Chapter 33

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Chapter 33: Invertebrates- Read chapter 33 feat investigation

A. Invertebrates

i. Hermaphrodites: animals that are both male and female

a. Many are but most can’t self-fertilize

B. Phylum- Porifera

i. The sponges

ii. Have no true tissues, nerves or muscles

iii. Sessile (: stay anchored to one place) during their adult lives

iv. Filter feeders/ Suspension feeders: eat the stuff floating in the water

v. Choanocytes (collar cells): flagellated cells that create currents and phagocytize food

vi. Have an outer and inner layer of cells

vii. Some contain silica, some calcium carbonate, and some a protein called spongin

C. Phylum- Cnidaria

i. Jellyfish, corals, hydras, and sea anemones

ii. Radiata

iii. Have 2 layers of tissue- the ectoderm, and the endoderm

iv. Most marine, some live in fresh water

v. Sac-like bodies

vi. Have jelly-like acellular material (mesoglea) between the 2 layers of tissue

vii. Have cells called cnidocytes that contain nematocysts: release toxins through a tube

viii. Have muscle-like fibers and a simple nerve net

ix. Take 2 forms (and some take both at different points in their lives):

a. Polyps: cylindrical shape, sessile

b. Medusa: flattened, rounded and free-swimming

D. Phylum- Ctenophora

i. Comb jellies (not actual jelly fish)

ii. Radiata

iii. All marine

iv. Use cilia for locomotion

v. Have cells with sticky threats (don’t sting)

vi. Most are bioluminescent

vii. Have a mouth and anus like jellies but still don’t have true tissues

E. Bilateral animals

i. There are 3 clades:

a. Lophotrocozoa -(protostomes)

b. Ecdysozoa –(protostomes)

c. Deuterostomia –(deuterostome)

ii. Lophotrocozoa

a. Bryozoans, brachiopods, phoronids, mollusks, annelids, flat worms, rotifers, and others

b. Posses specialized feeding structures (lophophores), or a distinct larval stage (trochophores), or similar structures.

F. Phylum Platyhelminthes

i. Flatworms

ii. Acoelomates

iii. Includes free-living predators and parasitic species

iv. Have a gastrovascular tract with a single opening

v. Free-living forms include the well-known planarians

vi. Most have a distinct head and ventral nerve cords

vii. They even have simple eyes that see light direction

viii. Flukes are parasites

ix. Schistosoma: blood flukes

x. Tapeworms: are parasites with no digestive tract, they absorb food

a. Have hooks to hook onto the host’s internal walls

G. Phylum- Rotifera

i. Rotifers

ii. Very small

iii. Most live in fresh water

iv. Pseudocoelomates

v. Have a crown of cilia that directs food into their mouths

vi. Have jaws to grind food

vii. A complete digestive tract, with a mouth ad an anus

viii. Little eye spots and a brain

H. Phylum- Lophophorate

i. Bryozoans, phoronids, and brachiopods

ii. All have a ciliated feeding structure called the lophophore

iii. They used to be considered deuterostomes because of their development

iv. Molecular evidence suggests they are more closely related to protostomes

I. Phylum- Nemertea

i. Ribbon worms or proboscis worms

ii. Acoelomates

iii. Have a complete digestive tract

iv. Have a closed circulatory system, with blood contained in blood vessels

J. Phylum- Mollusca

i. Snails, slugs, oysters, clams, chitons, octopuses, squid and many more

ii. > 100,000 living species

iii. Coelomates- protostomes

iv. Mostly marine, some freshwater and some terrestrial

v. Have soft bodies, but many have a protective shell of calcium carbonate

vi. Mollusks have a muscular foot

vii. Visceral mass- contains most of the organs

viii. Mantle: a fold of tissue over the visceral mass, secretes the shell

ix. Radula: a rasping feeding organ found in many (not all) mollusks

x. Most have an open circulatory system with their hemolymph (blood) directly bathing their organs

xi. Have ventral nerve cords

xii. 8 classes:

a. Gastropoda

1. Snails and slugs

2. Marine, freshwater or terrestrial

3. Most with coiled shells, but shell absent in slugs and nudibranchs

4. Radula present

b. Bivalvia

1. Clams, oysters, mussels, and scallops

2. Marine or freshwater

3. Shell with two halves or valves

4. Mostly sessile

5. filter feeders with siphons

c. Cephalopoda

1. Squid, octopuses, cuttlefish, and nautiluses

2. Most have internal shells- squid and cuttlefish (octo have none at all)

3. Have a closed circulatory system

4. Complex brain

5. predatory with tentacles around mouth, often with suckers

6. jet propulsion via siphon

d. Polyplacophora

1. Chitons

2. 8-plated shells

K. Phylum- Annelida

i. Segmented worms

ii. Earthworms, leaches, tubeworms, and polychaete worms

iii. Coelomates- protostomes

iv. Have a segmented body

v. Ventral nerve cord

vi. Closed circulatory system

vii. Metanephridia: paired excretory tubules located in each segment

viii. Brian-like cerebral ganglia

ix. Earthworms are cross-fertilizing hermaphrodites

x. Tube-like worms are sessile as adults

xi. Leaches have a history in medicine

a. Have anti-coagulant and anesthetic properties

xii. Polychaetes are marine worms with parapodia: structures that look like legs

L. Ecdysozoa

i. Nematodes and arthropods

ii. Exhibit ecdysis: periodic molting of a cuticle (:non-living cover offering support and protection)

