REMEMBER THE TERMS
WAT IS ‘N BEVOLKING?
What is a population?
Individue van …
 dieselfde spesie wat
 in ‘n afgebakende
(spesifieke) gebied bly
en
 wat lukraak kan inteel.
Individuals of …
 the same species
 living in a demarcated
(specific) area and
 that are able to
interbreed randomly.
Examples of populations
Gemeenskappe
 Gemeenskappe sluit al
die bevolkings van ‘n
gebied in bv. Al die
springbokke, leeus,
doringbome en
bosluise in die Kruge
Nasionale Park.
 Of al die walvisse,
haring en plankton in
die Noordsee.
Community structure
Various organisms form part of a community
We want to know three things about a
population:
 Size – how big is the
population (how
many are there)?
 The density of the
population- how many
per unit of habitat/
environment.
 The distribution
patterns of the
individuals in the
population.
Prickly Pear (Opuntia) an alien invader
population in the Karoo-Nama biome
nataliteit
Vier dinamiese parameters beïnvloed die
grootte van ‘n bevolking
immigrasie
Geboorte
natality
Grootte van
bevolking
emigrasie
mortaliteit
Sterfte
mortality
Factors that influence size of
population
 Birth – Natality – new individuals that are born into
the population.
 Death – Mortality – individuals in the population
that die.
 Immigration – individuals move into the population.
 Emigration – individuals leave the population.
These are the four dynamic population
parameters.
More dynamic parameters
 The four dynamic
parameters are: natality,
mortality,
immigration and
emigration.
 Growth is a parameter
for population size if the
population is measured
in biomass.
 Migration plays a
seasonal role.
Hoe meet ons die grootte van ‘n bevolking?
 DIREKTE METODES:
 DIRECT METHODS:
Organismes is groot
genoeg en beweeg nie
rond nie. ‘n Sensus word
geneem – tel bv. Mense
of mossels op rotse.
 INDIREKTE METODES
gee ‘n benaderde syfer.
Individuals are big
enough and do not move
a lot. A census is takencount e.g. people or
mussels.
 INDIRECT METHODS
give an estimated
number.
How do we determine the size of a
population?
1. DIRECT METHODS – give accurate size of
population e.g. counting/ census. Organisms
must be ...
• big enough
• stationary (not moving) or slow-moving
• not too many in too big an area
How do we determine the size of a
population?
2. INDIRECT METHODS – gives an estimate,







not exact number. Can be accurate enough to
use in planning, management.
Sampling
Quadrants & transects
Mark-recapture methods (Petersen)
Repeated sweeping
Counting nests or burrows
Calling/singing
Droppings
INDIREKTE METODES
 1. KWADRANTE:
 Deel area in aantal ewe
groot blokke.
 Tel individue in paar van
blokke.
 Kry gemiddeld en maal
met totale aantal blokke.
 Benaderde grootte van
bevolking.
 Veral geskik vir plante.
Gebruik vir bv. klein plantjies,
insekte, duisendpote ens.
QUADRANT METHOD USED TO DETERMINE
POPULATIONS AND COMMUNITIES ON SEA BED
MARK-AND-RECAPTURE METHOD
 Especially suitable for fish





in dam.
Catch number of
individuals.
Mark and throw back into
dam.
Allow to disperse.
Make another catch.
Count number of marked
individuals in second
catch.
 Use the following formula
to estimate size of
population:
P=MxC
R
or
= number of first catch x second catch
marked in second catch
Formula for mark-recapture:
N=MxC
R
N = estimated population size
M = number of individuals caught and marked in 1st
catch
C = total number of individuals in 2nd catch
R = number of marked individuals in 2nd catch
Formule vir merk-hervang metode
(Petersen metode)
N=MxC
R
N = verwagte bevolkingsgrootte
M = getal individue gevang en gemerk in
die 1ste vangs
C = totale getal individue in 2e vangs
R = getal gemerkte individue in 2e vangs
How could this estimate be
improved – made “more
accurate”?
Make 3rd and 4th catches.
Use the formula for each of
these catches.
Get an average number.
VOORSORGMAATREËLS
 Vang op manier wat individue nie seermaak nie.
 Merk moet individue nie hinder nie.
 Merk moet “permanent” wees m.a.w. moet duur vir
tyd van studie.
 Laat genoeg tyd tussen vangste sodat individue
kan versprei.
 Moenie te veel tyd tussen vangste laat sodat
geboortes/ sterftes ens. Invloed kan hê nie.
PRECAUTIONS – WHAT TO DO TO
ENSURE SUCCESS ...
1. Catch and handle organisms carefully, don’t hurt
them.
2. Marker should be visible after time e.g. paint in
water.
3. Marker should not hinder organism.
4. Catches should be timed so that organisms have
time to disperse after they were returned to
habitat.
5. Catches should not be too far apart to allow new
births to influence results.
VOËLS MET GROOT SORG GERING
SODAT HULLE NIE SEERKRY NIE
How do we illustrate population growth?

