Title: Invertebrates
1Chapter 33
2Lets meet the Invertebrates
3Life Without a Backbone
- Invertebrates
- Are animals that lack a backbone
- Account for 95 of known animal species
Xmas Tree Worm
4A review of animal phylogeny
5Invertebrate diversity
6Invertebrate Diversity
7Invertebrate Diversity
8Sponges (Phylum Porifera)
- Sponge characteristics
- Sessile
- Porous body
- Choanocytes flagellated collar cells generate a
water current through the sponge and ingest
suspended food by phagocytosis - Live in both fresh and marine waters
- Lack true tissues (groups of similar cells that
form a functional unit). All animals except
sponges belong to the clade Eumetazoa, the
animals with true tissues - Most sponges are hermaphrodites (each individual
functions as both male and female)
9Sponges
- Sponges are suspension feeders
- Capturing food particles suspended in the water
that passes through their body
10Cnidarians (Phylum Cnidaria)
- A diverse range of both sessile and floating
organisms including hydras, jellies, sea
anemones, and corals - Cnidarian characteristics
- radial symmetry
- gastrovascular cavity (digestive compartment)
- Cnidocytes
movie
11Cnidarian Body Plan
- Relatively simple diploblastic (two germ layers),
radial body plan - Basic body plan of a cnidarian is a sac with a
central digestive compartment, the gastrovascular
cavity - A single opening functions as both mouth and anus
- There are two variations on this body plan
- The sessile polyp and the floating medusa
12Cnidarian Feeding
- Cnidarians are carnivores
- That use tentacles to capture prey
- The tentacles are armed with cnidocytes
- Unique cells that function in defense and the
capture of prey
Threads can inject poison into the prey, or stick
to or entangle the target
13Classes of Phylum Cnidaria
14Hydrozoan Life Cycle
The zygote develops into a solid ciliated
larva called a planula.
The planula eventually settles and develops
into a new polyp.
5
6
15Classes Hydrozoa, Scyphozoa, Cubozoa, and
Anthozoa
16Cnidarian Classes
- In the class Hydrozoa
- Most hydrozoans alternate between polyp and
medusa forms. Freshwater Hydras exist only in the
polyp form. - In the class Scyphozoa
- Jellies (medusae) are the prevalent form of the
life cycle - In the class Cubozoa, which includes box jellies
and sea wasps - The medusa is box-shaped and has complex eyes
- Class Anthozoa includes the corals and sea
anemones - Which occur only as polyps
Hydra
Purple coral
17Hydra movie 1
18Hydra movie 2
19Coral reproduction
20Jellyfish movie
21Bilateria
- Most animals have bilateral symmetry
- The vast majority of animal species belong to the
clade Bilateria - Which consists of animals with bilateral symmetry
and triploblastic development
22Flatworms
- Members of phylum Platyhelminthes
- Live in marine, freshwater, and damp terrestrial
habitats. Some are parasitic. - Are flattened dorsoventrally and have bilateral
symmetry - Undergo triploblastic development
- Are acoelomates (lack a coelom) with
gastrovascular cavities. - Lack a digestive system entirely and absorb
nutrients across their body surface.
