1. Table of Contents Living Things and the Environment
Studying Populations
Interactions Among Living Things
Changes in Communities

2. Living Things and The Environment
All living things must interact with their surroundings.
Organism —a complete and whole living thing
Habitat —a place where an organism lives. It
provides food, water, shelter and a place to
reproduce. Ex: a woodpecker’s habitat is
the trees in a forest.
Niche —the role of an organism in its community. How it makes a living. Ex: a
woodpecker’s niche is catching and eating
insects.

3. Biotic and Abiotic Factors
Biotic Factors —all living parts of an organism’s
habitat.
Abiotic Factors —all nonliving parts of an
organism’s habitat. (water, sunlight,
oxygen, temperature, soil)

4. Levels of Organization
The living things in an environment must be organized into
larger and larger groups within their environment.
Species —a group of organisms that are physically
similar and can mate with each other and produce offspring that can also mate and reproduce.
Populations —all the members of one species in a
particular area.
Community –- all the different populations that live
together and interact with each other in a particular area.

5. Levels of Organization
Ecosystem —the community of organisms that
live in a particular area, along with their
nonliving surroundings. Ex: pond, garden, forest
Biosphere —the entire region of the world where
living things are found.
Ecology —the study of how living things interact
with each other and with their environment

6. Levels of Organization
Living Things
and the Environment
Levels of Organization
The smallest level of organization is a single organism, which belongs to a population that includes other members of its species.

7. Levels of Organization
Living Things
and the Environment
Levels of Organization
The population belongs to a community of different species.

8. Levels of Organization
Living Things
and the Environment
Levels of Organization
The community and abiotic factors together form an ecosystem.

9. Four Characteristics of a Self-sustaining Ecosystem
A self-sustaining ecosystem has four characteristics:
1. A constant source of energy (usually the sun)
2. Transfer of energy into organic compounds
(usually through photosynthesis)
3. Interactions between biotic factors
(predator/prey, mutualism, commensalism)
4. Cycling of materials (water cycle, nitrogen cycle,
oxygen/carbon dioxide cycle, nutrient cycle)

10. Studying Population Size
Four methods of determining population size:
1. Direct Observation —count all members of a
population.
2. Indirect Observation —observe and count signs of a
population. Ex: count nests or dens observed
3. Sampling —make an estimate of the population by
counting the number of organisms in a small area
(a sample), and then multiplying to find the number
in a larger area. Estimate —an approximation of a
number.
4. Mark-and-Recapture Studies —capture, mark, and
release organisms several times to calculate their
population number.

11. Changes in Population Size
Populations can change in size when members either leave or join the population. Population size can change by births, deaths, immigration or emigration.
Birth rate —number of births in a population in a
certain amount of time.
Death rate —number of deaths in a population in
a certain amount of time.
Birth rate > Death rate = population increase
Death rate > Birth rate = population decrease
Immigration —organisms move into a population
Emigration —organisms move out of a population

12. Changes in Population Activity
Studying
Populations
Changes in Population Activity
Click the Active Art button to open a browser window and access Active Art about changes in population.

13. Population Density Population Density —the number of individuals in a
specific area.
Population Density = Number of individuals
Unit area

14. Changes in Population Density
Studying
Populations
Changes in Population Density
In many situations, it is helpful to know the population density–the number of individuals in a specific area.
Population density =

15. Limiting Factors
Limiting Factor —an environmental factor that causes a population to decrease. They include:
food, water, space, and weather conditions
Limiting Factors help determine the carrying capacity of an environment.
Carrying Capacity —the largest population that an
area can support .

16. Inequalities Studying Populations
The population statement is an example of an inequality. An inequality is a mathematical statement that compares two expressions. Two signs that represent inequalities are:
< (is less than)
> (is greater than)
For example, an inequality comparing the fraction to the decimal 0.75 would be written
< 0.75

17. Inequalities Practice Problems
Studying
Populations
Inequalities
Practice Problems
Write an inequality comparing each pair of expressions below.
5 __ –6
5 > –6

18. Inequalities Practice Problems
Studying
Populations
Inequalities
Practice Problems
Write an inequality comparing each pair of expressions below.
0.4 __
0.4 <

19. Inequalities Practice Problems
Studying
Populations
Inequalities
Practice Problems
Write an inequality comparing each pair of expressions below.
–2 - (–8) __
–2 - (–8) >

20. Changes in Population Size
Studying
Populations
Changes in Population Size
Populations can change in size when new members join the population or when members leave the population.

21. Asking Questions Studying Populations
Before you read, preview the red headings. In a graphic organizer like the one below, ask a question for each heading. As you read, write the answers to your questions.
Question
Answer
How do you determine population size?
Some methods of determining population size are direct observation, indirect observation, sampling, and mark-and-recapture studies.
What causes populations to change in size?
Some factors include birth, death, immigration, and emigration.
What are limiting factors?
These are factors that can limit population growth if they are unfavorable for the organisms in the population. Food and water, space, and weather conditions can be limiting factors.

22. Adapting to the Environment
Each organism in a community has unique characteristics that allow them to interact with each other and to survive.
Adaptations —the behaviors and physical characteristics
that allow organisms to live successfully in their
environment.
Natural Selection —individuals with the best adaptations
will survive to pass on these traits to their offspring.
These better characteristics will therefore become
more common in the population.

