Chaper 14

1. Chaper 14 PowerPoint by Jacob Rondinella

2. 14-1 Populations & how they grow • 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 poultwill 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.) • Existing organisms reproduce. • Their offspring's reproduce. • Their offspring's offspring reproduce. Exponential Growth Ex) a bacteria divides every ½ hour. @ 30 min  2 bacteria @ 60 min  4 bacteria @ 90 min  8 bacteria @ 120 min 16 bacteria

4. Population of deer

5. 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.

6. 14-2 Why populations stop growing • Population growth may be limited by several factors – EX) Size 7 density. • Population Densityis the number of organisms in a given area. • Density – Dependent limiting Factors • Operate on large, dense population • Species whose populations are controlled by D.D.L.F. tend to have fairly stable populations. • Competition, predation, parasitism, and crowding are examples. • Competition • When 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.

7. (Disclaimers: This graph is not accurate)

8. Predation • Predators and their prey usually coexist over long periods of time. • Predators in turn develop their own defenses such as strong jaws + sharp teeth, powerful digestive enzymes, or keen eyesight. • Parasitism • A parasite is an organism that takes nourishment from its host. • Parasites live at the expense of their hosts, weakening them and cavsins disease and sometimes death. • Parasites work most effectively when hosts are present in large numbers. • Parasites are often host-specific  they grow best in members of a single species. • Crowding helps parasites travel from one suitable host to another. • Crowding and Stress • Most animals have a built in need for space  hunting, nesting. • Organisms fight among themselves if they become overcrowded. • 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 factors • Boom and bust • Weather • Human activities – toxic waste pesticides

9. 14-3 Human Population growth • Human populations grew slowly for most of human existence. • About 300 years ago, the world’s population started growing more rapidly. • Agricultural and industrial revolutions made human life easier. • Foods became more notorious. • Doctors cured and prevented diseases. • Better health care reduced infant mortality. • Birth rates became considerably higher than death rates • This led to the human population growth exponentially. • 1800  1 Billion people • 1900  2 Billion people Global human population • 1950  4 Billion people • 1963  5 billion people • 2000’s  180 people are born every minute. •  92 million new humans every year.

10. Estimate world population as of February 2010 6,802,198,448

11. Controlling human Population • Over the last century, human population growth has slowed down dramatically in some countries. • Biologists say that these populations passed through demographic transition is a change in growth rate resulting from changes in birth rate. • Demographic transition consists of three stages • First stage  there is a high birth rate and a high death rate. • Second stage  improvements are made in living conditions. • Third stage  birth rate decreases for a variety of reason. • p. 321 Section Review 14-3

14. 14-4 Population Growth and Carrying Capacity • 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 Growth • This depends on how many people of different ages are living in that country today  this is called age-structure diagram.

16. Demographers – People who study population growth use age-structure diagrams to make predictions about future growth. • Rapid growth • EX) 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 Growth • EX) 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 Capacity • What 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