Animals, Part I Invertebrates
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Transcript of Animals, Part I Invertebrates
Animals, Part IAnimals, Part IInvertebratesInvertebrates
• Introduction to Animals (Chapter 34)• Sponges and Jellyfish (Chapter 35)• Simple Worms (Chapter 36)• Mollusks and Annelids (Chapter 37)• Arthropods (except Insects) (Chapter 38)• Insects (Chapter 39)• Echinoderms (Chapter 40)
Animal Features• Animals are:
– Eukaryotic• Their cells have proper nuclei, but no cell walls
– Multicellular• Most animals have differentiated, specialized
tissues.– Heterotrophic
• They must get nutrition from other organisms– Most are herbivores (eat plants) or carnivores (eat meat)– But a few are parasites (consume living hosts) or
symbiotic (live in mutually beneficial relationship)
In addition, most animals are mobile (they can move around, at least during some part of their life) and very responsive (most have a nervous system). Animals range in size from tiny (about a millimetre) to huge (a blue whale is over 30m long)
Kingdom Animalia
• Part 1. The invertebrate animals
The Lower Invertebrates
• Phylum Porifera, the Sponges• Phylum Cnidaria, the Jellyfish and corals• Phylum Ctenophora, the comb jellies• Phylum Platyhelminthes, the flat-worms• Phylum Rotifera, the rotifers• Phylum Nematoda, the round-worms
Evolution of Invertebrates
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Protists
Sponges
Jellyfish
Annelids and Arthropods
Echinoderms
Sponges
• Sponges look plant-like, but they are in fact animals.
• Adult sponges are sessile, that is, they attach to rocks and don’t move around.
• Sponges feed by filtering food out of the sea water.
Jellyfish and RelativesJellyfish and Relatives
Phylum CnidariaPhylum CnidariaPhylum CtenophoraPhylum Ctenophora
Jellyfish, Hydra and Coral (Phylum Cnidaria)
• Cnidaria can have two basic body shapes, the “polyp shape” and the “medusa shape”
• The two shapes are similar, with tentacles, a mouth opening, an epidermis and a jelly-like mesoglea.
• In the “polyp” shape, the tentacles open upwards,
• In the “medusa” shape the tentacles hang downwards.
• Jellyfish are medusa, hydra, coral & sea anemone are polyp
Nematocysts (ouch!)
• Jellyfish have stinging cells called nematocysts on their tentacles. These can kill or paralyze small prey, allowing the slow-moving jellyfish to consume them.
• The Portuguese-man-of-war is a colonial relative of the jellyfish. It can be quite deadly
Comb Jellies (Phylum Ctenophora)
• A more distant relative of the jellyfish is the elusive comb jelly.
• Comb jellies lack stinging cells.
• Some display bioluminescence – the ability to glow in the dark
Flatworms, Rotifers and Flatworms, Rotifers and RoundwormsRoundworms
Phylum PlatyhelminthesPhylum PlatyhelminthesPhylum RotiferaPhylum Rotifera
Phylum NematodaPhylum Nematoda
PlatyhelminthesThe Flat Worms
• Flatworms include harmless free-living organisms like the planarian
• There are also parasitic flatworms, like tapeworms (cestodes) and flukes (trematodes)
Rotifers
• Rotifers are microscopic and near-microscopic animals. They may be spherical or worm-like
NematodesThe “Roundworms”
• Nematodes are cylindrical worms, usually pointed at each end.
• They range in size from microscopic to about a meter long.
• They include both free-living and parasitic varieties, with the parasitic ones being larger.
A microscopic roundworm
Ascaris, a parasitic intestinal roundworm
Warning: close your eyes if you are squeamish!
Child infested with ascaris roundworms. It is unusual to see them on the mouth & nose. Usually they come out the other end!
Roundworms & Disease
• Nematodes cause several diseases– Trichinosis: a disease of the muscles and
nerves caused by microscopic worms from uncooked meat (especially pork)
– Hookworms: intestinal parasite (cause bleeding)– Pinworms: intestinal parasite (cause itching)– Skin conditions: (worms enter cracks in feet)
– Heartworms: (common in dogs, can kill)
Trichina worm in Muscle
Pinworms are very common. It is estimated that between 30 and 80 percent of children in North America have been infected by pinworms at some point.
