Topic 8 Flashcards
Ecological Interactions:
Competition
Herbivory and Predation
Mutualism, Parasitism & Disease:
Interspecific Ecological Interactions
What effect does the interaction with species B have on species A?
1st symbol is species B, 2nd symbol is species A.
+ + = mutualism
O + = Commensalism
- + = Exploitation (e.g., predation, parasitism, herbivory)
O O = Neutralism
O - = Amensalism
- - = Competition
Plants typically compete for:
Which resource is limiting depends on the habitat
Temperate trees: Above-ground competition for light
Creosote bush in deserts: Below-ground competition for water
Agricultural crops: Below-ground competition for N
plants compete for:
- light
- water
- nutrients
- space > below and above ground
Animals typically compete for:
Slace shelter. Territories, nest sites. Food. and access to mates
may be asked what resource is the object of competition.
Herbivory and Predation: Introduction
exploitation: interaction that enhances fitness of one individual while reducing fitness of the exploited individual herbivores tend to not kill the plants they are feeding on while predators usually kill their prey
Herbivory: Plant Defences
Plants with reduced fitness due to herbivory will be under natural selection to increase plant defences
Some examples of plant defence traits:
• Morphological defences e.g. thorns
• Chemical defences
e.g., Toxins that kill or repel herbivores
e.g., substances that reduce digestion
some can respond to herbivory by changing chemicals present in their leaves
Predation: Predator Avoidance - Animal Display
Aposematic colouration
Aposematic colouration: bright or distinct colouration in prey - advertises that prey are toxic or are distasteful
Predation: Predator Avoidance - Animal Display
Müllerian mimicry
Müllerian mimicry: several species of toxic animals share similar warning colouration or pattern.
Cycles of abundance in snowshoe hare & their predators
population influence between species > fluctuate together
Lynx and snowshoe hare populations show long-term cycles in population density.
This record of population cycles led ecologists to explore the role that predation may play in producing population cycles in a wide variety of northern animal species.
Parasites
Parasite: organism that feeds on another living organism typically without killing it
parasite infestation can be high level enough to cause physical distress / disease in their hosts.
Ectoparasites: ticks on a turtle
- Ectoparasites occur on the outside body of their host
- parasite is benefitted and host is harmed
Endoparasites: dog heartworm (nematode)
- endoparasites occur on the inside their hosts
Ghost Moose and Winter Ticks
winter ticks are ectoparasites that suck the blood of moose and when in high numbers they cause damage to the mooses fur causing them to have light coloured hair or patchy
number of ticks in the current year depends on the number of moose in the previous year
interconnectedness of predator and prey and host and parasite
Tick populations are related to last years’ host density.
Behaviour Modification by Parasites
Parasites may alter behaviour of host to benefit parasite transmission & reproduction.
e.g. Spiny-headed worms; starling host; isopod intermediate host
Example:
- cordyceps fungus - infect ants
> causes ants to climb up high, grab onto vegetation > fruiting body of fungus grows out of the ants body and spreads the spores to other ants > helps make it so that no species gets the upper hand
Mutualism and protection: Ants & Bullshorn Acacia
Mutualism:
Ants live on Acacia trees
Trees provide shelter, food, nectar
Ants provide protection and remove competition of other plants around it and remove bugs off it that try to eat it
Protection:
(3 ways trees benefit from ants (quantifying the benefits)
- Acacia shoots occupied by ants grew much faster.
- Survival of acacia suckers was much higher where they were occupied by ants.
- Acacia shoots without ants have much larger numbers of herbivorous insects.
