Midterm 2 Flashcards
What are the characteristics of a predator?
-capture, kill and remove prey from populations
What are the characteristics of Parasites?
- consume part of their hosts
- usually don’t kill hosts directly
What are Parasitoids?
- wasps and flies whose larvae consume the tissues of living hosts
- usually ending in death of the host upon pupation
- (have similarities to both parasites and predators)
What do Herbivores eat?
-eat plants and other primary producers
What is the difference between grazers and browsers.
- grazers eat herbaceous vegetation and algae
- browsers eat woody vegetation
What do detritivores and scavengers eat? And what are they especially important for?
- consume the tissues of dead organisms
- no direct feedback to the dynamics of their prey
- important for nutrient recycling
What are adaptations for consumers to exploit their prey?
- dentition (horse, deer, wolf)
- digestion (difference in carnivore and herbivore digestion)
- Jaw/mouth morphology (snake)
- behaviour (wolves, snake, pike)
What are the adaptations for prey to escape predators?
- crypsis (colouring matches the environment. Ex. Deer, owl)
- chemical defence (ex. Skunk. Some are not harmful just annoying and some are harmful)
- mimicry of noxious organisms (batesian and mullerian mimics)
- mechanical and morphological defenses (puffer fish, armadillo)
- behaviour (flocking, schooling)
What is Batesian Mimicry?
-palatable organisms that look like noxious ones
What is Mullerian Mimicry?
- noxious organisms that share a warning colour.
- Some are evolving to have less and less chemical defenses
How do copepods avoid predation?
-they stay in deep water during the day and migrate to the surface at night to get food
What are plant defenses against herbivory?
- structural (thorns, bark, etc.)
- chemical (alter the palatability and digestibility of plants)(inhibition, secondary compounds)
Examples of generalized inihibition for chemical defenses (plants)
- oak leaves vs. Lettuce leave
- tannins reduce availability of plant proteins to consumers, inhibit digestion
- poor growth of moth larvae (caterpillars)
What are the components of secondary compounds in chemical plant defenses?
- by products of plant metabolism, not used interfere with specific animal metabolism pathways, physiology, palatability
- many plant products used by humans are based on secondary compounds (eg. nicotine, caffeine, cocaine…)
Why are chilies hot to humans?
- plants that produce fruit want something to eat the fruit and disperse seeds
- small mammals don’t like hot chillies but birds don’t care
- birds have the highest (only) germination of seeds from chillis so the chillis have evolved to only allow birds to eat them
What are constitutive defenses?
-always at high levels (eg. oak leaves)
What are induced defenses?
- turned ‘on’ by herbivore damage
- eg. Mechanical damage to apical meristems (and saliva) stimulate higher leaf growth
Can herbivores control plant populations?
- grazers on a field
- outbreaks of spruce budworms that kill all the plants
What are exclosure experiments used for and what are the cons?
- used to quantify effects of herbivores on plant communities
- fences often do a lot more than keep organisms out. They could keep out wind, sunlight etc.
What is the optimal foraging theory?
-provides a formal framework with which to make predictions about foraging behaviour of predators
(What prey does a consumer choose to eat?)
(How far will a predator travel to capture prey?)
(How long will a predator search before giving up and moving on to another spot?)
How can the profitability of prey be ranked?
In terms of relative cost: benefit ratio
What does optimal foraging theory assume in respect to diet selection by consumers?
- consumers have adaptations to feeding on certain prey types
- all prey have certain benefits and costs associated with them
- profitability of prey can be ranked in terms of their relative costs and benefits
What are the predictions from optimal foraging theory for diet selection?
- when proffered prey are abundant, predator diets are dominated by the most profitable prey
- as preferred prey become scarce, predators begin to include less profitable prey in their diets
- diets are more diverse at low prey densities
Do predators reduce the densities of prey populations?
- predators often reduce prey below their carrying capacity. (Mite populations on strawberry plants)
- however, the severity of this predator control of prey varies widely among taxa, ecosystems and through time
What are some examples of predator prey cycling? When do these occur?
- Lynx and Hare (documented during fur trade)
- also occurs in rodents, fishes, insects etc.
- occur when there is a strong single predator-single prey interaction
How are predator prey interaction modeled?
- with math
- Lotka-Volterra predator-prey model
What is the prey equation?
dR/dt=rR-cRP
- r=prey growth rate
- c=capture efficiency
- R=prey
- P= predator
What is the Predator equation?
dP/dt=acRP-dP
- a=predator conversion efficiency
- c=capture efficiency of the predator
- d=predator death rate
What is the type 1 predator functional response?
