4.2 Describing Populations

Which type of population distribution is found most often in nature?

Clumped

How can high population density be helpful to a population?

Makes it easier for organisms to group together and find mates

How can high population density be harmful to a population?

Overcrowded organisms may also become more vulnerable to the predators that fed on them, and close contact among individuals can increase the transmission of infectious disease

Types of Population Distribution

Uniform Random Clumped

Age Structure

also called age distribution, describes the relative numbers of individuals at each age within a population, they help to predict how the population will change in the future.

Which piece of information is used along with population size to calculate population density?

area

A population's destiny describes how

crowded the population is

If a population size begins to _________ rapidly, this can be a signal that extinction is coming

declines

Population distribution

describes how organisms are arranged within an area

Population size

describes the number of individual organisms present in a given population at given time

Population density

describes the number of individuals within a population in a certain area

Age structure

describes the relative numbers of organisms of each age within a population

Describe how to use an age-structure diagram to determine how many males and females are in a population

determined by age groups

When a population size ___________ or remains steady, this is often a sign of healthy population

increases

Random Population Distribution

individuals are arranged with no particular pattern, occurs if resources are abundant or evenly distributed

Uniform Population Distribution

individuals are evenly spaced throughout an area, happens when individuals hold a territory or compete for space

Clumped Population Distribution

individuals arrange themselves according to the availability of resources, such as around a water source or a stable food source.

Sex ratio

proportion of males to females

Sex Ratio

ratio of males to females, if there is an unbalanced sex ratio, may more females or males, it can be difficult for organisms to find a mate

Instead of counting each organism individually, ecologists use __________ methods to estimate population sizes

sampling

What will happen to a population made up mostly of individuals that are past reproductive age?

unbalanced sex ratio--individuals will be left without a mate

Age structure diagram

visual tools scientists use to show the age structure of populations