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Population Dynamics and Regulation: Understanding Ecosystem Balance

This document explores the key concepts of population dynamics within ecosystems, focusing on aspects like population density, carrying capacity, and the factors influencing population stability and change. It discusses the roles of density-dependent and density-independent factors in population growth, predator-prey relationships, and the assessment of populations through scientific monitoring. Additionally, it emphasizes the importance of preserving biodiversity, managing resources sustainably, and recognizing indicator species to evaluate environmental health.

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Population Dynamics and Regulation: Understanding Ecosystem Balance

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  1. Control & Regulation Regulation & Monitoring of Populations Mr G Davidson

  2. Populations • A population is a group of individuals of the same species which makes up part of an ecosystem. • The number of individuals of the same species in a unit area/volume of habitat is called the population density. G Davidson

  3. Population Stability • When an environment is colonised by a species, the population grows to the highest level supportable by the environment. • The limit is known as the carrying capacity. G Davidson

  4. Population Stability • The population level is now relatively stable save short-term oscillations from generation to generation. • It is said to be in a state of dynamic equilibrium. G Davidson

  5. Factors influencing change • Every species has a large reproductive potential, but population increase is restricted by environmental resistance, which consists of factors such as: • Food - Water • Space - Oxygen • Light - Shelter • Predation - Disease • Climate G Davidson

  6. Factors influencing change • A density independent factor is one which affects population growth regardless of density, e.g. weather extremes, forest fire, flood, etc. • A density dependent factor is one which affects a population once it has grown to a certain size and density. G Davidson

  7. Factors influencing change • Once a population reaches this level, it is inevitably affected by one such factor, e.g. • competition  starvation • build up of population’s toxic wastes • disease • predation G Davidson

  8. Factors influencing change • Predator and prey populations are linked and balanced. • If conditions favour prey, their numbers will increase. • As a result, there will be more food for predators, whose numbers will also rise. • An increase in predator numbers will increase predation and therefore prey numbers will fall. G Davidson

  9. Factors influencing change • Increased competition following this reduction in food will cause predator numbers to drop as some die of starvation. • This brings the population back to its original state. • Since there tends to be less predators than prey, population graphs of predator and prey numbers are usually very similar: G Davidson

  10. Prey Predator Numbers of Population Time Factors influencing change G Davidson

  11. Monitoring Populations • Many species of wild plants and animals are surveyed closely by scientists to monitor population numbers and affecting factors. • This data is needed for: • management of species which provide food or raw materials • pest control • pollution assessment • protection and conservation of endangered species G Davidson

  12. Food Species • The maximum sustainable yield of a population is a measure of the maximum rate at which individuals can be removed without affecting the population’s future productivity. • This keeps populations in check, e.g. • fish – prevent over-fishing by quotas. • keep down red deer populations with cullings. G Davidson

  13. Pests • Pests are species which threaten mankind’s health or economy. • They can include insects, fungi and vermin which spread disease and ruin crops. • Noted examples are: • green fly - pathogenic fungi • locusts - mosquitoes • brown rats G Davidson

  14. Indicator Species • Environmental health can be assessed by examining certain indicator species. • Fresh water indicator species include mayfly and stonefly, which show that pollution is low. • Birds of prey are affected by over-use of pesticide sprays as toxic chemicals move up the food chain and accumulate in the bird’s diet. G Davidson

  15. Indicator Species • If, however, water is polluted, it can be shown by the presence of rat-tailed maggots and sludgeworms. • On land, air pollution levels can be shown by lichens. • The presence of lichens indicates low air pollution. G Davidson

  16. Indicator Species • Phytoplankton, microscopic, oceanic plants acts as the first link in the marine food chains. • They convert much CO2 into O2 during photosynthesis and could possibly make a big difference to the greenhouse effect. G Davidson

  17. Endangered Species • Rare species may have values ranging from medicinal to aesthetical. • To prevent extinction, the areas in which some endangered species live in are converted into nature reserves. • Over-hunting, poaching, picking and harvesting are controlled or restricted to maintain species numbers. G Davidson

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