Population Growth and Resource Availability (3.5)

**Size (N)**

total # of individuals in a given area at a given time

larger size (N)

safer from population decline

**Density**

number of individuals/area

Higher density

higher competition, possibility for disease outbreak, possibility of depleting food source

**Distribution**

how individuals in a population are spaced out compared to each other

random: trees

uniform: territorial animals

clumped: herd/group animals

**Sex Ratio**

**ratio of males to females**closer to 50:50 ideal for breeding

die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

factors that influence population growth based on size

Examples

food

light

competition for habitat

water

disease

All these things limit population growth based on their size

**Density-Independent Factors**

factors that influence population growth independence of their size.

examples

natural disasters

floods

hurricane tornado

fire

It doesn’t matter how big or small a pop. is, natural disasters limit them both

**Ex. of Density-Dependent Factor**

**Food**is a density dependent factor. (also a limiting resource)When twice as much food was added to the dish, both species increased carrying capacity by about 2x

**Biotic Potential**Max potential growth rate with no limiting resources

May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

**Biotic potential**

exponential growth

**Logistic growth**

initial rapid growth, then limiting factors limit pop. to K

**Size (N)**

total # of individuals in a given area at a given time

larger size (N)

safer from population decline

**Density**

number of individuals/area

Higher density

higher competition, possibility for disease outbreak, possibility of depleting food source

**Distribution**

how individuals in a population are spaced out compared to each other

random: trees

uniform: territorial animals

clumped: herd/group animals

**Sex Ratio**

**ratio of males to females**closer to 50:50 ideal for breeding

die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

factors that influence population growth based on size

Examples

food

light

competition for habitat

water

disease

All these things limit population growth based on their size

**Density-Independent Factors**

factors that influence population growth independence of their size.

examples

natural disasters

floods

hurricane tornado

fire

It doesn’t matter how big or small a pop. is, natural disasters limit them both

**Ex. of Density-Dependent Factor**

**Food**is a density dependent factor. (also a limiting resource)When twice as much food was added to the dish, both species increased carrying capacity by about 2x

**Biotic Potential**Max potential growth rate with no limiting resources

May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

**Biotic potential**

exponential growth

**Logistic growth**

initial rapid growth, then limiting factors limit pop. to K