1. Ecology Unit: Populations

2. Vocabulary Chapter 5 Age structure Immigration Emigration
Exponential growth
Logistic growth
Carrying capacity
Limiting factor
Density-dependent limiting factor
Density-independent limiting factor
Chapter 6
Renewable resource
Non-renewable resource
Desertification
Deforestation
Biological magnification
Biodiversity
Habitat fragmentation

3. Learning Targets
I can describe the growth of populations including exponential and logistic growth.

4. How Populations Grow
Three important characteristics of a population are:
Its geographic range
Its density and distribution
Its growth rate

5. Geographic range describes the area in which a population lives.
It can vary in size from very small, a few cubic centimeters to millions of square kilometers.
A small area could be a rotting apple where some worms live to the area a group of migrating whales cover in the Pacific Ocean.

7. Population density is the number of individuals per unit area.
This number can vary depending on the species and its ecosystem.
Low density is where only a few organisms live.
High density might be where thousands or millions of one species live.

8.  Low Density
High Density 

9. Growth Rate
The growth rate of a population tells if the population is growing, shrinking or staying steady.

10. Age Structure
The age structure of a population is the number of males and females of each age in the population.
This is important because only the females in a group can reproduce and can reproduce only at a certain age range.

11. Population Growth
Three factors can affect population size:
the number of births
the number of deaths
the number of individuals that enter or leave the population

12. Basically, a population increases or decreases depending on how many individuals enter or leave the population.
B > D
If the birthrate and death rate are fairly equal, the population size is stable.
B=D
If the death rate exceeds the birthrate, the population size decreases.
B < D

13. Immigration is the movement of individuals into an area
Immigration is the movement of individuals into an area. This can cause the population to grow.
Emigration is the movement of individuals out of an area. This can cause the population to shrink.

14. Exponential Growth
If a population has plenty of space and lots of food; is protected from predators and illness, it will grow.
Exponential growth occurs when the individuals in a population reproduce at a constant rate.
Under ideal conditions with unlimited resources, a population will grow exponentially. Bacteria are a good example of this type of growth. “J” Curve

15. “J” Curves

16. Logistic Growth
In time the rate of a population should naturally start slowing down. This is due to several factors. As resources become less available, the growth of a population slows or stops.
Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth. “S Curve”

17. Logistic Growth Curve
“S”
Curve

18. Carrying Capacity
The largest number of individuals an area can support. The population size may fluctuate but overall remains steady.

19. Points to Ponder With a partner:
Define and describe logistic and exponential growth.
Give an example of both types of growth.

20. Learning Target
I can describe the growth of populations including exponential and logistic growth.

21. Learning Target
I can explain the factors that can limit population growth.

22. Limits to Growth Limiting Factors
A limiting factor is anything that causes population growth to decrease. Examples of limiting factors are:
Competition
Drought and other climate extremes
Predation
Human disturbances
Parasitism and disease

23. Density-Dependent Limiting Factors
A density-dependent limiting factor is a limiting factor that depends on population size.
These factors only become limiting when the population density—the number of organisms per unit area—gets to a certain point.

24. These factors are most strong when a population is really big and dense; (Lots of critters in a small space). Density-dependent limiting factors include:
competition,
predation,
parasitism and
disease.

26. Density-Independent Limiting Factors
Affect all populations regardless of the size of the population and regardless of how dense the population may be.
Density-independent limiting factors can be unusual weather, natural disasters, seasonal cycles, and human activities.
After such an event, a population may crash and take many years to come back.

27. Points to Ponder
Explain the two types of limiting factors we discussed and give an example.

28. Learning Target
I can explain the factors that can limit population growth.

29. Learning Target
I can discuss and describe current environmental concerns.
I can discuss how our daily activities can affect the environment?

30. The Effect of Human Activity
People affect the environment through
Agriculture
Development
Industrial growth
These activities can affect the quality of Earth’s natural resources:
Soil
Water
Atmosphere \

31. Sustainable Development
Uses natural resources to meet human needs without causing long term damage to the environment.

32. Sustainable Development
Renewable resources:
Can be made or replaced in a healthy ecosystem
A new tree can be grown in place of an older, harvested tree

33. Sustainable Development
Non-renewable Resources:
Cannot be replaced in a reasonable amount of time
Fossil fuels
Took millions of years to form

34. Using Resources Wisely
Why is soil important?
Soil allows plants to grow.
Plants feed all living beings
How do we protect the soil?
Crop rotation
Leaving stems and roots in the soil to prevent erosion and loss of nutrients
Cutting only some mature trees can protect the soil.

35. Using Resources Wisely
Desertification
Process where overfarming, overgrazing, seasonal drought and climate change cause areas to dry out and become more desert-like.
About 40% of Earth’s surface is thought to be at risk.

36. Using Resources Wisely
Deforestation
The destruction of forests for development
More than half of all old growth forests have been lost
Old growth forests are areas that have never been cut.
Can lead to severe soil erosion.

37. Using Resources Wisely
How can we sustain the soil?
Leave stems and roots in the soil between plantings can help hold it in place
Rotate crops
Contour plowing/planting
Cut only mature trees and replace the ones that are cut with new trees

38. Using Resources Wisely
Freshwater Resources
Only 3% of the Earth’s water is fresh water (little to no salt)
In many areas on Earth, fresh water is very limited

39. Using Resources Wisely
Water pollution
A pollutant is any harmful materials that can enter the land, water or air.
Point source pollutant: a pollutant enters water from a specific source (a factory, oil spill)
Non-point source pollutant: grease and oil washed off of roads; chemicals released into the air, fertilizers from farms.

40. Using Resources Wisely
Biological magnification:
The increasing concentration of a harmful substance in organisms at higher tropic levels in a food chain or food web.
DDT

41. Points to ponder
What are three ways that humans can affect life on Earth?
Differentiate between a renewable resource and a non-renewable resource.

42. Learning Target
I can discuss and describe current environmental concerns.
I can discuss how our daily activities can affect the environment?

43. Learning Target
I can discuss the importance of biodiversity and the factors that affect it.

44. Biodiversity
Biodiversity is the sum total of the genetically based variety of all organisms in the biosphere.
Huh? Biodiversity is all the different living organisms in the world.
Scientists look at biodiversity in three ways
Ecosystem diversity
Species diversity
Genetic diversity

45. Types of Biodiversity
Ecosystem diversity: includes the variety of habitats, communities, and ecological processes
Species diversity: the number of different species in the biosphere; we have identified about 1.5 million so far and suspect there are millions more species to be discovered
Genetic diversity: sum total of all the different forms of genetic information carried by all living organisms

46. Biodiversity
Is one of Earth’s greatest natural resources. Species of many kinds have provided us with foods, industrial products, and medicine.
One plant, the rosy periwinkle, is the source of a cancer treatment medicine.

47. Threats to Biodiversity
Habitat fragmentation occurs when development can split an ecosystem into pieces
Remaining pieces become ecological islands
The smaller the island the fewer species can live there making them more vulnerable

48. Threats to Biodiversity
Biological magnification is the increasing concentration of a harmful substance at higher trophic levels in a food chain or food web.
DDT levels were more toxic at the tertiary consumer trophic level than at primary consumer levels.
DDT was banned in 1970s

49. Threats to Biodiversity
Invasive species are plants and animals that are usually innocently introduced into an ecosystem.
The invasive species reproduce rapidly and have few, if any, predators to control their growth.
Zebra mussels and kudzu

50. Learning Target
I can discuss the importance of biodiversity and the factors that affect it.