M. Phylum- Nematoda

i. Unsegmented round worms

ii. Pseudocoelomates

iii. Found in aquatic habitats, in soil, and as plant and animal parasites

iv. Very abundant

v. Could be as many as 100,000 species

vi. Most are very small (microscopic)

vii. Plant parasites are of major economic importance

viii. In humans can block the lymph ducts and cause elephantiasis

N. Phylum- Arthropoda

i. Jointed feet

ii. Crustaceans, spiders, insects, millipedes, centipedes, and many others

iii. Coelomates-protostomes

iv. At lease 1 million names species, probably several million species in total

v. They all have jointed legs, a hard exoskeleton, and segmentation

vi. Exoskeleton: the cuticle of arthropods

a. Constructed of layers of chitin and protein

b. Provides protection, water resistance, and something for muscles to work against

c. Molting: periodical discarding of exoskeleton for growth

vii. Many of their sensory organs concentrated on their heads

viii. open circulatory system

ix. Onychophorans: walking worms

a. May resemble arthropod ancestors

x. Trilobites: a large group of extinct arthropods

xi. 4 major subphyla of phylum Arthropoda

a. Chelicerata

1. Arachnids, sea spiders, horseshoe crabs, and eurypterids (extinct)

2.Body usually with cephalothorax and abdomen only

3. 6 pairs of appendages- including 4 pairs of legs, 1 pair of fangs and 1 pair of pedipalps

4. Terrestrial

5. Predatory or parasitic

6. Have chelicerae: feeding appendages

7. Have no antennae and most have simple eyes (one lens)

8. Most are Class Arachnida

-Spiders, harvestmen, scorpions, ticks, mites, and others

- Most have 2 major body regions and 4 pairs of legs

- Most spiders utilize book lungs for respiration

b. Myriapoda

1. Centipedes, millipedes, and others

2. Body with head and highly segmented trunk

3. Class- Diplopoda

- Millipedes

-Each segment with two pairs of walking legs

-Terrestrial and herbivorous

4. Class- Chilopoda

-Centipedes

- Each segment with one pair of walking legs

- Terrestrial, predatory (carnivorous), have poisonous jaws that inject venom

5. Have antennae (1 pair) and mandibles

6. Multi-legged, worm-like, species ate thought to be more “primitive” than insects

c. Crustacea

1. Crabs, lobsters, shrimp, barnacles, pill bugs, and others

2. Body with head, thorax, and abdomen

3. 3 or more pairs of appendages are mouthparts modified for biting, chewing, sucking, or lapping

4. Usually with 2 pairs of wings and 3 pairs of legs

5. Mostly terrestrial, some freshwaters

6. Herbivorous and parasitic or predatory

7. Heavilu modified appendages

8. 2 pairs of antennae

9. Most have gills for respiration

10. Krill is a very important part of the marine food chain

11. Important members of the zooplankton (animal plankton) of marine and freshwater

d. Hexapoda

1. Mostly insects

2. Body of 2 to 3 parts

3. 3 or more pairs of legs

4. Chewing mouthparts

5. Usually marine

6. Class- Insecta

- More species than all other animals combined

-Many have 2 pairs of wings (1 pair modified)

- The only invertebrates that can fly

-3 body regions: head, thorax and abdomen

-3 pairs of legs, 1 pair antennae, 2 ventral nerve cords

- Have trachea for respiration: chitin-lined tubules in the insect body

- Malpighian tubules: used for excretion

- Many have compound eyes (with many lenses)

O. Metamorphosis

i. Incomplete metamorphosis

a. The young (nymphs) look like small adults but can’t fly or reproduce

b. Go through several molts

ii. Complete metamorphosis

a. There are larval stages

b. Transforms to adults during the pupal stage

P. Deuterostomes

i., Include echinoderms, chordates and others

ii. Share similar patterns of development (zygotic cleavage’s first opening turns into anus ?)

Q. Phylum- Echinodermata

i. Spiny skin animals

ii. Deuterostomes

iii. Starfish, brittle stars, sea urchins, sand dollars, sea lilies, and sea cucumbers

iv. They have a hard skeleton covered with thin skin

v. Radial symmetry as adults and bilateral symmetry as larvae

vi. Have a water vascular system: hydraulic canals connected to tube feet

a. Which is unique to them

b. Can generate suction

1. Can pry own shells for food

c. Use for locomotion (very slow), feeding and respiration

vii. Have 5-fold radial symmetry as adults and a bilateral larvae stage (which is also an important part of the zooplankton)

viii. Have a nervous system (has simple nerve net) but no brain

ix. Hard to kill, can regenerate an arm and are essentially immortal (can life extremely long)

x. Has a kind of endoskeleton that is embedded into their skin