Parasitism Flashcards
What is a parasite?
o Lives on or in host and benefits
o Causes harm
o Evolved multiple times; it is not a taxa – it’s a “lifestyle”
Example: guinea worm/fire worm
(super painful, mostly in Africa etc.) –> infected by drinking contaminated water; after about a year it developed and makes its way into our leg/feet and makes a blister and it really burns –> naturally we want to put our extremities in water which makes it burst in water and it starts life cycle again/recreates (it manipulates its host) cut down incidences from 3.5 mil to 25 by studying life cycle
How does parasitism occur?
o Shared environment; Lots of contact over time
o Pre-adapted; It doesn’t come out of nowhere
Ex: Feeding – attachment
Example: phoresy -
Phoretic just means it catches a ride; but that phoretic organism can easily become parasite because it’s already there
Massive diversification
- Evolved many times
- Lifecycles
- Morphology
What is ecosystem health?
o Recent idea
o Small or large scale
o Measures the stability of an ecosystem; Biodiversity, connectivity
Ecology describes ecosystems
- connections (predator-prey) by trophic level
- Number of species
Food Webs
- complex or simple
- often leave out parasites
Why do parasites make good models?
- continuous throughout trophic system
Recent studies on parasite biomass
- Parasite biomass estimates to be higher than top level predators (birds, crabs)
o Thought that parasites help facilitate stable ecosystems
o They are omnivorous feeders - Travel through trophic levels
- Through interactions
o Add stability - Help control predator prey interactions
o May also serve as early warning system of ecosystem failure (parasites often feel effects first)
Predator vs. parasite vs. parasitoid
o Predator; multiple prey in lifetime, larger than prey, kill prey
o Parasite; one host per life stage, smaller than host, typically doesn’t want to kill host (it can’t benefit off it if it’s dead)
o Parasitoid; always kills host, single host per life stage, refers to specific insects (free living adults, eggs into host, host dies)
Ecto vs. endoparasites
o Ectoparasite; lives on host and feeds off host tissue
o Endoparasite; lives in host
Micro vs. Macroparasites
o Microparasite; small, multiply within host; ex: plasmodium
o Macroparasite; larger, release progeny outside of host; ex: helminths (essentially worms)
Direct vs. Indirect lifecyles
o Direct life cycle, monoxeous, simple
- Only one host; may or may not leave the body at some point
o Indirect life cycle, heteroxeous, complex
- Multiple hosts (different species or not)
Host-Parasite coevolution
o Species A evolved an adaptation in response to species B and species B evolves in response to the adaptation of species A
o Hosts and parasites change evolutionarily in response to each other
o Resistance; Ability of the host to combat the parasite
o Virulence; Ability of the parasite to harm the host
o Red Queen Hypothesis: Basically a coevolutionary arms race (One is always trying to get ahead of the other, but they’re both just evolving at the same rate)
Parasites can manipulate host - why?
- Increase transmission rate
- Ranges from subtle to not
