Test 2 - Species Interactions Flashcards
Name the 6 species interactions
- Competition
- Predation
- Herbivory
- Parasitism
- Disease
- Mutualism
Definition of Competition
two organisms use the same resource, or seek that resource, to the detriment of both
Disease
an association between a pathogenic microorganism and a host species in which the host suffers physiologically
Predation
one animal species eat all or part of a second animals species
Herbivory
one animal species eat all or part of a plant species
Parasitism
two species live in a physically close, obligatory association in which the parasite depends metabolically on the host
Mutualism
two species live in close association with one another to the benefit of both
Resource Competition
Last test should remember
occurs when a number of organisms, of the same or different species, use common resources that are in short supply
Interference Competition
occurs when the organisms seeking a resource harm one another in the process, even if the resource is not in short supply
Gauses hypothesis
“As a result of competition, two similar species scarcely ever occupy similar niches, but displace each other in such a manner that each takes possession of certain kinds of food and modes of life in which it has an advantage over its competitor
When does competition exclusion occur in labs (3 things)
- environment is unstable - not reached equilibrium
- Resources are not limiting
- The environment fluctuate such that direction of competition reverses before extinction
Why in stable environments do species often live together
- Competition was always rare in nature - resources often not limiting
- Competition has been common in nature but could adapt away
how do Dendroica warblers survive alongside each other
- Feed at different positions on tree
- different areas
- different ways of moving
How do they feed alongside each other - tern species on Christmas island
Same way and resources but different sized fish depending on beak size
If observed differences in resources need to know if …
- Competitions in past
2. Speciation
Where is strength of competition mostly seen
Herbivores
Due to competition how can species diverge where they occur
- reinforce reproduction barriers in closely related species
- If overlap character differences may mean they keep distance
Beak sizes of Darwins finches characteristics
Fortis and fuliginosa when separate very similar but when together fortis beak bigger and vice vera
r-selected animals
Seldom suffer pressure from interspecific competition during colonization and establishment - evolve no competition
Evolove to invest enery in reproduction - small
k-selected animals
Suffer pressure from interspecific competition at or near the carrying capacity
evolve to get bigger have less offspring but invest in offspring
what is a competitive strategy and give an example
Low intensity of stress and intensity of disturbance
e.g trees
(k)
What is a ruderal strategy
Low intensity of stress and high intensity of disturbance
e.g weeds
What is a stress-tolerant strategy
High intensity of stress and Low intensity of disturbance
e.g evergreen
5 types of predator
- Carnivore
- Herbivore
- Insect parasitoid
- Parasite
- Cannibal
Insect parasitoid
lay eggs on insect host, which is killed and eaten
Indirect effects with and without predator competition
with - exploitation of shared prey
without - competition between prey drives pattern
what does predation do ?
- restricts competition
- Affects the organisation of a community
- Drives natural selection and adaption
the 3 case studies on affect of abundance of prey
Skunk - duck eggs
Dingo - red kangaroo
Sea Lamprey - local trout 4
Skunk case study
Removal of skunks increased duck eggs massively
4 components of predation
- numerical response
- Functional response
- Aggregative response
- developmental response
Numerical response
The density of predators in a given area increases by reproduction
- wolves increase with moose density until territoriality restricts numerical
Functional response
The number of prey eaten by individual predators changes, often with prey density
- Handling time
- quicker species can eat prey more can be eaten
Developmental response
One in which individual predators eat more or less prey as predators grow towards maturity
- two different eating patterns means more or less prey consumed
Aggregative response
One in which individual predators move into and concentrate in the study area
Bay breasted and budworm
Individuals saturated quickly
more food =more birds
as insects become more abundant they then become swamped
budworm sometimes lads sometimes none
’ the world is green’
- controlled by true predators, releasing plants from herbivory
- some plants or part of plants are inedible, evolved to restrict effect of herbivory
how do plants adapt defences against herbivores
- Structural - thorns, tough leaves
2. Chemical - secondary plants substances
English oak (pedunculate)
- Dominant tree in deciduous woodland
- leaves attacked by more herbivore species than any other tree
Why is the English oaks leaves mostly attacked in spring
Leaves become less palatable with age, get tougher than young ones
Do larvae feed on both old and young leaves when they are ground up, full or both
ground up
what is the difference between species tat feed in spring and summer
Summer species have a slower growth rate as old leaves are low in nutrients
what are tannins
A secondary plant substance that binds proteins in complexes, reducing the palatability of leaves for herbivores
How much tannin is needed in an Oak leaf to reduce winter moth larva
1%
How do species feed in summer with tannins around
They feed onto parts of the leaf tannins are not found
How do herbivores compensate with oak trees defending themselves both chemically and structurally
concentrate feeding in early spring, altering their life cycles
Name a mutualistic system and explain
Ants and acacias in neotropics
- acacia depends on ants for defence while ants depend on acacia for food
Serengeti plains - why do large grazing mammals interact
food, limited or cooperate to harvest plant material
how many : wildebeest, gazelles, zebra, buffaloes?
1,000,000
600,000
200,000
65,000
what parts of the plant do zebras, wildebeest and gazelle eat
zebras - mostly stems, sheaths
Wildebeest - more sheaths, leaves
gazelle - sheaths, other herbs others don’t consume
Compare population sizes of gazelle, wildebeest and zebra to rainfall and grass
rainfall peak being of spring, grass similar but delayed compared
wildebeest - high spikes when rainfall and grass lowest
zebra - population highest when both grass and rainfall is too
gazelle - peaks when wildebeest and zebra low
What does wildebeest do to grass
Reduces plant biomass by 85% and plant height by 56%
What is there no evidence for on the Serengeti plains
The 3 animals competing for food
zebra breaks down grass for wildebeest and they then prepare grass for gazelles
Lots of different types of algae
name a small, medium and large
small - Prostrate
medium - stalked filamentous
large - filamentous
what are single celled algae
diatoms
effect of grazing of benthic algae by herbivourous stream insects
unglazed tiles places in stream
- algae rose quickly in first 2 weeks
- fell when helicopsyche rises
- rise again when helicopsyche loses instrest
Algae can be controlled by herbivores but most plants aren’t why?
algae are so small relative to herbivore where as in other places there is not that difference
herbivourous invertebrates can affect
- biomass
- taxonomic composition
- physiognomy
species richness
Effects of grazing depends on
- herbivore density and consumption rate
- match between grazer mouthparts and algal structure
- productive capacity of algae
