Dr. Kathy S. Williams (email kwilliams@sunstroke.sdsu.edu)
Return to Invertebrate Introduction Return to Syllabus
(scored using the rubric)
(4 pts) a multicellular eukaryotic heterotroph that ingests
food
(6 pts) It’s an organism made up of cells containing membrane-bound
nuclei and organelles (a eukaryote), that gets organic carbon from eating
other organisms or their by-products. Examples are sponges, worms, dogs,
birds, fish.
(4 pts) It’s a living organism that moves, reproduces,
and has physiological functions. It breathes oxygen and goves of CO2.
It has a musculoskeleton system and internal organs, like an elephant or
mouse.
(2 pts) a warm-blooded creature that breathes, sleeps,
and consumes food
n class writing 3/15/00 Sample answers - graded but won't count
In Cnidaria gas exchange is through water being pumped in and out of the gastrovascular cavity. O2 & nutrients are passed over the cells and cells excrete their waste in exchange.
Within the gastrovascular cavity circulation is performed by taking in and expelling water. The single opening makes these processes happen concurrently. The entire body is constructed around this cavity and therefore uses the movement of animal to respire and circulate nutrients/O2.
Gastrovascular cavity circulates water through the animal which helps bring the nutrients to the body walls where cells pick up what they need from the water. Excretion occurs at the cell level into water.
Gas exchange and circulation in Cnidaria occurs by diffusion. Since no cell is very far from the water environment, gasses and other nutrients can diffuse relatively easily from the environment to all cells. Diffusion occurs based on differences in concentration. Water movement through the gastrovascular cavity helps this process by bathing cells w/water.
I think they respire by osmosis. The water probably runs over the organisms cells which extract the O2 ? sort of like how gills work in fish. As far as circulation, the organism probably pushes water in and out through its movements which causes a flow of water in and out of the gastrovascular cavity.
Gas is exchanged through simple diffusion. The water passes by cells & O2 is diffused into the cells. Likewise nutrients also are circulated by simple diffusion into each cell. Water movement is aided by the gastrovascular cavity.
Adequate (4 pts)
With the hydrovascular system, Cnidaria are able to close off the gastrovascular cavity. When closed, it absorbs nutrients in water and excretes wastes through the cavity.
A cniderian engulfs food particles through its mouth/anus. The gastrovascular cavity pushes it through the body where it is digested. The epidermis also absorbs nutrients.
Needs Improvement (2 pts)
Gas exchange occurs through its body cavity. The circulation passes through the nerve net so it is more efficient, which also passes through the body cavity.
Nutrients and food enter Cnidaria due to flagella in choanocytes. The flagella create a current bringing in food and tentacles capture it. The amoebocytes inside are specialized cells that digest food and circulate nutrients. Respiration happens that way too.
Food and nutrients are captured by the tentacles which bring them into the mouth of the Cnidaria. After that, the nutritients are spread through the animal through the body cavity. All waste is disposed through the anus, which is where it came in.
They circulate gasses & nutrients by absorption from cells.
Cnidaria respires using hydrolysis. They would take in dissolved O2
and release CO2 by opening the mouth. Special absorption cells take in
nutrients inside the gastrovascular cavity.
Put only your SSN and lab day and time on the form.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Select the single best answer for each:
(1 1/2 pts each)
1. If an animal is diploblastic, you know that means it will have:
a) tissues2. Protonephridia ...
b) choanocytes
c) bilateral symmetry
d) protonephridia
e) none of the above
a) are found in hydrozoans3. Briefly explain 1 feature that distinguishes Cnidaria from Platyhelmenthes. (3 pts: using 3/2/1 pt rubric)
b) excrete digestive wastes
c) are part of the circulatory system
d) allow animals to live in fresh water
e) aid in respiration
Cnideria Platyhelmenthes
radial symmerty bilateral symmetry
no excretory system protonephridia (flame bulbs)
two embryonic layers three embryonic tissue layers
diploblastic triploblastic
cnidocytes none
tentacles (appendages) none
no special sense organs eyespots
nerve net ladder-like nerves & brain
no muscle tissues
longitudinal & circular muscles
Examples of …
Exemplary answer: A distinguishing feature involves nerve cells. Cnidaria have a nerve net while Platyhelmenthes have neurons arranged in a laderlike design and a brain.
