Chapter 13

Population A is defined as a group of INDIVIDUALS of the same SPECIES living together in the same time and place. Population Growth and Decline The population of an organism is determined by , death rate, immigration and emigration. Death rate is the number of individuals of a population that DIE within a certain TIME (usually a year). Predation,disease and competition for food affect the death rate of a population. Immigration means coming to an area and increase the size of the population. Population, birth rate,

Continued… Birth rate is the main cause of a population’s INCREASE. It is the number of BIRTHS produced by a population in a period of time. is affected by 1) ENVIRONMENTAL CONDITIONS, 2) NUTRITION 3) DENSITY OF POPULATION Emigration means leaving an area and it decreases the size of the population. Birth rate

Limiting Factors Factors such as limited amounts of , WATER and space slow or stop population growth. Most populations can not grow beyond a certain size, at some point the population uses up the resources that the environment has to offer and the population size levels off. This means that the population has reached its . FOOD, carrying capacity

Limiting Factors Factors in the non-living, physical environment can limit population growth, these are called limiting factors and include water, matter and weather . Biotic limiting factors are ways that interaction among living organisms may affect the size of a population. abiotic

Biotic Limiting Factors Organisms that live on or in other living organisms are called . Parasites usually weaken, but do not kill their host. The relationship between a parasite and a host is called parasitism. A predator is an animal that catches and kills another animal the prey. Predators usually go after sick or weak individuals. Animals and plants compete against each other for nutrients, water, light and shelter. PARASITE