What does blood do? It carries oxygen to tissues, it carries glucose to tissues, it carried immune cells to tissues, it removes waste products like CO2, and it keep the body cells at an optimum pH and osmolarity.
Osmolarity is the concentration of saltiness.
Animals without blood: porifera (sponges), chidaria (jellyfish and corals), and platyhelminths (flatworms).
Filter of waste means no blood is required for regulation.
Flatworms have a large surface area to volume ratio which is good for absorption.
How do animals survive without blood?
- they have a large surface area to volume ratio
- live in water/damp conditions
- live inside another animal
- actively move sea water through their body
Obtaining oxygen without blood: relies mainly on diffusion: oxygen concentration high in air than inside the animal's cells, to make this work, animals need to either be flat or small.
Jellyfish oxygen storage: jellyfish and sponges are neither small nor flat, they help the diffusion process along by keeping seawater flowing through and around them. Jellyfish also have another trick; they can store oxygen in their gelatinous mesalea for when environmental oygen levels drop.
Animals with blood: chordates, molluscs, arthropods and annelids.
Oxygen carrying pigments: proteins complexed with divalent cations that bind oxygen. Can circulate in blood or be restricted to certain tissues with high oxygen demand.
Haemoglobin: contains iron (Fe^2+), red, found mainly in annelids, deep sea tube worms and vertebrates, circulates in…