Invertebrates

Sponges

• Simplest Animal• Lack symmetry• Range from a diameter of 1cm to as large as 2m• Most are bag-shaped and have a large internal

cavity• Most are sessile (they attach themselves firmly

to the sea bottom or submerged surface and stay there for life)

• Consist of specialized cells embedded in a gel-like substance called mesophyl

• Resembles chopped fruit in gelatin

Sponges

Plankton and other tiny organisms are trapped as the water moves through the sponges’ body

Waste is carried out the sponges’ as the water moves out

Sponges are found mostly in warm shallow seas

Some live at great depthsA few are even found in fresh water

Sponges

Grouped by into three types based on skeletal composition

1.Calcareous sponges have spicules (tiny needle composed of silica or calcium carbonate)

Sponge Reproduction

Can reproduce asexually Can regenerate when cut into piecesWill reproduce by shedding a piece then it

regenerates into a new spongeSexual reproduction can take place Most sponges are hermaphrodites (produce

both eggs, and sperm)Egg and sperm are produced at different

times so that self-fertilization is avoided

Cnidarians

Diverse group with two main body types:1.Medusa: free floating jelly like and often

umbrella shaped.2.Polyp: tube-like and are usually attached to

rocks or other objects

Medusa

Polyp

Cnidarians

Have a gastrovascular cavity The opening is surrounded by tentacles

which have stinging cells called cnidocytes.Each cnidocytes has a small barbed harpoon

called a nematocyst Extracellualr digestion: digestion takes place

outside of the cell. This is where we first see this, but it takes place in all other species of animals,

Cnidarians

Hydrozoans: The most primitive of the cnidarians.

Live in coloniesLife cycle includes both polyp and medusa

stages,Can be both freshwater and marine Reproduce asexually by forming a bud Many have the ability to reproduce sexuallyBest known is the Portuguese man of war.

Portuguese Man-of-War

Cnidarians

Scyphozoans: “True Jellyfish”Store toxins inside the nematocysts (some

species are extremely potent)Active predators the catch and sting prey in

their tentacles

Phylum Platyhelminthes

Phylum Platyhelminthes-Commonly known as flatworms

Simple animals, un-segmented bilaterally symmetrical and 3 cell layers

One body cavity: gutSome are parasitic No respiratory or circulatory systemMost can reproduce sexually or asexuallyOxygen and nutrients pass into body through

diffusion

Phylum Platyhelminthes

Phylum Nematoda

Phylum Nematoda: roundwormsEpidermis secretes hard and flexible cuticleHead has a few very tiny sense organs and

mouthNo respiratory or circulatory systemBilaterally symmetrical worm-like organismReproduce sexuallyMost are dioecious (organisms that have

either male or female parts)

Phylum Nematoda

Phylum Mollusca

Phylum Mollusca: snails, squid, clams, octopuses, and scallops

Soft bodies usually have a “head” and “foot”Often have a exoskeletonUsually have open circulatory systemHave sensors to detect chemicals, vibrations, and

touchUse the same organ for many functions (for

example: the heart and kidneys are important parts of the reproductive, circulatory, and excretory systems)

Phylum Mollusca

Phylum Annelida

Phylum Annelida: segmented worms (earthworms), leeches

Body usually has bristles Live in a variety of aquatic and land habitatsLocomotory, respiratory, and exretory organs

are repeated in segments through the bodyShare a common nervous system, circulatory

system, and gutUsually reproduce sexually, but some have

the ability to reproduce asexually

Phylum Annelida

Phylum Arthropoda

Phylum Arthropoda: spiders, insects, scorpions, and crawfish

Exoskeleton made of chitinSegmented bodySegments are sometimes fused into 3 parts: head,

thorax and abdomenJointed appendagesBilaterally symmetricalMost have a pair of compound eyesHave an open circulatory systemMost lay eggs

Phylum Arthropoda

Phylum Echinodermata

Phylum Echinodermata: sea cucumbers, sea urchins, and starfish

Many have five-fold symmetryHave a system of internal water filled canalsLive in marine habitatsHave separate male and femalesDecentralized nervous systemSkeleton composed of calciumHave simple but complete digestive gutSimple radial nervous system

Phylum Echinodermata

Phylum Rotifera

Phylum Rotifera: microscopic aquatic animalsSoft bodiesHave specialized organ systems and a

complete digestive tract including a mouth and anus

Eat plants or animals through filter feedingUnusual reproduction can reproduce

asexually or sexuallyBilaterally symmetricalHave a small brain and nervous system

Phylum Rotifera