HW due Thurs Read chapter 5 pg. 118-127 Do Making Connections pg.127 Aim: How do abiotic (physical) limiting factors affect growth and survival in an ecosystem ? HW due Thurs Read chapter 5 pg. 118-127 Do Making Connections pg.127

Ecosystems and Growth One of the features of an ecosystem is that its growth is limited under normal conditions by competition for resources within the system and by external factors such as environmental changes The biotic elements in this pond ecosystem are; birds, plants, fish, phytoplankton, zooplankton. What are environmental elements? Temperature, precipitation, sunlight, minerals

If the presence or absence of a factor limits the growth of the ecosystems elements, it is called a limiting factor . There are several abiotic factors that limit ecosystem growth, including temperature, precipitation, sunlight, soil configuration, and soil nutrients.

Observation of ecosystems in very different geographical regions Two readily observed limiting factors are temperature and precipitation. Vegetative vigor, or the amount of plant growth, can be compared in two different geographical regions to understand how temperature and precipitation affect growth in the ecosystem. Some of you will be analyzing data from the North American Tundra and others will analyze data from the South African Wooded Grassland

Identify the maximum and minimum values and describe the overall shape of the graph These values represent vegetative vigor, or the amount of vegetation that grows in a particular location. Look at the graphs you were given. Make sure your understand the key for surface temperature and monthly precipitation. What do these graphs tell us?

Your task… What limits the North American Tundra ecosystem? Explain your reason and point out evidence from the graphs that support your answer. What limits the South African Grassland ecosystem? Explain your reason and point out evidence from the graphs that support your answer. Work in groups – 5 minutes

North American Tundra Answer: The vegetation vigor period shown on the graph more closely corresponds to the potential growing season based on temperature. The limiting factor in the ecosystem is temperature.

South African Wooded Grassland The evidence shows that growth in the South African wooded grassland ecosystem is limited by precipitation rather than by temperature. The temperature remains relatively constant and warm enough for the vegetation to thrive; yet the vegetation vigor shows large changes that match changes in precipitation.

What are limiting factors to population growth ? Interest Grabber What are limiting factors to population growth ? Section 5-2 A situation that causes the growth of a population to decrease is called a limiting factor. Some limiting factors depend on the size of the population. Other limiting factors affect all populations in similar ways, regardless of the population size. Go to Section:

Different factors can limit population growth How is the population size affected by these factors?

population growth… Logistic Figure 5-4 Logistic Growth of Yeast Population population growth… Logistic Section 5-1 Carrying capacity Number of Yeast Cells Yeast cells grow in a closed container. So we have to look at the capacity of the system (whatever that system is) to support continued growth. What do the yeast cells need to grow? Space, nutrients, oxygen Any one of these elements can become the limiting factor. What happens if food is limited? …….space is limited. ………oxygen is limited. Time (hours) Go to Section:

Exponential Growth Unlimited resources Absence of predation No disease A Density-Dependent Limiting Factor Exponential Growth Section 5-2 Growth of Aphids Unlimited resources Absence of predation No disease This is the graph produced under ideal conditions. Go to Section:

Concept Map Population Growth Logistic Exponential growth Limits on Section 5-1 Population Growth can be Exponential growth Logistic characterized by represented by characterized by represented by Falling growth rate S-shaped curve Limits on growth No limits on J-shaped Constant Unlimited resources which cause a Go to Section:

Figure 5-7 Wolf and Moose Populations on Isle Royale How would you explain what is happening to the moose and wolf population ? Section 5-2 60 2400 50 2000 40 1600 30 1200 20 800 10 400 1955 1960 1965 1970 1975 1980 1985 1990 1995 The relationship between moose and wolves on Isle Royale illustrates how predation can affect population growth. In this example changes in food supply and disease could affect the populations. Moose Wolves Go to Section:

Human population growth Is there a Carrying Capacity for Homo sapiens? Section 5-3 Industrial Revolution begins Agriculture begins Bubonic plague Plowing and irrigation The human population growth of the last century has been truly phenomenal. It required only 40 years after 1950 for the population to double from 2.5 billion to 5 billion. This doubling time is less than the average human lifetime. The world population passed 6 billion just before the end of the 20th century.  Present estimates are for the population to reach 8-12 billion before the end of the 21st century. During each lecture hour, more than 10,000 new people enter the world, a rate of ~3 per second! Of the 6 billion people, about half live in poverty and at least one fifth are severely undernourished. The rest live out their lives in comparative comfort and health. The factors affecting global human population are very simple. They are fertility, mortality, initial population, and time. The current growth rate of ~1.3% per year is smaller than the peak which occurred a few decades ago (~2.1% per year in 1965-1970), but since this rate acts on a much larger population base, the absolute number of new people per year (~90 million) is at an all time high. The stabilization of population will require a reduction in fertility globally. In the most optimistic view, this will take some time.