The Higher Invertebrate Phyla
• Phylum Mollusca, the mollusks– Clams, oysters, snails, slugs, octopus, squid
• Phylum Annelida, the segmented worms– Earthworms, seaworms, leeches
• Phylum Arthropoda “arthropods” The joint-legged invertebrates.– Crustaceans, insects, arachnids
• Phylum Echinodermata, the echinoderms– Starfish, sand-dollars, sea urchins, sea cucumbers
MollusksMollusks
Phylum MolluskaPhylum Molluska
Mollusks
• There are three main types of mollusk– Bivalves (clams, oysters, scallops etc) have
two shells surrounding the soft mollusk inside– Gastropods (snails, sea-snails, slugs) often
have a spiral shell and crawl on a belly-foot– Cephalopods (octopus, squid, cuttlefish,
nautilus) have multiple tentacles attached to their “head”. Cuttlefish have an internal shell or “bone” and nautilus have a spiral, chambered shell.
Bivalve means
“two shells”
Gastropod means
“belly-foot”
Cephalopod
means head-foot
Mollusks- Class 1: Bivalves
• Most bivalves are filter-feeders
Mollusks, Class 2: Gastropods
snail
slug Sea snail
Gastropods crawl on their bellies. They scrape up food with a tongue-like organ called a radula.Most gastropods have two small eyes at the end of tentacle-like stalks above their “heads”Slugs lack shells, but most gastropods have spiral shells with torsion. Sea snails include many species, such as whelks and conchs.
Radula
Eyes
Mollusks, class 3: Cephalopods
• Cephalopods include octopus, squid, cuttlefish and nautilus
• Most cephalopods are carnivorous predators with tentacles or “arms”
octopus squid cuttlefish nautilus
Cephalopods in Action
Parts of a Squid
Differences in cephalopodsCephalopod type
Shell type if present
Tentacles*(arms + tentacles)
Tentacle features
Fun Facts
Squid None 10 (8+2) Suckers and hooks
Colossal squid are the largest invertebrates
Octopus None 8 (8+0) Suckers Secrete “ink” to escape predators
Cuttlefish Internal “cuttlebone”
10 (8+2) No suckers The most intelligent invertebrates. Chameleons of the sea.
Nautilus Spiralchambered
Up to 90(≈90 + 0)
No suckers Most of its shell is empty chambers used for buoyancy
* The term tentacle is used here for all tentacle-like limbs. In fact, the smaller limbs of the squid are properly called “arms”, and only the longer ones are “tentacles”.
The Colossal Squid
For over 100 years, scientists had suspected that there were some really large squid lurking in the deep oceans.
Jules Verne wrote a fictional account of such a creature in his 1870 novel “20000 Leagues Under the Sea”
In 2003 a complete specimen of a young squid was found (shown on table above)
In 2007 one weighing over 1000 lb was captured near Antarctica (upper left)
Largest Invertebrate Ever?
Possible length of adult?
Convergent EvolutionMollusks and vertebrates have evolved separately for nearly a billion years, so they have no close common ancestors. Nevertheless, some features of cephalopods are remarkably similar to features found in some vertebrates. This is a case of convergent or parallel evolution.
octopus eye
Cat’s eye
octopus beak
Parrot beak
Convergent Evolution
cuttlefish camouflage
chameleon camouflage
• 1. Define a mollusk• 2. List the three types of mollusk, and give
an example of each.• 3. What is the largest known mollusk?• 4. What is convergent evolution?• 5. Give three examples of convergent
evolution features that appear in mollusks, and state what other organism they are convergent to.
AnnelidsAnnelids
Phylum AnnelidaPhylum Annelida
Annelids: the Segmented Worms
• Examples– Earthworms– Sandworms– Leeches
Geological Timescale (Arthropods)
Paleozoic Mesozoic Cenozoic
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AnnelidAncestor(Worm)
Crustaceans (Shrimp, Lobsters, Crabs etc.)
Trilobites
Chelicerates
Sea ScorpionsHorseshoe Crabs
Arachnids (spiders, scorpions, mites, ticks)
Uniramia
Sea spiders
Myriapods (Millipedes & Centipedes)
Insects
Extinct
Extinct
Giant EarthwormThe Largest Annelid
Facts about annelids• Annelids are called “segmented worms” because
their bodies appear to be made of about a hundred similar segments stuck tightly together.
• Most annelids are hermaphrodites, they have both male and female sex organs, but they must still mate with different worms.
• Earthworms have no real heart, but they have five pairs of “aortic arches” that pump blood
• Annelids have “setae” that extend from their body like tiny legs. Earthworms’ are hair-like and retractable, but sandworms have paddle-like setae.
