
A
Use pre-formed organic materials as energy and carbon source
Predators
Herbivores
Filter feeders
Parasites
Detritivores
Omnivore
Animals have specific digest organs
4
Q
Multicellularity
A
Important evolution innovation, only once in animals
Advantages:
1.Cells become specialized to carry out specific functions
2. Longer lifespan
3. Organisms can grow in size
5
Q
Large-cell problem
A
Low surface area, surface area-to-volume ratio
Large cell hard to exchange nutrients
Larger, exchange capacity decrease
Multicellularity overcomes the constraint on growth resulting in requirements for development
6
Q
Tissue
A
Tissues: groups of similar cells organized into a functional unit
4 basic types:
Muscle-active contrastive tissue
Nervous-comprises the central nervous system or the peripheral nervous system and irregulars and controls many body activities
Connective-made up of cells that are separate by non living materials which is called an extracellular matrix
Epithelial- cells cover the organ surfaces
7
Q
Organs
A
Tissue function together as organs to complete complex tasks
Eg. digestion, absorption
villi
8
Q
No cell wall, what support structure?
A
Hydrostatic skeleton
Exoskeleton
Endoskeleton
9
Q
Hydrostatic skeleton
A
Found in soft bodied organisms
1.Muscles contract against fluid-filled cavity
2.simple but efficient movements
3.limited possibility for the attachment of limbs
4.dependence of a humid environment
Muscle fiber: longitudinal muscles and circular muscles
10
Q
Exoskeleton
A
1.Firm, rigid structure
2.Non-living covering
3.Does not grow with animal
4.Molting-ecdysozoans
11
Q
Endoskeleton
A
1.rigid structure inside body
2.internal support
3.vertebrate-living tissue
4.some invertebrates-non living tissue (spicules in sponges and cuttlebone in cuttlefish)
12
Q
Motile at some life stage
A
- Movement reduces competition
- Enhances genetic diversity
- Expends the distribution of range
Eg. Barnacle larva
13
Q
Somatic cells are diploid
A
Germ cells N
Fertilization
Zygote 2N
Mitosis
Body cells 2N
Meiosis
Germ cells
Exceptions: the male of the honeybee is haploid
14
Q
Animals are diplontic
A
Diploid dominant life cycle
15
Q
Evolution of Animals
A
About 35 phyla
10 million estimate
1.4 million classified
97% invertebrate
Moniphyletic
Time animals evolve: Late Precambrian
First animal: 700 MYA
16
Q
The Cambrian Explosion
A
542-488 MYA
The most explosive wave of diversification
Chengjiang
Burgess Shale, BC
17
Q
Animals are monophyletic
A
- Similar gene sequences (hox genes: the organization in of the hox genes in the chromosome is the same as the order of their expression)
- Similar extracellular matrix molecules (collagen fibers, proteoglycan complex)
- Unique type of junctions among cells (tight junction, desmosome, gap junction)
18
Q
Tight junction
A
Seal cells together and are found in the epithelial tissue
Special protein in cell membrane form a water tight seal
Common in epithelial tissue
19
Q
Desmosomes
A
Connect the cytoskeleton of cells
Abundant in epithelial tissue
20
Q
Gap junction
A
Act as channels between cells
Found in muscle and nerve tissues(where rapid communication is important）
21
Q
Embryonic development: zygote to multicellular organism
A
1.Fertilization: single sperm combining with a single egg cell
2.Zygote: first cell of next generation, diploid cell resulting form union of 2 haploid gametes, combined from zygote
3.Embryo: young animal, contain within a protective structure(egg shell or uterus)
22
Q
Process during embryonic development
A
- Cleavage: multiple rounds of rapid cell divisions(mitotic), but the overall size of the embryo is not changing(because the cytoplasm is not replenishing during this time). Finally become a morula
Create Blastomere 卵裂球
During this stage, cleavage cytoplasm it determinants found in specific location in the egg cytoplasm, these determinants will determine the fate of the cells. 基因调控分化
- Gastrulation: infolding , invagination to create the embryonic tissue layers (2 or 3 tissue layers). During this stage, the body need a well defined head, tail axis
