topic 7 - r and k selection

Question 1

r and k selection theory?

Answer 1

• MacAurthur & Wilson (1967)
• Organisms can be classified as r or K strategists based the
relative importance of r & K in their life cycles

Question 2

r vs k selection?

Answer 2

Ability to compete near K (K-strategists)

– Ability to rapidly colonize (r-strategists)

Question 3

empty island - how would r strategy work? when is it favored?

Answer 3

• Initially, natural selection would favour:
○ r -strategists
– Organisms that can reproduce rapidly in an uncrowded
resource-rich environment
– Organisms with large r
• Populations would eventually increase
• Crowding = competition for resources

Question 4

empty island - when would k selection be favored

Answer 4

Populations would eventually increase
	• Crowding = competition for resources
	• Natural selection favours
	– Organisms able to sustain population growth near carrying
	capacity
	• K-strategists
• Strong competitors

Question 5

describe r selected species

Answer 5

• r-selected species
– Good colonizers (high r)
– Rapid growth when resources are abundant
– Habitats with high level of disturbance

Question 6

describe k selected species

Answer 6

• K-selected species
		– Populations near K
		– Limited resources
		– Traits favoring efficient use of resources
		(good competitors)

Question 7

r selected survivorships? look at graph

Answer 7

type II 
high juv. mortality 
not near K 
high repro rates 
thrive in unpredicted environments (high r) 
ex. plants

Question 8

K selected species survivorship?

Answer 8

type I
low juv mortality
near K, crowed (experience effects of density)
low repro rates
thrive in stable environments, depend on future repro
ex. humans

Question 9

is it easy to classify as one of these? ex that falls between?

Answer 9

• Many organisms fall between r and k - hard to classify all species like this
ex corals, type ii survivorship curve