populations

Question 1

what determines how pop change in size through time?

Answer 1

• immigration / emigration
• death
• birth rates

Question 2

3 mechanisms of density dependence?

Answer 2

• competition
• predation
• disease

Question 3

demography

Answer 3

study of rates of…

• births
• deaths
• immigration
• emigration

and factors that cause them to vary

Question 4

life tables

Answer 4

• summarises survival & reproductive rates in diff age groups
• based on single cohort
• requires long-term study of pop with marked individs (birds, mammals, plants)

Question 5

cohort analysis

Answer 5

start with large no. individ at birth (ages between 0 and 1) -> see how long it takes them to die

Question 6

sessile organisms

Answer 6

cannot move on their own / lack ability for self-locomotion

eg. oysters

Question 7

population def

Answer 7

group of individ of same species…

• in a given geographical area…
• that is more or less distinct from other groups

Question 8

suggest why pop studies can sometimes be inaccurate

Answer 8

edge of pop not well defined as hard to judge where one pop ends

-> edge is human determined not geographical

Question 9

some def for a pop include that individuals in a pop can interbreed, but that is a bit restrictive
-> why?

Answer 9

-> juveniles cannot breed

-> social interaction limitations for some sp

-> some species breed asexually

Question 10

suggest why density of a pop is better measured by measuring ‘individ per unit area’ not by measuring absolute pop size

Answer 10

• may occupy v large area
• easier to make comparisons between pops

Question 11

measuring pop density

Answer 11

• count all individ
• count individ in random samples / along a transect
• convert from density of indicators (nests, burrows, fecal droppings, mole hills)

-> as some species are really hard to find (nocturnal, camouflage, rare, etc)

Question 12

capture-mark-recapture

Answer 12

• capture set of individs
• mark and release them
• capture another set
• % marked individs in 2nd set = % that 1st was of total pop

Question 13

logistical model

Answer 13

• growth slows down at higher densities (bigger pop size)
• implication: birth-rate, death-rate, migration-rate change with pop density

Question 14

density of a pop

Answer 14

no. individs per unit area/vol

eg. no. of oak trees per km²

Question 15

dispersion

Answer 15

pattern of spacing among individs within boundaries of the pop

Question 16

density dependent examples

Answer 16

• a death rate that ↑ with pop density
• a birth rate that ↓ with ↑ density

Question 17

density independent factors

Answer 17

• eg. temp & precip.

-> can cause dramatic changes to pop size

Question 18

mechanisms of density dependence

Answer 18

-

Question 19

density dependence regulation

Answer 19

influence of pop density on birth rates & death rates

• as pop density ↑…
• resources become more limited
• competition for resources ↑
• factors like predation, disease & intraspecific competition may lead to ↑ death rates or ↓ birth rates

Question 20

disease in density dependence

Answer 20

• disease transmission
• ↑ density –> more contacts -> ↑ transmission
• e.g. resp diseases (flu & TB)

-> but less so for sexually transmitted diseases

Question 21

causes of pop fluctuations

Answer 21

• change in abiotic env
• scramble/contest competition
• predator-prey interaction
• disease
• metapops -> group of spatially sep. pops of same sp which interact at some level
  -> where suitable habitat occurs in patches in land/sea