February 23, 2016 Bell Work: Which do you think is larger in the world, the population of ants or the population of humans? Objective: The student will be able to… Define ecology. Describe populations and what affects them.

Today in History 1836 The siege of the Alamo began in San Antonio, Texas. 1997 Scientists in Scotland announced they had cloned an adult mammal, producing a lamb named Dolly.

Ecology

Ecology Ecology: The study of the interactions of living organisms with one another and with their environment Ecosystems: a community of organisms and their abiotic environment

Populations Do you know the population of world?

Populations A population consists of all the individuals of a species that live together in one place at one time This definition allows scientists to use similar terms when speaking of different organisms.

Fun Fact The world’s human population has nearly tripled since the 1930’s. The world’s population will double by 2050

Write It Down! What causes populations to grow? What determines how fast they grow? What factors can slow their growth?

Populations Populations tend to grow because individuals tend to have multiple offspring over their lifetime Limited resources in an environment limit the growth of the population Demography is the statistical study of all populations Demographers study the composition of a population and try to predict how the size of the population will change.

Questions Are there environmental resources that will limit the human population? How does the human population support the population density of large cities? How do we support large population densities of domesticated animals?

Key Features of Populations Population size: the number of individuals in a population. One of the most important features of a population Affects the population’s ability to survive Smaller populations are more likely to become extinct

Key Features of Populations Random events or natural disturbances (i.e. fire, flood) endanger smaller populations more than they endanger larger populations Smaller populations tend to practice more inbreeding (breeding with relatives) which results in a more uniform population Can reduce a population’s fitness The more genetically identical a population, the higher chances are that one disease can wipe that population out

Key Features of Populations Population Density: the number of individuals that live in a given area The more dispersed a population is, the lower the probability that individuals will come into contact, which can make reproduction rare The more compacted a population is, the higher probability that the larger numbers can have a negative impact on their environment.

Key Features of Populations Dispersion: the way individuals of a population are arranged in space Random: self-determined or determined by chance Even distribution: located at regular intervals Clumped: individuals are bunched together in clusters

Key Features of Populations Each pattern reflects the interactions between the population and its environment.

Quick Review What is a population? What are three key features to populations?

Modeling Population Growth A population model is a hypothetical population that attempts to exhibit key characteristics of a real population Demographers use a population model when they try to predict how a population will grow Demographers can predict what might occur in a real population by making a change to the model

Population Growth Growth rate: the rate of population growth as the difference between the birthrate and the death rate Birthrate: the number of individuals that are born in a given time frame Death rate: the number of individual that die in a given time frame

Population Growth In human populations, birth and death rates are usually expressed as the number of births and deaths per thousand people per year. A population grows when more individuals are born than die in a given period.

Horseshoe Problem A farrier (a person who shoes horses) charges one cent for the first nail, the price duplicates for each of the following nails. What will the total cost be? A horseshoe has 8 nails Each horse has four horseshoes

Population Growth Exponential growth curve: a curve in which the rate of population growth stays the same As a result, the population size increases steadily

Exponential Growth Curve Example: A single bacterial cell that divides every thirty minutes will produce more than one million bacteria after only ten hours

Population Growth To calculate the number of individuals that will be added as the population grows multiply the current population (N) by the rate of growth (r) Populations do not typically grow unchecked Growth can be limited by predators, disease, and the availability of resources Some populations stabilize (become constant)

Population Growth The carrying capacity (K) is the population size that an environment can sustain It is denoted by K

Population Growth Limited resources become depleted as the population grows Density-dependent factors are a variable affected by the number of organisms present in a given area (affected by density of individuals in a given area) These include food and water

Population Growth The logistic model is a population model in which exponential growth is limited by a density-dependent factor This is the population model that takes into account the declining resources available to populations.

Questions Are there environmental resources that will limit the human population? How does the human population support the population density of large cities? How do we support large population densities of domesticated animals?

Vocabulary- Populations Highlight these words in your notes! Population size Population density Dispersion Population model Exponential growth curve Carrying capacity Density-dependent factor Logistic model Density- independent factor R- strategist K- strategist

Ticket Out What is a density-dependent factor?