Interspecific Interactions in Communities and Keystone Species

types of interspecific interactive relationships

• predator-prey

• parasite-host

• interspecific competition for resources

presence of predators helps control prey populations

• get rid of the genetically unfit and old

density - dependent or independent

density-dependent - larger and more crowded populations are more vulnerable

more individuals are grouped together, making them an easier and more noticeable target for predators

less hiding spots

Predator-prey relationships

• crash in prey population

  • predator population crashes - no food

• no predators - prey population increases

  • predators population now increases as food is abundant

• predators increase and the prey population crashes

cycle continues

why are the two populations out of sync

• it takes some time for the effects of one population to be felt by another population

why are there less predator then prey

• because a predator feeds on more then one prey due to being at a higher trophic level and only 10% of the energy being transferred from one to the other.

• Prey animals often reproduce more quickly than predators

how could these predator prey relationships vary in the wild

• predators may have different prey species so they wouldnt die out when one of their prey sources did.

• density dependent factors such as overgrazing, disease arent taken into consideration

how do parasites work

• attack and weaken their designated host species

• make them more vulnerable to disease/predators and increase mortality rate

parasites; density-dependent/independent

• density dependent because in crowded populations parasites can more easily spread

conventional parasites

• feeds off organism internally or externally p

parasitoids

• kill their prey

  • only if the host has fed the parasite well enough

parasitic castrators

• effect reproductive potential of their prey

  • brood parasites and mimics

name an example of

conventional parasite

internal parasite

external parasite

parasitoid

parasitic castrator

brood parasite

1. tapeworm, mosquito

2. tapeworm, athlete’s foot, ringworm

3. tick

4. wasp

5. bee’s orchid

6. cuckoo

Coevolution

• predator and prey kill the least genetically fit of prey

• only the fittest survive to reproduce, meaning each generation gets fitter and fitter

• predators and parasites also get better and better at catching the prey

• ‘arms race develops’

list different strategies or adaptations evolved by predators to capture and subdue prey

• venom, small predators can subdue larger prey then theym

• pursuit

• pack hunting

  • ambush

list different adaptations evolved by prey to avoid or deter predators

• poison, bad taste

• armor/spines

• diversion tactics

• camouflage

• fear factor (Making urself larger than you acc are)

• safety in herds

list different adaptations evolved by plants to deter grazing

• toxins

• spines

• aromatic herbs

• height

• tougher tissues

keystone species

• population with a disproportionality large effect on the community as its presence maintains a high biodiversity

how do keystone species maintain a high biodiversity

• controlling dominant species in the community

  • providing critical resources needed by several species

what happens if the keystone species dissapears

• massive plummet in biodiversity

  • not all communities have a keystone species but if they do it is important to maintain that

critical to env health and community stability

example of keystone species

• Ochre sea star - preys on mussels

• if removed mussels take over and biodiversity decreases from 25 species to about 2 or 3

• sea otters and sea urchin

• grey wolves in greater Yellowstone ecosystem

why is the study of keystone species important in biodiversity conservation projects

• if you mistake the keystone species you could destroy an ecosystem