Adequate answer: Cnidaria have cnidocytes, and Platyhelmenthes have eyespots.
Needs Improvement: Platyhelmenthes have a complete digestive
tract and Cnidaria have a gastrovascular cavity.
Explain why the circulatory system of most mollusks limits their activity (i.e., ability to move rapidly for very long).
* FIG. 42.17 Role of gas exchange in bioenergetics; Gas exchange across a respiratory surface
* FIG. 42.2 Open and closed circulatory systems
* FIG. 33.16 Basic plan of mollusks — note reduced coelom & enlarged area that is hemocoel
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The open circulation system
limits the efficiency of moving oxygen & nutrients to muscles (and
removing N wastes).
In an open circulatory system,
fluids rich with O2 are mixed with fluids that are depleted of O2, so muscles
can’t function as efficiently as when supplied with blood coming just from
the gills.
Adequate 4 pts
Most mollusks have an open
circulatory system.
Needs Improvement 2 pts
Mollusks move slowly because they have a heavy shell.
not answers:
a) removes digestive wastes from the body [refers to the digestive
system]
b) requires arteries & veins. [refers to closed circulatory
systems]
Homework
for Wed. 3/29 = Homework/quiz
#4 (worth 6 pts)
In a half page or less,
Explain
how a metanephridium works.
Make sure you use your own words. Do not copy from text.
Exemplary:
Correctly explains how metanephridia function in osmoregulation
and excretion of nitrogenous wastes.
Metanephridia function by drawing body fluids through internal openings called nephrostomes. The fluid enters a network of tubes where needed solutes are actively transported into body and re-enter capillaries. All the excess water creates dilute urine so it and the nitrogenous wastes remain in the tubes and are eventually excreted through external openings called nephridiopores.
Metanephridia is the excretion & osmoregulation system of the annelid. The system collects fluids from the coelom and separates nitrogenous wastes from useful solutes. Capillaries surrounding the tubules that make up the metanephridia reabsorb useful solutes and the remaining excess water and nitrogenous wastes are eliminated. The collected fluid enters tubules through the funnel-like nephridiostome. Cilia on the nephridiostome draw fluids in to the tubes from coelom. As fluid travels through tubules, useful solutes like salts are actively transported from fluid in tubule back into coelom. The remaining fluid then is collected in a bladder and is eventually eliminated through the nephridiopore. This selective excretion of excess water balances the inflow of fresh water surrounding the annelid’s body.
A metanephridia is the way most annelids excrete their metabolic wastes and balance water and salts. The metanephridia collects fluids through a nephridiostome, and actively reabsorbs the salts, while nitrogenous wastes stay behind in the tubes. Then the waste exits out of the nephridiopore as dilute urine, balancing osmotic intake of fresh water surrounding the annelid.
In each segment throughout a worm runs a tube system called the metanephridia.
At the open end of the tubes, bodily fluids are collected and passed through
a long tube where nutrients like vital salts are actively passed back through
the tube into the organism and a solution of excess water and nitrogenous
waste are excreted through small pores.
Adequate:
Has errors OR correctly describes structure & mentions both
waste and excess water removal & salt retention.
Metanephridia expel excess fresh water and nitrogenous wastes from the body of the animal (annelids, for example). It takes in water and the tube collects all the necessary nutrients and expels the rest through a nephridiopore.
The metanephridia are the structures that annelids use to excrete metabolic wastes. There are metanephridia tubules in each segment of the worm body, opening to the body with a funnel-like structure, the nephridiostome. Together the structures function to remove waste from the blood as well as excess coelomic fluids (water). The waste travels through the tubules, where salt is reabsorbed, and exits through exterior pores.
