Chapter 33 Invertebrates.

Chapter 33 Invertebrates

Overview: Life Without a Backbone Invertebrates
Kingdom Animalia Overview: Life Without a Backbone Invertebrates Are animals that lack a backbone Account for 95% of known animal species Figure 33.1

Animal phylogeny Figure 33.2 Ancestral colonial choanoflagellate
Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata Figure 33.2

Porifera Sponges are sessile and have a porous body and choanocytes (Collar cells) Sponges, phylum Porifera

Porifera · Asymmetrical · Sessile · Filter (Suspension) Feeders
· 5000 salt water species 150 fresh water spp · No tissues, organs, or organ systems · Reproduce sexually (Most are hermaphrodites) or asexually (Budding/Fragmentation) · Believed to have evolved from protists

Sponges are suspension feeders
Porifera Sponges are suspension feeders Capturing food particles suspended in the water that passes through their body Azure vase sponge (Callyspongia plicifera) Osculum Spicules Water flow Flagellum Collar Food particles in mucus Choanocyte Phagocytosis of food particles Amoebocyte Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes. Spongocoel. Water passing through porocytes enters a cavity called the spongocoel. Porocytes. Water enters the epidermis through channels formed by porocytes, doughnut-shaped cells that span the body wall. Epidermis. The outer layer consists of tightly packed epidermal cells. Mesohyl. The wall of this simple sponge consists of two layers of cells separated by a gelatinous matrix, the mesohyl (“middle matter”). The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes. Amoebocyte. Amoebocytes transport nutrients to other cells of the sponge body and also produce materials for skeletal fibers (spicules). 5 6 7 4 3 2 1 Figure 33.4

Choanocytes, flagellated collar cells
Porifera Choanocytes, flagellated collar cells Generate a water current through the sponge and ingest suspended food

Cnidaria Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes All animals except sponges Belong to the clade Eumetazoa, the animals with true tissues Phylum Cnidaria Is one of the oldest groups in this clade

Cnidaria Radial Symmetry (Diploblastic) Made of only 2 layers of cells
(Outer layer for protection, inner layer for digestion) 9000 species e.g. jellyfish, coral, sea anemones, hydra Have two forms (Sessile polyp and mobile medusa) Has a simple nerve net…1st organized nervous tissue in animals Reproduce sexually and asexually (budding) 1st predators 1st digestive cells (Gastrovascular cavity)

The 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
Cnidaria There are two variations on this body plan The sessile polyp and the floating medusa Mouth/anus Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Body stalk Medusa Polyp Figure 33.5

Cnidaria 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 Tentacle “Trigger” Nematocyst Coiled thread Discharge Of thread Cnidocyte Prey Figure 33.6

Cnidaria classes Table 33.1

Cnidaria Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa Figure 33.7a–d
(a) These colonial polyps are members of class Hydrozoa. (b) Many species of jellies (class Scyphozoa), including the species pictured here, are bioluminescent. The largest scyphozoans have tentacles more than 100 m long dangling from a bell-shaped body up to 2 m in diameter. (c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison, which can subdue fish and other large prey, is more potent than cobra venom. (d) Sea anemones and other members of class Anthozoa exist only as polyps. Figure 33.7a–d

Hydra Anemone Hydra Coral

Most animals have bilateral symmetry
Bilateria 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

Protostome vs Deuterostome Differentiation

Spiral vs Radial Cleavage

Members of phylum Platyhelminthes
Flatworms Members of phylum Platyhelminthes Live in marine, freshwater, and damp terrestrial habitats Are flattened dorsoventrally and have a gastrovascular cavity Although flatworms undergo triploblastic development They are acoelomates

Flatworms Bilateral symmetry Phylum Platyhelminthes
species e.g. Tapeworms, flukes, planaria 1st animal with nerve cord 1st animal with defined head (planaria) 1st animal with a pharynx (throat) Have only one opening to the body (pharynx) Planarians can regenerate (cut in half and each half will regenerate) Reproduce sexually (most are hermaphroditic) or asexually (regeneration)

Flatworms are divided into four classes
Table 33.2

Turbellarian Turbellarians
Are nearly all free-living and mostly marine Figure 33.9

