1 ecology of individuals and populations chapter 56
TRANSCRIPT
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Ecology of Individuals and Populations
Chapter 56
Ecology
• Ecology– “Study of how organisms relate to one
another and to their environments”– Organisms respond to the abiotic
environment where they live.
Populations and Environment
• The environment determines which organisms live in a particular climate.–Temperature–Water availability–Sunlight–Soil
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Environmental Challenge
• When environmental changes occur an individual’s response can be short or long term.
• Long term responses:– Physiological responses
• Physiology – “processes or functions in an organism or in any of its parts“
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Environmental Challenges
• Long term responses:– Morphological capabilities
• Morphology – “the form and structure of an organism considered as a whole”
• Behavioral responses
Bird Bone
Range• Population range – “area where a population occurs”• Populations aren’t static.
• Individuals move into/out of an area on purpose and by accident.
Ex. Climate change Cattle egrets, fire ants
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Environmental change Moving to better habitats
Spacing Patterns
• Spacing of individuals within a range can tell us about population structure and organism behavior.
• Populations exhibit different spacing patterns:– Random spacing– Uniform spacing– Clumped spacing
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Population Change over Time
• Survivorship– “Percent of an original population that
survives to a given age”• Survivorship curve
– Shows survival rate at different ages– Three survivorship types:
• I, II and III
Survivorship Curves
Life History
• Natural selection favors traits that maximize the number of surviving offspring left in the next generation by an individual organism– 2 factors affect this quantity
• There’s a trade-off between survivorship and reproduction.
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• Biotic potential – a species maximum growth rate – there are no limitations on the population
• Result of unchecked exponential growth is a population explosion
• All populations eventually reach some limit in their growth
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Environmental Limits to Population Growth
Population Growth Curve
• The formula below is used to calculate population sizes as they reach K (carrying capacity)
dN/dt = rN (K – N)/K
– dN/dt = rate of growth– r = rate of increase– N = number of individuals in the population– K = carrying capacity
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Environmental Limits to Population Growth
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Population Types
• There are two ‘types’ of populations based on their reproductive rates:– Opportunist or r – selected species– Competitor or K - selected species
Factors That Regulate Populations
• When resources are limited, the cost of reproduction is high. When resources are abundant, costs of reproduction are low.
• Resource availability affects life history adaptations – (whether a species will adapt to be an ‘r’ or a ‘K’ selected species).
Human Population Growth
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Factors That Negatively Regulate Populations
• Density-dependent– Factors that affect the population and
depend on population size• Density-independent
– Other factors, such as natural disasters, decrease populations size regardless of population density
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Factors That Regulate PopulationsAllee effect: “Growth rates increase with increase in population size”
Locust
Puffins
• Population Pyramid– Bar graph displaying the number of
individuals in each age category
– Can be used to determine the stability and future size of a population
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Population Pyramids
Population Pyramids