Symbiosis
Symbiosis
• Symbioses - species living in close
association
• Parasitism +,- parasite benefits, host harmed
• Commensalism +,0 or 0,0 can have positive
effect for one species or for neither
• Mutualism +,+ both species benefit
Gopher Tortoise – Commensal Host
Gopher Tortoise Distribution
Epiphytes
Bird’s Nest
Fern
Nalini Nadkarni
studying
epiphytes
Epiphytes
Figure 1: Hypothetical tree illustrating how
vascular epiphytes in humid forests tend to
partition substrates illustrating sensitivity to
micro climate, particularly humidity, and
associated development of the organic rooting
media required by some populations.
Parasitism and Disease
Lyme Disease Cycle in the UK
Parasitism
• Parasitism - intimate association between
two species in which the parasite obtains its
nutrients from a host - parasite usually
causes some degree of harm to its host either reduced growth or reproduction
• Pathogen – disease causing agent
• Disease – abnormal condition of host due to
infection by a pathogen that impairs
physiological functioning
Parasites on
Plants
Insects are green,
Fungi are brown,
Worms are blue,
Protozoa are yellow
Parasitism occurs on a continuum from:
• ectoparasites - live outside hosts body and
experience same conditions as host - ticks, mites,
fleas, aphids
• endoparasites - live inside host's body cavity buffered from outside conditions - tapeworms,
flukes
• intracellular parasites - live inside individual cells
of the host - viruses, bacteria, protozoa - often
called microparasites
Or another way to divide parasites:
• microparasites - viruses, bacteria, protozoa small, often live intracellularly, main point is that
they reproduce in host and will have very large
numbers in host
• macroparasites - tiny to very large - nematodes,
tapeworms, flukes - larger individuals that grow in
host but multiply by producing infective stages
that are shed by host to environment where they
infect new hosts
Parasite Transmission
• Direct transmission – from one host to
another of the same species via air, water,
coughing, blood, feces, etc.
• Indirect transmission – from one host to
another of the same species via another
species called a vector
• Vector – species which transmits parasite or
pathogen from one host to another
Microparasites
Macroparasites
Direct transmission
HIV virus,
Amoebic dysentery,
Mildews on plants
Lice, fleas, ticks, aphids,
hookworm, pinworm,
mistletoe
Indirect transmission
Plasmodium (mosquito), Tapeworms,
Plant viruses (aphids),
Schistosomes (snails),
Trypanosoma (tsetse fly) Rust fungi
Powdery Mildew on Grape Leaf
Powdery Mildew Life Cycle
Head Lice and Life Cycle
Mistletoe
Mistletoe Life Cycle
Malaria disease cycle
Schistosomiasis - Life cycle of the
schistosome worm
Worldwide incidence of schistosomiasis
Worldwide incidence of schistosomiasis
Rust Fungus Canker
Rust Fungus Life Cycle
Two ways to study parasite numbers
• Prevalence – percent of host population that
is infected – best for microparasites
• Intensity – number of parasite individuals
per host – usually best for macroparasites
European rabbits as pests in Australia - 1938
Introduced pests in Australia –
red fox, rabbit, cat, pig, & goat
Moose and White-tailed Deer
Deer – Moose brain worm interaction
Fungal parasites alter insect behavior
Giant ant w/o and with fungus
Avian malaria occurs in areas below
white line on Island of Hawaii
Hawaiian Crow – Extinct in Wild
I’iwi Honeycreeper – highly
susceptible to avian malaria
Akiapolaau Honeycreeper –
restricted to high elevation today
Amakihi Honeycreeper – shows
evidence of evolving resistance