Lecture 1 (4/3) Flashcards
Helminths
Parasitic worms infecting humans and other animals
Three general phyla of worms
Flatworm (Platyhelminthes)
Roundworm (Nemadota)
Segmented worm (Annelida)
Flatworms
Body shape
What is their role in nature?
Circulatory system
Digestive system
Approximately how many species?
Flat and thin bodies
Most are animal parasites
Lacks a circulatory system
Incomplete digestive system
~20k species
Phylum: Platyhelminthes
What are some examples of flatworms?
Tapeworms and planarians
Tapeworms absorb nutrients through their skin
Segmented worms
Body shape
What is their role in nature?
Circulatory system
Digestive system
Approximately how many species?
Consist of repeated units called segments
Most feed on decaying organic matter, some parasitic
Closed circulatory system
Complete digestive system
Approx 12k species
Phylum: Annelida
Examples of segmented worms
Earthworms and leeches
Round worms
Body shape
What is their role in nature?
Circulatory system
Digestive system
Approximately how many species?
Unsegmented, multicellular, bilaterally symmetrical
Free-living or parasites
Lacks a circulatory system
Complete digestive system
Approx 25k species
Phylum: Nematoda
Common names of roundworms
Roundworms, threadworms, eelworms, needle worms
Relative sizes of animal-parasitic, free-living, and plant-parasitic nematodes
Animal parasitic: big and sometimes visible to the human eye
Free-living: microscopic
Plant-parasitic: microscopic
Nematode body plan
Tube within a tube
Typical nematode life cycle
How many life stages and how many each of egg, juvenile, and adult?
Six life stages: 1 egg, 4 juvenile, 1 adult
How many genes are there in C. elegans (the nematode)?
20-22k protein coding genes
What is the size of longest nematode?
The longest known nematode is Placentonema gigantissima, which can grow to lengths of up to 8.8 meters
What does the majority of marine nematodes feed on?
Organic matter: they are detritivores
How nematodes exchange gas with atmosphere?
Through diffusion