That’s why some people (inaccurately)say that worms have
Five hearts
ArthropodsArthropods
Phylum ArthropodaPhylum Arthropoda
Arthropods
• Joint-legged invertebrates– Trilobites (extinct)– Crustaceans– Insects– Arachnids)– Centipdes &
Millipedes• See phylogenetic
tree (p. 745)
Arthropod Features
Segmented body
Jointed legsventral nerve
Tough exoskeleton
• All arthropods have…– An exoskeleton (external skeleton containing
a tough carbohydrate compound called chitin)– Jointed appendages (legs and/or claws)– Segmented body design– Ventral nerve cord (their main nerve goes
down their belly side instead of their back side)
• Most (but not all) arthropods also have these features…– Compound eyes
• Eyes containing hundreds of individual lenses
– Moulting • As the arthropod grows is must shed
its old exoskeleton several times.
Arthropods, Subphylum 1: Trilobites
• Trilobites were ocean-dwelling arthropods of the Palaeozoic era.
• Trilobites are all extinct. They are found only as fossils
Trilobite fossil Artist’s conception of trilobite
Arthropods Subphylum 2: Crustaceans
• Most crustaceans are aquatic:– crabs*, lobsters, crayfish, barnacles and
shrimp.
• Two types of crustaceans are terrestrial, and are often mistaken for insects.– Sow-bug, pill-bug
*except the horseshoe crab, which is more closely related to the arachnids
Sow bug pill bug
Body Parts in a CrustaceanThe body is divided into two main
regionsa) The cephalothorax ( a fused
head & thorax protected by a tough “shell” or carapace)
b) The abdomen (segmented tail area)
Most crustaceans are decapods (meaning 10 legs). They have four pairs of walking legs and one pair of claws (chelipeds).
In addition to their main legs, they have several other appendages
• Antennae and antennules• Swimmerets• Maxilla and maxillipeds• A telson (tail-piece) and
uropods (tail)
Internal Anatomy of a CrustaceanThe heart of a crustacean is on its dorsal (back) side, and its largest blood vessel runs along its back.
It has a complete digestive system, with a two-part stomach, a digestive gland and an intestine.
Its largest nerve runs along its ventral (belly) side, from the brain to the tail, with several nerve bundles or ganglia along it.
Respiration is through gills under the carapace.
Arthropods Subphylum 3: Chelicerates
• Chelicerates include:– Sea scorpions (extinct but huge)– Horseshoe crabs– Sea spiders– Arachnids
(arachnids are the onlygroup we will examine indetail.)
ArachnidsPhylum Arthropoda, Subphylum Chelicerata, Class Arachnida
• Arachnids include spiders, scorpions, ticks and mites.
• Most arachnids have four pairs of walking legs (“eight-legged freaks”), but may also have additional appendages…– Scorpions have a pair of chelicerae (claws)– Spiders & scorpions have pedipalps near their
mouth.
Arachnid Facts
The world’s largest spider is the Goliath “bird-eater” tarantula… over 30 cm (one foot!) long with 5 cm fangs.
Eriophyid mites are among the smallest of all arthropods, measuring only 125 to 250 μm in length
The most venomous spider in the world is the Brazilian wandering spider
Arthropods, Subphylum 4: Uniramia*
• Uniramia include:– Myriapods (centipedes and millipedes)
– Insects (over 750 000 species of them!)
*in older classification systems, Mandibulata is sometimes used instead of Uniramia
Myriapods: centipedes & millipedesCentipede
Millipede
Ok, they don’t really have exactly 100 or exactly 1000 legs.
‘nuff said.
Insects, the hexapodsPhylum Arthropoda, Subphylum Uniramia*, Class Insecta
• Insects are the most widespread of all invertebrates.
• Insects exist in nearly every climate, and there are over 750 000 species (that’s ¾ of a million different types of insect!)
Insect Features• Insects have the features of arthropods,
plus– Three pairs of walking legs (6 legs total)– Three distinct body divisions
• Head (front end of body)• Thorax (“chest”or central region of body)• Abdomen (back end of body) (In a few insects, eg. Grasshopper, the head and
thorax are partially fused into a “cephalothorax”)
Some insects also feature:– Metamorphosis (complete or incomplete) – One or two pairs of wings in the adult stage.
