chapter 20 lab biology chapter 26 honors biology
TRANSCRIPT
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Chapter 20Lab BiologyChapter 26
Honors Biology
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Does this represent a population of dolphins?
Anticipatory Set: Count the number of
dolphins in this picture…
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Grp. Of organisms of the same species in a particular place at the same time.
Population Size no. of individuals it contains (how do we measure it?)
Population Density measures how crowded a population is (indiv. Per unit of area or volume)Dispersion spatial distribution of individuals
within the populationClumped
Evenrandom
Properties of Populations
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Population Dispersion
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Birth rate – no. of births occurring in a period of time
Death rate – number of deaths in a period of time
Life expectancy –how long on average an individual is expected to
live
Population Dynamics
(change over time)
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Age Structure the distribution of individuals among different ages in a population
Patterns of Mortality tends to conform to one of three curves on a graph called survivorship curves they show the likelihood of survival at
different ages throughout the lifetime of the organism.
Continue…
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Growth rate the amount by which a population’s size changes in a given time
This depends on 4 processes:
Birth
Death
Emigration
immigration
Population Growth Rate
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Loss…Birth rate – death rate = growth rate
(per capita use 1,000)
Gain…To find the no. of new indiv. That will be added to
the population in a yr. Multiply the per capita growth rate by the no. of indiv. In the popul.
Formulas for growth rate!!
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Exponential Model describes a population that increase rapidly after only a few generations
Exponential Growth the larger the population gets the faster it grows
Exponential Model
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View population growth over time
Represented by a J – shaped curve
Predictions Based on the Exponential
Model
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Exponential growth occurs only under rare conditions and for short periods of time
Why: resource get depleted and waste
builds up
Limiting factor – a factor that restrains the growth of a population
Limitations of the Exponential Model
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A population growth builds on the exponential model but accounts for the influence of limiting factors
Carrying capacity: the no. of indiv. The environment can support over a long period of time.
Logistic growth
Logistic Model
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Environmental resistance can be classified into two broad categories
Density-independent factors
Density-dependent factors
Environmental Resistance
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2 Kinds of limiting factors control population size:
1. Density-independent factors: limit populations regardless of their density
Examples: climate, weather, floods, fires, pesticide use, pollutant release, and overhunting
2. Density-dependent factors: can cause birth rates to drop and/or death rates to increase
Population growth slows resulting in an S-shaped growth curve (or S-curve)
Population Regulation
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Some species have evolved means of limiting their losses
Examples: seasonally migrating to a better climate or entering a period of dormancy when conditions
deteriorate
Density-Independent Factors
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Density-dependent factors can cause birth rates to drop and/or death rates to increase
Population growth slows resulting in an S-shaped growth curve (or S-curve)
Density-Dependent Factors
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Carrying capacity is determined by the continuous availability of resources
Density-Dependent Factors
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Include community interactions
Predation
Parasitism
Competition
Density-Dependent Factors
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1. Development of Agriculture – “agricultural revolution” stabilized and increase available food
supply
2. Population Explosion –
3. Population Growth today –
- developed countries
- developing countries
History of Human Population Growth