Biodiversity of Animals + Nutrients

Cephalisation

Development of the head

Head has sensory organs + brain

Tissue / Germ layers

Mass of cells that originate in embryo and can be distinguished into 2-3 layers

Diploblastic

• 2 germ layers

• Animals with radial symmetry

• No organs developed ( tisue level of organisation)

Triploblastic

• 3 germ layers

• Animals with Bilateral symmetry

• Organ level of organisation

Coelom

• An internal fluid-filled cavity

• In the mesoderm of Triploblastic animals

Acoelomate

No coelom (flatworms)

Pseudocoelom

• Coelom is not surrounded by mesoderm tissue

• (roundworms)

Coelomate

Has a true coelom

Importance of a coelom

1. Seperates digestive tract from body wall (so that each can function independently)

2. Fluid-filled coelom can act as a hydrostatic skeleton

3. Allows for organs to develop (helps animals to reach a considerable size and become more complex)

4. Coelomic fluid acts as a transport medium for gases, nutrients and waste

Blood System

Transports nutrients to cells and removes waste

Open circular system

blood leaves vessels and flows into body cavity (arthropoda)

Closed circular system

blood moves through closed vessels (Chordata)

Ingestion

Intake of food

Egestion

removal of undigested remains

Incomplete digestive tract

• only one opening (no anus)

• process is discontinuous

Complete digestive tract

• mouth opening and anus present

• process is continouos (can continue during ingestion and egestion)

• different regions can become specialised

Cellular level of organisation

Different cells specialised to perform different functions

Osculum

Large opening of a sponge

Spicule

Skeleton of a sponge (used to identify the species of sponge)

Polyp

Cnidaria

• Cylindrically shaped

• Sessile, attaches to a substrate

• Occurs in colonies

• Non attached side has a whorl of 6 to 8 tentacles around the mouth

Medusa

• Cnidarian

• Flattened umbrella shape

• Tentacles on edges

• Mouth is on underside and can also be used for excretion

• Free swimming

Nematoblasts

• Highly specialised cells on tentacles

• Adapted to catch and paralyse and hold prey

• Cnidocil

• Has Nematocysts

Nematocyst

• invaginated sac-like structures filled with toxic fluid

• Thread like filament in the nematocyst discharges upon stimulation

• Forced into prey and toxins are released

• Some have barbs to hold on more efficiently

Nematoblast

Cnidocyte, Cnidoblast, Nematocyte

After paralysis from Cnidaria

1. Tentacles pull prey into the mouth

2. Food gets digested in coelentron and endoderm

3. Undigested remains are egested via mouth

Flame cell

Specialised cells that excrete metabolic waste

Protostome

• Mouth develops first

• Mostly invertebrates

Deutrosome

• anus develops first, mouth last

• both invertebrates and vertebrates

• mostly bilateral symmetrical organisms