5.2 Limits to Growth 2015

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Population Growth:

Population Biology Population Growth


Target 1. I can list three things that affect population size. 2. I can define birth rate, mortality rate, immigration, and emigration 3. I can explain what a survivorship curve is and the three types. Take notes using the worksheet


Recall that a population is a group of the ______ species living in the________ area. Same Same

Key features of populations:

Key features of populations Population size – is the number of individuals in a population. – has an important effect on the ability of the population to survive. A small population is more likely to become extinct: -in the case of random events or natural disaster -due to inbreeding where the population is more genetically alike. Recessive traits are more likely to appear. -with reduced variability it is harder to adapt to changes.


Populations Populations—large and small— are DYNAMIC - Meaning, they change over time Humans face the same problems as large and small populations in nature

4 Factors That Influence Population Size:

4 Factors That Influence Population Size Population growth rate is determined by: Natality or Birth rate Death rate Immigration – move into population Emigration – move out of population

Populations Growth:

Populations Growth Three factors can affect population size: number of births the number of deaths the number of individuals that enter or leave the population.

Immigration & Emigration:

Immigration & Emigration Immigration the movement of individuals into an area, is another factor that can cause a population to grow. Emigration the movement of individuals out of an area, can cause a population to decrease in size .

Word Origin:

Word Origin Immigration is formed from the Latin prefix in-, meaning “in,” and migrare , meaning “to move from one place to another. If the Latin prefix e - means “out,” then which of the following means “migration out”? A.) emigration B.) migration C.) Immigration


A limiting factor is something that keeps the size of a population down. Limiting factors can depend on the density of individuals in the population or not.

Limits on Population Growth:

Limits on Population Growth Limiting Factors- any factor that causes a population to decrease Density Dependent Limiting Factors Depends on the size of the population Ex. Food, Water, Shelter, Disease, Competition Density Independent Limiting Factors Can affect populations regardless of their density Ex. Weather, Climate Floods, Drought, Tornadoes, Fire, Volcanoes Water and shelter are critical limiting factors in the desert. Fire is an example of a Density independent Limiting factor.

Limiting Factors:

Limiting Factors If the presence or absence of a factor limits the growth of the ecosystems elements, it is called a limiting factor . There are several abiotic factors that limit ecosystem growth, including temperature, precipitation, sunlight, soil configuration, and soil nutrients.

Types of Limiting Factors:

Types of Limiting Factors Density-dependent factors Disease Competition Predators Parasites Food Density-independent factors Volcanoes Temperature Storms Floods Drought Habitat disruption

Limiting Factors:

Limiting Factors Which limiting factors are represented by the images above? What are examples of additional limiting factors?

Other population factors:

Other population factors Predation Competition

Survivorship Curves:

Survivorship Curves Patterns of Mortality Populations show three patterns of mortality or survivorship curves : Type I (low mortality until late in life) Type II (constant mortality throughout life) Type III (high mortality early in life followed by low mortality for the remaining life span)

Survivorship in Populations:

Survivorship in Populations

Survivorship in Populations:

Survivorship in Populations

Rapid Life History Pattern Type III Survivorship:

Rapid Life History Pattern Type III Survivorship Type III Species: have high reproductive rates tend to occur in unpredictable environments Ex. Fish, Plants

Slow Life History Pattern Type I Survivorship:

Slow Life History Pattern Type I Survivorship Type I Species: occur near carrying capacity experience effects of population density have low reproductive rates, high parental care Ex. Humans, Elephants


A population crash is a dramatic decline in the size of a population over a short period of time.

Reproductive Strategies:

Reproductive Strategies Rapid (maximum growth rate, below carrying capacity) Early reproduction Short life span High mortality rate Little or no parental care Large investment in producing large numbers of offspring Below carrying capacity Examples: Bony fish Grasshoppers Slow (maximizes population size near carrying capacity) Late reproduction Long life span Low mortality rate Extensive parental care Greater investment in maintenance and survival of adults At or near carrying capacity Examples: Sharks Elephants


1. Why don’t populations of organisms grow indefinitely? 2 . What is the relationship of births to deaths in a population before the population reaches the environment’s carrying capacity? 3 . What happens when the population exceeds the carrying capacity? 4 . What are some limiting factors that can curb population growth?

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