Two types of growth
patterns:

Two groeipatrone kom
voor:
1.
Exponential growth
(geometric or J-curve).
1.
Eksponensiële groei
(geometries of Jkurwe).
2. Logistic growth form
(sigmoid or S-curve).
2. Logistiese groeivorm
(sigmoïede of Skurwe).
WAYS TO PRESENT DATA ON
POPULATION GROWTH:
EXPONENTIAL GROWTH
Exponential growth (geometric
growth) = J-curve
J-graph indicated by two phases:
 1.
LAG PHASE – growth slow, population still
 2.
small.
EXPONENTIAL PHASE – growth is
accelerating.
Population can increase dramatically until
environmental resistance causes it to
crash.
Examples: Bacteria, insects, fish (r strategy)
Environmental resistance
equilibrium
Carrying capacity
Decelerating phase
Point of inflection
Accelerating phase
Initial lag phase
S-curve
LOGISTIC (SIGMOID) GROWTH:
S-curve
FASES VAN ‘N LOGISTIESE
GROEIKURWE (S-VORMIG)
 SLOERFASE – stadige groei,
bevolking klein, moet
paringsmaat vind, moet aanpas
by omgewing.
 TOENEMENDE GROEIFASE
(ook genoem die eksponensiële
groeifase) – groei maksimum
(vinnige tempo) - baie
geslagsrype individue wat kan
voortplant, oorlewing is hoog.
K strategy e.g. antelope
 AFNEMENDE GROEIFASE –
groeitempo verminder
geleidelik met toename in
omgewingsweerstand.
 EWEWIGSFASE –
bevolkingsgroei stop en
kurwe plat af, aantal sterftes =
aantal geboortes,
bevolkingsgrootte fluktueer
rondom dravermoë.
Soos wat die digtheid van ‘n bevolking toeneem,
neem die omgewingsweerstand ook toe.
 Tekorte aan water en




voedsel
Shortage of oxygen
(especially aquatic
populations)
Afwesigheid van lig – in
woude (nodig vir
fotosintese)
Predators
Parasites
 Gebrek aan skuiling
 Siektes
 Build-up of toxic waste
 Tekort aan/ afwesigheid
van gebied
(territorialiteit)
 Sal sterftetempo
verhoog of
geboortetempo
verlaag
DRAVERMOË
 Die getal individue wat
die gebied kan
onderhou.
 Soos bepaal deur
beperkende faktore/
omgewingsweerstand
 Geboortes en sterftes
kanselleer mekaar uit.
CARRYING CAPACITY
 The NUMBER of individuals that can be
supported by a certain
environment/habitat/ecosystem.
 Can be different for different species in same area e.g. a
meadow can support 15 cows, but 1000 tiny insects.
 Carrying capacity determined by environmental
resistance:
1. Amount of food, water available
2. Shelter
3. Disease etc.
Wanneer bevolkingsgrootte dravermoë oorskry,
word die habitat gedegradeer en dravermoë
verlaag.
YOU MUST BE ABLE TO ...
 Draw population growth graph from table given.
 Identify the type of graph.
 Identify different phases.
 Explain the trend during each of these phases.
 Determine the carrying capacity.
 Suggest type of organism that will exhibit similar
growth pattern.
 Interpret given graph as above.
POPULATION CONTROL
 Digtheidsafhanklike
 Density independent
faktore:
 Digtheid van bevolking
bepaal effek bv. Siektes het
groter effek in digte
bevolking as in ylverspreide een.
 Hoe digter bevolking, hoe
groter kans dat faktor kan
voorkom bv. voedseltekort.
factors:
 Density of population will
not have influence on
occurrence of factor e.g.
earthquake or tsunami.
Decide whether the following are density
dependent or independent factors:
Viral diseases
Tiger marking territory
predators
drought
MENSLIKE BEVOLKING
TOTALE GEBOORTESYFER
 AANTAL NAKOMELINGE PER DUISEND VROUE
 GEBOORTES – STERFTES = BEVOLKING
FAKTORE WAT GEBOORTE EN
STERFTESYFERS BEïNVLOED
 KULTUUR
 EKONOMIE (WAARDE VAN KINDERS)
 OUDERDOM VAN VROUE VOOR EERSTELING
 VERSTEDELIKING
 OPVOEDING
 GESINSBEPLANNING
 BABASTERFTES
Watter faktore dra by tot groei van menslike
bevolking?
 Verhoogde
voedselproduksie (al
het ons gebiede van
hongersnood).
 Behandeling vir
siektes.
 Manipulering van
tegnologie.
FACTORS INFLUENCING HUMAN
POPULATION GROWTH
WAYS TO PRESENT POPULATION
COMPOSITION
MENSLIKE BEVOLKINGSGROEI
 BEVOLKINGSPIRAMIEDE
 HOEKOM IS DAAR MEER VROUENS AS MANS?
GEVOLGE VAN OORBEVOLKING
 LAER STANDAARD VAN LEWE
 HONGERSNOOD
 VERNIETIGING VAN HABITAT
 KOMPETISIE NEEM TOE