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

Paleozoic Mesozoic Cenozoic

Cam

bria

n

Ord

ovic

ian

Silu

rian

Dev

onia

n

Car

boni

fero

us

Per

mia

n

Tria

ssic

Jura

ssic

Cre

tace

ous

Tern

ary

Qua

tern

ary

265144206245290363409439510543

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

Cam

bria

n

Ord

ovic

ian

Silu

rian

Dev

onia

n

Car

boni

fero

us

Per

mia

n

Tria

ssic

Jura

ssic

Cre

tace

ous

Tern

ary

Qua

tern

ary

265144206245290363409439510543

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