Population Dynamics Unit 1 Ecology Z Walker SB

Population Dynamics Unit 1: Ecology Z. Walker SB 4: 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?

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: 1. 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. 2.

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

What are the steps in Primary Succession?

VENN DIAGRAM – Comparing 1 o and 2 o Succession Secondary Succession Primary Succession • 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 • 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

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

Limiting Factors 2 -Main Categories Density-dependent Density-independent Only become limiting when a population reaches a certain size Factors: competition, disease, predation Limiting no matter the size of the population Factors: weather, natural disasters, seasonal cycles

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? ______

Graph 2: Average Toe Length a. In 1800, about how many people surveyed had a 3 cm toe? _____ b. How many in 2000? ______ c. The data shows that _____ selection has occurred. d. In 2000, what is the average toe length? _____ e. What is the average toe length in 1800 ______

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

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. 1. 4. 2. 5. 3.

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.

• 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. ___________