Chapter 4 Population Biology

1. Chapter 4Population Biology Growth of population Regulation of population size

2. Biotic Potential - highest rate of reproduction under ideal conditions Population – a group of organisms, of the same species, living in a specific area Population Growth - increase in the size of a population 1. J-shape growth curve 2. S-shape growth

3. Population Growth Curves • Linear growth shows a steady and constant increase (linear or straight line graph) • J-curve: exponential growth, no limiting factors • Initially a slow growth • Rapid growth that continues upward • S-curve: good growing conditions but limiting factor(s) are present • Initial period- slow growth • Rapid growth • Population growth flattens due to limiting factors

4. Limiting Factors-conditions that keep a population from reaching its biotic potential Limiting factors- temperature, predators, disease, lack of food, water and space

6. S-shape and J-shape population curves pg. 93

7. Population Growth Rate Curve • Alters as the environmental conditions change (up or down) • Carrying Capacity - Number of organisms of one species that an environment can support.

8. Population Growth Rate Curve

9. CARRYING CAPACITY MOVIE

10. Carrying capacity • Deaths begin to exceed births and the population falls below carrying capacity. Carrying capacity

11. Dispersal Patterns – the arrangement of populations formed as they grow 1. Random – no distinct pattern 2. Clumped – groups of individuals 3. Uniform – individuals evenly spaced apart

12. Density-independent limiting factors: limiting factors that are not related to thedensity of the populations Ex. Temperature, amount of oxygen, pH, salinity, natural disasters Density-dependent limiting factors: limiting factors that are influenced by the density of the population Ex. Disease food parasites predation Population Density-size of population in given area at a given time

13. Regulation of Population Size • Predation and Food • Predation-feeding of one organism on another • can act as a limiting factor • Prey Population size is checked by predation • Predation as a Density-dependent factor • increase in prey population leads to an increase in predator population (and the reverse!!) • Predation as Beneficial • Keeps prey population healthy --killing the old and diseased • Keeps prey population near carrying capacity, so they will not over graze producers

14. Predator – prey populations The Predator growth curve is shifted to the right of the Prey curve The graph lines for each species oscillate

15. Prey pop. rises Predator pop rise due to increase in prey Prey pop falls due to increase Predator pop falls due to decline in prey Prey population rises due to decline in predators

16. Interspecies Competition - competition between different species • Extinction - where one species dies out • Movement - one species will move into another area • Adaptation-spurs evolution in which one species evolves different traits over time

17. Intraspecies competition - competition between organisms of the same species • Intraspecies competition -is more severe because all the organisms have the exact same habitat and niche requirements They want the same things!!

18. Natural selection can occur over time –organisms that are best adapted will survive and pass their genes on to the next generation

19. Overcrowding (stress)causes behavioral and reproductive changes --Increased aggression --Increased spread of disease --Hormonal changes reduce litter size --Young eaten by mother (seen in rodents and even dogs) --No young produced or young abandoned

20. Demography – the study of population growth characteristics • 1. Population growth rate • 2. Population age structure • a. pre-reproductive (not reproducing) • b. actively reproducing • c. post-reproductive (not reproducing) • 3. Population geographical distribution • Why????

21. Emigration - individuals moving out of the area Immigration- individuals moving into an area

22. Human Population Growth in humans is unlike other animals because we can escape limiting factors and resulting in a population explosion (almost a J-curve).