blastocoel囊胚腔——blastula 囊胚——early gastrula - Cellular differentiation: immature cell take on individual characteristics and reach their mature form and function
23
Q
major feature of the gastrula
A
- Blastocoel: 细胞里的腔
- Archenteron: digestive space
- Blastopore(mouth and deuterostomes肛门)
Germ layers:
1.Ectoderm: outer skin, developed to epidermis, nervous system
2.Endoderm: inner skin, developed to digestive and respiratory tracts
3. Mesoderm: another layer on the top of the endoderm, developed to muscles, skeletal system and part of gonads(most internal organs)
Organism with 2 germ layers are diploblastic(2 buds), 3 germ layers are triploblastic
24
Q
Body symmetry
A
- Asymmetry: no axis divides body into equal halves
Eg. sponges - Radial symmetry
Eg. Jellyfish - Bilateral symmetry: midsagittal plane(between eyes)
dorsal, ventral, anterior, posterior
Eg. Most animals
Some animals will shift to another body symmetry when they grow up (sea star: larva bilateral symmetry, adult radial symmetry)
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Sponges (Phylum Porifera)
Earliest animals, fossil record (700 MYA)
**Sessile as adults, motile as larvae (dispersal)**
-Primitive features (specialized cells but **no true tissues or organs**)
-**Endoskeleton**: spicules and a network of elastic fibres for support
~9,000 species, mostly marine
Inhabit a wide range of habitats
26
Anatomy of a sponge for Filter Feeding
Digestion: intracellular
Respiration and excretion排泄: diffusion
-Choanocyte: collar cells, have flagella (similar structure with the choanoflagellate protist)
-Osculum: water blow out via osculum, locate at the top of central cavity
27
Anatomy of a Sponge
3 layers:
1.outer layer: **epidermal cell**, flat cells
2.middle layer: gelatinous **mesohyl** (jelly matrix), with **amoebocyte** cell embedded in
Also have endoskeleton made up by **spicule and spongin** and fibers.
3.inner layer: **choanocyte with their endoflagella**
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Support structure in the middle layer
1.Extracellular matrix: non-cellular, collagen and glycoproteins ,some support
2.Spicules: CaCO3, SiO2, provide rigidity (some have SiO2-rigid structure)
3.Spongin: protein fibers and flexible support
29
Asexual reproduction of Sponges
1.Fragmentation:
external budding, not self-induced, brought about by waves or predators(crack, and part of it continue to grow)
2.Internal budding:
Gemmules 芽球: clone of parent, happen in internal buds
Enclosed by a protective covering
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Sexual reproduction of Sponges
-Hermaphroditic: most species, can produce both eggs and sperms, but only produce one at one particular time, so cannot self-fertilize
-Broadcast sperm: release all the sperm all at ones
-Choanocytes: trapped the sperm
-Mesohyl: eggs store, fertilize, and develop in the matrix
-larve released back to water, can swim using cilia, later settle on suitable substrate基底
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Cnidaria, Cnidarians
Diploblastic
Radially symmetrical
Simple nervous and muscular tissue
~11000 species most marine, diverse in body size
jellyfish, sea anemones, corals, hydrozoans
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Generalized body plan of a cnidarian——Diploblastic
Mouth/anus: from blastopore, top of the cavity
Gastrovascular cavity: from archenteron, bottom of the cavity
Gastrodermis: inner layer, from endoderm
Epidermis: outer layer from ectoderm
Mesoglea: inner part between gastrodermis and epidermis, collagen and proteoglucans
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Cnidarian Body Orientation
1.polyp: mouth open upward
eg. sea anemone
2.medusa: mouth open downward
free to move eg.jellyfish
Most life cycles include both body plans: polyp is usually in the asexual stage, medusa is usually in the sexual stage (corals is one of the exceptions)
34
How do cnidarians obtain energy?
