Chapter 26: Animals the Invertebrates

Chapter 26: Animals – The Invertebrates

General Characteristics of Animals  Multicelled  In most cases cells form tissues that become arranged as organs and organ systems  Body cells of nearly all species have diploid chromosome number  Heterotrophs  Require oxygen for aerobic respiration  Reproduce sexually and asexually  Most animals are motile during at least part of their life cycle  Stages of embryonic development  Embryonic cells give rise to primary tissue layers ectoderm, endoderm, and mesoderm

Diversity in Body Plans  Vertebrates – animals with backbone  Invertebrates – no backbone  Animals are radial or bilateral  Radial Symmetry – body parts arranged regularly around a central axis  Bilateral Symmetry – right and left halves are mirror images of each other.  Gut – a tubular or saclike region in the body in which food is digested then absorbed.  Saclike guts - have one opening (mouth) for taking in food and expelling wastes  Tubelike guts - have 2 openings (mouth and anus) a complete digestive system  Body cavity – between gut and body wall  Coelom – unique tissue lining called peritoneum  This lining also encloses organs and helps hold them in place (diaphragm)  Some invertebrates don’t have a body cavity and tissues fill this region  Pseudocoel (false coelom) – a body cavity with no peritoneum  Segmented animals have a repeating series of body units  They may or may not be similar to one another

Puzzles About Origins  Animals originated between 1.2 billion and 670 million years ago  Probably evolved from protistans Sponges – Success in Simplicity  Sponges (Porifera) – animals with no symmetry tissues or organs  Most live in marine  Body of a sponge is not symmetrical  Made of spongin - a protein and the sharp glasslike spicules are made of calcium carbonate or silica  Water flows into the sponge body through microscopic pores and chambers  Collar cells – line inner body and beat flagella to move water through. Food particles get trapped in microvilli  Reproduce sexually  Release sperm into water  Some reproduce asexually  Fragmentation – small fragments break away from the parent

Cnidarians – Tissues Emerge  Cnidarians – tentacled, radial animals  Most live in seas  Nematocysts – capsules that house dischargeable tubular, threads  Some deliver toxins  Some deliver a sticky ooze to entangle prey  Body Plans  Medusae  Float  Look like bells or upside-down saucers  Mouth centered under bell  May have extensions to help with feeding and capture prey  Polyps  Tubelike body with a tentacle-fringed mouth at one end  Other end attached to substrate  Epithelium – a tissue having a free surface that faces the environment  Nerve cells – in epithelium and these cells receive signals to detect changes in surroundings  Contractile cells – carry out response by shortening  Hydrostatic Skeleton – any fluid-filled cavity or cell mass against which contractile cells can act.

Various Stages in Cnidarian Life Cycles  Some species, Obelia, Physalia, etc, include both polyp and medusa body forms  Medusa is the sexual stage  Has gonads – primary reproductive organs  Releases gametes by rupturing (lysis)  Planulas – a zygote that is a swimming or creeping larva  Forms into a polyp

Comb Jellies  Radial symmetry  Weak – swimming predators in plankton communities  Eight rows of comblike structures made of thick fused cilia  Do not produce nematocysts

Acoelomate Animals – And The Simplest Organ Systems  When we move beyond cnidarians in our survey, we find animals that range from flatworms to humans. All of these animals have simple or complex organs  Organ – an association of one or more kinds of tissues arranged in particular proportions and patterns  Organ System – two or more organs that are interacting efficiently in the performance of some task

Flatworms (Platyhelminthes)  Turbellarians, flukes, tapeworms  Bilateral  Simple organ systems in a flattened body  Saclike gut  Most are hermaphrodites – have female and male gonads  Has a penis so two flatworms can reproduce sexually by exchanging sperm  Tubellarians  Live in seas, planarians live in freshwater  Eat tiny animals or suck tissues from dead or wounded ones  A planarian can divide in half and regenerate missing parts  Reproduce asexually by transverse fission  Flukes  Parasitic worms  Life cycle has sexual and asexual phases  One to four hosts  Tapeworms  Parasitize intestines of vertebrates  Scolex – attach to intestine wall and has suckers, hooks or both  Ribbon Worms  Bilateral  Soft-bodied elongated predators  Swallow or suck tissue fluids from small worms mollusks and crustaceans  Shallow marine habitats