The best-known turbellarians, commonly called planarians
Have light-sensitive eyespots and centralized nerve nets Pharynx. The mouth is at the tip of a muscular pharynx that extends from the animal’s ventral side. Digestive juices are spilled onto prey, and the pharynx sucks small pieces of food into the gastrovascular cavity, where digestion continues. Digestion is completed within the cells lining the gastrovascular cavity, which has three branches, each with fine subbranches that provide an extensive surface area. Undigested wastes are egested through the mouth. Ganglia. Located at the anterior end of the worm, near the main sources of sensory input, is a pair of ganglia, dense clusters of nerve cells. Ventral nerve cords. From the ganglia, a pair of ventral nerve cords runs the length of the body. Gastrovascular cavity Eyespots Figure 33.10

Trematodes that parasitize humans
Flukes Trematodes that parasitize humans Spend part of their lives in snail hosts

Tapeworm Tapeworms Scolex parasitic lack a digestive system
Proglottids with reproductive structures 200 µm Hooks Sucker Scolex Figure 33.12

Rotifers are smaller than many protists
But are truly multi-cellular and have specialized organ systems 0.1 mm Figure 33.13 1st alimentary canal Separate mouth & anus

Rotifers Rotifers have an alimentary canal
A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom Rotifers reproduce by parthenogenesis In which females produce more females from unfertilized eggs

Members of phylum Nemertea
Nemerteans Members of phylum Nemertea Are commonly called proboscis worms or ribbon worms Figure 33.15

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 Have no heart

Mollusca Molluscs have a muscular foot, a visceral mass, and a mantle
Phylum Mollusca Includes snails and slugs, oysters and clams, and octopuses and squids 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

Phylum Mollusca Bilateral symmetry
3 classes (Gastropoda, Bivalvia, Cephalopoda) Gastropods (Stomach footed) e.g. Periwinkles, slugs, snails, & conches Bivalves (Two shells) e.g. Clams, oysters, and scallops have two shells connected by a ligament Cephalopods (Head footed) e.g. Octopi, Squid Coelomates Have digestive tract with mouth and anus · 1st animals with simple brain and paired complex eyes · 1st open circulatory system with 2 or 3 chambered heart · Respiration through gills · Excretion of metabolic wastes through nephridia Reproduce sexually (Many are hermaphroditic)

Molluscs All molluscs have a similar body plan with three main parts
A muscular foot A visceral mass A mantle- Membrane surrounding internal organs

Mollusc Anatomy Heart. Most molluscs have an open circulatory
Visceral mass Mantle Foot Coelom Intestine Gonads cavity Anus Gill Nerve cords Esophagus Stomach Shell Radula Mouth Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph. Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces). The organs of the mollusc are thus continually bathed in hemolymph. The long digestive tract is coiled in the visceral mass. Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward- curved teeth slides back and forth, scraping and scooping like a backhoe. The nervous system consists of a nerve ring around the esophagus, from which nerve cords extend. Figure 33.16

Most molluscs have separate sexes
Mollusca 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

4 Classes of Mollusca Table 33.3

Class Polyplacophora is composed of the chitons
Oval-shaped marine animals encased in an armor of eight dorsal plates Figure 33.17

About three-quarters of all living species of molluscs
Gastropods About three-quarters of all living species of molluscs Belong to class Gastropoda A land snail (a) A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution. (b) Figure 33.18a, b

Gastropods Most Slugs lack a shell
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

Gastropods The most distinctive characteristic of this class
Is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head Anus Mantle cavity Stomach Intestine Mouth Figure 33.19

Molluscs of class Bivalvia
Bivalves Molluscs of class Bivalvia Include many species of clams, oysters, mussels, and scallops Have a shell divided into two halves Figure 33.20

Bivalves The mantle cavity of a bivalve
Contains gills that are used for feeding as well as gas exchange Hinge area Gut Coelom Heart Adductor muscle Anus Excurrent siphon Water flow Incurrent Gill Mantle cavity Foot Palp Mouth Shell Figure 33.21

Cephalopods Class Cephalopoda includes squids and octopuses
Carnivores with beak-like jaws surrounded by tentacles of their modified foot

Cephalopods Most octopuses Creep along the sea floor in search of prey
Figure 33.22a (a) Octopuses are considered among the most intelligent invertebrates.

Squids use their siphon
Cephalopods Squids use their siphon To fire a jet of water, which allows them to swim very quickly Figure 33.22b (b) Squids are speedy carnivores with beaklike jaws and well-developed eyes.

One small group of shelled cephalopods
` One small group of shelled cephalopods The nautiluses, survives today Figure 33.22c (c) Chambered nautiluses are the only living cephalopods with an external shell.

