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2 Populations
- 1. Populations
- 20. Tolerance
- 24. Predation
Notes de l'éditeur
- Mortality (death rate) Decreases population density Emigration (number of organisms moving out) Decreases population density Natality (birth rate) Increases population density Immigration (number of organisms moving in) Increases population density
- Many individuals die withou reproducing, predators,
- Open-New orgs born and immigrate while others die or emigrate - Most ecosystems in nature Closed - Usually in a laboratory or game reserve situation
- Competition for food Increase in predator population Increase in parasites Environmental resistance Factors which cause resistance to population growth Carrying capacity The population size that a habitat can sustain Lag phase Period of adaptation to new conditions Low initial numbers Exponential Growth Constant cell division High natality rate Transition Period Natality rate slows Affected by overcrowding Slowing Phase Rate of natality slows further Stationary Phase Natality = mortality Population growth stops
- Average life expectance at birth The age half the individuals born will survive to Maximum length of life for a species Annuals - 1 year Biennials - 2 year
- More energy into numbers = less into rearing offspring Or Less energy into numbers = more energy into rearing offspring Fish lay many eggs No parental care Few survive Mice reproduce early and often Dogs have smaller annual litters
- Percentage of populaiton in different age clases - pre-reproductive, reproductive and post reproductive Sweden diminshing populaiton (urn shape curve) - few pre reproductive, post reproductive Mexico - expanding population - pyramid curve - most pre reproductive - very few post reproductive USA - stable - bell shape - widest at bottom - pre and reproductive similar - post reproductive less
- Substrate - plants in rocky areas - grow between rocks
- Optimum range When conditions are most favourable Zone of physiological stress When conditions are “uncomfortable” Upper and Lower limits of tolerance Organisms die