Carnivorous: inject toxins and capture prey
-Cnidocyte: usually located near mouth or in tentacles
-Nematocyst: with barbs and contains toxins
Extracellular digestion in gastrovascular cavity
Corals and anemones can obtain a large proportion of their energy from symbiotic algae (through photothesis)
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Cnidarians: diversity
1.hydrozoa
2.scyphozoa
3.cubozoa
4.anthozoa
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Hydrozoa
freshwater
no medusa stage
moves by gliding, somersaulting or floating
Have a Bubble for floating and sinking, mouth, basal disk
-Hydra: simple nerve net (No integration of signal), radial symmetry so sensory info can com in from any direction
-Life cycle of the hydrozoan Obelia
-Portuguese man-of-war: colonial polyps specialized for different functions; gas-filled float: pneumatophore; tentacles contain cnidocytes
37
Scyphozoa (true jellyfish)
Large\thick mesoglea
Bell shape-all the sensory cells clustered at the edge of the bell
Some has strong nematocysts(刺细胞)
Prey on fish larvae and zooplankton, important food for leatherback turtles
Eg. Cassiopeia
Upside down jelly
Symbiotic algae in the tentacles(触手)
Get O2 and nutrients from symbionts
Lives in mangrove swamps(红树林沼泽)
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Cubozoa (box jellyfish)
Cube shaped Medusa
Very painful stink, and some times deadly for human
39
Anthozoa (flower animals)
~6000 species
-Sea anemones:
Retract tentacles in defense, have cnidocytes
Mutualistic relationships (+/+) with particular species of fish and shrimp
-Corals:
Form colonies of a lot of genetically identical polyps, polyps secrete calcium carbonate for the hard skeleton, creating framework of the coral reef
Coral also have mutualistic relationships with dinoflagellates(need clean water), coral protect them and they can do photosynthesis, produce nutrients and O2, help coral remove waste
Coral bleaching: caused by many factors , water temp, UV, pollution, disease
40
Body cavities (3 body plans)
1. Coelomate (Eucoelomate): coelom = cavity
The body cavity is completely enclosed, surround by mesoderm
2. Pseudocoelomate: false coelom
Mesoderm lines the outside of pseudocoel
Eg. Nematoda, Rotifera
3. Acoelomate: no body cavity
No body cavity, solide except digestive space
Eg. Flatworms
41
Two ways to make a coelom
1.Schizocoely
Splitting within the mesoderm
**Protestomes**
Mouth at the bottom
2.Enterocoely
Mesoderm forms pocket form gut
**Deuterostomes**
Mouth at the top
42
Platyhelminthes—flatworms
Protostomes
Blastopore develops into mouth
Triploblastic
No body cavity
Aquatic or terrestrial(moist) habitat (gas exchange through the surface)
Scavengers or parasitic
Blind gut (just one opening for both ingestion of food and elimination fo waste)
Cephalization
1mm-10m
~25000
43
Cephalizaiton
Linked to directed movement
-Concentration fo neurons and sensory structures at the anterior end, enables directed locomotion
-have multiple sensory structures: mechanoreceptors for touch; chemoreceptors for taste and smell, and photoreceptors for light
Simple nervous system: longitudinal nerve cords, 2 cerebral ganglia(primitive brain, concentration of neurons)
44
Diversity of Platyhelminthes
Free living
1. Turbellaria (planarians)
Parasitic (+/-)
2. Monogenea (flukes, mostly ectoparasitic)
3. Trematoda (flukes, mostly endoparasitic)
4. Cestoda (tapeworms, endoparasitic)
45
Turbellaria (planarians)
Primitive group, most marine, some are freshwater
-Ability to regenerate body(due to the presence of adult somatise stem cells, 30% of cells in adult worm)
-Anterior end will always develop into a head
-reproduce asexually by fission & sexually (mostly hermaphroditic)
46
Monogenea
**Mainly Ectoparasites
Do not need intermediate hosts, attach them selves to the surface of the host** (hooks and clamps)
Flukes: important ectoparasite on fish
Some species are endoparasites
47
Trematoda
-Mainly endoparasites
-Sexual reproduction in human