Annelids Are segmented worms Annelids
Have bodies composed of a series of fused rings

Phylum Annelida Bilateral symmetry & Coelomates
species e.g. Earthworm, leeches Digestive tube with mouth and anus 1st gizzard (Used to grind food) 1st developed central nervous system (Ventral nerve cord connects brain to EACH segment) Closed circulatory system Have chaetae (setae) for locomotion Have nephridia to eliminate metabolic waste Reproduce sexually (most are hermaphroditic) Segmentation is important in the evolution of specialized body tissues

The phylum Annelida is divided into 3 classes
Table 33.4

Oligochaetes (class Oligochaeta)
Are named for their relatively sparse chaetae, or bristles made of chitin Include the earthworms and a variety of aquatic species

Annelida 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

Members of class Polychaeta
Polychaetes Members of class Polychaeta Possess paddlelike parapodia that function as gills and aid in locomotion Parapodia Figure 33.24

Members of class Hirudinea
Leeches Members of class Hirudinea Are blood-sucking parasites, such as leeches Figure 33.25

Are nonsegmented pseudocoelomates covered by a tough cuticle
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

Phylum Nematoda Bilateral symmetry 12 000 species
1st tubular digestive system 1st animal with 2 body openings (mouth & anus) Pseudocoelomates Ascaris – found in soil. Eggs enter human children’s mouth, develop in the intestines, enter the bloodstream and travel to the lungs. Adults are coughed up and swallowed.

Ascaris

· Pinworms – Most common roundworm infection in the U. S
· Pinworms – Most common roundworm infection in the U.S. Eggs are ingested (usually by children) and develop in the intestines. Adult females exit child’s anus while child sleeps. Symptoms of infection are an itchy anus · Trichinella – Found in undercooked pork Trichinella or wild game

· Hookworm – common in warm climates
· Hookworm – common in warm climates. Found in contaminated soil and enters the body through the feet when people walk barefooted.

The cylindrical bodies of nematodes (phylum Nematoda)
Are covered by a tough coat called a cuticle 25 µm Figure 33.26

Two out of every three known species of animals are arthropods
Arthropoda 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

General Characteristics of Arthropods
The diversity and success of arthropods Are largely related to their segmentation, hard exoskeleton, and jointed appendages

Early arthropods, such as trilobites
Showed little variation from segment to segment Figure 33.28

· 1st animal with jointed appendages · All have an exoskeleton
· Bilateral symmetry · Coelomates · All are segmented · 1st animal with jointed appendages · All have an exoskeleton · Exoskeleton pros: External protection, support for muscle attachment · Exoskeleton cons: They are heavy, limit movement, can’t grow, limits size of organism, arthropod must molt [Ecdysis] (New exoskeleton is soft and does not protect against predators) Have 3 fused body segments (Head, thorax, and abdomen) Have complete digestive system including specialized mandibles (Jaws) Have open circulatory system with a heart Use spiracles and tracheal tubes for respiration

Antennae are used to detect motion, sound, and to smell (Pheromones)
· · Use malpighian tubules for excretion of metabolic wastes · Nervous system includes brain, nerve cord, simple or compound eyes, and antennae. Simple eyes have one lens, compound eyes have many lenses. Antennae are used to detect motion, sound, and to smell (Pheromones) Reproduction is sexual (Two types of development: Metamorphosis and Incomplete metamorphosis) Metamorphosis includes 4 stages (Egg  Larva  Pupa  Adult) · Incomplete metamorphosis includes 3 stages (Egg  Nymph  Adult) · Evolved from annelids Classes of arthropods include: Arachnida (Spiders, mites, ticks, & scorpions), Crustacea (Crabs, lobsters, shrimp, crayfish, & barnacles), and Insecta

Arthropods As arthropods evolved
The segments fused, and the appendages became more specialized The appendages of some living arthropods Are modified for many different functions Antennae (sensory reception) Head Thorax Swimming appendages Walking legs Mouthparts (feeding) Pincer (defense) Abdomen Cephalothorax Figure 33.29

The body of an arthropod
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

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

Molecular evidence now suggests
That living arthropods consist of four major lineages that diverged early in the evolution of the phylum Table 33.5

Cheliceriforms, subphylum Cheliceriformes
Are named for clawlike feeding appendages called chelicerae Include spiders, ticks, mites, scorpions, and horseshoe crabs

