Transcript Opuntia stricta

Predation
Great White Shark and Fur Seal
Plant defenses are developed at a cost
to fitness when:
1. Organisms evolve more defenses if they are exposed
to much damage and fewer defenses if cost of defense
is high
2. More defenses are allocated within an organism to
valuable tissues that are at risk
3. Defense mechanisms are reduced when enemies are
absent and increased when plants are attacked mostly true for chemicals not structures
4. Defense mechanisms are costly and cannot be
maintained if plants are severely stressed by
environmental factors
Pine beetle infestation – British Columbia
Pine Beetle and Pitch Tube
Serengeti Grazing System
Serengeti Grazing System
Serengeti Grazing System
Grazing facilitation
• Grazing facilitation occurs when the feeding
activity of one herbivore species improves the
food supply for a second species
Opuntia stricta – prickly pear
Prickly pear infestation in Australia
Area infested with prickly pear before biocontrol
Same area after biocontrol
Biocontrol Agent – Cactoblastis cactorum
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
Indirect
transmission
Plasmodium
(mosquito),
Plant viruses
(aphids),
Trypanosoma
(tsetse fly)
Lice, fleas, ticks,
aphids,
hookworm,
pinworm,
mistletoe
Tapeworms,
Schistosomes
(snails),
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
Frequency of infection
Parasites usually occur in aggregated distributions – due
to 4 possible factors:
1) random colonization events followed by asexual
reproduction in hosts that do get parasitized
2) environmental "hot spots" where parasite eggs and
infective stages survive well
3) dispersal constraints - geographic or behavioral
barriers limit dispersal of parasites to just a few hosts
4) variation in susceptibility of individual hosts - due to
nutrition, genetics
European rabbits as pests in Australia - 1938
Introduced pests in Australia –
red fox, rabbit, cat, pig, & goat