3 - Populations, Survivorship Curves & Competition

Define a life table

a numerical summary of the products of fecundity and mortality of a population

What does a life table allow us to do?

look at the changing nature of populations and predict future trends

Life tables: define a_x

number alive at the start of a stage

Life tables: define l_x

proportion of the original cohort surviving to the start of stage x.

Life tables: define d_x

proportion of the original cohort that “dies” in that stage

Life tables: define q_x

stage specific mortality rate (d_x / l_x)

Life tables: define F_x

total fecundity - the number of offspring produced by the cohort at that stage

Life tables: define m_x

individual fecundity (F_x / a_x) - how many offspring are being produced on average per individual

Life tables: define l_x m_x

the fecundity per original cohort member (Fx / ao)

Life tables: define R_o

basic reproductive rate - mean number of offspring produced per individual at the end of cohort

Ro = 1

population is stable

Ro < 1

population is in decline

Ro > 1

population is increasing / too high

Survivorship curves

plotting out mortality over time to see changes of development

State the 2 major reproductive strategies

r and k

Define r selection strategy

having very numerous young, but with little investment per individual

Define k selection strategy

having few offspring but investing heavily in each one

State population structure as a result of r strategy

will have a population structure heavily biased to juvniles

State population structure as a result of k strategy

will have a population structure biased towards adults

Define interspecific competition

competition between species

Define direct interspecific competition

two species directly fighting over a resource

Define indirect interspecific competition

two species eating the same resource but with no direct fighting

Define intraspecific competition

competition between individuals of a single species

State the two extremes of intraspecific competition

scramble and contest competition

Define scramble competition

all individuals scrambling for the resource with none likely getting enough to sustain them

Define contest competition

direct fight as to who gets a resource, with the winner getting enough to sustain them

Define population density

population size over a given area

State two measurements of population density

absolute and relative