- Linear increase with increasing prey assumed by Lotka-Volterra
- assumes that the feeding rate of the predator continues to increase linearly as the number of prey it encounters in nature increases
- uncommon in nature
What is the type two predator functional response?
- predator consumption saturates
- limited by handling time and digestion (satiation)
What is the type three predator functional response?
- accelerating phase at low densities
- saturation at high densities
- caused by prey switching/hiding places at low densities and satiation at high densities
What are the three predation components?
1) searching for prey (the more prey, the less time required to find one to attack)
2) attacking prey (most predators are well adapted for attacking their prey)
3) handling and digesting prey (handling time determines how many prey a predator can actually consume at any given prey density)
In the lab experiment what happened in ;the absence of refuges and immigration?
-both prey and predator populations became extinct
In the lab experiment what happened when they added a refuge?
-allowed the prey population to persist but the predators still became extinct
In the lab based experiment what happened when the allowed refuges and immigration?
-predator-prey populations maintained oscillations
What factors stabilize predator-prey systems?
- predator inefficiency
- density-dependence of predators or prey
- alternative food sources for predator
- refuges for prey
- reduced time delays in predator response to prey dynamics
How common are predator prey cycles in nature?
- pretty rare
- occur mostly in arctic ecosystems
What is the definition of competition?
The use of a resource by one individual that reduces its availability to other individuals
What is interspecific competition?
Occurs between species
What is intraspecific competition?
Occurs within species (eg. Logistic growth)
What is resource (exploitative) competition?
When organisms use common resources that are in short supply
What is interference competition?
Organisms seeking a resource harm one another in the process
What is allelopathy?
The chemical inhibition of one plant by another, due to the release of substances into the environment acting as germination or growth inhibitors
(Ex. Sage brush exuding toxins)
How to Eucalyptus trees out compete other species in the environment?
- they promote hot fires (oil)
- the fire kills seedlings and youth trees of potential competitors
- leaves the eucalyptus relatively unharmed
- thrives post-fire in lower competition
- similar to allelopathy
What were tansley’s conclusions in the common garden experiment?
1) species presence/absence could be due to competition
2) environmental conditions can affect competition
3) present species distributions could indicate competition from the past
4) closely related species often experience intense competion
What is an example of a nonrenewable resource?
Space
-once occupied, it is not replenished until the organism leaves
What are examples of renewable resources?
Nutrients, food etc.
-continuously replenished
What are the 3 types of renewable resources?
1) Externally supplied (rainfall, sunlight)
- weak or no feedbacks to consumers
2) Regenerated directly within the ecosystem (predator-prey, plant-herbivore)
- affected by consumer
3) Regenerated indirectly within the ecosystem (nutrient recycling by herbivores)
- weak but important feedbacks
What is the competitive exclusion hypothesis?
-2 species can not co-exist indefinitely on the same limiting resource or co-exist in the same niche
What is the fundamental niche?
- a species ‘role’ in the community
- overlap of all the tolerable conditions for that species
- impossible to measure
- infinite number of possible variables
- would need to measure species in the absence of competition/predation/etc.
What is the realized niche?
- the observe resource use of a species in the presence of competition
- can be a tiny fraction of the fundamental niche
What population growth are invasive species?
-an example of rapid population growth that can be modeled by the simple exponential or geometric growth equation (Nt=Noe^(rt))
Where are invasive species able to grow rapidly?
- Where there are no/few predators
- Where there is lots of food
- Where they start off as small populations below carrying capacity
What are native species?
-live in their place of origin/where they evolved and are called ‘endemic’ or ‘indifenous’ as well as ‘native’ at some spatial scale
What is an introduced species?
Live outside their place of origin, such as farm animals and many garden plants, and most have been moved because of humans, but can’t persist well in environments without the help of humans
What are invasive species?
Are introduced species that take hold, do not require human intervention to proliferate, and outcompete many native species for resources because they now live in a region where they have no predators or diseases to control their population growth
Why has the mountain pine beetle taken over some areas?
Forest fire depression has allowed them to exponential grow
-native species go through rapid population growth if humans remove predators or increase food sources and reduce mortality
Why are Humboldt squid expanding their range?
-due to climate change
What is the pathway to becoming an invasive species?
