EE27

Question 1

what is density dependence?

Answer 1

when the per capita rate (ie mortality or growth) changes with density

Question 2

define intra-specific competition

Answer 2

individuals of the SAME species competing for resources (food,space,mates) and leading to a reduction in growth,survivorship or reproduction of at least SOME of the competing organisms`

Question 3

big populations grow faster because there are more reproducing individuals - is this density dependent?

Answer 3

no, density dependence is per capita

Question 4

does the per capita growth rate change if r is constant?

Answer 4

no

Question 5

if you increase N (effective population size) what happens to per capita growth rate

Answer 5

it decreases

Question 6

when N is low what density dependence effect is there and is there lots of growth?

Answer 6

little density dependence effect but small pop size so growth is limited

Question 7

when population size is 50% of K what density dependent effect is there and is there lots of growth?

Answer 7

both growth rate and pop size middling so max new individuals added

Question 8

when N is high what effect does density dependence have?

Answer 8

strong density dependence therefore growth is limited despite large population.

Question 9

what is the mechanism for density dependence?

Answer 9

competition

Question 10

Give specific examples of animal competition leading to density dependence.

Answer 10

1) rabbits-overgrazing
2) trees-light and nutrients
3) Eagles-hunting territory/nest sites
4) caterpillars-resource comp,produce pathogens

Question 11

what is antibiosis?

Answer 11

an antagonist association between 2 organisms in which one is adversely effected e.g poisoning,spirochetes

Question 12

explain exploitation vs interference

Answer 12

exploitation-indirect,individual responds to level of resource,resource is limited
Interference-direct interaction.individual prevents another exploiting resources e.g defending territory or harem ownership

Question 13

define scramble competition

Answer 13

all individuals have equal access to a scarce resource and eventually all individuals adversely affected and none survive

Question 14

define contest competition

Answer 14

dominated and hierarchy based,some individuals have access to adequate resources (those with territory) whilst others will have no access and may die

Question 15

what is more stabilising scramble or contest comp?

Answer 15

contest. low pop everyone gets territory and in high pop only some do but this means at least some individuals always reproduce e.g florida scrub jays

Question 16

examples of scramble comp (4)

Answer 16

1) cows grazing in a grassland
2) forest defoliators. If their larvae can find shelter and food then survival is possible, but when all the foliage is destroyed then the population decreases.
3) success of small beetles over large beetles. While larger beetles, similar to larger animals in general, tend to win more often in contest competition, the opposite can be true in a scramble competition
4) Tribonium beetles in a jar of dried peas

Question 17

interference comp example

Answer 17

ant Novomessor cockerelli and red harvester ants, where the former interferes with the ability of the latter to forage by plugging the entrances to their colonies with small rocks.

Question 18

what is apparent competition

Answer 18

occurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both prey of predator C. The increase of species A may cause the decrease of species B, because the increase of As may aid in the survival of predator Cs, which will increase the number of predator Cs, which in turn will hunt more of species Bccurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both prey of predator C. The increase of species A may cause the decrease of species B, because the increase of As may aid in the survival of predator Cs, which will increase the number of predator Cs, which in turn will hunt more of species B

Question 19

what 3 types of competition are there by mechanism

Answer 19

interference,exploitation and apparent

Question 20

define competition

Answer 20

an interaction between organisms or species in which the fitness of one is lowered by the presence of another

Question 21

what is the competitive exclusion principle?

Answer 21

species less suited to compete for resources should either adapt or die out (but this is rarely found in natural ecosystems)

Question 22

what is the room to roam hypothesis?

Answer 22

competition within and between species for resources plays a very relevant role in natural selection, however, competition may play less of a role than expansion among larger clades

Question 23

what is compensation?

Answer 23

the degree to which larger population numbers are compensated for by higher mortality and lower fecundity

Question 24

define overcompensation and what comp type is there a tendency towards?

Answer 24

many more die or less are born in the large population, so much so that the large population becomes smaller than the initial small population after a fixed period. Tendency towards scramble comp

Question 25

what organism has exact compensation?

Answer 25

brown trout. populations will match

Question 26

define undercompensation

Answer 26

more die in the larger population or less are born in the larger population but the larger population still remains larger than the initially smaller population after a fixed period

Question 27

describe the compensation types and density dependence of the flour beetle at different times?

Answer 27

1) density independent at low density
2) under compensating density dependence at intermediate density
3) overcompensating density dependence at high density

Question 28

what compensation does scramble competition lead to?

Answer 28

extreme overcompensation and the increase in numbers is not matched to the decrease in growth rate until all the resources are used and the population crashes

Question 29

what competition leads to exact compensation?

Answer 29

contest competition.As numbers increase growth rate decreases because there is an exact number of “places” available in the population

Question 30

what is an allee effect?

Answer 30

sometimes increasing density dependence increases the per capita growth rate or decreases the per capita mortality rate

Question 31

what are examples of the allee effect?

Answer 31

whales-mate location
wildbeast herds-predator swamping
pathogen invasion-thresholds for infection success

Question 32

In humans is selection stabilising or destabilizing?

Answer 32

birth rates decline with density increase so we are destabilizing

Question 33

what is stabilizing selection?

Answer 33

a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value.

Question 34

Why is stabilizing selection thought to be the most common action for natural selection?

Answer 34

This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time.

Question 35

what does stabilizing selection make use of?

Answer 35

negative selection.

Question 36

what is negative selection/purifying selection ?

Answer 36

The selective removal of alleles that are deleterious. This can result in stabilizing selection through the purging of deleterious variations that arise.

Question 37

The logistic model has linear dependence of per capita rates on density-why is this mode flawed? (4)

Answer 37

1) Individuals with territories have access to adequate resources, others get nothing
2) Equal access to resources for all (past population size threshold not linear (all die)
3) undercompensation and overcompensation
4) allee effects

Question 38

what is an example of positive density dependence?

Answer 38

Guillemots

Question 39

what is logistic population growth model with K put in?

Answer 39

dN/dt = rN(1-N/K)