Zoology Test 2a Flashcards Preview

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Flashcards in Zoology Test 2a Deck (39):
1

What are Platyhelminthes?

- flatworms
- acoelomates

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acelomates

without a body cavity (coelom)

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What is in between the epidermis and gastrodermis?

parenchyma

4

How does embryo of Platyhelminthes differ form that of Cnidarians?

- triploblastic rather than diploblastic
- ectoderm, mesoderm and endoderm
- mesoderm gives rise to true muscle tissue, bones, circulatory system and other internal organs

5

symmetry of platyhelminthes

bilaterally symmetrical
- must actively search for food and mates
- body flattened dorso-ventrally
- cephalization

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anterior

front

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posterior

back

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dorsal

back

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ventral

front

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cephalization

- possess head where central nervous system and sensory organs are located

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digestive system in platyhelminthes

incomplete digestive system
- mouth but no anus
- some of these worms don't have a mouth and absorb nutrients through their specialized skin
- tegument with microtrix to enlarge surface area for absorption

12

excretion and respiration in platyhelminthes

- simple diffusion
- flattened body aides in process, easier for diffusion to occur

13

Platyhelminthes

- Turbellaria
- Monogenea
- Trematoda
- Cestoda

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types of turbellaria

- free living flatworms
- dugesia (planaria)

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types of monogenea

- small ectoparasites

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types of trematoda

- larger 'flukes'
- endoparasites

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types of cestoda

- tapeworms

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Dugesia

- type of turbellaria
- also called planarian
- freshwater, tremendous powers in regeneration

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digestive system of dugesia

- y-shaped with reversible pharynx for feeding

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turbellaria reproduction (dugesia)

- asexually by fission (fragmentation)
- sexually via complex organ system (syngamy)
- monoecious

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characteristics of Monogenea

- ectoparasite
- don't harm host
- attach via a haptor to host
- only sexual reproduction (only produce one adult at a time)

22

characteristics of Trematoda

- parasitic flukes with two or three hosts per life cycle
- snail is always found in life cycle (intermediate host)
- vertebrate is almost always definitive host
- Clonorchis (human liver fluke)
- both asexual and sexual reproduction

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parasites

- loss of sensory structures
- loss of organ systems
- increased reproductive ability

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definitive host

where parasite has sexual reproduction

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intermediate host

parasite has asexual reproduction

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characteristics of cestoda

- includes tapeworms
- are endoparasites of vertebrate digestive system with highly specialized anatomy
- anatomy consists of series of proglottids and a 'head' bearing a scolex
- monoecious

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types of cestoda

- Taenia (beef tapeworm)
-

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scolex

hooks or suckers

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What is found inside a proglottid?

- reproductive organs (both male and female)
- nerve cords
- flame cells for excretion, excretory ducts, muscles and parenchyma

30

characteristics of platyhelminthes nervous system

- have up to five pairs of nerve cords
- freshwater flatworms, there is a ladder-type = one pair of lateral nerve cords connected to cerebral ganglia

31

osmoregulation in platyhelminthes

- flame cells lined with cilia drive fluids through a series of tubules which open to outside through series of pores

32

life cycle of clonorchis

- ingested and burrows into the bile duct of the liver
- egg containing miracidium (larvae) travels through intestines and defecated
- snail ingests the egg
- the egg hatches and the miracidium feed on the snail tissue and becomes germ tissue (redia) via asexual reproduction
- this germ tissue is called a sporocyst, they release redia
- redia release cercaria via asexual reproduction which travel through water and imbed themselves in fish
- they become the metacercarial cyst in the fish muscle and wait to be ingested by final host
- cyst develops into adult and sexually reproduces to begin life cycle again

33

Clonorchiasis

- caused by Clonorchis sinensis
- life cycle is broken by sanitary disposal of human feces and cooking fish throughly

34

Schistosomiasis

- infects 300 million worldwide
- caused by human blood fluke, Schistosoma sp.
- female lives an external canal of male
- dioecious

35

differences in life cycle of schistosoma

- cercariae burrow directly into skin of humans wading in water
- cercariae enter human blood stream and give rise directly to adults

36

causes of eggs in schistosoma

- pass from circulatory system to digestive system and are voided in feces
- considerable damage occurs; eggs cause ulceration of linings of intestines and urinary bladder
- can cause cirrhosis of liver

37

Swimmer's Itch

- caused by cercaria of trematode fluke
- temporary dermatitis in human skin
- humans are the wrong definitive host for fluke, so cercariae penetrate human skin, but don't survive

38

life cycle of beef tapeworm

- gravid proglottid is released through fecal matter of humans
- shelled larvae is released
- contaminated grass is eaten by the cow and ingested
- cysts form in the muscle of the cow
- develop into a invaginated scolex/cysticercus
- the meat is then cooked and if not cooked throughly it will continue to live and then be ingested into human and repeat life cycle

39

tapeworm facts

- only about 1% of cattle are infected with this in america
- throughly cook meet to avoid it
- can live in dogs, cats, humans
- can be found in meat, poultry or fish
- some encyst in organs
- some cause more serious pain