practical lab 3 part 1
in early development of many animals the embryo has how many layers
3
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
3
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
pseudocoelomate