Invertebrate Animals

What Characteristics Define the Animal

Kingdom?• Eukaryotic Cells -

Heterotrophs• Multicellular - Cells lack

cell walls

Invertebrate or Vertebrate?

• Inverts have no backbones – can be microscopic to very

large – 95% of animals are inverts

• Vertebrates have a backbone– 5% of animals– Birds, reptiles, fishes,

amphibians, mammals

What are some animals that are invertebrates?

• Worms • Mollusks• Insects • Crustaceans• Arachnids• Jellyfish • Sponges• Starfish

Probable Animal Ancestor

Protists – any organism that is not a plant, an animal, a fungus or a prokaryote

Classification

• Protists are a very diverse groups of organisms

• Different groups of Protists evolved independently from archaebacteria

• Protists are generally classified by the way they obtain food. There are three main categories of Protists

• Animal-like (Protozoa)• Plant-like (Algae)• Fungus-like

Animal-Like Protists (Protozoans)

• Classified by their method of movement.

• There are four phyla of Protozoans• Zooflagellates• Sarcodines• Ciliates• Sporozoans

Zooflagellates

• Animal-like Protists

• Use Flagella to move

• Absorb food through their cell membrane

• Live in lakes, streams, and inside other organisms

• Form the basis of many food chains

• Asexual reproduction by means of binary fission

• Ex. Giardia- water borne protozoa that causes severe intestinal distress

–Trichonympha –helps termites digest wood

Sarcodines

• Animal-like• Use pseudopods for feeding

and movement• Asexual reproduction by

means of binary fission• Ex. Amoeba

Ciliates• Use Cilia for feeding

and movement

• Cilia- short hairlike projections

• Found in lakes, streams, and oceans

• Use self-defense mechanisms known as a trichocyst

• Reproduce by binary fission and conjugation

• Ex. Paramecium

Sporozoans• Do not move on their own

• Considered parasites

• Complex life cycle, involve more than one host

• Reproduce by sporozoites– Attach to host,

penetrate it, and live within it

• Ex. Pneumocystis carinii. – causes pneumonia in AIDS patients– Plasmodium vivax –

causes malaria

Cambrian Explosion- a period in time where the first known representatives of most

animal phyla evolved

•600 million years ago•Great increase in diversity•Better fossil record•More skeletons /symmetry•No backbones

Burgess Shale- a priceless record of soft-bodied Cambrian marine organisms- one of very few sites in the world where specimens like this are preserved.

Fossil Formation- Works better with shells & bones

Evolutionary Trends

- Trends are towards typically increasing complexity

- Example – Sponge → Worms → Arthropods → etc

What Makes an Animal Complex?

• Cell specialization• Symmetry: radial or bi-lateral• Cephalization• Segmentation• Coelom: acoelomate,

pseudocoelomate, coelomate• Homeostasis (endotherm or

ectotherm)

Symmetry

Radial Bilateral

Coelom Development

Acoelomate

Pseudocoelomate

Coelomate

Porifera (Sponges)

Exs. – Bath Sponge and Glass Sponge

• Multicellularity• First Animals• Division of labor• No movement• Filter feeding• No symmetry

Water Flow

Cnidarians• Ex. - Jellyfish &

Coral• Tissue

development• Radial symmetry• Carnivorous• Some movement

Platyhelminthes (Flatworms)

Ex. – Planarian

• Organ development

• Bilateral symmetry• Movement• Cephalization

(brain up front)

• Acoelomate(no body

cavity)

Nematodes (Roundworms)

Ex. - Heartworm & Ascaris

• Psuedocoelom (false cavity)

• Digestive systems with 2 openings (mouth & anus)

• Mostly parasitic

Dog Heartworm

Ascaris

African Eye Worm

(Loa Loa)

Annelids (Segmented Worms)

Ex. - Earthworm & Leech

• Coelom (body cavity)• Segmentation• Closed circulatory

system• Hydrostatic skeleton

(water)• True digestive system

MollusksEx. - Clams, Snails,

Squid

• Shells (in most)• Mantel• Foot• Visceral Mass

Mollusk Anatomy

ArthropodsEx. – Spiders,

Insects & Crustaceans

• Jointed appendages

• Exoskeleton• Segmented Body• Most successful

EchinodermsEx. - Starfish, Sea

UrchinSand Dollar & Sea

Cucumber

• Pentaradial Symmetry• Spiny skin• Internal skeleton• Water Vascular

System

Water Vascular System

Biological Processes of Invertebrates

(Things that must be done to keep them

alive)

Feeding/Digestion

•Function - Obtain energy & Nutrients

•Examples:–Filter feeding (sponges)–Parasitism (roundworm)–Predation (octopus)

Respiration

•Function - release energy from food, but needs

oxygen•Examples -

Moist Skin (worm)Gills (clam)Trachea/Book Lungs

(spider)

Moist Moist SkinSkin

GillsGills

Trachea/Book Lungs Trachea/Book Lungs

Circulation

•Function - distribute nutrients

& gases (O2 & CO2)

•Examples:–Diffusion (flatworm)–Open System (arthropod)–Closed System (octopus)

Diffusion

Open System

Closed System

Sensory / Response

•Function - Sense the environment

•Example:–Eyespot (flatworm)–Cephalization (“flatworm up”)•Brain (earthworm)

Eyespot (Ocelli)

Auricles

Sensory / Response

Cephalization

Movement/Support

•Function – Form body/ Give shape

•Examples: – No skeleton/ Hydrostatic

(earthworm)

– Exoskeleton (insect)– Endoskeleton (vertebrate)

Hydrostatic Skeleton

Exoskeleton

Endoskeleton

Reproduction

•Function - Continuation

of the species•Examples:

–Asexual - 1 parent (sponges)

–Sexual - 2 parents

Asexual Reproductio

n

Sexual ReproductionSexual Reproduction

Early Development: (page 661)

• Animals that reproduce sexually begin life as a zygote.

• Through mitosis, the zygote undergoes a series of divisions to form a blastula.

• A blastula is just a hollow ball of cells that changes shape.

• As it changes shape a single opening forms called a blastopore.

• The blastopore leads into a central tube that runs the length of the developing embryo.

• This tube becomes the digestive tract and can form in one of two ways:

1.) a protosome - an animal whose mouth develops from the blastopore; most invertebrates

• 2.) a deuterosome - an animal whose anus is formed from the blastopore.

• This includes echinoderms and all vertebrates

During early development, the cells of most animal embryos differentiate into 3 layers.

The 3 germ layers are:

• Endoderm - innermost layer that develops into the linings of the digestive tract and respiratory system

• Mesoderm - middle layer that develops into the muscles, circulatory, reproductive, and excretory system

• Ectoderm - outermost layer, develops into sense organs, nerves, and outer layer of skin

Germ Layers