Invertebrates

- Two sides of the body mirror each other

- There is no line of symmetry

- Symmetry is found all around the center point

Bilateral

3 Main Body Plans

Invertebrate

1. Bilateral

- Organism without a backbone

Radial

3. Asymmetrical

2. Radial

Asymmetrical

- Space surrounding the gut

- Can have other organs within

Ganglion

- All animals except sponges have nerves

Gut - A pouch used to break down food

- Concentrated mass of nerve cells

Coelom

- Nerves allow animal to sense environment

Invertebrate Characteristics

- Live in water

Regeneration

- Simplest invertebrates

- Asymmetrical

- Can regenerate broken or missing parts

- Ability to grow back a body part

Sponges

Pores -Holes on the outside of body-Water brings in food and oxygen

Osculum -Hole on top of sponge that allows water to leave

- Swims through waterMedusa

- Ex: Jellyfish, Anemones

- Two body forms: Medusa or Polyp

- Usually attach to a surface

- Radial symmetry

Cnidarians

Polyp

-complex tissue and a gut

-simple nerve cells

-stinging cells

Classes of Cnidarians

Hydrozoans -common cnidarians-live in both fresh and salt water-most spend lives as polyps

Jellyfish -use tentacles to catch food-spend most of lives as medusas

Sea anemones -brightly colored-spend lives as polyps

Coral -polyps-brightly colored-made of calcium carbonate-live in colonies-build reefs

- Many are parasites Trichinella spiralis

- Some infect humans pinworms and hookworms

- decomposers

- Simple nervous system

- Brain is a ring of ganglia

- Bilateral symmetry

Round Worms

- Cannot see through eyespots, but sense light

- Clearly defined head

- Two large eyespots

Planarian

- Bilateral symmetry

Flatworms

- Some can be parasitic

- 3 main type

-Live in freshwater-predators-well developed nervous system

Flukes -parasites-no eyespots-contain suckers and hooks to attach to other animals

Tapeworm -parasites-no gut or eyespots-attach to the intestines of other animalsAbsorb nutrients-can infect humans

Mollusks and Annelid Worms

Mollusks-Most live in the ocean-some live in freshwater and land

-complex ganglia

-contain a circulatory system

-Bodies are made of :

-Muscular foot-used for movement

-Visceral mass- contains gut, gills, and other organs

-Mantle-covering used for protection if no shell

-Shell-hard covering used for protection

Gastropods -slugs and snails

-eat by using a radula tongue with curved teeth

3 Classes of Mollusks

Bivalves - 2 shells

-clams and other shellfish-use gills to filter food from water

Cephalopods -Octopus and squid-use tentacles to get food and a powerful jaw to eat it

-contain large brain connected to ganglia

Annelid Worms

-segmented worms

-bodies are in segments identical repeating body parts-bilateral symmetry

-circulatory system

-Complex nervous system with brain-Live in salt water, freshwater or on land

-3 major groups

Earthworms -most common-decomposers

-leave casting in soil produce rich soil

Use stiff hairs or bristles to move

Marine Worms -Colorful-Live in ocean

-Polychaetes covered in bristles

-Eat mollusks or filter water for food

Leeches -Parasites that suck blood produces a chemical that thins blood can be used medically

-Scavengers that eat dead animals

Arthropods and Echinoderms

4. Compound Eyes

3. External Skeleton (Exoskeleton)

Exoskeleton

Four Characteristics Shared by Arthropods

1. Segmented and specialized body

2. Jointed limbs

- Several identical light-sensitive unitsCompound Eye

- Body parts bend at joints

- Hard covering of the body

- Feelers that sense touch, taste, and smellAntennae

Ex: Shrimp, Crab, Lobster

- Have compound eyes

Mandible

Crustaceans

- Have gills, antennae, and mandibles

- Mouthparts that can pierce objects

- Simple eyes

- 4 pairs of legs

Arachnids

- 2 body parts: Cephalothorax and Abdomen

-spiders, scorpions, mites, ticks

- 3 main body parts

- Six legs

Insects

- Largest group of arthropods

1. Head

2. Thorax

3. Abdomen

Metamorphosis

- Grows from smaller youth to larger adult

Complete Metamorphosis

- Change from young to adult

- Organism goes through a complete change

- No major changes in organismIncomplete Metamorphosis

- Internal bones and cartilage

- Means “spiny skinned”

Endoskeleton

Echinoderms

Sea stars, Sand Dollars

- Simple nervous system

- contains a mouth

- Radial symmetry

- System of canalsWater Vascular System

- Used to move, eat, sense environment, breathe

- Circulates water

Types of Echinoderms

Brittle Stars Basket Stars

Sea UrchinsSand Dollars

Sea LiliesFeather Stars

Sea Cucumbers

-long slim arms-smaller than sea star

-round with no arms-shell-like structure

-use spines and tube feet to move

-have multiple feathery arms

-no arms and worm-shaped