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Populations and Communities

Populations and Communities. = Population. A group of individuals of the same species, living in a shared space at a specific point in time. Factors affecting population size. births. deaths. Population. Emigration. Immigration. How big is this population?. 11. 6. 6.

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Populations and Communities

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  1. Populations and Communities

  2. = Population • A group of individuals of the same species, living in a shared space at a specific point in time

  3. Factors affecting population size births deaths Population Emigration Immigration

  4. How big is this population? 11 6 6

  5. Counting populations I - Counting individuals - Counting by sampling: Average number of individuals per section total study area Population size = x Area of section - Counting by recapture %:

  6. Counting by recapture % d d d # of marked animals # of marked recaptured animals = Population size # of captured animals

  7. Population density • Factors influencing population density: • Access to water and food • Presence of predators • Parasites, diseases # of individuals Pop. Density = Space occupied (area / volume)

  8. Population distribution clumped uniform = the way in which individuals are dispersed within their habitat random http://www.youtube.com/watch?v=1yKxUNP_XVo&list=PL9CE54703E2B8E92F

  9. random clumped uniform

  10. Ecological factors = aspect of a habitat that can affect the organisms living there Related to the action of living organisms Physical or chemical origin • amount of light • soil / water pH • terrain • temperature • air humidity • birth rate • disease • amount of food • predation • competition • human activity Biotic Abiotic

  11. Limiting factor • A factor that limits the growth of a population • Light • Temperature • Water • Food / nutrients • …

  12. Limiting factor • Is low temperature limiting growth of vampire bat population? • Vampire bat colonies Mean minimal temperature for January > 10°C

  13. Is nesting space limiting? pied flycatcher Density (pairs / ha) Providing more nesting spaces increases population density  Nesting space was limiting 12 m 200 m Distance between nest boxes

  14. Biological cycles in populations • Population cycles are composed of alternating rise and fall of population size. • Periods are of fixed duration and are repeated continually.

  15. Populations • Counting methods • Density (number/ area) • Distribution (clumped/ random / uniform) • Ecological factors – limiting factors Polpulation cycles commuities

  16. Communities: A set of populations of different species sharing the same habitat population community organism

  17. Biodiversity The variety of species living in a community Relative species abundance: Number of individuals of one species in relation to total community Species richness: Number of different species in a community

  18. Same species richness; community 2: species abundance not even  Lower biodiversity • Biodiversity is high when: • number of species high • relative abundance of species similar

  19. Interactions between individuals Competition: Living organisms seek access to the same resource in their habitat. Mutualism: Interaction between two species beneficial to both. Predation One feeds on the other. Commensalism: One organism benefits from relationship while other remains unaffected.

  20. Competition interspecific intraspecific

  21. Predation: prey may or may not die parasite host Parasite lives either on or inside the host. Host is harmed from the interaction. prey predator

  22. mutualism Clown fish gains protection Anemone gains prey (attracted by clown fish) Bee gains food Flower gains fertilization

  23. Commensalism Bird gains food Human remains unaffected Bird gains protection tree remains unaffected

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