BIO 370 Lecture Notes - Lecture 33: Euglena, Natural Selection, Chromosome
Evolution, Disease, and Aging
From a strictly biological perspective, why do we die is the wrong question.
• ALL forms of life face the conundrum of finding energy to maintain order while avoiding
becoming food for something else!
– Our pathoges do’t fae an easy road either.
– There are constant trade-offs
– Natural seletio does’t result i perfetio, oly iproed fit to spatially ad
temporally local conditions.
– Natural selection has to modify existing systems.
Coevolutionary Arms Races Between Pathogens and Hosts
Across the tree of life, hosts have evolved immune systems that isolate pathogens, minimize
the harm that they cause, and, if possible, eliminate them from the body. We will focus on the
human immune system but
there are generalities true for most host-pathogen interactions.
Why are e ulerale to pathoges i the first plae? Why has’t atural seletio proided
us with impenetrable immune defenses?
Pathogens for their part evolve sophisticated and effective ways to avoid being eliminated by
their hosts’ iue systes.
Euglenoids
• Mostly photosynthetic
• Mostly freshwater
About 1,000 species, most in 3 genera
find more resources at oneclass.com
find more resources at oneclass.com
Parasitic relatives of Euglena
• Trypanosomes
– One flagellum
– Exclusively parasitic
– Mainly in insects
– In humans, they cause diseases such as leishmaniasis (ulcers of the skin and
viscera), and trypanosomiasis (sleeping sickness).
• http://pathmicro.med.sc.edu/lecture/trypanosomiasis.htm
Trypanosome morphology
The key to the trypaosoe’s suess is atigei variation
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
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