1) transport to a new area
2) establishment
3) population increase and range expansion
4) ecological or economic impact/harm
Why are degraded ecosystems more prone to invasion?
- overexploitation removes competitors/predators (low biotic resistance)
- habitat destruction creates high levels of disturbance (opens niche spaces, increase invasion)
How do you deal with invasive species?
- Prevention of transport to a new area
- Eradication during the establishment phase
- Control once it has reached the population increase and range expansion phase
When is eradication of a species successful?
- restricted geographic range
- small population size
- habitats easily accessible
- invader easily removed
Intentional transport
- species that are important to humans
- horticulture, agriculture, pet trade
Unintentional transport to a new are
- species that are small and go unnoticed
- fungus on vegetables transported across the globe
- invertebrates or larva in ship ballast water
What are inconsistent characteristics of introduced species that are able to establish and increase?
1) short generation time
2) multiple life stages
3) frequent reproduction
4) large number of offspring
5) vegetative reproduction
6) habitat generalist
7) small body size
8) able to disperse easily
9) few predators in native and introduced range
10) generalist predator
Biotic resistance
The ability of an ecosystem to resist invasion or establishment of an introduced species when native species diversity is high because all niches are being used and there ar few resources available for introduced species to use
What is the intermediate disturbance hypothesis?
Species diversity is highest at medium/intermediate levels of disturbance because competitive exclusion is not allowed to occur, but there is time enough for slower growing or slow to emigrate species to become present in a region. Most populations cannnot establish at high disturbance frequencies except for weedy fast growing species. At intermediate or high disturbance frequency levels niches open often enough that invasive species have a higher chance of establishing between disturbances.
What is the aim of invasive species control?
To reduce the population size below a damage threshold in hopes to restore native biodiversity to a desirable level
When prevention has failed and eradication and control are too expensive, or not working, what can managers do to conserve native biodiversity?
- monitor population and range expansion to learn more about how invaders will utilize and ecosystem and possibly learn about new climate, geographic, or ecological boundaries that may restrict the invader or predict which new habitat it will use
- focus conservation efforts on native species in areas where the invader is not or will not become present
How do we characterize a community?
The group of species living together in a particular area
What are assemblages?
-particular taxonomic groups within a community
Holistic community
Evolved, organized interdependent ecological unit (boundaries discrete/closed)
-closed communities
Individualistic community
- coincident group of species that occur in the same place, who can tolerate the local physical and biological conditions (boundaries subjective/open)
- open communities
What are ecotones?
- areas where environmental gradients are steep, and thus, species composition changes abruptly
- environmental gradients we can’t see
What is the simplified food web?
- Producer
- Primary Consumer
- Secondary Consumer
- Tertiary Consumer
What are the three types of food webs?
- Connectedness (shows feeding relationships among organisms)
- Energy Flow (shows connections quantified as energy flux)
- Functional or Interaction (emphasizes the influence of populations on growth rates in other populations)
What is the keystone species concept?
- some consumers can control community structure
- these consumers are called ‘keystones’ because when they are removed the entire community reorganizes
- requires experimental removals of particular species to test this
What is the difference between dominant species and keystone species?
-Both impact the community but dominant species have a high relative biomass
What is a food web?
- complementary way to characterize communities
- diagrams that show who eats whom in a community
- derived from an interest in understanding how energy moves through the organisms in an ecosystem
Tropic Cascades
Refer to the phenomenon whereby a top predator can affect the entire trophies structure and productivity of a community through its top-down effects
Omnivory
A species that feeds at multiple tropic levels
What happens to the food web when you have an omnivorous species?
You get a more complex food web
What is bottom-up control of a community structure?
-the abundance of trophic groups is determined by the productivity of producers
What is top down control of a community?
The abundance of trophic groups is determined by predation (from above)
What is species richness?
- count of the number of species in a community
- rarest species counts the same as the most abundant
How do you calculate species diversity?
-many way, but all of them require knowing the relative abundance of a species
What is an example of a positive indirect effect?
-trophic cascades
What is commensalism?
-species pairs where one benefits and the other is not affected
-not well-studied
-assumption of neutral effects for one species may not always be correct
(Ex. Barnacles on whales)
What is Mutalism?
-species pairs where both benefit
What are the three types of mutualism?
- Trophic: complimentary ways organisms obtain energy and nutrients
- Defensive: one species receives food/shelter in return for defense
- Dispersive: one species receives food in return for dispersal