Roundworms (Nematoda)  Pseudocoelomate worms  Thrive in nearly all environments  Most abundant animals alive  20,000 known species  bilateral  cuticles – a tough, flexible body covering  simplest animal with a complete digestive system  parasitic species can severely damage their hosts, humans, cats, dogs, cows, sheep, soybeans  help decompose and recycle nutrients

Rotifers (Rotifera)  bilateral  false coelom  most live in freshwater  eat bacteria and microscopic algae  have a pharynx, esophagus, digestive glands, stomach, intestine, anus  a crown of cilia at the head end  two “toes”

Two Major Divergences  Protostomes  Spiral cleavage  First infolding forms mouth  Archenteron – is an internal cavity that the tissues split at sides to form coelum  Ex. Mollusks, annelids, arthropods  Deuterostome  Radial cleavage  First infolding forms anus  Archenteron – an internal cavity that the outpouching forms coelum  Ex. Echinoderms, chordates A Sampling of Molluscan Diversity  Have fleshy soft bodies  Bilateral  Have a small coelom  Most have a shell  Mantle –  Most mollusks have a fleshy foot  Chitons – slow moving with dorsal shell divided into eight plates  Bivalves – two shells, clams, oysters, mussels  Cephalopods – squids, octopus  Octopuses have a highly developed nervous system with a large complex brain

Twisting and Detwisting of Soft Bodies  Soft snail body  Its anus dumps wastes near the mouth  As the gastropod embryo develops a cavity between its mantle and shell twists  Torsion – twisting of internal organs

Hiding Out One Way or Another  A shell is an advantage against predators  Dig into sand to hide

On the Cephalopod Need For Speed  Cephalopods lost their thick external shell and became streamlined and active  Nerves connect their brain to muscles that respond swiftly to food or danger  Jet Propulsion – force a jet of water from mantle cavity and a funnel-shaped siphon

Annelids – Segments Galore  Bilateral and segmented  Phylum name means “ringed forms”  Setae – bristles on each side of segments  Provide traction to move through dirt  Earthworms (oligochaetes) have few setae  Leeches have no setae

Advantages of Segmentation  Individual parts can undergo modification and become highly adapted for specific tasks

Annelid Adaptations – A Case Study  Earthworms  Partitions divide their body into a series of coelomic chambers  Gut extends through all chambers  Has a cuticle but it is permeable to water as well as to gases (have to live in moist habitats)  Scavengers  Aerate soil and lift nutrients to surface

Arthropod  Trilobites (extinct)  Chelicerates – spiders  Crustaceans – barnacles and crabs  Uniramians – centipedes, millipedes, insects  Arthropod means jointed foot

Adaptations of Insects and Other Arthropods  Hardened exoskeleton  Cuticle of chitin, proteins, surface waxes and calcium carbonate  Exoskeleton – protective external skeleton  Defense against predation  Waxy surface restricts water evaporation  Molting – periodic shedding of body structures that are too small, worn out or both  Jointed Appendages  Cuticle is thinner at joints for motility  Led to appendages as diverse as wings, antennae and legs  Fused and Modified Segments  Many fused together segments are modified to perform more specialized functions  Different segments fused to form 3 regions – head, thorax and abdomen  Respiratory Structures  Aquatic arthropods depend on gills  Insect tracheas begin as pores on the body surface and branch into tubes that deliver oxygen directly to tissues  Specialized Sensory Structures  Many species have a wide angle of vision and can process visual information from many directions

Division of Labor  Many species divide the job of surviving and reproducing among different stages of development  Juvenile – a miniaturized version of the adult  Metamorphosis – body form changes from embryo to adult  Adult stage specializes in dispersal and reproduction

A Look At Spiders and Their Kin  Chelicerates originated in shallow seas  Marine species – mites, sea spiders, horseshoe crab  Land species – spiders, scorpions, ticks, chigger mites (arachnids)  Spiders and scorpions are predators  Bites of ticks can transmit disease  Mites are free-living scavengers  Arachnids have segments fused into forebody and hindbody  Forebody – 4 pairs of legs, 1 pair pedipalps (sensory), 1 pair of chelicerae that inflict wounds and discharge venom  Hindbody – spin silk threads  Open circulatory system – a heart that pumps blood into body tissues

