practical lab 3 part 1

in early development of many animals the embryo has how many layers

what are the three layers of the embryo called

germ layers
ectoderm endoderm and mesoderm

ectoderm

covers surface of the embryo, gives rise to the outer covering of the animal and sometimes to the central nervous system

endoderm

the innermost layer, lines the primative gut, and gives rise to the lining of the digestive tract and its out-pocketings such as the liver and lungs of vertabrates

mesoderm

the embryo layer in the middle, forms the muscles and most of the other organs between the gut and the outer coverings of the animal

how many ways can the body be organized around cell layers

the acoelomate body plan

no cavity between the digestive tract and outer body wall, the space between is loosely filled with mesodermal cells called parenchyma

the pseudocoelomate body plan

fluid-filled cavity (pseudocoelom) between the digestive tract and outer body wall. layer of mesoderm underneath the outer body wall but not surrounding the organs (cavity is not completely lined) internal organs are free in the pseudocoelom

pseudocoelom

the fluid filled cavity in pseudocoelomates

flatworms have what body organization

acoelomate

roundworms have what body organization

pseudocoelomate

coelomate body plan

body cavity (coelom) completely lined with mesoderm. layer of mesoderm under the outer body wall and another surrounding the organs. 2 layers of mesoderm connect to form mesenteries that suspend the organs in the coelom

body cavity functions

prevent internal injury by cushioning organs, allows internal organs to move independently from the body wall

phylum nematoda

long cylindrical worms (roundworms)
largest of the animal phyla
have a pseudocoelom and a complete digestive tract

feeding habits of nematoda are

can be carnivorous, herbivorous, or parasitic depending on the environment and way of life

nematode digestive system

mouth - muscular pharynx - intestine - anus

muscular pharynx

acts as a pump bringing food from the mouth to the intestine

in nematoda digestive enzymes are produced

by the singular layer of epithelial cells lining the intestine

in nematoda digestion begins within the intestinal lumen but is completed _

extracellularly intracellularly

nematodes lack _ and _ systems

respiratory and circulatory

nematodes are largely inhabitants of the

interstitial spaces of aquatic sediments and soils

nematodes are essentially always in a ___ environment

moist

free living nematode species obtain oxygen from

diffusion from the environment

reproduction in nematoda

live in human intestines - eggs pooped out and if contaminate food are introduced to a new host - larvae hatch in intestine - burrow into bloodstream - lungs - alveoli - crawl up trachea - esophagus

female ascaris sp. reproductive system (nematoda)

genital pore - short vagina - two uteri - oviduct - thread like ovaries

female ascarus sp. (nematoda) reproduction

eggs produced in the ovaries - move to the oviducts - to the uterus - fertilization in the uterus

male ascaris sp. (nematoda) reproduction

sperm produced in the testes - mature as they move along the vas defrens - seminal vesicle - sperm enter the cloaca before going into the female

male ascaris sp. (nematoda) reproductive system

anus is for poop and cum - copulatory spicule (hook) holds the female open - cloaca is on the outside of the anus and holds poop and cum from either the intestine or seminal vesicle

nematode body system