Flukes lay eggs in human host, egg exit and develop in water into a larva, and find a second host (snail)
-Asexual reproduction in snail, cause multi larva, can penetrate the skin and blood vessels of human
-intermediate host-shorter transitional stage
Eg. Schistosomiasis, cause diseases
48
Cestoda
Tapeworms, endoparasites
-Have special epidermis for nutrient absorption
-primary host is vertebrate and intermediate host are usually invertebrate
-scolex: suckers, hooks
-proglottids: reproductive segments
-no mouth, no digestive system
protective cuticle forms around embryos & terminal proglottids break off, passed via feces
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Lophotrochozoa
- Feeding structure called Lophophore
- A type of larva called trocophore
- Similar DNA sequences
50
Annelida
- Segmented(ringed) worms
- Body divided into segments
- Aquatic, terrestrial (moist environements)
- Coelome, used as a hydrostatic skeleton
51
Segmentation-structure and advantages
Segments are similar(similar inner organ), but each can be modified for different functions
Advantages:
1. multiple copies of important organs, structures - ex: nephridia, parapodia
2. efficient nervous control
- ganglion in each segment
- faster responses
- efficient localized movement
3. increases body size by unit repetition
4. regeneration
52
Annelid systems
1.Nervous system:
Anterior **brain**
Segmental ganglia
Ventral nerves cord: thickness varies
2.Respiratory system: skin or gills
3.excretory system: tubular nephridia (原肾)
4.digestive system: distinct regions
5.circulatory system: closed, dorsal and ventral blood, aortic arches=hearts
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Advantages of closed circulatory system
1. Improved exchange between deeper tissues and surface (O2, CO2)
2. Faster transport of nutrients and gases
3. Permits development of a thicker body (gas exchange is not happening through the body wall)
54
Annelid diversity
1. Polychaeta
2. Clitellata
- Oligochaeta — earthworms
- Hirudinea — leeches
3. Echiura & Sipuncula
unsegmented worms
55
Polychaeta
Mainly marine
detritivores, filter-feeders
crawling, burrowing, swimming, pelagic, tube-dwelling or boring forms
- More mobile forms have eyes, palms, tentacles
Parapodia (侧足): muscular flaps with setae, for **locomotion, respiration**
- Separate sexes with external fertilization(trochophore larvae-free swimming)
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Oligochaeta
- Terrestrial and few aquatic
- No parapodia
- Light sensitive cells, also can sense vibration
- Detritivores
- Hermaphroditism
—clitellum: secretes a cocoon for embryo development
- No specialized larval stage
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Hirudinea
- mainly freshwater
- ectoparasitic and carnivorous
- no setae
- anterior & posterior suckers
- hermaphroditic: clitellum, no specialized larval stage
- medicinal uses – hirudin
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Mollusca (Phylum)
- 2nd largest animal group after arthropods
- terrestrial or aquatic
- highly diverse:
morphology; modes of nutrition; reproduction; response to environment
- bilaterally symmetrical
- triploblastic
- protostomes with reduced coelom
- trochophore larvae
- variations on an ancestral molluskan
body plan
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Mollusk body plan
1. Foot: large muscle for movement and acts as hydrostatic skeleton
2. Mantle—mantle cavity, many secrets a calcium carbonate shell
3. Visceral mass: contain main internal organs, the stomach, the heart, the nephridia gonads
The coelom highly reduced, circulation is open in some group, the blood will flow into the body cavity
**radula** mouth; digestive gland; stomach; heart; anus gills; shell; mantle cavity
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Modification of the ancestral molluskan body plane
Polyplacophora
Bivalvia
Gastropoda
Cephalopoda
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Polyplacophora
- segmented shell (8 overlapping plates)
