1. 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.

2. 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.

3. Ecology

4. 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

5. Populations
Do you know the population of world?

6. 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.

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

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

9. 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.

10. 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?

11. 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

12. 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

13. 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.

14. 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

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

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

17. 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

18. 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

19. 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.

20. 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

21. 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

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

23. 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)

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

25. 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

26. 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.

27. 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?

28. 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

29. Ticket Out
What is a density-dependent factor?