Group 3 - Sarah Rios, David Jung, Steven Lee
Key Concepts
Density and Dispersion (pg 1137-1139)
-Density
is the number of individuals in a certain area. Dispersion is the pattern of
spacing between individuals of the species.
Dispersion
Types:
|
Type
|
Definition
|
Example
|
Uniform
|
Organisms are
evenly spaced
|
Penguins
|
|
Random
|
Organisms are
spaced randomly, with no apparent system
|
Dandelions
|
Clumped
|
Organisms are
found in groups.
|
Wolves, Human |
Image: examples of uniform, random
, and clumped dispersion.
Demography (pg 1137- 1141)
Demography
is the study of population statistics and how they change over time. Shown
using life tables following a cohort (group or individual of the same age), or
a survivorship curve.
Types of
Survivorship Curves:
I: Rate
of death increases as the individuals get older. Organisms get lots of parental
care
II: An intermediate curve between types I and III.III: Rate
of death decreases as the individuals get older. Organisms get little to no
parental care.
Life History Traits are Producers
of Natural Selection (pg1141)
An
organism’s traits reflect evolutionary history and the development, physiology,
and behavior of the species. Life history is made up of the schedule of
reproduction of an organism, such as how many offspring are produced.
Life History Diversity (pg 1141-1142)
There
are two types of Reproduction.
-Semelparity
“Big Bang Reproduction”: When an organisms reproduces only once, but produces a
large amount of offspring.
-Iteroparity: “Repeated
Reproduction”: When an organism produces multiple times during its life, but produces
one of few offspring each time.
''Tradeoffs" and Life Histories (pg 1112-1143)
Organisms
have finite resources, and limited resources such as nutrients and energy mean
trade-offs. Age at maturity, brood size, and level of parental care depend on
the environment. For example, plants and animals with high mortality rates tend
to produce more offspring in hopes some will survive.
Per Capita Rate of Increase (pg 1143-1144)
If immigration and emigration is ignored, changes in population during a period of time can be summed up as this:
Change in population size during time interval= Births during time interval- Deaths during time interval
Exponential Growth (pg 1144-1145)
Exponential Growth represents the potential growth without taking resource restrictions and carrying capacity into consideration. This model is shown using a J shaped curve, and predicts a larger rate of growth the larger the population is.
Equation: dN = change in population, dt= change in time, r= maximum rate for the species, N = population
The
Logistic Growth Model Includes the Concept of Carrying Capacity (pg 1145)
Logistic Growth incorporates (K), carrying capacity because exponential growth cannot continue forever. All populations are limited by the amount of resources in their environment. The Logistic Growth Model (pg 1145-1146)
In the logistic growth equation, population is known to ‘level
off’ and grow much more slowly as it approaches carrying capacity.
Equation: Similar to exponential growth model, but now includes K which = carrying capacity
The Logistic Model and Real Populations (pg 1146)
The Logistic Model and Life Histories (pg 1147)
Population Change and Population Density (pg 1148)
Density Dependent Population Regulation (pg 1148-1150)
Density dependent rates of birth and death is a type of negative feedback, or a regulation mechanism to turn a process on or off. This is due in part to several factors such as competition for resources like food and space to live, increased predators, increased risk of health problems like infection, and the buildup of toxic wastes.
Population Dynamics (pg 1150-1151)
The study of population dynamics focuses on the abiotic and biotic factors that cause changes in population size. Temperature and environmental fluctuations can cause dramatic change in even stable populations. Population size is also affected by emigration and immigration, especially in metapopulations, which are made of several populations linked together.
Population Cycles (pg 1151- 1152)
Image: Population cycles of snowshoe hares and lynx.
Populations go through 'boom and bust' cycles of regular highs and lows. Cycles vary from 3 to 4 year cycle in lemmings and voles, to a 10 year cycle of snowshoe hare and lynx. These cycles are influenced by both biotic and abiotic factors.
The Global Human Population (pg 1152-1155)
The human population has grown exponentially since 1650, when there was 500 million people. The population reached 1 billion within the next 2 centuries, and 2 billion between the years of 1850 and 1930. The annual rate of growth has been slowing since the 1960's, at it's highest it was 2.19% and is now 1.16%. It is predicted by 2050 the rate of growth will drop to 0.4%. Rates of infant mortality and life expectancy differ between developed and developing nations.
Global Carrying Capacity (pg 1155-1156)
There are several different estimates for global carrying capacity ranging from less than 1 billion to a trillion people, the average of them is somewhere between 10 to 15 billion. Ecological footprint is the concept of calculating carrying capacity by finding the aggregate land and water area to sustain the people of a nation. Ecological capacity varies by nation, and is defined as the ability of an ecosystem to maintain it's condition and produce goods. The world is already exceeding ecological capacity.