- the most primitive group of mollusks
- herbivores: radula scrapes algae & bryozoans
- Separate sexes, external fertilization
– Trochophore larva
Chitons：
- large muscular foot, hard shell
-ability to roll into a ball
- gills located in mantle grooves
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Bivalvia
- 2 hinged shells
- Reduction of head, enlargement of foot and gills
- Mantle cavity modified by **siphons**
- Filter feeders—no radula
- **dioecious or hermaphroditic**(雌雄异体or同体): broadcast spawners, external fertilization, trochophore larvae
- **siphons**: water flows back, filters for food, extensions of posterior mantle
-free living, small eyes can detect the light and movement
Eg. Scallops
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Gastropoda
- Terrestrial or aquatic
- Shelled or shell-less
- herbivores, predators, scavengers
- more complex head and eyes
- Reproduce sexually or asexually
- internal or external fertilization
- either dioecious or hermaphroditic – veliger larvae
- **torsion of body** : 180 degree rotation of visceral mass: mantle cavity, anus moved over head
- **coiling of visceral mass** 内脏团卷绕
- well developed radula
Land snails have lung, highly vascularized血管化, lay egg in the soil
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Nudibranchs
- No shell, no torsion
- Some are poisonous, other use bright color to mimic more poisonous relatives
- Generally carnivores
- Some cansue the stinging cells
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Cephalopoda characteristic
- Big brain, complex eyes
- Subdivided foot, to arms and tentacles
- Powerful radula
- Shell reduced
- Strong muscle can create strong jet for locomotion
Classified to
1. Decapodiforms (8 arms and 2 tentacles)
2. Octopodiforms (8 arms, no tentacles)
Arms are strong suckers and hooks
Predators with excellent vision
Complex behavior: visual communication through color and texture, cryptic coloration隐蔽色; inking
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Cephalopod reproduction
Separate sexes with **elaborate courtship**
Internal fertilization: males transfer sperm via specialized arm = hectocotylus
Females die after laying eggs or after eggs hatch
**no trochophore larva**
67
Cephalopod——Nautilus & Ammonites
Cephalopod:
80-90 arms
Regulate buoyancy (浮力) with gases in chambered shell (compartment间隔)
only extant shelled cephalopod
Ammonites: dominant invertebrate predator, but later extinct
68
Ecdysozoa蜕皮动物—diversity
- Nematoda (round worms)
- Tardigrada (water bears)
- Onychophora (velvet worms)
- Arthropods
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Nematoda (Round worms)
Pseudocoelomates
Triploblastic, prostostom organism
Unsegmented
Circular in cross-section
Limbless
Body protected by an elastic cuticle that is molted
Distributed in all possible habitats
Feed on detritus, bacteria, fungi; many are parasites
70
Tardigrade (water bears)
- segmented, eight short legs
- Live in marine, freshwater and semi-terrestrial (moist area)
- Feed by sucking fluids from plants and animals, some are detritivores
- **Cryptobiosis** (suspending metabolism for more than 30 years), can go without food for more than 30 years, but not extremophiles
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Onychophora
Segmented animals with lobe like appendages
Terrestrial, humid environments
Nocturnal, ambush predators
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Arthropoda
Segmented animals with jointed appendages and an exoskeleton
Reduced segmentation to specific body regions, fusion of segments(tagmosis) cause the formation of tagma
All environments
Use specialized mouth parts to consume a variety of foods
73
Characteristic features of Arthropods
1. segmented body plan
Segments are specialized and fused to form tagma
Number of segments varies
2. Jointed appendages
Bigamous or uniramous
Specialized functions
3. Highly developed sense organs
Highly cephalized
Elaborate sensory organs including statocysts, antennae, simple or compound eyes, sensitive hairs