A Look At The Crustaceans  Shrimp, lobsters, crabs, barnacles, pillbugs  Have an exoskeleton  Majority live in marine habitats  Many have 16 – 20 segments  2 pairs of antennae  1 pair of jawlike appendages (mandibles)  molt repeatedly How Many Legs  millipedes  have about 100 legs  each segment has 2 pairs of legs  scavenge decaying plants  centipedes  have 15-177 pairs of legs  each segment has 1 pair of legs  fast-moving aggressive predators outfitted with fangs and venom glands  prey on insects earthworms snails

A Look At Insect Diversity  have a head, thorax, and abdomen  3 pairs of legs  2 pairs of wings usually  most successful insects are…  small in size  great reproductive capacity  are winged  life cycle proceeds through stages that allows for exploitation of different resources  nymphs – small versions of the adult  larvae – maggots specialized for eating  pupa (cocoon) – an enclosure  metamorphosis – a dramatic change in body form  our most aggressive competitors, they destroy crops, wool, paper, etc.

The Puzzling Echinoderms  feather star, sea urchin, sea cucumber, brittle stars, sea biscuits, sand dollars  coelomate deuterostomes  usually have a complete digestive tract  adults are radial symmetry  body wall bears a number of spines, plates made of calcium carbonate  have no brain  water-vascular system – system of canals that delivers water throughout the body. By redistributing water they can move Chapter 26: Animals – The Invertebrates

General Characteristics of Animals

 In most cases cells form tissues that become arranged as organs and organ systems

 Body cells of nearly all species have ______chromosome number

 Require oxygen for aerobic respiration

 Most animals are motile during at least part of their life cycle

 Embryonic cells give rise to primary tissue layers ectoderm, endoderm, and mesoderm

Diversity in Body Plans

 Vertebrates –

 Invertebrates –

 Animals are radial or bilateral

 Radial Symmetry –

 Bilateral Symmetry –  Gut – a tubular or saclike region in the body in which food is digested then absorbed.

 Saclike guts –

 Tubelike guts –

 Body cavity –

 Coelom –

 This lining also encloses organs and helps hold them in place (diaphragm)

 Some invertebrates don’t have a body cavity and tissues fill this region

 Pseudocoel (false coelom) –

 Segmented animals have a repeating series of body units

 They may or may not be similar to one another

Puzzles About Origins

 Animals originated between 1.2 billion and 670 million years ago

 Probably evolved from ______

Sponges – Success in Simplicity

 Sponges (Porifera) –

 Body of a sponge is not ______ Made of spongin –

 Water flows into the sponge body through microscopic pores and chambers

 Collar cells –

 Reproduce sexually

 Some reproduce asexually

 Fragmentation –

Cnidarians – Tissues Emerge

 Cnidarians –

 Most live in ______

 Nematocysts –

 Some deliver ______

 Some deliver a sticky ooze to entangle prey

 Body Plans

 Medusae

 Look like bells or upside-down saucers

 May have extensions to help with feeding and capture prey  Polyps

 Other end attached to substrate

 Epithelium –

 Nerve cells –

 Contractile cells –

 Hydrostatic Skeleton –

Various Stages in Cnidarian Life Cycles

 Some species, Obelia, Physalia, etc, include both polyp and medusa body forms

 Medusa is the sexual stage

 Has gonads –

 Releases gametes by rupturing (lysis)

 Planulas –

 Forms into a polyp Comb Jellies

 ______symmetry

 Weak –

 Eight rows of comblike structures made of thick fused cilia

 Do not produce ______

Acoelomate Animals – And The Simplest Organ Systems

 When we move beyond cnidarians in our survey, we find animals that range from flatworms to humans. All of these animals have simple or complex organs

 Organ –

 Organ System –

Flatworms (Platyhelminthes)

 Turbellarians, flukes, tapeworms

 Simple organ systems in a flattened body

 Most are hermaphrodites –

 Has a penis so two flatworms can reproduce sexually by exchanging sperm

 Tubellarians

 Live in ______, planarians live in ______ Eat tiny animals or suck tissues from dead or wounded ones

 A planarian can divide in half and ______missing parts

 Reproduce asexually by transverse fission

 Flukes

 Life cycle has sexual and asexual phases

 Tapeworms

 Scolex –

 Ribbon Worms

 Soft-bodied elongated predators

 Swallow or suck tissue fluids from small worms mollusks and crustaceans

Roundworms (Nematoda)

 Thrive in nearly all environments

 Most abundant animals alive

 ______known species 

 Cuticles –

 Simplest animal with a ______digestive system

 Parasitic species can severely damage their hosts, humans, cats, dogs, cows, sheep, soybeans

Rotifers (Rotifera)

 Most live in ______

 Eat bacteria and microscopic algae

 Have a pharynx, esophagus, digestive glands, stomach, intestine, anus

 A crown of ______at the head end

Two Major Divergences

 Protostomes

 First infolding forms ______

 Archenteron –

 Ex.  Deuterostome

 First infolding forms ______

 Archenteron – an internal cavity that the outpouching forms coelum

 Ex.

