Round worms Flashcards
What are some general characteristics of a round worm?
Bilateral symmetry.
3 cell layers (ectoderm, mesoderm, endoderm).
Have complete digestive system with mouth and anus.
Organ level organization.
Exhibit cephalization.
Not segmented and have thick cuticle covering the epidermis.
How do roundworms ingest food?
Food enters the mouth and travels down the pharynx.
Pharynx identifies a muscular tube
which helps push the food along.
How do roundworms digest food?
Food is passed into the gut which is composed of intestine.
Food is broken down by enzymes produced by the cells of the gastrodermis, then absorbed across the intestinal walls by diffusion into the fluid filled pseudocoelom surrounding it.
How do round worms go through elimination?
Undigeded foods (feces) leaves through the anus.
it is a “one way” digestive tract.
What is their circulation?
Nutrients are dissolved in the fluid of the pseudocoelom.
All the tissues and organs are bathed in this fluid or within a short distance of it, so nutrients can diffuse into the cells of the entire body.
How do they go through respiration?
O2 enters the body across the cuticle and ectoderm by diffusion
into the pseudocoelom.
It circulates in the same way as
food.
CO2 leaves via the same pathway. from the body cells, to the pseudocoelom, and the epidermis.
How do round worms go through excretion?
Excretory system is made up of a system of tubes.
N-wastes and excess H2O diffuses from tissues into the pseudocoelom.
Then enters 2 longitudinal excretory tubules that empty into 2 excretory pores at the head of the worm.
What are roundworms nervous system?
Exhibit cephalization (have a brain).
Contains a nerve ring at the head end with attacted nerve cord.
Some have sense organs that detect chemicals.
How do roundworms move?
Their muscles stimulate by the ‘nervous system’ allows for coordinated movement.
Hydrostatic skeleton helps by providing support and movement.
How do roundworms sexually reproduce
Have separate sexes (dioecious).
Have organs that produce egg or sperm.
Fertilize internally.
What are unique characteristics of a round worm?
Have a ‘tube within a tube’ body cavity called a pseudocoelom between the gut and ectoderm.
The cavity is NOT completely lined by the mesoderm (only next to the ectoderm).