4. Rigid exoskeleton (ecdysozoan)
Non-living, secreted by epidermis
Covers all external surfaces , digestive tract and tracheae
Composition varies(chitin, protein, cuticle, CaCO3)
74
Advantages of a rigid exoskeleton (5)
- Physical support and protection
- Place for muscle attachment
- Jointed appendages and allow faster locomotion
- Opportunity to change morphology between Laval and adult stages
- Location of pigments
75
Disadvantages of a rigid exoskeleton (4)
- inflexible and heavy
- continuous growth in size is not possible, must be periodically shed
- requires energy to form shed
- respiration through skin in most cases is not possible, need spiracles and tracheae 气管
76
Molting and metamorphosis
**Insects stop moulting as adults**
-complete metamorphosis (4 stages, often change in habitat)
-incomplete matamorphosis (3 stages)
**Crustaceans continue to molting as adults**
77
Complete metamorphosis
- egg, larvae, pupa, adult
- Abrupt changes in form
- Often major habitat changes
- Includes four stages, one of which is a resting stage (pupa)
Eg. caterpillars: herbivorous, eating, only stop when molting, interval between molting is called (instar), later become pupa, and adult
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Incomplete metamorphosis
Gradual changes in form
Three stages with no “resting” stage
Egg—nymphs—adults
Often no habitat change
Eg. Grasshoppers, crickets, termites, mites
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Regulation of molting
Wigglesworth’s experiment
-kissing bug
-molt after blood meal, can live after decapitated
Hypothesis: control substance need time to spread to the body from head
Observation: Decapitation 1 hour after blood meal didn’t molt/ 1 week after blood meal molt
Methods: link these 2 bugs with glass tube, they both molt, shows the spread of the substance triggering a molt
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Hormones
Chemical messengers
Secreted by endocrine cells
Distributed by blood, bind to target cell receptors
81
Neuroendocrine pathway
Stimulus, sensor cell detected, neural signal, CNS, Neuroendocrine signal (hormone), effector cell, response
Can be more complex to become Neuroendocrine-to endocrine pathway
82
Arthropod, moulting hormones
1. PTTH brain hormone
- produce and store in the brain
- productions influence by environmental stimulas
- control the **prothoracic gland**
2.Ecdysone
- Produced by prothoracic gland
- secreted into blood
- target cell is epidermis
- response ecdysis
3. Juvenile hormone
- high concentration of juvenile hormone will let the bug stay in larvae stage
-low concentration of juvenile hormone let molting occur under the control of ecdysone
83
Respiratory systems in Arthropods
Insects and most myriapods:
- Tubular tracheae with holes
- carry O2 to body cells
Crustaceans: gills
Chelicerates: some have tracheae and spiracles
Some have book gills or book lungs
84
Circulatory systems in Arthropods
**open systems**
- Dorsal tubular heart(1 chamber) with pores (Ostia), drives hemolymph into hemocoel spaces
-one-way valves
Advantage: require less energy for distribution
85
Musculo-skeletal systems in Arthropods
-Skeletal muscles: need a resistor to act against (eg. skeleton)
-Often found in antagonistic pairs, extensors and flexors act in opposite directions
-External skeleton
Vertebrate have internal skeleton
86
Arthropod diversity
Myriapods多足类
Chelicerates螯肢动物
Crustaceans甲壳纲
Insects
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Myriapods-countless feet
2 body regions:
- Head (with one pair of antennae, simple eyes, two jaws (lower and upper))
– Trunk (segmented)
Centipedes (chilopoda)
- 1 pair of appendages per segment
– Carnivores
Millipedes (diplopoda)
- 2 pair of appendages per segment
- detritivores, herbivores
Eg. Scutigera coleoptrata
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Chelicerates
- 2 body regions:
• cephalothorax – appendages
• abdomen – no appendages
- No jaw (mandibles) and no antennae
- Sexes are separated