A Sampling of Molluscan Diversity

 Have fleshy soft bodies

 Have a small ______

 Mantle –

 Most mollusks have a ______

 Chitons –

 Bivalves –

 Cephalopods –

 Octopuses have a highly developed nervous system with a large complex brain Twisting and Detwisting of Soft Bodies

 Soft snail body

 As the gastropod embryo develops a cavity between its mantle and shell twists

 Torsion –

Hiding Out One Way or Another

 A shell is an advantage against predators

 Dig into sand to hide

On the Cephalopod Need For Speed

 Cephalopods lost their thick external shell and became streamlined and active

 Nerves connect their brain to muscles that respond swiftly to food or danger

 Jet Propulsion –

Annelids – Segments Galore

 Phylum name means ______

 Setae –

 Provide traction to move through dirt

 ______(oligochaetes) have few setae

 ______have no setae Advantages of Segmentation

 Individual parts can undergo modification and become highly adapted for specific tasks

Annelid Adaptations – A Case Study

 Earthworms

 Partitions divide their body into a series of ______chambers

 Gut extends through all chambers

 Has a cuticle but it is permeable to water as well as to gases (have to live in moist habitats)

Arthropod

 Trilobites (extinct)

 Chelicerates –

 Crustaceans –

 Uniramians –

 Arthropod means ______Adaptations of Insects and Other Arthropods

 Hardened exoskeleton

 Cuticle of ______, proteins, surface waxes and calcium carbonate

 Exoskeleton –

 Defense against predation

 Waxy surface restricts water evaporation

 Molting –

 Jointed Appendages

 Cuticle is thinner at joints for motility

 Led to appendages as diverse as ______, ______and ______

 Fused and Modified Segments

 Many fused together segments are modified to perform more specialized functions

 Different segments fused to form 3 regions – head, thorax and abdomen

 Respiratory Structures

 Aquatic arthropods depend on ______

 Insect tracheas begin as pores on the body surface and branch into tubes that deliver oxygen directly to tissues

 Specialized Sensory Structures

 Many species have a wide angle of ______and can process visual information from many directions Division of Labor

 Many species divide the job of surviving and reproducing among different stages of development

 Juvenile –

 Metamorphosis –

 Adult stage specializes in dispersal and reproduction

A Look At Spiders and Their Kin

 Chelicerates originated in shallow seas

 Marine species –

 Land species –

 Spiders and scorpions are ______

 Bites of ticks can transmit disease

 Mites are free-living scavengers

 Arachnids have segments fused into ______and ______

 Forebody – 4 pairs of legs, 1 pair pedipalps (sensory), 1 pair of chelicerae that inflict wounds and discharge venom

 Hindbody –

 Open circulatory system –

A Look At The Crustaceans

 Have an ______

 Majority live in marine habitats  Many have 16 – 20 segments

 2 pairs of ______

 1 pair of jawlike appendages (mandibles)

How Many Legs

 Millipedes

 Each segment has _____ pairs of legs

 Scavenge decaying plants

 Centipedes

 Each segment has _____ pair of legs

 Fast-moving aggressive predators outfitted with fangs and venom glands

 Prey on insects earthworms snails

A Look At Insect Diversity

 Have a head, thorax, and abdomen

 _____ pairs of legs

 _____ pairs of wings usually  Most successful insects are…

 Life cycle proceeds through stages that allows for exploitation of different resources

 Nymphs –

 Larvae –

 Pupa (cocoon) –

 Metamorphosis – a dramatic change in body form

 Our most aggressive competitors, they destroy crops, wool, paper, etc.

The Puzzling Echinoderms

 Feather star, sea urchin, sea cucumber, brittle stars, sea biscuits, sand dollars

 Usually have a ______digestive tract

 Adults are ______symmetry

 Body wall bears a number of spines, plates made of calcium carbonate

 Water-vascular system –