Lecture 16: Pop Dynamics continued Flashcards
Special problem of small populations
Allee effects may be occurring
Positive density dependence
You need enough individuals before population can exist
Threshold when population drops and will not recover on its own
Small populations more susceptible to
stochastic (random) variation- more susceptible to random events
Great chance of complete of population extinction
Greater chance of no reproduction
Stronger genetic drift: great probability of increase of bad alleles and loss of good alleles
All populations are finite and dependent on stochastic variation in…
everything!
(rainfall, predator populations, fecundity, surivvial, etc)
Demographic parameters can be strongly influenced by
weather
Population dynamics driven by
immigration
Metapopulation
a set of spatially isolated populations linked to one another by dispersal
Consists of source/sink populations and years
Source population
λ > 1, r > 0 (population increasing, constant rate of per capita pop growth)
population is thriving and support individuals to disperse to other areas
Sink population
λ < 1, r < 0 (population decreasing, constant rate of per capita pop growth)
population is decreasing, less likely to migrate
Population viability analysis (PVA)
Estimate the probability of extinction within
a given time period, given allee effects and
effects of stochastic fluctuations
What is recommended for population viability for maintaining to keep extinction risk ?
Population size to maintain to keep extinction risk below 5%
Why is habitat fragmentation bad for population viability?
turns big populations into many smaller ones, vulnerable to stochasticity
Habitat fragmentation amelioration (help)
Add corridors for species specific effectiveness
One large reserve better than many small reserves
Ex. Fish ladder
Not all individuals contribute in the same way to
population dynamics
Type 1 Survivorship Curve
Mortality increases with old age
Type II Survivorship curve
Constant mortality
Type III
High initial mortality for young age
Survivorship curves scale are
log/linear scale
Stage structure: Dependence of ____ on individual stage
vital rates
Stages include
Sex
Age
Size
Developmental stage
Common life history tradeoffs
Allocate to current population OR growing bigger first (risking death) and reproducing more
Few large offspring OR many small offspring
fast r-selected
species that do well under high resource conditions, immediately after disturbance
slow k-selected
species that are competitive and do well when resources are limiting
Community
Populations that live together in a defined area
Competition
(-/-)
interaction hurts both species
Predation
(+/-)
Benefits one and hurts other
Herbivory
(+/-)
Benefits one and hurts other
Parasitism
(+/-)
Benefits one and hurts other
Disease
(+/-)
Benefits one and hurts other
Mutualism
(+/+)
each species benefits the other
Commensalism
(+/0)
One species benefits while the other is unaffected
Types of carnivores and their food sources
- Predator, prey
- Parasite, host
- Parasitoid, host
- Pathogen, host
Carnivore: Predator, prey
Predator kill and eat all of an individual of a resource species
Predators usually larger than their prey
Ex. Lion, antelope
Carnivore: Parasite, host
Parasite live off resources of a host, but rarely kill the host
Often lie inside host, usually smaller
Ex. Tick, cow
Carnivore: Parasitoid, host
Parasitoids are combination parasite/predators
Certain fly or wasp species larvae-live in a host insect, eat it kill it when or just before emerging as adults
Ex. baconoid wasp, tabacco hornworm
Carnivore: Pathogen, host
A pathogen is a parasite that is a bacterium, virus, or other microorganism that causes disease
Much smaller than their hosts
Live in or on the body, may or may not kill the host
Ex. malaria, human
vector: mosquito
Types of herbivores
- Grazers
- Browser
Herbivore: Grazers
Eat mostly grass
Ex. cow
Herbivore: Browser
twigs and buds also major part of their diet
Ex. deer
Other vertebrates herbivores eat grass and also..
seeds, nectar, or other plant parts
Ex, hummingbird eating nectar and squirrel eating acorn of trees
Herbivore: leaf miners
insect larvae that live and feed within the leaf tissue of plants.
Most herbivorous insects are
specialists on only one or few plant species
Plant pathogens
plant disease causing microorganisms
Ex. fungi, bacteria, or viruses
Why is adaptation for jaws and teeth benefit for herbivores?
Grinding surfaces (ex. molars) good for eating plants with lots of cellulose, and lignin like grasses and twigs
Why is adaptation for jaws and teeth benefit for carnivores?
Shearing surfaces, like canines, have for cutting meat and holding prey
Ex. mountain lion
Long rows of pointed teeth for catching, holding, and eating aquatic prey
Ex. killer whale
Adaptations from hiding
Hide when predators are present, less time for foraging food
Ex. Bullfrog tadpoles are hunted by fish and dragonfly larvae
Crypsis
Adaptation of blending with environment to hide from predators
Adaptations: mobile escape
Ability to sprint at fast speeds to run from predators
Ex. pronghorn antelope
Adaptations: physical protection
Physical protection helps escape from predators
Ex. shell of turtle to hide, or thorns on plants
