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Population Ecology

Population Ecology. Ecologists study life at many levels, from individual organism to the entire biosphere . . Ecology: “eco” means house “ ology”means study of . Levels of organization Cells – Tissue - Organs – Organ systems - Organisms.

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Population Ecology

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  1. Population Ecology

  2. Ecologists study life at many levels, from individual organism to the entire biosphere.

  3. Ecology: “eco” means house • “ology”meansstudy of.

  4. Levels of organization • Cells– Tissue-Organs – Organ systems -Organisms

  5. Population – a group of individuals of the same species that live in the same area at a given time

  6. Example: a group of white-tailed deer in an oak-hickory forest in southeastern PA

  7. Community - groups of living organisms that interact with one another in a particular area.

  8. Example: deer, mice, bushes and snakes in the forest community

  9. Ecosystem: a community together with its physical environment

  10. Biosphere: all parts of the earth that hosts life, with all of its organisms and environments.

  11. Ecosystems include both biotic and abiotic factors. Biotic factors are parts of the ecosystem that are living.

  12. Abiotic factors are parts of the ecosystem that are non-living.

  13. Biotic factors:

  14. Abiotic:

  15. Organisms depend on resources provided by their habitat for survival.

  16. The specific environment in which an organism lives is its habitat.

  17. A habitat provides an organism with resources. A resource is anything an organism needs to survive.

  18. Describing Populations…. • Theoverallhealth of a population can often be monitored by tracking how its size changes.

  19. Population size describes the number of individual organisms present in a given population at a given time.

  20. Population Ecology • Deals with the # of individualsof a particular species that are found in an area and how and why those numberschange or remain fixed over time.

  21. Population ecologists study… • How populations respond to its environment • Competition for resources, predations, disease and other environmental pressures

  22. Determine population size by sampling. Instead of counting every individual, ecologists count every organism in a small area than estimate the number of individuals in the larger area.

  23. Population density describes the number of individuals within a population per unit area. • For example: 1500 golden toads per 4 sq. kilometers

  24. In general, larger animals have lower population density because they need more resources.

  25. High population density can make it easier to find mates and group together. However, it also leads to more competition for resources.

  26. Overcrowded organisms can also lead to increase of disease and vulnerable to predators.

  27. Age structure diagrams show the number of males & females in different age groups within a population.

  28. Age structuredescribes the relative number of organisms of each age with in a population.

  29. Age structure diagrams are a visual toolto show the age structure of populations.

  30. Stable – approximately the same number of individuals at each age grouping, mix of young and old

  31. Growing– mostly young

  32. Declining – the largest portion of population is older

  33. A population’s growth rate is determined by births, deaths, immigration and emigration.

  34. All things being equal, when a population birthrate is greater than its death rate, population size will increase.

  35. When death rate is greater than its birth rate, population size will decrease.

  36. In addition to births & deaths, population size can also change by individualsmoving in & out.

  37. Immigration– movement of individuals into a population • Emigration – movement of individuals into a population

  38. Birthrate– number of livebirths per 1000 in a given year • Death rate– number of deaths per 1000 in a given year

  39. CALCULATING GROWTH RATE • Growth rate (r) = birth rate (b)+ I – death rate (d) + E

  40. Population growth is typically reported as a net change per 1000 individuals.

  41. Exponential growth is when a population increases by a fixed percentage each year.

  42. Exponential growth occurs in nature only when the starting population is small & the environmental conditions are ideal.

  43. This type of growth usually does not last long. Most populations are constrained by limiting factors.

  44. Limiting factors are characteristics of the environment that limit population growth. Limiting factors determine a population’s carrying capacity.

  45. Example: New population is introduced…mold growing on bread.

  46. Logistic Growth describes how a population’s initial exponentialincreaseis slowed & finally stopped by limiting factors.

  47. Carrying capacities are not fixed. Carrying capacity is the largest population size a given environments can sustainably support.

  48. Examples of limiting factors: 1) Food 2) Disease 3) Predators 4) Space 5) Water

  49. Limiting factors have more of an effect in densepopulations & other limiting factors affect all populations in the same way.

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