- Mainly predators but some are scavenger, or parasites, herbivores
-partially digest
- 6 pairs of appendages: 1 chelicerae-connect to the venom gland, 2 pedipalps-(modified in different way)sensory organs and for locomotion, 3456-walking legs
- sea spider, debate whether is true spider, carnivore predator or scavengers
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Crustaceans
**Paraphyletic**(insect are include)
- Dominant marine, but also in freshwater & terrestrial environments
- Make up large part of zooplankton
- Head + thorax (head and thorax can fuse to cephalothorax) +abdomen
- 1 pair of mandible, 2 pairs of maxilla, 2 pairs of antennae, 3 pairs of feeding appendages on head
- separate sexes (few hermaphroditic or asexual reproduction)
Daphnia
90
Daphnia
- Freshwater cladoceran
- Zooplankton
- Important trophic link
- Phenotypic plasticity
- Model organism for toxicology and ecological genomics
- Reproduces by **cyclical parthenogenesis**
Cyclical parthenogenetic life cycle
Obligate parthenogenetic life cycle
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Copepods
Small crustaceans
Zooplankton
Important trophic link
Huge first antenna
2 sacks of fertilize
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Insects
- land and freshwater, few marine species
- 3 body regions:
1. Head with antennae, mouthparts (e.g., mandibles), compound eyes.
2. Thorax with 3 pairs of walking legs may have wings (one or two pairs)
3. Abdomen with no appendages
-sexual reproduction with separate sexes and metamorphosis
93
Unique feature to insects
1. External mouthparts
– highly diverse: herbivores, detritivores, fluid-drinkers, predators, scavengers, parasites
-top-down: labrum, mandible, maxilla, maxillary palp, labium, labial palp
2. Wings
2 nd and 3rd thoracic segment
Wings of insect and gill of a crayfish are homologous
**Homologous**/ **Analogous**
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Ecosystem & Insect
– Pollination by native insects
– Decomposers: dung burial by dung beetles
– Biological control of pests
– Food source for other mammals, birds, fish
– Dispersal agents
-Decline reason:
Insecticides
Habitats lost
Degeneration
Decline or disappear of plants and animals they interact with
Displacement by nonnative species
Pollution
Insect disease
95
Deuterostomes
- radial cleavage
- blastopore develops into anus
- mouth forms later
Phylum Echinodermata
96
Phylum Echinodermata
Similarities with other deuterostomes:
– Triploblastic
– Complete digestive tract
– Eucoelomate body cavity
– Bilateral symmetry during larval stage
Lost of a number of ancestral characters retained by other Deuterostomes:
– Segmentation
– Cephalization
– Bilateral symmetry in the adult form
Derived characters special to the Echinoderms
– **Water-vascular system**：water-filled tubes, end in tube feet, used for locomotion, feeding, excretion, gas exchange, sensation structures(chemical, tactile触觉)
– **Dermal endoskeleton**：composed of CaCO3 plates (ossicles) and spines, continuous growth (enlarge, add new), covered by thin layers of skin & muscles
– Hemal system
– Pentaradial symmetry
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Diversity of Phylum Echinodermata
- Crinoidea(sealiliesandseafeathers):
suspension feeders
- Asteroidea(seastars):
often predator, evert stomach, secrete enzymes to digest prey and then engulf partially digested prey
- Ophiuroidea(brittlestars):
Long arms connect to a central disk, many arm spines, filter-feeders, predators, detritivors
- Holothuroidea(seacucumbers):
Mainly detritivores, scavengers, filter-feeders, reduced endoskeleton, 5 rows of tube feet
- Echinoidea(sea urchins an sand dollars):
• Endoskeleton formed of distinct fused plates, retain the pentaradial symmetry
• Spines (some venomous)-locomotion and defense
• Have a structure called Aristotle’s lantern for scraping algae off of rocks
98
Phylum Chordata
- Cephalochordata-lancelets
- Tunicata(Urochordata)-tunicates
- Vertebrata(Craniata)-vertebrates
Developed notochord
