Biological Interactions Flashcards
limiting factor
key physical factor determining survival/growth/reproduction of an organism
Environmental gradient
temperature, moisture, light
Density
population abundance per unit area
carrying capacity
number of individuals / m^2 or ha
Broad environmental range
- ecologically tolerant
- eurytopic
- generalist
narrow environmental range
- ecologically intolerant
- stenotopic
- specialist
niche
- 2 dimensional representation of species environment
Predation
geographic range of predator is limited to geographic range of prey
stenophagus predator
- narrow range of prey species
- most plant eating insects
euryphagous predator
- most birds and mammals
- few exceptions
Why are some animals stenophagous?
- Prey with highest ratio of food energy relative to energy used for foraging: Optimal Foraging Theory
- Insects with resistance to toxins of 1 plant species
- Micro-environmental conditions for whole life-cycle provided by a single plant
Competition
- interaction between populations where both suffer
- for a common resources that is limited
intraspecific competition
members of same species
interspecific competition
members of different species
competitive exclusion
no 2 species can co-exist on same limiting resources
scramble competition
- resource competition
- when 2 or more populations use the same resource (food or territory) which is in limited supply
- indirect competition
- 1 population reduces the amount of food/territory available to the other
red squirrel
- prefers coniferous forest but also lives in deciduous forest
- major decline in geographic range 1920-1925 due to disease
- grey squirrel took advantage of this decline
grey squirrel
- adapted to deciduous forest but can colonise conifers
- introduced from USA to UK late 19th & early 20th century
- expanded by out-competing red squirrel for resources
how does grey squirrel out compete red squirrel
- grey better at foraging for acorns
- red prefer hazelnut
- red less able to neutralise acorn polyphenols
- post war decline in hazel coppicing
contest competition
- interference competition
- direct interaction between individuals (plants in competition for light)
Allelopathy: - chemical released by one plant species to inhibit growth of another plant species
- phytotoxic substances
overlapping rages of caiman species
- different environmental niche
- different prey
- not competing for the same resource
symbiosis
- close association between 2 species, resulting from co-evolution
- impacts geographic distribution
mutualism
benefits both specie
- lichen
- honey bee/humming birds and plants
commensalism
benefits one species but no impact on the other
- clown fish and sea anemone
parasitism
benefits one species at expense of the other
- tick
- lice
- tape worm
mimicry
- one species evolves the appearance or behaviour of another
Batesian mimicry
- one species that is neither poisonous or unpalatable evolves same appearance as another that is poisonous/unpalatable
Muelllerian mimicry
- both species evolve same appearance and equally unpalatable or poisonous to common predator