23Flatworm Classes
24Turbellarians
- Are nearly all free-living and mostly marine
25Turbellarians
- Planarians are common examples of turbellarians
- They have light-sensitive eyespots and
centralized nerve nets
26Monogeneans and Trematodes
- Live as parasites in or on other animals They
parasitize a wide range of hosts - Most monogeneans are parasites of fish
- Trematodes (Flukes) that parasitize humans spend
part of their lives in snail hosts
27Tapeworms (Class Cestoda)
- Are also parasitic and lack a digestive system
28Rotifers (Phylum Rotifera)
- Are tiny animals that inhabit fresh water, the
ocean, and damp soil - Rotifers are smaller than many protists
- But are truly multicellular and have specialized
organ systems - Rotifers have an alimentary canal
- A digestive tube with a separate mouth and anus
that lies within a fluid-filled pseudocoelom - Some species of rotifers reproduce by
parthenogenesis - In which females produce more females from
unfertilized eggs
29Rotifers (Phylum Rotifera)
30Rotifer movie 2
31Three Phyla of Lophophorates Ectoprocts,
Phoronids, and Brachiopods
- Lophophorates have a lophophore
- A horseshoe-shaped, suspension-feeding organ
bearing ciliated tentacles that trap suspended
food particles
32Ectoprocts
- Are colonial animals that superficially resemble
plants
33Phoronids
- Are tube-dwelling marine worms ranging from 1 mm
to 50 cm in length
34Brachipods
- Superficially resemble clams and other
hinge-shelled molluscs - But the two halves of the shell are dorsal and
ventral rather than lateral, as in clams
35Nemerteans (Phylum Nemertea)
- Commonly called proboscis worms or ribbon worms
- The nemerteans unique proboscis
- Is used for defense and prey capture
- Is extended by a fluid-filled sac
- Nemerteans also have a closed circulatory system
- In which the blood is contained in vessels
distinct from fluid in the body cavity
36Molluscs (Phylum Mollusca)
- Phylum Mollusca Includes snails and slugs,
oysters and clams, and octopuses and squids - Mollusc characteristics
- Body plan muscular foot, visceral mass, and a
mantle - Mantle is a fold of tissue that drapes over the
visceral mass and secretes the shell. - Most molluscs are marine, though some inhabit
fresh water and some are terrestrial - Molluscs are soft-bodied animals, but most are
protected by a hard shell - Most molluscs have separate sexes with gonads
located in the visceral mass - The life cycle of many molluscs includes a
ciliated larval stage called a trochophore
37Mollusc anatomy
38Classes of molluscs
39Chitons
- Class Polyplacophora is composed of the chitons
(Oval-shaped marine animals encased in an armor
of eight dorsal plates)
40Gastropods
- About three-quarters of all living species of
molluscs belong to class Gastropoda
41Gastropods
- Gastropod characteristics
- Most are marine, but there are also many
freshwater and terrestrial species - Possess a single, spiraled shell
- Slugs lack a shell or have a reduced shell
- The most distinctive characteristic of this class
is a developmental process known as torsion,
which causes the animals anus and mantle to end
up above its head
42Bivalves (Molluscs of class Bivalvia)
- Include many species of clams, oysters, mussels,
and scallops - Have a shell divided into two halves
43Bivalves
- The mantle cavity of a bivalve contains gills
that are used for feeding as well as gas exchange
44Clam locomotion
45Cephalopods
- Class Cephalopoda includes squids and octopuses
- Carnivores with beak-like jaws surrounded by
tentacles of their modified foot
46Octopus
- Most octopuses creep along the sea floor in
search of prey
47Squid
- Squids use their siphon to fire a jet of water,
which allows them to swim very quickly
48- One small group of shelled cephalopods
- The nautiluses, survives today
49Annelids
- Annelids
- Segmented worms
- Have bodies composed of a series of fused rings
- 3 Classes Oligochaeta, Polychaeta, Hirudinea
50Classes of Annelida
51Oligochaetes
- Oligochaetes (class Oligochaeta)
- Are named for their relatively sparse chaetae
(bristles made of chitin) - Include the earthworms and a variety of aquatic
species - Earthworms eat their way through the soil,
extracting nutrients as the soil moves through
the alimentary canal - Which helps till the earth, making earthworms
valuable to farmers
52Earthworm anatomy
53Polychaetes
- Members of class Polychaeta possess paddlelike
parapodia that function as gills and aid in
locomotion
54Leeches
- Members of class Hirudinea are blood-sucking
parasites, such as leeches
55Nematodes (roundworms)
- Nematodes are nonsegmented pseudocoelomates
covered by a tough cuticle - Among the most widespread of all animals,
nematodes, or roundworms - Are found in most aquatic habitats, in the soil,
in moist tissues of plants, and in the body
fluids and tissues of animals
56Nematode movie
57Nematodes
- The cylindrical bodies of nematodes are covered
by a tough coat called a cuticle
58Nematodes
- Some species of nematodes are important parasites
of plants and animals
Trichinella spiralis encysted in human muscle
tissue
59Arthropods
- Arthropods are segmented coelomates that have an
exoskeleton and jointed appendages - Two out of every three known species of animals
