Invertebrates Comparative Anatomy

I. Comparison by Cavity Type A. COELOM – LIQUID FILLED BODY CAVITY B. COELOMATES – ORGANISMS WITH A BODY CAVITY

II. CLASSIFICATION OF COELOMATES A. CLASSIFICATION BY CAVITY STRUCTURE B. CLASSIFICATION BY EARLY DEVELOPMENT C. CLASSIFICATION BY CLEAVAGE TYPE

III. CLASSIFICATION BY. CAVITY. STRUCTURE A. ACOELOMATE 1 III. CLASSIFICATION BY CAVITY STRUCTURE A. ACOELOMATE 1. Prefix “A-” “without” 2. Organism having a cavity without a lining

PSEUDOCOELOMATE 1. Prefix “PSEUDO-” “FALSE” 2. Organism having an incompletely lined cavity

C. EUCOELOMATE 1. Prefix “EU-” “TRUE” 2. Organism having a true cavity that is completely lined Eucoelomate (Earthworm)

IV.CLASSSIFICATION BY EARLY DEVELOPMENT A. BLASTULA – hollow ball of cells B. BLASTOPORE - opening formed by the folding of the blastula Early evolutionary branches are formed based on events in development of bilateral symmetry. Divisions include acoelomates, pseudcoelomates, and coelomates based on the structure of the body cavity.

1. Formation of mouth from blastopore 2. Anus is secondary formation PROTOSTOME 1. Formation of mouth from blastopore 2. Anus is secondary formation Early evolutionary branches are formed based on events in development of bilateral symmetry. Divisions include acoelomates, pseudcoelomates, and coelomates based on the structure of the body cavity.

D. DEUTEROSTOME 1. Formation of anus from the. blastopore 2 D. DEUTEROSTOME 1. Formation of anus from the blastopore 2. Mouth is the secondary formation Early evolutionary branches are formed based on events in development of bilateral symmetry. Divisions include acoelomates, pseudcoelomates, and coelomates based on the structure of the body cavity.

V. CLASSIFICATION BY CLEAVAGE TYPE CLEAVAGE- DIVISION OF EARLY EMBRYONIC CELLS B. EMBRYONIC CLEAVAGE 1. Determinate Cleavage –creates high probability of unequal daughter cell survival Division of this group is based not on a body cavity but events in early development.

2. Indeterminate Cleavage – division allows greater probability of equal daughter cell survival

3. Holoblastic Cleavage a. Def. -complete cleavage in embryos having a small yoke b. Four Types 1) Bilateral 2) Radial - Deuterostomes 3) Rotational - mammals 4) Spiral – Protostomes (Annelids & Mollusks)

4. Meroblastic Cleavage a. Def.- incomplete cleavage in embryos having a large yoke b. Two Types 1) Discoidal – fish, birds, reptiles (yolk at one end) 2) Superficial - insects (yolk in the center)

B. PROTOSTOMES – SPIRAL CLEAVAGE C. DEUTEROSTOMES – RADIAL

VI. Movement and Support Three Types * In most animals the muscles work together with some sort of skeletal system that provides firm support. There are three main kinds of skeletal systems: 1) Hydrostatic skeletons – no hard structures such as bones or chitin plates 2) Exoskeletons – hard nonliving coating that encloses internal organs and muscles. 3) Endoskeletons – frameworks located in the body of animals.

1. Hydroskeleton – lacking hard structures (bones) Cnidarians Flatworms Roundworms Earthworms Mollusks

2. Exoskeleton - hard nonliving. coating that encloses internal 2. Exoskeleton - hard nonliving coating that encloses internal organs and muscles. Mollusks Arthropods

3. Endoskeleton – bony internal framework Echinoderms Chordates

VII. Digestion Three Methods A digestive system must accomplish several tasks Ingestion of food Mechanical breakdown of food particles Chemical breakdown of food particles Absorption of nutrients Elimination of waste Intracellular All digestion occurs within individual cells of the animal Incomplete extracellular There is only one opening for absorption and elimination Complete extracellular There are two openings. A mouth for absorption and an anus for elimination.

1. Intracellular - All digestion occurs within individual cells of the animal Poriferans

2. Incomplete Extracellular -Only one opening for absorption and elimination. Cnidarians Platyhelminthes

3. Extracellular - Two openings:. A mouth for absorption and 3. Extracellular - Two openings: A mouth for absorption and an anus for elimination. Cnidaria Echinodermata Arthropoda Moullusca

VIII. Respiration All animals require Oxygen (O2). Respiration also produces a byproduct CO2 that is toxic. These two needs are accomplished by a process of gas exchange. No respiratory system Low energy needs, Low metabolism, Uses little O2. Small/flat/narrow -No cell too far from surface Moist skin - Helps with diffusion External respiratory system - Larger animals need O2 to enter in bulk Gills are on outside of the body and are elaborate, folded structures that increase surface area. As water passes over the gills, oxygen then diffuses into capillaries of a circulatory system. The circulatory system transports O2 to cells where it is exchanged for CO2. Internal respiratory system - Insects use a system of tubes called tracheae to get O2 close to cells. Most vertebrates use lungs to exchange gases.

A. No Respiratory System –. diffusion is used to get A. No Respiratory System – diffusion is used to get oxygen through surface Sponges, Cnidaria, Nematoda, & Echinodermata

B. External Respiratory. System – diffusion through B. External Respiratory System – diffusion through skin or special structures such as gills

C. Internal Respiratory System –Use lungs or tubular system (insects)

X. Internal Transport Used to exchange gases with the respiratory system and body cells. It also transports those gases between the respiratory system and body cells. No circulatory system - Animals that are small enough to diffuse gases in and out of the body also tend to use diffusion to transport those gases throughout the body. Open circulatory system - A heart pumps blood into the body cavity where it moves past the organs and tissues. It is picked up by openings in the heart, which draws it up and then pumps it back out. Closed circulatory system - The heart pumps blood through gills or lungs to exchange gases (except annelids). It uses arteries to pump away from the heart and veins to move it towards the heart. Capillaries are small blood vessels that are one blood cell in diameter where gas exchange with the body cells occurs.

A. No Circulatory System Also Nematoda & Echinodermata

B. Open Circulatory System – has no vessels

C. Closed Circulatory System – has vessels (veins/arteries)

IX. Environmental Response A. Nerve nets B. Cephalization – having a head; anterior centralizaton of sense organs C. Central nervous system Neuron – cell that carry messages for the nervous system - Messages take the form of electrical signals called impulses. - Receives and relays information about activities within the body. - Monitors and responds to internal and external changes.

XI. Reproduction A. Asexual – one parent B. Sexual – two parents All Living things reproduce. Types of Reproduction Asexual – only one parent Budding – a small version of the animal grows off the parent. When it grows large enough it breaks off. Fission – the adult splits in half. Each half then regenerates the rest of the body. Parthenogenesis – an egg develops without the addition of sperm from a male. Sexual – two parents, one supplies the sperm & the other supplies the egg. Hermaphrodite – each parent is both male and female. Male/Female – male supplies the sperm while female supplies the eggs. External Fertilization – parents release both the egg and sperm into the environment. (Spawning) Internal Fertilization – the male places the sperm inside the female’s body. Required, if reproduction is to occur on land.