Population Ecology

Front 1

Begon, Townsend and harpers definition of ecology (2006)

Back 1

the scientific study of the distributions abundance and relations of organisms and their interactions with the environment

Front 2

what are the main effects on population size

Back 2

In: immigration, birth

Out: emigration, death

Front 3

what are the influences on these rates (abiotic and biotic)

Back 3

abiotic: meteorological conditions, seasonal temperature fluctuations, terrain

biotic: interaction with conspecifics and heterospecifics

Front 4

what are individuals?

Back 4

individual of a species pass through different life history stages showing variation in condition within each stage

Front 5

details on modular organisms

Back 5

genets - gentic individuals

modules - shoots/polyps

sometimes better to count modules

Front 6

what is a population

Back 6

group of individuals of a species

may be discrete units, may be dispersed and studied at density level

counts impractical, estimates based on extrapolation

Front 7

name 4 methods of counting organisms per unit area

Back 7

quadrats

capture recapture

removal methods

abundance indices

Front 8

problems with measuring birth and death rates

Back 8

birth - may not occur when and where can be counted

death- remains short lived in environment

- capture recapture can estimate but confounded with emigration rate

Front 9

two primary factors that vary with age

Back 9

fecundity, mortality

Front 10

terms for reproduction in life history

Back 10

semelparous - single reproduction period

iteroparous - multiple episodes of reproduction

Front 11

2 types of life table

Back 11

cohort: follows individudals through time

static: cross section of population

Front 12

explain a simple annual cohort life table

Back 12

seasonal changes drive annual synchrony

every individudal breeds then dies

discrete generations

Front 13

What defines the reproductive value (RV)

Back 13

life history can be viewed by contribution to fitness

measures of fitness combine suvivorship and fecundity schedules

Front 14

example of reproductive cost (RRV)

Back 14

Pseudotsuga menziesii - the higher the number the cones (reproductive) the lower the growth of the annual ring

Front 15

investment in offspring - trade offs between number and what 3 fitness for individuals

Back 15

size vs number

survivorship vs number

developmental rate vs number

Front 16

4 life history variables

Back 16

growth

differentiation

storage

reproduction

Front 17

What are possible high cost of reproduction scenarios

Back 17

intense competition amongst established individuals, high reproduction affects RRV very negativley

small individuals vulnerable to mortality - outgrowing predation risk

Front 18

Possible low cost of reproduction scenario

Back 18

mortality homogenous

benign habitat

high mortality rates on large individuals (size selective predation

Front 19

offspring size sensitivty scenarios

Back 19

size sensitive - reproductive value rises significantly with size, small number of large offspring expected (e.g size increases in guppie offspring when predation focusses on smaller individuals

size insensitive scenario - reproductive value not strongly associated with size

Front 20

What does habitat cost of reproduction affect?

Back 20

reproductive allocation

age at maturity

semelparity / iteroparity

Front 21

age at maturity?

Back 21

maturity delayed in high cost of reproduction habitats

trade off between juvenile survival and reproductive value at maturity

Front 22

r - K Selection (MacArthur and Wilson) Describe K habitat with high CR, offspring size sensitive

Back 22

stable environment

crowded, maximal population

intense adult competition

high juvenile mortality

Front 23

characteristics of K habitat organisms (5 points)

Back 23

large

deferred reproduction

low reproductive allocation

few, large offspring

most short lived

Front 24

r habitat description with low CR, offspring size insensitive

Back 24

unpredictable environment

periods of indiscriminate mortality

mortality highly variable

mortality independent of density and individual condition

Front 25

characteristics of r habitat organisms:

Back 25

smaller size

earlier maturity

high reproductive allocation

many smaller offspring

survivorship depends on environment

Front 26

how can r - K be an over-simplification

Back 26

adult and offspring habitats may not be linked

r - K characteristics may arise from other pressures (e.g size specific predation)

Front 27

Begon, Townsend and Harpers definition of competition

Back 27

competition is an interaction between individuals, brought about by shared requirment for a resource, and leading to a reduction in the survivorship, growth and/or reproduction of at least some of the competing individuals

Front 28

intraspecifc competition in cave beetles

Back 28

beetle fecundity is correlated with cricket fecundity, beetles eat cricket eggs and reduce cricket density

higher density of beetles reduced the foraging and consumption of eggs in experiment

Front 29

asymmetrical competition?

Back 29

one individual may exert a much stronger effect on another individual

strong competitors may contribute disproportionately to the next generation, weak may not contribute at all

Front 30

density dependence in intraspecific competition

Back 30

higher densities effect competition

reduces birth rates and increases death rates with increasing density

but other factors produce density dependent effects

Front 31

defining density

Back 31

abstract concept that may be defined in different ways

per unit area

in or on habitat patches (e.g parasites on hosts), resource weighted density

problem defining density for sessile, modular organsisms, only compete with neighbours

Front 32

how does intraspecific competition regulate population size?

Back 32

as density increases so does competition. the mortality rate rises, and the birth rate lowers reaching a point where maximum density occurs (K). past this point the population reduces in size thefore density falls.

Front 33

Definition for the carrying capacity (K)

Back 33

the population size that can be maintained by environmental resources without a tendency for increase or decrease

in practice unpredictable environmental fluctuations lead to variation in k, so density dependent processes acting on birth and death rates tend to maintain population size within a range of values

Front 34

where is K not relevant?

Back 34

strongly overcompensating populations : there may be cycles or chaotic variation in population size