Metamorphosis• Metamorphosis is a major change in body
form as an organism matures• Metamorphosis is found in several types of
animal, but most notably in:– Insects– Amphibians
• The younger life stage is usually called the larva, the older life stage is the adult.– Some forms of metamorphosis have
additional stages, such as nymph or pupa.
Types of Metamorphosis
• Incomplete metamorphosis:– The body change is usually minor, such as
the growing of wings or a slight change in body shape. Eg. Grasshopper
– When metamorphosis is incomplete, the term nymph is often used instead of larva.
• Complete metamorphosis:– The body change is major, and the adult
appears completely different from the young organism.
Incomplete metamorphosis of Grasshopper
Complete Metamorphosis
Adult
Egg
Pupa
3rd InstarLarva
1st InstarLarva
2nd InstarLarva
A Few of the Many Orders of Insect
• Coleoptera: beetles, ladybugs
• Diptera: flies, mosquitoes
• Orthoptera: Grasshoppers, crickets
• Lepidoptera: butterflies, moths
• Hymenoptera: bees, wasps, ants
“Float like a LepidopteraSting like a Hymenoptera”
Insect Systems• Respiratory system
– Insects have no lungs. They have holes called spiracles on the sides of their abdomen. The spiracles lead air into a system of tubes called tracheae. Their blood does not carry oxygen (no hemoglobin)
• Digestive system:– Contains crop and gizzard (foregut); the stomach with
several caeca or storage sacs (midgut); and the intestine with rectum and anus (hindgut)
• Excretory system:– Insects do not have kidneys as such. Instead they
have a cluster of tubes called Malpighian tubules that gather liquid wastes into the intestine.
spiracle
The myth of giant insects…• If an ant were the size
of a human, it could lift 2000 pounds over its head
• Giant radioactive insects terrorize Nevada towns.
• Cockroaches could survive nuclear wars
MYTHMYTH
BustedBusted
MOVIE MYTH
MOVIE MYTH
BustedBusted
PlausiblePlausible
If an ant were the size of a human
It couldn’t even liftits own body weight
due to the “square-cube”law. Strength increases
as the square of size,but weight increases
as the cube of size
The Truth• Insects and other arthropods have very heavy
exoskeletons. Increasing the size of an insect would increase its exoskeleton to the point where it would be difficult to lift.
• Insects also have a primitive respiratory system. Without proper lungs large insects have a difficult time getting oxygen.– Fact: Much larger (but not truly gigantic) insects existed
in the paleozoic era (200 million years ago) when there was more oxygen in the atmosphere.
Titaneus giganteus Palaeozoic DragonflyToday’s largest insect 300 million years ago
(a model, not the real thing)
EchinodermsEchinoderms
Starfish and their relativesStarfish and their relatives
Phylum EchinodermataThe Echinoderms
• Echinoderms include:– Starfish
– Sea Urchins
– Sand dollars
– Sea cucumbers
– Sea lilies
Echinoderm Features• All Echinoderms are aquatic• Echinoderms are deuterostomes
– This means their digestive system develops from both ends, no just from the mouth end.
– It also means that they are more closely related to vertebrates than their appearance would suggest.
• Echinoderms have radial symmetry.– Rather than more common bilateral symmetry.– Most have five lines of symmetry (pentaradial)
but a rare few have up to two dozen*.
*see page 784 bottom right
Five lines of symmetry
Echinoderm Movement
• Echinoderms have a “water vascular” system that pumps water through “canals” in their bodies
• The water vascular system also operates many tiny “tube-feet” underneath the body to allow the echinoderm to crawl along the bottom.
Structure of a StarfishDigestive system in pale greenWater vascular system in pale orangeReproductive system in purple
ChordatesChordates
Phylum CordataPhylum CordataThe vertebrates and their relativesThe vertebrates and their relatives
Non-vertebrate Chordates
• Phylum Chordata includes all organisms with a dorsal nerve chord and with a “notochord” at some stage of life.
• A notochord is a tough, flexible rod that protects the nerve.
• Most chordates are vertebrates, that is they develop a backbone around their notochord, but… – Lancelets (eg. Amphioxus) keep their notochord for life
and never develop a true backbone.– Tunicates (Sea squirts) lose their notochord and never
develop a backbone
Dorsal means running along the
backside, as opposed to the belly side
Amphioxus sp. (a lancelet)
Photograph of a lancelet
Diagram of a lancelet
Tunicates (sea squirts)
Sea squirt diagram
A whole colony of sea squirts
End of the Invertebrates
Now its time to develop some
Backbone, like the rest of the chordates