A metanephridia is an excretory and osmoregulatory organ. Metanephridia are found in most annelids, like earthworms. The metanephridia are tubules, which are immersed in fluid within the coelom and covered by a network of capillaries. The nephridiostome is the open end of the metanephridia and is where coelomic fluids, including metabolic wastes, enter the tubules. Dilute urine (water + nitrogen wastes) exit through nephridiopores. Not only does the metanephridia act function for excretion, it also acts in osmoregulation. It helps the worm not lose salt by excreting dilute urine
Metanephridia are tubules in annelids, like earthworms. It is an apomorphy of most annelids. Metanephridia keep balance of fluids and nitrogenous wastes. Some salts are pumped back into the blood. It’s an osmotic system that results in making dilute urine.
Needs improvement:
Doesn’t say how system works - doesn’t mention both functions (excretion
& osmoregulation)
Metanephridia is an excretory system found in a majority of annelids. It functions by removing wastes from blood through nephrostomes. Urine and other dissolved wastes then exit the body of the worm through nephridiopores.
Metanephridia acts as a kidney for an earthworm. Basically it releases excretory waste from the worm.
Metanephridia are tubules that move water in and out of the animal. In salt water the tubules are short, since salt is abundant. This makes it easy to keep salts in the body. In fresh water, salt tends to flow out with the water, so tube are longer.
These segmented body parts contain funnels that help remove wastes from the blood and they end in external pores that release the waste that is accumulated within the worm. Metanephridia are essential for survival of the worms. Without the tubes, the worm would be poisoned by built up wastes. Animals using this type of waste disposal include annelids.
The metanephridia is in each segment of annelids. They take in fluids from adjacent anterior segments, they balance salt and water, and get rid of excess water.
Quiz
# 5: Match the best answer to the following 3 statements:
(3 questions @ 2 pts each)
1. Give one evolutionary link between the Annelida and Arthropoda. (In
other words, what character indicates that they have a more recent common
ancestor than Mollusca and Arthropoda?)
a both have a hemocoel
b. both have trachea
c. both have Malpighian tubules
d. both have a nerve net
e. both have segmentated
bodies
2. Which group of animals contains animals with jointed appendages?
a. Mollusca
b. arthropods
c. Annelida
d. chitons
e. all of these
3. Which of these features for gas exchange is MISMATCHED?
a. epidermis ? Platyhelmenthes
b. mantle cavity - terrestrial Gastropoda
c. gills ? Crustacea
d. trachea - Annelida
e. book lung - Arachnida
You’re walking along a beach on a tropical island and come across a bunch of echinoderms in a tide pool … You find an unusual animal among them and want to determine what it is. You decide that is marine, has jointed appendages, and you see its bilaterally symmetrical larvae swimming around. You dissect one and find that it has a true coelom and complex excretory organs.
(2 pts) Is this an echinoderm? YES / NO (pick one) No
(4 pts) Briefly explain your answer (give only one feature that is critical - or diagnostic).
Sample responses
Exemplary ---
It is not an echinoderm because ...
... it has a complex excretory system and echinoderms don't - they're marine, so they don't need very complex excretory systems
... the novel animal has jointed appendages and echinoderms actually don't - brittle stars have 'articulated' arms - meaning that the endoskeletal plates can move under the echinoderm skin.
Needs improvement ---
It is an echinoderm because ... it has bilaterally
symmetrical larvae.
- most animals with bilaterally symmetrical adults have bilaterally symmetrical young.
1. Which of the following is NOT associated with a parasitic
lifestyle as seen in Cestoda and Trematoda?
a. complex
digestive systems
b. flattened body
c. extensive reproductive organs
d. life cycles with multiple hosts
e. reduced gastrovascular cavity
2. The presence of a true coelom is advantageous because
…
a. it is the third germ layer.
b. it permits development of open
circulatory systems
c. it provides
a space for the development of internal organs.
d. it is necessary for a digestive
system.
e. it functions in performing excretion.
3. Write one main idea about invertebrate biology
you learned about today. (2 pts)
stay tuned for sample responses ...