Invertebrates I Bio 1108

Invertabrates

• Animals without a backbone

• Comprise over 95% of animal species

• Changing environmental conditions, enhanced locomotion and predator-prey relationships fueled evolution through natural selection

• Adaptation and counter adaptation led to the diversity of contemporary invertebrate animals

Parazoa

• Includes Phylum Porifera

• Loosely organized and lack tissues

• Multicellular with several types of cells

• 8,000 species, mostly marine

• No apparent symmetry

• Adults sessile, larvae free-swimming

Sponges

• These organisms are part of the Phylum Porifera

• Simplest animals

• All are aquatic

• No true tissues

• Asymmetrical

• Adults are sessile abut larvae have motility

• Filter feeders

• Reproduce sexually (hermaphroditic) and asexually through budding

Choanocytes

defining feature of sponges that facilitate filter feeding by drawing water through the sponge’s body where food particles are trapped and ingested

Phylum Cnidaria

• This phylum consists of sea anemones, corals, and jellies

• Have radial symmetry

• Mostly marine

• Diploblastic

  • Mesoglea connects layers

cnidocytes

specialized cells containing a stinging organelle called a nematocyst used for prey capture and defense

nematocysts

a specialized cell in the tentacles of a jellyfish or other coelenterate, containing a barbed or venomous coiled thread that can be projected in self-defense or to capture prey

Polyp and Medusa

Two forms of Cnidarians

Cnidarian Functional Anatomy and Reproduction

• Asexually reproduce via budding

• Sexually reproduce by releasing gametes into the water

• Primitive nervous system - nerve net

• Gastrovascular cavity: one opening for both mouth and anus

• Carnivorous

Platyhelminthes

Phylum that is an acoelomate

Lophotochozoans and Ecdysozoans (sometimes Platyhelminthes)

Phylums that are protostomes and coelomates

Echinoderms and chordates

Phylums that are deuterostomes and coelomates

cephalization

concentration of nerve tissue in the head (anterior) of the animal

cephalization

this enhances an organism’s ability to sense its environment, find food, and evade predators

lophophore

a crown of ciliated tentacles that are used to filter feed and in gas exchange; includes Bryozoans, Brachiopods, Rotifers

trochophore

a free-swimming, ciliated larval stage; includes Mollusks, Annelids, Platyheminthes (flatworms)

Platyhelminthes

This phylum consists of flatworms, lacks a specialized respiratory or circulatory system (respire by diffusion); among the first animals with an active predatory lifestyle, bilaterally symmetrical with head; have a gastrovascular, can be free-living or parasitic

flame cells

specialized excretory cells, found in simple invertebrates like flatworms, rotifers, and nemerteans, that function like a kidney, removing waste materials and maintaining osmotic balance

Classes of Flatworms

• Class Turbellaria - planarian

• Class Monogenean - monogeneans

• Class Trematoda - flukes

• Class Cestoda - tapeworms

Rotifera

This phylum in known as “wheel-bearer”, microscopic and mostly aquatic and get their name from the corona

corona

pair of ciliated feeding structures that appear to rotate when viewed under the light microscope

Bdelloid Rotifer

• This organism is a pseudocoelomate divided into head, trunk, and foot

• Covered by a culitcle and contains skeletal and visceral muscles

• Free-swimming or planktonic; uses sticky material on foot for adhesion

• Filter feeders and consume algae and microscopic organisms

• Dioecious with sexual dimorphism; some species exhibit

  • Also can reproduce through parthenogenesis

• Capable of extended dormancy to survive harsh conditions

haplodiploidy

a sex-determination system where males develop from unfertilized, haploid eggs, and females develop from fertilized, diploid eggs