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Presentation on theme: "DEMOGRAPHIC TRANSITION"— Presentation transcript:

Way to explain changes in population composition e.g. high to low birth rate. FOUR STAGES: STAGE ONE: Both death and birth rate high (pre-industrial). Balance in population.

DEVELOPING COUNTRIES Death rates drop dramatically – better food and sanitation, less disease. Better education, healthcare, access to technology, better farming techniques. Birth rates continue to be high. Increase in population occurs, pressure on economy, health care, education etc.

DEVELOPING TO DEVELOPED COUNTRIES Birth rates fall – contraception, higher wages, urbanisation, decrease in subsistence agriculture, increase in education and status of women, children don’t work, parents invest in children’s education. Population growth begins to level off.

DEVELOPED COUNTRIES Low birth rates, low death rates. Birth rate may drop to below replacement level (Germany, Italy, Japan). Death rate may increase due to lifestyle diseases and ageing population. Threat to industries relying on population growth. Economic burden on shrinking working population.

5 Factors that can cause a decrease in population growth
Diseases such as HIV/AIDS, bird flu, H1N1 etc. Better living conditions and better education leading to better family planning. Better contraceptives. Wars. Natural disasters. Kaposi sarcoma, a skin cancer typical of HIV/AIDS

6 Factors that influence community structure
Predasie Kompetisie Kompeterende uitsluiting Hulpbronafbakening Simbiose Suksessie Predation Competition Competitive exclusion Resource partitioning Symbiosis Succession



Direct link between predator and prey numbers. As prey increase, there will be more food for predators, so will predators increase. Increase in predator numbers put pressure on prey numbers. Prey will decrease. Decrease in prey will mean less food for predators, numbers will decrease etc.

10 ROL VAN KOMPETISIE Kompeteer om dieselfde, maar beperkte bronne bv. Water, lig, voedsel, gebied, paarmaat. Intraspesifiek – dieselfde spesie. Interspesifiek- verskillende spesies. Hyena and lion Intraspecific or interspecific? Explain your choice

11 Competition 1. Intraspecific competition: the competition between organisms of the same species depending on the same resources like food, space, shelter, water and access to mates.

12 Competition 2. Interspecific competition: the competition between organisms of different species depending on the same resources e.g. light, space, water, shelter, food

13 Specialisation for specific modes of life – RESULT OF INTERSPECIFIC COMPETITION
When two similar species co-exist, they will start to specialize in their habitats and feeding habits and undergo character displacement to reduce the severity of interspecific competition. This is demonstrated by Galapagos finches described by Charles Darwin.  The ancestral bird from the mainland of Ecuador had an intermediate-sized beak to consume insects and seeds of all sizes. Notice, however, how the break size has changed, to reflect specialization in feeding habits.  (In fact, there is one finch, the woodpecker finch, which uses a twig as a tool to dig out insects from holes in trees.)

14 COMPETITIVE EXCLUSION: The competition in which one of the two competing species is much more successful that the other, to such an extent that the successful species survives and the other species disappears. Kompeterende uitsluiting: Een van die spesies is ‘n baie beter kompeteerder; wanneer hy saam met ‘n ander spesie in diese3lfde habitat is, sal hy oorleef en die ander uitsterf.

15 Competitive exclusion
Wie is die beter kompeteerder?

16 RESOURCE PARTITIONING: The kind of competition situation in which competing species coexist in the same habitat since they use the resources slightly differently. HULPBRONAFBAKENING: Kompeterende spesies kan saam bestaan en oorleef omdat hulle bronne op verskillende maniere benut.

17 Resource partitioning amongst plants

18 Resource partitioning: co-existing shore birds

19 Wat is simbiose? Simbiose beteken letterlik “saamleef” – sym = saam, en bio = lewe. Die saamleefverhouding is gewoonlik lewensbelangrik vir ten minste een van die partye. Dit is ‘n langtermyn saamleef en nie toevallig of tydelik nie.

20 MUTUALISME Tot voordeel van beide partye.
Geen party word benadeel nie. Voorbeeld: vlinder en blom – blom word bestuif, vlinder kry nektar.

21 Verpligte mutualisme Die saamleef-verhouding is lewensbelangrik vir albei partye. Ligene (korsmosse) – swamme verskaf blyplek en absorbeer water; alge fotosinteer en verskaf voedsel.

22 Nie-verpligte mutualisme
Die saamleef-verhouding is steeds belangrik,maar nie noodwendig tussen twee spesifieke individue nie bv. Die vlinder en blom (reeds genoem). Die bosluisvoël kry voedsel en die wildsbok is vry van parasiete.

23 KOMMENSALISME Die een party word bevoordeel – die ander party word nie bevoordeel of benadeel nie bv. Beesryer wat hier ‘n saamry-geleentheid kry, maar goggas op grond vreet waar bees vroetel.

24 Nog kommensalisme … Die remora-suigvis gebruik die haai as ‘n taxi en vreet van die afvalstukkies voedsel wanneer die haai vreet. SUIER AAN BO-KANT VAN REMORA

25 PARASITISME Een party word bevoordeel, die ander word beslis benadeel.
Parasiete wat op diere teer (en self diere is), kan ektoparasiete of endoparasiete wees.

26 Plantparasiete Semi-parasiete is slegs vir water en minerale van die gasheer afhanklik en kan self fotosinteer bv. voëlent (Viscum). Holoparasiete is geheel en al afhanklik van die gasheer en bevat geen chlorofil nie bv. Dodder.

27 Community change over time: Ecological succession
3. Secondary succession: the sequence of organisms that occupy a disturbed habitat or when an established community has been disturbed in a catastrophic manner. 4. Climax community: the final stage in the process of succession that refers to a mature community of plants that will remain stable with few, if any, changes over time TERMINOLOGY IMPORTANT 1. Primary succession: the sequence of organisms that occupy a new habitat. 2. Pioneer plant: a plant that can colonise bare soil and that is part of the community that forms the first stage in the process of succession


29 PLANT SUCCESSION The gradual replacement of one plant community by another through natural processes over time

30 Succession

31 PRIMARY SUCCESSION colonization of new sites by communities of organisms – takes place on bare rock

32 PRIMARY SUCCESSION New bare rock comes from 2 sources:
1. volcanic lava flow cools and forms rock

33 PRIMARY SUCCESSION New bare rock comes from 2 sources:
2. Glaciers retreat and expose rock; ALSO FLOODS AND LANDSLIDES

34 PIONEER ORGANISMS the first organisms to colonize a new site
E.g.: lichens are the first to colonize lava rocks

35 As lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

36 Simple plants like mosses and ferns can grow in the new soil
The simple plants die, adding more organic material. The soil layer thickens, and …..

37 … grasses, wildflowers and other plants begin to take over

38 These plants die, and they add more nutrients to the soil.
Shrubs and trees can survive now

39 Waar eens kaal rots was, is daar nou ‘n florerende gemeenskap.
Wanneer pionierplante bygedra het tot die ontstaan van `n plantgemeenskap, begin diertjies om hulle daar te vestig. Waar eens kaal rots was, is daar nou ‘n florerende gemeenskap.



42 Primary Succession- Rock

43 SECONDARY SUCCESSION Begins in a place that ALREADY has soil and was once the home of living organisms Occurs faster and has DIFFERENT pioneer species than primary succession.

44 Secondary succession-
Example: After a forest fire Or when a farmer plows his field

45 Secondary succession-

46 CLIMAX COMMUNITY a stable, mature community that undergoes little or no succession


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