APES: 3.5 Population Growth and Resource Availability - Alexis Lee

What limits population growth?

Environmental factors (specifically the available resources and space)

What is limited/finite over all scales of time?

Resource availability and total resource base

What happens when the resources needed for population growth are abundant?

The population usually accelerates

What happens when the resource base of a population decreases?

There will be an increased potential for unequal distribution of resources which increases mortality and/or decreases fecundity --> population growth declines to or below the carrying capacity

What does size (N) mean?

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

What is a benefit of a larger population?

Larger means safer from population decline

What does density mean?

number of individuals per area

What are the outcomes of a high density population?

higher density means higher competition, possibility for food disease outbreak, and possibility of food depletion

What does distribution mean?

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

What are the three types of distribution?

1. random (trees)
2. uniform (territorial animals)
3. clumped (herd/group of animals)

Define sex ratio

sex ratio is the ratio of males to females
* Closer to 50:50 most ideal for breeding (usually)

Define density-dependent factors

factors that influence pop. growth based on size
* ex. food, competition for habitat, water, light, even disease
* limits population growth based on size

Define density-independent factors

factors that influence pop. growth independent of their size
* ex. natural disasters (flood, hurricane, tornado, fire)
* natural disasters limit both big and small populations

Define carrying capacity

the number or quantity of people or things that can be conveyed or held by a vehicle or container

Define biotic potential

maximum potential growth rate, with no limiting resources
* can occur initially, but limiting resources (like competition, food, disease, predators) slow growth, & eventually limit population to carrying capacity (k)

How to calculate population change?

(Immigrations + births) - (emigrations + deaths) = population growth

Calculate the population change:
An elk pop. of 52 elk has 19 births and 6 deaths in a season, and 5 new elk immigrate to the herd and 0 elk emigrate from the heart

Growth: (In + Birth) - (Exit + Death)
(5 + 19) - (0 + 6) = +18 elk
Total = Original + Growth
52 + 18 = 70 elk

What is the difference between exponential growth and logistical growth?

"The exponential growth model describes a population with unlimited resources, which keeps growing bigger and faster over time. The logistic growth model describes a population that has limited resources or other limits to growth, which grows more slowly as it gets larger." (hhmi/BioInteractive)