module 12 Flashcards
exploration can affect competition consumer-resource(exploitation) detritivore-detritus mutualism
a population (-)(-) (+)(-) (+)(0) (+)(+)
Exploitation predators parasistes parasitoids pathogens
Interaction between populations
Enhances fitness of one individual while reducing fitness of the exploited individual.
Predators – Kill and consume other organisms.
Parasites – live on host tissue and reduce host fitness
Do not generally kill the host.
Parasitoid – insect larva that consumes the host.
Pathogens induce disease.
3 Feeding Methods of Heterotrophs:
Herbivores: Feed on plants.
Carnivores: Feed on animal flesh.
Detritivores: Feed on non-living organic matter.
Herbivory grazing browsing granivore frugivory nectivory
Consumption of plants or plant parts Grazing – eating grass or forbs Browsing – Eating leave or young shoots Granivory – seed predation Frugivory – consumption of fruiting bodies Nectivory – consumption of nectar
Substantial nutritional chemistry problems
Plant composition differs from Animal composition
-plants have ____ concentrations
must overcome plant defenses
physical and chemical
low nitrogen concentrations
Must overcome plant defenses Physical Thorns Waxes & Resins Cellulose, lignin, silica
Chemical
Toxins
Digestion Reducing Compounds
Detritivores consume food rich in often poor in dead leaves has fresh detritus may still have
Consume food rich in carbon and energy
Often poor in nitrogen
Dead leaves may have half nitrogen content of living leaves.
Fresh detritus may still have considerable chemical defenses present.
Carnivores
consume ______ preg
can’t choose prey at will
Consume nutritionally-rich prey Cannot choose prey at will -Availability & Capturability of prey -Risk involved -Select whole organisms Not nutrients
-Most are well balanced nutrtionally
May selectively consume parts
predators and seed predators
high probability of death low duration of association
parasitoids
high death high association
grazers and browsers
low death short duration
parasites and anrthropod herbivores
low death high high durations
Parasites That Alter Host Behavior
Spring-Headed Worm (Acanthocephalans)
- Changes behavior of amphipods
- Make it more likely that infected amphipods will be eaten by a suitable vertebrate host.
- Infected amphipods
- Swim toward light
- Usually indicative of shallow water
- Closer to predators.
-make it susceptible to predators to continue life cycle and spread
Herbivores Effect on Plants
short term effects
Short Term Effects -strict negative-decreases when fed on compensation Morphological & physiological adjustments counter losses up to a threshold -compensate for loss -after a while can't compensate
Overcompensation
increase in performance, growth, or fitness under low to moderate grazing
Long Term Effects?
why does Compensation occur
increased Plant Activity
Timing & Intensity
Increased Ecosystem Functioning
-nutrients go back to increase production through feces or death
Elton
and Keith
proposed driven by variation in solar radiation.
increase radiation, increase production-population goes up at the same time cycle
Keith- Suggested overpopulation theories: Decimation by disease and parasitism. Physiological stress at high density. Starvation due to reduced food. -overpopulation occurs decrease because of stress disease starvation
Snowshoe Hares - Role of Food Supply
In winter browse on buds and stems Shrubs and saplings such as aspen and spruce 2 Effects Greatly reduce Food Supply Greatly reduce food biomass Late November = 530 kg/ha Late March = 160 kg/ha ~ 70% reduction in food supply Alter Food Supply Shoots produced after heavy browsing Increase levels of plant chemical defenses Reducing usable food supplies
-increase chemical defenses when hares feed heavily, this makes it harder to get nutrients and causes decrease of hares- easy to prey Ono
Snowshoe Hares - Role of Predators
Predation
60-98% of mortality during peak densities.-easier prey since they have no more nutrients they ate it all
Lynx
Classic specialist predator
Other Specialist predators have similar responses
Coyotes may also play a large role.
Complementary role of predations & Food:
Hare populations increase
Causes:
Food supplies to decrease
Starvation and weight loss
May lead to increased predation
All decrease hare populations
Lotka-Volterra assumes Host population :
limited by
Grows exponentially
limited by parasites, pathogens, and predators:
rhNh =
Exponential growth by host population.
Opposed by:
p =
Nh =
Np =
p = rate of parasitism / predation. Nh = Number of hosts. Np = Number of parasites / predators.
Lotka Volterra assumes:
Parasite/predator growth rate is determined by:
- Rate of conversion of food into offspring
- Minus mortality rate of parasitoid population:
c p Nh Np
Conversion rate of hosts into offspring.
p Nh Np
Rate at which exploiters destroy hosts.
c=
Conversion factor
-Rate at which prey biomass transformed into predator offspring
Model Behavior
Host(prey) population dynamics
more predators=
larger predator population eventually
in turn ______ predator population
Growth
-Exponential
- Growth opposed by exploitation.
- -Host reproduction immediately translated into destruction by predator.
- –Increased predation = more predators.
- –More predators = higher exploitation rate.
- –Larger predator population eventually reduces host population
- –In turn reducing predator population.