are arthropods - Members of the phylum Arthropoda
- Are found in nearly all habitats of the biosphere
60Arthropod Characteristics
- The diversity and success of arthropods
- Are largely related to their segmentation, hard
exoskeleton, and jointed appendages - Arthropods have an open circulatory system
- In which fluid called hemolymph is circulated
into the spaces surrounding the tissues and
organs - A variety of organs specialized for gas exchange
have evolved in arthropods - The body of an arthropod is completely covered by
the cuticle, an exoskeleton made of chitin - When an arthropod grows it molts its exoskeleton
in a process called ecdysis
61Segmentation
- Early arthropods, such as trilobites showed
little variation from segment to segment - As arthropods evolved the segments fused, and the
appendages became more specialized - The appendages of some living arthropods are
modified for many different functions
62Subphyla of Arthropoda
63Cheliceriforms
- Named for clawlike feeding appendages called
chelicerae - Includes spiders, ticks, mites, scorpions, and
horseshoe crabs - Most of the marine cheliceriforms are extinct
- But some species survive today, including the
horseshoe crabs
64Cheliceriforms
- Most modern cheliceriforms are arachnids
- A group that includes spiders, scorpions, ticks,
and mites
65Arachnids
- Arachnids have an abdomen and a cephalothorax
- Which has six pairs of appendages, the most
anterior of which are the chelicerae. (4 pairs of
walking legs)
66Myriapods
- Subphylum Myriapoda
- Includes millipedes and centipedes
- Millipedes, class Diplopoda
- Have a large number of legs
- Each trunk segment has two pairs of legs
- Centipedes, class Chilopoda
- Are carnivores with jaw-like mandibles
- Have one pair of legs per trunk segment
67Insects
- Subphylum Hexapoda, insects and their relatives
- Are more species-rich than all other forms of
life combined - Live in almost every terrestrial habitat and in
fresh water - The internal anatomy of an insect includes
several complex organ systems
68Insect anatomy
69Insects
- Flight is one key to the great success of insects
- An animal that can fly can escape predators, find
food, and disperse to new habitats much faster
than organisms that can only crawl
70Metamorphosis
- Many insects undergo metamorphosis during their
development - In incomplete metamorphosis, the young, called
nymphs - Resemble adults but are smaller and go through a
series of molts until they reach full
size (example grasshoppers) - Insects with complete metamorphosis have larval
stages specialized for eating and growing that
are known by such names as maggot, grub, or
caterpillar - The larval stage looks entirely different from
the adult stage - Metamorphosis from the larval stage to the adult
stage occurs during a pupal stage
71Metamorphosis
movie
7226 Orders of Insects
7326 Orders of Insects
74Crustaceans
- While arachnids and insects thrive on land
- Crustaceans, for the most part, have remained in
marine and freshwater environments - Crustaceans, subphylum Crustacea
- Typically have biramous (branched) appendages
that are extensively specialized for feeding and
locomotion
75Decapods
- Decapods are all relatively large crustaceans
- And include lobsters, crabs, crayfish, and shrimp
76Decapod movie
77Planktonic crustaceans
- Planktonic crustaceans include many species of
copepods - Which are among the most numerous of all animals
78Barnacles
- Barnacles are a group of mostly sessile
crustaceans whose cuticle is hardened into a shell
79Deuterostomes
- Echinoderms and chordates are deuterostomes
- Chordates and echinoderms share the
characteristics of deuterostomes - Radial cleavage
- Formation of the mouth at the end of the embryo
opposite the blastopore
80Echinoderms
- Echinoderm characteristics
- Sea stars and most other echinoderms are
slow-moving or sessile marine animals - A thin, bumpy or spiny skin covers an
endoskeleton of hard calcareous plates - Unique to echinoderms is a water vascular system
- network of hydraulic canals branching into tube
feet that function in locomotion, feeding, and
gas exchange
81Echinoderm movie
82Echinoderm anatomy
83Echinoderm classes
84Sea Stars
- Sea stars, class Asteroidea
- Have multiple arms radiating from a central disk
- The undersurfaces of the arms bear tube feet,
each of which can act like a suction disk
85Brittle Stars
- Brittle stars have a distinct central disk and
long, flexible arms
86Sea Urchins and Sand Dollars
- Sea urchins and sand dollars have no arms, but
they do have five rows of tube feet that function
in movement
Sand Dollar
87Sea Lilies and Feather Stars
- Sea lilies live attached to the substrate by a
stalk - Feather stars
- Crawl about using their long, flexible arms
88Sea Cucumbers
- Sea cucumbers do not look much like other
echinoderms - They lack spines, and their endoskeleton is much
reduced
89Sea Daisies
- Sea daisies were discovered in 1986
- And only two species are known
90Chordates (Phylum Chordata)
- Chordates
- Two subphyla of invertebrates as well as the
hagfishes and the vertebrates - Share many features of embryonic development with
echinoderms
91Review of Animal Phyla