Cheliceriformes Most of the marine cheliceriforms are extinct
But some species survive today, including the horseshoe crabs Figure 33.30

Most modern cheliceriforms are arachnids
Cheliceriformes Most modern cheliceriforms are arachnids A group that includes spiders, scorpions, ticks, and mites Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger. (a) Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM). (b) Web-building spiders are generally most active during the daytime. (c) 50 µm Figure 33.31a–c

Arachnids Arachnids have an abdomen and a cephalothorax
Which has six pairs of appendages, the most anterior of which are the chelicerae Digestive gland Intestine Heart Stomach Brain Eyes Poison Pedipalp Chelicera Book lung Sperm receptacle Gonopore (exit for eggs) Silk gland Spinnerets Anus Ovary Figure 33.32

Myriapods Subphylum Myriapoda Includes millipedes and centipedes

Millipedes, class Diplopoda
Myriapods Millipedes, class Diplopoda Have a large number of legs Each trunk segment Has two pairs of legs Figure 33.33

Centipedes, class Chilopoda
Myriapods Centipedes, class Chilopoda Are carnivores with jaw-like mandibles Have one pair of legs per trunk segment Figure 33.34

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

Flight is obviously 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

Insect Development 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

Insect Development 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 Larva (caterpillar) (a) (b) Pupa (c) Pupa (d) Emerging adult (e) Adult Figure 33.6a–e

While arachnids and insects thrive on land
Crustaceans 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

Decapods are all relatively large crustaceans
And include lobsters, crabs, crayfish, and shrimp Ghost crabs (genus Ocypode) live on sandy ocean beaches worldwide. Primarily nocturnal, they take shelter in burrows during the day. (a) Figure 33.38a

Planktonic crustaceans include many species of copepods
Which are among the most numerous of all animals Planktonic crustaceans known as krill are consumed in vast quantities by whales. (b) Figure 33.38b

Barnacles are a group of mostly sessile crustaceans
Whose cuticle is hardened into a shell The jointed appendages projecting from the shells of these barnacles capture organisms and organic particles suspended in the water. (c) Figure 33.38c

Echinoderms Echinoderms and chordates are deuterostomes

Characteristics of deuterostomes
Radial cleavage Development of the coelom from the archenteron Formation of the mouth at the end of the embryo opposite the blastopore

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

Echinoderms Unique to echinoderms is a water vascular system
A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange Stomach Anus Ring canal Gonads Ampulla Podium Radial nerve Tube feet Spine Gills A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk. The surface of a sea star is covered by spines that help defend against predators, as well as by small gills that provide gas exchange. Madreporite. Water can flow in or out of the water vascular system into the surrounding water through the madreporite. Branching from each radial canal are hundreds of hollow, muscular tube feet filled with fluid. Each tube foot consists of a bulb-like ampulla and suckered podium (foot portion). When the ampulla squeezes, it forces water into the podium and makes it expand. The podium then contacts the substrate. When the muscles in the wall of the podium contract, they force water back into the ampulla, making the podium shorten and bend. Radial canal. The water vascular system consists of a ring canal in the central disk and five radial canals, each running in a groove down the entire length of an arm. Digestive glands secrete digestive juices and aid in the absorption and storage of nutrients. Central disk. The central disk has a nerve ring and nerve cords radiating from the ring into the arms. Figure 33.39

The radial anatomy of many echinoderms
Evolved secondarily from the bilateral symmetry of ancestors

(a) A sea star (class Asteroidea)
Sea 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 (a) A sea star (class Asteroidea) Figure 33.40a

A brittle star (class Ophiuroidea)
Brittle Stars Brittle stars have a distinct central disk And long, flexible arms A brittle star (class Ophiuroidea)

Sea 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 (c) A sea urchin (class Echinoidea) Figure 33.40c

(e) A sea cucumber (class Holothuroidea)
Sea Cucumbers Sea cucumbers Upon first inspection do not look much like other echinoderms Lack spines, and their endoskeleton is much reduced (e) A sea cucumber (class Holothuroidea) Figure 33.40e

Chordates Chordates Phylum Chordata
Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates Shares many features of embryonic development with echinoderms

A summary of animal phyla
Table 33.7

Chapter 33 Invertebrates.

Similar presentations

Presentation on theme: "Chapter 33 Invertebrates."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Chapter 33 Invertebrates.

Similar presentations

Presentation on theme: "Chapter 33 Invertebrates."— Presentation transcript:

Similar presentations

About project

Feedback