PowerPoint by Jacob Rondinella

Population is a group of organisms of a single species that live in a given area.EX) Whitetail deer living in a forest

*Populations mostly remain the same from year to year but they can vary.EX) Flooding will lower the turkey population because most of the poult will drown.

*Populations will change size depending on how many organism are added to it and how many organisms are removed from it.

This change in population size is called growth rate.

*A population will grow if more organism are born than die.Populations living with ideal conditions (equal food, shelter, and protection from predators.)

1.Existing organisms reproduce.2.Their offspring's reproduce.3.Their offspring's offspring reproduce.

Exponential GrowthEx) a bacteria divides every ½ hour.@ 30 min 2 bacteria@ 60 min 4 bacteria@ 90 min 8 bacteria@ 120 min 16 bacteria

Population of deer

Populations do not have exponential growth forever.Growth will stop or at least slow down.

Zero population growth – the size of a population stays the same because it’s growth rate is zero.

Carrying capacity – the largest # of individuals that can survive over long periods of time in a given environment.

If the population gets larger than the carrying capacity, it birth rate falls or death rate rises.

If the population gets larger than the carrying capacity, it’s birth rate falls or death rate rises.

*Some organisms of a species reach a peak population size (boom) and then crash dramatically (bust).Known as boom and bust Fig 14-4 p. 314

P. 314 Section Review # 1-3.

Population growth may be limited by several factors – EX) Size 7 density.Population Density is the number of organisms in a given area.

Density – Dependent limiting Factors1.Operate on large, dense population2.Species whose populations are controlled by D.D.L.F. tend to have fairly stable populations.3.Competition, predation, parasitism, and crowding are examples.

CompetitionWhen populations become crowded, individual plants or animals may compete with one another for food, H2O, space, sunlight, etc.The more individuals there are in an area, the sooner they will use up the available resources.Competition for limited resources is often once of the most important factors in deterging the carrying capacity of an environment for a particular species.

(Disclaimers: This graph is not accurate)

Predation1.Predators and their prey usually coexist over long periods of time.2.Predators in turn develop their own defenses such as strong jaws + sharp teeth, powerful digestive enzymes, or keen eyesight.

Parasitism1.A parasite is an organism that takes nourishment from its host.2.Parasites live at the expense of their hosts, weakening them and cavsins disease and sometimes death.3.Parasites work most effectively when hosts are present in large numbers.4.Parasites are often host-specific they grow best in members of a single species.5.Crowding helps parasites travel from one suitable host to another.

Crowding and Stress1.Most animals have a built in need for space hunting, nesting.2.Organisms fight among themselves if they become overcrowded.3.Fighting causes high levels of stress, which can upset their hormone balance.Upsetting animals behavior so they neglect, kill, or even eat their own offspring.

Density – Independent and limiting factors1.Boom and bust2.Weather3.Human activities – toxic waste pesticides

•Human populations grew slowly for most of human existence.•About 300 years ago, the world’s population started growing more rapidly.1.Agricultural and industrial revolutions made human life easier.2.Foods became more notorious.3.Doctors cured and prevented diseases.4.Better health care reduced infant mortality.

Birth rates became considerably higher than death ratesThis led to the human population growth exponentially.

1. 1800 1 Billion people2. 1900 2 Billion people Global human population3. 1950 4 Billion people4. 1963 5 billion people

2000’s 180 people are born every minute. 92 million new humans every year.

Controlling human PopulationOver the last century, human population growth has slowed down dramatically in some countries.1.Biologists say that these populations passed through demographic transition is a change in growth rate resulting from changes in birth rate.

2.Demographic transition consists of three stagesa. First stage there is a high birth rate and a high

death rate.b. Second stage improvements are made in living

conditions.c. Third stage birth rate decreases for a variety of

reason.

p. 321 Section Review 14-3

In most western countries and China, the global population is still growing exponentially. Because most people live in countries that have no yet completed the demographic transition.

•US, Canada, Japan. And other countries of Europe have gone through all three stages of demographic transition in these countries the population growth is slow.•Countries is Asia, Africa, and South America have not yet completed the demographic transition 80% of the world’s population live there This provides severe economic problems.

Future Population GrowthThis depends on how many people of different ages are living in that country today this is called age-structure diagram.

Demographers – People who study population growth use age-structure diagrams to make predictions about future growth.

Rapid growthEX) Mexico Majority of the population is under the age of 15.•The largest percentage of people have not yet reached their child Bering years.•This means that Mexico can expect to grow even more.

Slow GrowthEX) Sweden There is almost equal numbers of people in each age group.EX) In the US The largest segment of the population belongs to people born after WWII Called the baby boomers

Earth’s Carrying CapacityWhat is the Earth’s carrying capacity for humans?This is a hard question to answer.Some say that the Earth can hold between 5-20 billion people.

p.325 Section Review 14-5 #’s 1-3