1. Chapter 5: Populations

2. Describing Populations
5.1 How Populations Grow?
Describing Populations
How do ecologists study populations?
Populations are studied by
Geographic range
Density and distribution
Growth rate
Rate structure

3. Geographic Range Area inhabited by a population
Can vary in size depending on the species

4. Density & Distribution
The number of individuals of a particular species at a specific place.
The number of individuals per unit area.
Distribution refers to how individuals in a population are spaced out across the range of the population.
Random, Uniform, Clumped Refer to Fig 5-2
For Example: the number of alligators per square mile of the everglades
population = individuals = 400 alligators = 10 alligators
density unit area km km2
By measuring the population density of a specific species can give us a better idea of the effects of the environment in a specific area.

5. Patterns of Distribution

6. Growth Rate
Indicates whether the size of a population increases, decreases or is sustained.

7. Age Structure
The number of males and females of each age contained in a population.

8. What factors affect population growth?
The factors that can affect population size.
birthrate
death rate
immigration & emigration rates
It depends on how many individuals are added or removed.

9. Exponential Growth
Is the growth of a population by a constant factor at constant time intervals.
Unlimited resources and absence of predation and disease, population will grow exponentially.

10. Logistic Growth
When a population’s growth slows and then stops following a period of exponential growth.

11. Phases of Growth Phase 1: Exponential Growth
Phase 2: Growth Slows Down
Phase 3: Growth Stops

12. The Logistic Growth Curve
It occurs when a population’s growth slows and then stops, following a period of exponential growth.

13. Carrying Capacity
Maximum number of organisms in a population that an environment can maintain.
When birthrate and the death rate are the same.
When immigration equals emigration.

14. Carrying Capacity
The population of seals before the early 1900’s kept this population below its carrying capacity. After the hunting was reduced, the seal population increased exponentially until it reached its carrying capacity. This S-shaped curve indicates a rapid increase in population for a period of time that will stabilize after reaching carrying capacity of the environment.
Carrying Capacity Video

15. 5.2 Limits to Growth What factors determine carrying capacity?
Condition that restricts a population's growth, such as space, disease, and food availability.

16. Density-Dependent Limiting Factors
Factor that limits a population more as population density increases.
Competition
Predation
Herbivory
Parasitism
Disease
Stress from overcrowding

17. Competition When populations become crowded, individuals compete for:
Food
Water
Space
Sunlight
Territories
Other essentials

18. Predation and Herbivory
Predator-Prey Relationships
Herbivore Effects
Humans as Predators
Refer to pages

19. Parasitism and Disease
Parasites and disease causing organisms feed at the expense of their host, weakening them and often causing disease or death.

20. Stress From Overcrowding
High level of stress can weaken the body’s ability to resist disease or it can cause females to neglect, kill, or even eat their own offspring.
Limiting Factor video

21. Density-Independent Factors
What limiting factors do not typically depend on population density?
Unusual weather such as hurricanes, droughts, floods.
Natural disasters such as wildfires.
Fig. 5-10
Limiting Factors Video

22. 5.3 Human Population Growth
How has human population size changed over time?
The human population, like populations of other organisms, tend to increase.

23. Historical Overview The human population has increased explosively.
Wide-scale farming began to replace hunting and gathering, providing a more plentiful food supply. More food meant people reproduced more and lived longer, and the population began to climb.
In the past few centuries, death rates have continued to decline because of improvements in nutrition, sanitation, and health care.

24. Predicting Future Population Growth
A city population's demands for food, water, energy and other supplies can strain resources far from the city.
New technology, especially in agriculture and medicine, enabled more people to survive and reproduce.

25. Patterns of Human Population Growth
Read
Page 144
Refer to Fig 5-12
Over
Population
video