1.3: Investigating population growth

Question 1

A habitat is an area with a particular set of features that is defined by two characteristics:

Answer 1

physical (abiotic)
biological (biotic)

Question 2

Population size is always changing due to:

Answer 2

new individuals are added through births (natality)
immigration (individuals moving into a population)
loss through death (mortality)
emigration (individuals moving out of a population)

Question 3

All populations are changed by the number of

Answer 3

births (b)
deaths (d)

Question 4

Some populations are also changed by:

Answer 4

immigration (i)
emigration (e)

Question 5

Impact of immigration and emigration on a closed population

Answer 5

Not changed

Question 6

Impact of immigration and emigration on an open

Answer 6

Changed

Question 7

Distance or Physical Barriers and Population Movement in a closed popualtion

Answer 7

Barriers that prevent movement in and out

Question 8

Distance or Physical Barriers and Population Movement on an open population

Answer 8

No barriers

Question 9

Define net population

Answer 9

means the change in population size after the combined effects of births, deaths, immigration, and emigration are accounted for.

Question 10

Equation for net population change

Answer 10

(b+i) - (d+e)

Question 11

Equation for percentage change in popualtion

Answer 11

(b+i)-(d+e)/n X 1000

Question 12

The four factors that affect population dynamics are:

Answer 12

births
deaths
immigration
emigration

Question 13

Population dynamics are the result of an interaction between:

Answer 13

internal factors (for example, reproductive ability)
external factors (for example, weather, food supply, predation, and disease)

Question 14

Some populations remain relatively stable over long periods of time, while others may

Answer 14

fluctuate dramatically or go through cycles.

Question 15

Studying how population are affected by internal and external factors can get complicated because populations are also affected by:

Answer 15

density, the amount of resources available, their environment, and interactions with other species.

Question 16

What is population ecology?

Answer 16

Population ecology is the area of biology that studies how populations change overtime in relation to their environment and other species.

Question 17

What are the three fundamental population growth models

Answer 17

the geometric growth model, the exponential growth model and the Logisitic growth model.

Question 18

Geometric growth is the simplest population growth model and it happens when

Answer 18

1. It happens in populations where individuals can only breed once per time period (like deer, which breed once per year).
2. If the birth and death rates per individual remain constant, then the population growth rate is constant over a fixed time period (for example, one year).

Question 19

Geometric growth can be modelled using the following equation:

Answer 19

Equation λ=N(t+1) / N(t)
or λ=Nt+1Nt
λ (the Greek letter “lambda”) is the fixed growth rate.
N(t) is the population size at a particular time, t (for example, a particular day).
N(t+1) is the population size at a time 1 unit after N(t). (if time is measured in days, N(t+1) would be the population size one day after N(t).

Question 20

Where is Exponential growth model used?

Answer 20

In a population where it can grow continuously since its not restricted to fixed time periods

Question 21

Describe the shape of a graph of exponential growth model

Answer 21

A graph of exponential growth looks almost identical to that of geometric growth, but it has a slightly steeper slope because it increases continuously. Both the geometric and the exponential growth graphs produce a J-shaped curve.

Question 22

Describe the shape of a graph of exponential growth model

Answer 22

A graph of exponential growth looks almost identical to that of geometric growth, but it has a slightly steeper slope because it increases continuously. Both the geometric and the exponential growth graphs produce a J-shaped curve.

Question 23

Here is the equation to determine exponential growth rate at a particular time:

Answer 23

dN/dt=rN

Question 24

What does an instantaneous growth rate of a population mean?

Answer 24

it tells you how much the population size is changing at any particular instant in time.

Question 25

What does a biotic potential means?

Answer 25

the maximum population growth rate that could occur under ideal conditions for an organism.

Question 26

How does a Ligistic growth graphs looks like?

Answer 26

S-shaped, it is sometimes also called a sigmoid curve (sigma is the Greek letter, S).

Question 27

As shown in the following figure, the logistic population growth model can be divided into three phases:

Answer 27

The Lag phase
The Log phase
The Stationary phase

Question 28

Mathematically, the logistic growth model is expressed using the following equation:

Answer 28

dN/dt=rN (K−N)/K

Question 29

The number of individuals in a given population is symbolized by the letter _____. The intrinsic rate of increase, also known as the ______________________, is the rate at which populations can grow if resources were unlimited, and is represented by the letter ____. Populations will grow to the limits of their ______________________, which puts a cap on the number of individuals; this number is called the _____________________ and is symbolized by the letter _____.

Answer 29

N/ biotic potential/ r/environment/ carrying capacity/ K

Question 30

The population growth model, which attempts to account for the amount of resources that a given population’s habitat has available to sustain it, is called the ____________ growth model. When graphed, the model displays an S-shaped or _________________ curve. This curve can be broken up into three phases. The first phase is characterized by a period of slow, constant, arithmetic increase and is called the _______________ phase. The second phase is characterized by very rapid growth, moving quickly from slow growth to an exponential growth pattern, and is called the ________________ phase. The third phase is characterized by the flattening out of the line into a plateau, indicating that the growth rate is __________ and thus, the population is no longer increasing. For this reason, it is called the _________________ phase. In natural populations, natural fluctuations will causes light fluctuations around the K value, showing that a state of dynamic population _____________________ has been reached.

Answer 30

Logistic/ sigmoid/ lag/ log/ zero/ stationary/ equilibrium

Question 31

c) Theoretically, what prevents the unlimited exponential growth of natural populations, causing them to eventually display a logistic growth pattern?

Answer 31

For natural populations, the resources are never unlimited. One or more resources determine the carrying capacity for a species, in a particular environment. As those resource limits are reached, the population growth slows down until it stops growing completely and levels off. This causes the initial exponential growth pattern (J-curve) to change into the sigmoid, or S-shaped curve, of the logistic growth model.

Question 32

Define density-dependent factors

Answer 32

The factors that affect a population’s growth rate because of its density

Question 33

For animals, these factors can include:

Answer 33

the amount of food
breeding territory available
social dynamics
predator avoidance opportunities
the risk of parasites and disease, and so on

Question 34

Examples of density-dependent factors

Answer 34

1. Predator focus
2. Resource availibility

Question 35

What are density-independent factors

Answer 35

Are factors that affect the population’s growth rate in ways that are not related to the population’s density

Question 36

Density-independent factors include biotic factors such as:

Answer 36

Extreme weather events
Fires
Droughts
Volcanic eruptions
Pollution

Question 37

2) Why does the population cycle of lynx usually lag behind the cycle of the hare by about one year? Answer the question below and check your response with the suggested answer.

Answer 37

The population increase in the lynx takes about a year to occur after the hare population increases, because the lynx only gives birth once per year in spring. As the abundance of hares declines, there is less food for the lynx, but this does not cause starvation or a decline in the lynx population until most of the hares are gone, and this takes many months to occur.