1. Population Dynamics Unit 1: Ecology Z. Walker
SB4: Assess the dependence of all organisms on one another and the flow of energy and matter within their ecosystems.
Element c: Relate environmental conditions to successional changes in ecosystems
Element d: Assess and explain how human activities influence the environment
Essential Question (s):
1). What are the costs and benefits of building a Wal-Mart closer
to a residential area?
2). What would happen to the schools’ baseball field if left
undisturbed?

2. How does an ecosystem work?
An ecosystem supports diverse communities. The number of species living within an ecosystem is a measure of its biodiversity.
An ecosystem changes over time. Species replacement is characterized by an ecological sucession in which one community slowly replaces another as the environment changes.
There are two types of sucession:
Primary which is the colonization of new land that is exposed by avalanches, volcanoes, or glaciers,
Secondary, which refers to the sequence of community changes that take place after a community is disrupted by natural disasters (hurricanes, earthquakes, etc) or human actions.

3. Reintroduction of Organisms
The first organisms to inhabit an area are called pioneer species (lichen).
The 2nd group of organisms to inhabit the area are bacteria, protists, mosses, and fungi
The 3rd group include insects & arthropods
The 4th group include grasses, herbs, shrubs, & trees

4. What are the steps in Primary Succession?

5. VENN DIAGRAM – Comparing 1o and 2o Succession
Primary Succession
Secondary Succession
Changes that takes place after a community is disrupted by natural disasters or human activities
Occurs in areas that previously contained life and on land that contained soil
Ex: abandoned farmlands return to their original “prairie” grassland state
Takes less time to reach a climax community
The colorization of new sites by communities of organisms
Occurs in areas that are empty or barren
Ex: volcanic islands of Hawaii or a rocky site
Takes a longer time to reach a climax community
The community of organisms inhabiting an area gradually changes

6. How is Population Growth Predicted?
K = carrying capacity refers to
the number of organisms of one
species an environment can
support.
Exponential Growth
(aka “J-shaped” curve)
occurs when population growth
starts slow then increases
rapidly.
Logistic Growth
(aka “S-shaped” curve)
occurs when population growth
reaches its carrying capacity
due to limiting factors and levels off.
A Limiting Factor is any biotic
or abiotic factor that
restricts the existence,
numbers, reproduction,
or distribution of organisms

8. Graph 1: Rabbits Over Time
a. The graph shows a __________ growth curve. b. The carrying capacity for rabbits is __________ c. During which month were the rabbits in exponential growth? ____________

9. Graph 2: Average Toe Length
In 1800, about how many people surveyed had a 3 cm toe? _________
How many in 2000? ___________
The data shows that _________ selection has occurred.
In 2000, what is the average toe length? __________
What is the average toe length in 1800 ___________

10. Graph 3: Mexico and US
In Mexico, what percentage of the population is between 0-4 years of age? ______
In the US, what percentage of the population is between 0-4 years of age? ______
Which population is growing the fastest? ________
Which age group has the smallest number in both countries? ________

11. Ecological Stages of Succession
The climax community in the area of Michigan is a beech-maple forest. After the
ponds are filled in, the area will undergo another series of stages of succession.
This is illustrated below. Briefly explain what is happening at each step in the diagram. 3.

12. Examining the Stages in Ecological Succession
Succession, a series of environmental changes, occurs in all ecosystems. The stages that any ecosystem passes through are predictable. In this activity, you will place the stages of succession of two ecosystems into sequence. You will also describe changes in an ecosystem and make predictions about changes that will take place from one stage of succession to another.
The evolution of a body of water from a lake to a marsh can last for thousands of years. The process cannot be observed directly. Instead, a method can be used to find the links of stages and then to put them together to develop a complete story.
The water level of Lake Michigan was once 18 meters higher than it is today. As the water level fell, land was exposed. Many small lakes or ponds were left behind where there were depressions in the land. Below are illustrations and descriptions of four ponds as they exist today. Use the illustrations and descriptions to answer the questions about the ponds.

13. Pond A: Cattails, bulrishes, and water lilies grow in the pond
Pond A: Cattails, bulrishes, and water lilies grow in the pond. These plants have their roots in the bottom of the pond, but they can reach above the surface of the water. This pond is an ideal habitat for the animals that must climb to the surface for oxygen. Aquatic insect larvae are abundant. They serve as food for larger insects, which in turn are food for crafish, frogs, salamanders, and turtles.
Pond B: Plankton growth is rich enough to support animals that entered when the pond was connected to the lake. Fish make nests on the sandy bottom. Mussels crawl over the bottom.
Pond C: Decayed bodies of plants and animals form a layer of humus over the bottom of the pond. Chara, a branching green algae, covers the humus. Fish that build nests on the bare bottom have been replaced by those that lay their eggs on the Chara.
Pond D: The pond is so filled with vegetation that there are no longer any large areas of open water. Instead, the pond is filled with grasses. The water dries up during the summer months.
Questions
1. Write the letters of the ponds in order from the youngest, to the oldest. _______________________________________________________
2. Black bass and bluegill make their nests on sandy bottoms. In which pond would you find them? ______________________
3. What will happen to the black bass and blue gill as the floor of the ponds fills with organic debris? ____________________________________
4. Golden shiner and mud minnows lay their eggs on Chara. In which pond would you find them? _____________________
5. Some amphibians and crayfish can withstand periods of dryness by burying themselves in mud. In which pond (s) would they survive? ____________
6. Dragonfly nymphs spend their early stages clinging to submerged plants. Then, they climb to the surface, shed their skins and fly away as dragonflies. Which pond is best suited for dragonflies?____________________________
7. In which pond will gill breathing snails be replaced by lung breathing snails that climb to the surface to breathe? ________________
8. Some mussels require a sandy bottom in order to maintain an upright position. In which pond will they die out. ______________________