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