Environmental Science Chapter 8 Populations Environmental Science Chapter 8

Understanding Populations Section 8.1

What is a Population? 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.

Density vs. dispersion 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. Population Density

Even Dispersion Even Clumped Random Clumped Random

How does a population grow? Births and immigration increase a population Deaths and emigration decrease a population Growth rate is the birth rate minus the death rate.

Growth Rates Positive: more births than deaths Negative: more deaths than births Zero: the average number of births equals the average number of deaths

How fast can populations grow? 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.

Reproductive potential increases when: Individuals produce more offspring at a time Reproduce more often Reproduce earlier in life

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

What limits population growth? 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.

Two types of population regulation 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

That’s all for 8.1 Time for a reading quiz

How species interact with each other Section 8.2

Habitat vs. niche 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. Habitat Niche

Competition is when different individuals or populations use the same limited resources 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. Niche overlap Niche division

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

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

mutualism Is when both species benefit from the relationship.

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

Symbiosis and 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. symbiosis coevolution

That’s all for 8.2 Time for reading quiz