Environmental Science Chapter 8 1

 Section 8.1 2

 A population is all the members of a species living in the same place at the same time.  The three main properties of a population are size, density, and dispersion. 3

Population Density  Density is the number of individuals per unit area or volume.  Dispersion is the relative distribution or arrangement of its individuals within a given amount of space. 4

 Even  Clumped  Random 5

 Births and immigration increase a population  Deaths and emigration decrease a population  Growth rate is the birth rate minus the death rate. 6

 Positive: more births than deaths  Negative: more deaths than births  Zero: the average number of births equals the average number of deaths 7

 Biotic potential is the fastest rate at which its population can grow.  Reproductive potential is the maximum number of offspring that each member of the population can produce. 8

 Individuals produce more offspring at a time  Reproduce more often  Reproduce earlier in life 9

 When a population grows exponentially because there are plenty of resources available and little or no predators. 10

 Carrying capacity: the maximum population that the ecosystem can support indefinitely.  Resource limits: consuming natural resources at the same rate they are being produced.  Competition: members of the population fighting over available resources. 11

 Density dependent means it depends on population size  Examples: competition and predator-prey  Density independent means it does not depend on the size of the population  Examples: severe weather and natural disasters 12

 Time for a reading quiz 13

 Section

HabitatNiche  Habitat is an organism’s location.  Think of it as your address.  Niche is the role of a species within its habitat.  Physical home, environmental factors, and interactions. 15

Niche overlapNiche division  Niche overlap  Insects feeding on same plant or same feeder but at different times of day.  Niche division or restriction  Birds feeding on different parts of the tree. 16

 Is when an organism feeds on another organism  Predator is the one feeding.  Prey is the one being fed upon. 17

 Is when one organism lives in or on another organism.  The one that benefits is the parasite.  The host is harmed. 18

 Is when both species benefit from the relationship. 19

 Is when one organism benefits and the other organism is not affected at all. 20

symbiosis coevolution  A relationship in which two different species live in close association with each other.  Three types: mutualism, commensalism, and parasitism  When two species evolve adaptations that reduce the harm or improve the benefit of the relationship. 21

 Time for reading quiz 22