23. Adapting to the Environment
Interactions Among
Living Things
Adapting to the Environment
Every organism has a variety of adaptations that are suited to its specific living conditions.

24. Interactions Among Living Things
There are three major types of interactions among organisms: Competition, Predation, and Symbiosis
1. Competition —the struggle for organisms to
survive as they attempt to use the same
limited resources.
Animals compete for food, water, shelter, territory and mates
Plants compete for sunlight, water and growing space

25. -It helps weed out diseased or less-fit members
2. Predation —one organism kills another for food.
Predator —does the killing Prey —is killed
-It helps control overpopulation of non-predatory
species.
-It helps weed out diseased or less-fit members
of a non-predatory species.
-Populations of predators and their prey rise and
fall in related cycles.

26. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
On Isle Royale, an island in Lake Superior, the populations of wolves (the predator) and moose (the prey) rise and fall in cycles. Use the graph to answer the questions.

27. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
Reading Graphs:
What variable is plotted on the x-axis? What two variables are plotted on the y-axis?
Year; numbers of wolves and moose

28. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
Interpreting Data:
How did the moose population change between 1965 and 1972? What happened to the wolf population from 1973 through 1976?
The moose population increased and then decreased; the wolf population increased.

29. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
Inferring:
How might the change in the moose population have led to the change in the wolf population?
As the moose population increased, more food was available to the wolf population and it increased.

30. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
Drawing Conclusions:
What is one likely cause of the dip in the moose population between 1974 and 1981?
The wolf population increased.

31. Predator - Prey Interactions
Interactions Among
Living Things
Predator - Prey Interactions
Predicting:
How might a disease in the wolf population one year affect the moose population the next year?
Disease would cause a decrease in the wolf population, so fewer moose would be eaten and the population could increase.

32. Predator/prey Activity

33. Interactions Among Living Things
3. Symbiosis —a close relationship between two species
that benefits at least one of the species. Three types:
-Mutualism —both species benefit
Example—lichens: a mutual relationship between algae and fungi: algae makes food for the fungi and the fungi makes living conditions better for the algae.
Example—bees visit flowers: bees get nectar and flowers get pollinated.

34. -Commensalism —one species benefits and the
other is neither helped nor harmed.
Example: barnacles attached to
gray whales: barnacles get a free
ride to find food and the whale is
unaffected. Gray whales can be
identified by their barnacle patches. Some may carry as much as 400 lbs of barnacles and whale lice.
Example: orchid growing on a tree: orchid gets a place to grow and the tree is unaffected

35. -Parasitism —one species benefits and the other
is harmed.
-Parasite —organism that benefits
-Host —organism that the parasite lives in or on and is
harmed.
1. Hookworm
2. Tapeworm
3. Tapeworm
eggs
4. Roundworm
5. Pin worm

36. Using Prior Knowledge Interactions Among Living Things
Before you read, look at the section headings and visuals to see what this section is about. Then write what you know about how living things interact in a graphic organizer like the one below. As you read, continue to write what you learn.
What You Know
Organisms interact in different ways.
What You Learned
Organisms are adapted to their environments.
Organisms have niches, which are their roles in their habitats.
Organisms compete for resources. Some organisms eat others, and this affects the size of populations.
Some organisms live together in symbiotic relationships, of which there is mutualism (both benefit), commensalism (one benefits, the other is not helped or harmed), and parasitism (one benefits, the other is harmed).

37. More on Population Interactions
Interactions Among
Living Things
More on Population Interactions
Click the PHSchool.com button for an activity about population interactions.

38. Changes in Communities
Communities change constantly---sometimes suddenly; sometimes slowly.
Succession —the series of predictable changes
that occur in a community over time. Two types:
1. Primary Succession —the series of changes that
occur in an area where no soil or organisms
exist. Example: Following a volcanic eruption.
Pioneer species —first species to populate such
an area. Examples: mosses and lichens

39. Primary Succession Changes in Communities Primary succession is the
series of changes that occur in
an area where no soil or organisms exist.

40. Changes in Communities
2. Secondary Succession —the series of changes that
occur in an area where the ecosystem has been
disturbed, but where soil and organisms still exist.
Examples: following fires, hurricanes, tornados,
farming, logging or mining.

41. Secondary Succession Changes in Communities
Secondary succession is the series of changes that occur in an area where the ecosystem has been disturbed, but where soil and organisms still exist.

42. Comparing and Contrasting
Changes in
Communities
Comparing and Contrasting
As you read, compare and contrast carbohydrates, proteins, and lipids in a table like the one below.
Factors in Succession
Primary
Succession
Secondary Succession
Volcanic eruption
Fire
Possible cause
No soil or organisms exist.
Soil and organisms exist.
Type of area No
Yes
Existing ecosystem?

43. Click the SciLinks button for links on succession.
Changes in
Communities
Links on Succession
Click the SciLinks button for links on succession.

44. Mark-and-recapture studies
Graphic Organizer
Main Idea
There are four main ways to determine the size of a population.
Detail
Detail
Detail
Detail
Mark-and-recapture studies
Direct observation
Indirect observation
Sampling