5 The Protosome Deuterostome divide

what new tissues does the mesoderm give rise to

muscles, gonads, excretory system

what is serial repetition

where specific body parts, organs or tissues are repeated one after another along the longitudinal axis of an animal

what do larger organisms need

transport systems for exchange to body regions beyond diffusion distance, enlarged exchange surfaces, internal spaces to allow organs to move relative to each other

how do body cavities help solve the issues that arise when animals get bigger

contain fluid for nutrient, gas, and waste exchange and defence, allow relative growth and movement of specialised organs, provide a space for storage of gametes

what groups of organisms have a coelom

all higher invertebrates and vertebrates

what is the structure of the coelom

surrounded by mesoderm, has a lining called the peritoneum, full of coelomic fluid, which can contain cells such as phagocytes, has exits to the outside of the body called coelomoducts, often modified for excretory or reproductive functions, the gut and organs are suspended in the coelomic fluid by thin walls of peritoneum tissue known as mesenteries

what are the two ways of making a coelom

deuterostomes, protostomes

which protostomes do have coeloms

annelids

what do molluscs, arthropods, and nematodes have instead of a coelom

a haemocoel

how is the haemocoel different from the coelom

not contained within mesoderm and not lined with peritoneum, organs are bathed directly in blood

which deuterostomes have coeloms

all of them

what parts of the coelom do humans retain

coelomoducts modified into our excretory and reproductive systems

what is the fluid filled space in an early embryo known as

blastocoel

what does the endoderm result from in all coelomates

from infolding along what will become the ventral midline of the animal

what is the name given to the hole or groove along which infolding takes place

the blastopore

what are the two main ways in which protostomes and deuterostomes differ

in the way theay make a mouth and in the way they make mesoderm and coelom

how do protostomes and deuterostomes make a mouth

protostomes use part of the original blastopore, while deuterostomes form a new second opening

how do protostomes and deuterostomes differ in the way they make mesoderm and coelom

protostomes form mesoderm from clumps of cells in the blastocoel, deuterostomes form outpockets of the gut

what are the three major lineages of the protostomes

ecdysozoa, trochozoa, platyzoa

what are the key features of the platyzoa

external cilia as larvae and adults, grow without moulting, no coelom, not segmented

what are the key features of the trochozoa

external cilia as larvae and adults, growth without moulting, often retain coelomic structures in adults, some are segmented and some are not

what are the key features of the ecdysozoa

no external cilia as adults, no ciliated larvae, grow by moulting, all have secondary haemocoels, some are segmented and some are not

what are the three most abundant molluscs

bivalvia, gastropoda, cephalopoda

what are the main characteristics of molluscs

most have a calcium carbonate shell secreted by the ectoderm, gills are usually in a fold in the mantle under the shell called the mantle cavity, primitive molluscs show serial repetition but no true segmentation, mouth is equipped with a radula ad a through gut, lifecycle often involves a ciliated trochophore larva, a key shared trait of annelids and molluscs

what is the name of the gills in molluscs

ctenidia

what is the difference in the radula between herbivores and carnivores

herbivorous radulae have many fine teeth while carnivores have a smaller number of longer, sharper, hooked teeth

what are the key features of the brachiopods

have bivalve shells in a top/bottom orientation (not left/right as in bivalve molluscs) and filter feed using a ciliated structure called a lophophore, no radula or creeping foot

what are the key features of halkieriids

have bivalve shells in a front/back orientation like a brachiopod with a dorsally armoured body in between, they had a creeping muscular foot and a radula, they went extinct in the cambrian

what are the key features of wiwaxids

dorsally armoured body with a creeping muscular foot and a radula, extinct in the cambrian

what are the key features of the machaeridians

fully segmented body with mineralised armour, extinct in the cambrian

what does the fossil diversity of the trochozoa suggest

it was not difficult to evolve new body plans, there was a strong selection for the evolution of armour