8. Classifying animal protists Flashcards
What must parasites be able to do in order to be considered ‘parasites’?
- survive lethal attacks from the immune cells
- survive toxins
- produce millions of eggs
- get eggs safely out of host
- eggs must survive outside the host
- must have a way to enter another host
- invade through huge barriers
• this must be repeated for endless generations
key aspects of viruses, and bacteria
- simple organisms - thus very rapid reproduction
* rapid mutation, thus genetic change
Key aspects of eukaryote ‘Protists’
- more complex but short life cycles - rapid reproduction
* alternation of sexual, asexual reproduction - thus high genetic variation
What phylum are flatworms in
Platyhelminthes
Simple body structure of Platyhelminthes
- ectoderm
- mesoderm
- endoderm
• no coelom (acoelomate)
What are the 2 classes of Phylum Platyhelminthes and provide examples
•Class Trematoda
- Flukes
• Class Cestoidea
- Tapeworms
Describe Class Trematoda of Phylum Platyhelminthes
- suckers
- branching gut
- complex reproductive organs
- most are hermaphrodites
Typical life cycle of Trematode
- unembryonate eggs released in feces (from cattle/sheep)
- seek out intermediate host - snail
- development in snail tissue
- free swimming cercariae encyst on aquatic vegetation
- metacercariae on vegetation ingested by definitive host (human)
- immature flukes penetrate intestinal wall
What phylum is Trematoda in
Platyhelminthes
Describe class Cestoidea in phylum Platyhelminthes
- scolex or head with suckers and hooks to hang onto the gut
- proglottids each with male and female reproductive organs
- no gut - food absorbed through body wall
Example of class Cestoidea
Tapeworm
Cestode typical life cycle
- eggs in feces and passed into environment
- cattle become infected by ingesting vegetation contaminated by eggs
- oncospheres hatch, penetrate intestinal wall and develop in muscles
- humans are infected by ingesting raw or undercooked infected meat
- scolex attaches to intestine
- released in feces
Example of organisms in phylum Nematoda
- Roundworms
- hookworms
- pinworms
- hairworms
Describe the structure of Phylum Nematoda roundworms
- moult their outer cuticle
- slender, round body, tapers at both ends
- 3 body layers
- pseudocoelom - space between muscle and gut
- no membrane around the cavity
What are the features of Nematode
- simple gut
- large, long reproductive organs fill up most of the body
- many different lifecycles
