POPULATIONS. Definition: All the members of a species that live in one place at one time.

Transcription

1 POPULATIONS Definition: All the members of a species that live in one place at one time.

2 PROPERTIES of Populations Geographic dispersion the way in which individuals of a population are spread in an area or volume. Eg. Bears, owls, tigers Eg. Dandelions Eg. Wolves, bison, elephants

3 Population Growth SIZE Definition Population SIZE The number of individuals in a population

4 Population Size Depends on: Birth + Death Emigration: movement of individuals OUT OF a population Immigration: movement of individuals INTO a population +

5 Population Size Calculation What if there were 1267 rabbits in a colony. In one year 1500 rabbits were born, 1285 died, 65 emigrated and 0 immigrated. What is the new size of the population? Answer: 1417 By how much did the population grow? 150 What would the number look like if there was a decline in population growth? Negative number

6 Population Growth RATE Population growth RATE The amount by which a population s size changes over time. Stop and complete the Population Dynamics Worksheet

7 2 Types of Population Growth Rate Exponential Logistic

8 EXPONENTIAL Model of Population Growth A population grows exponentially when resources are abundant. If a population grows exponentially the population size increases dramatically over a period of time.

9 Do the Math Fill in the chart with the correct quantities Time (minutes) Formula Number of Cells

10 Positive Feedback Exponential growth is an example of positive feedback. The more organisms there are, the more babies will be born who, in turn, grow up to have babies themselves and so on.

11 Positive Feedback Positive feedbacks can be expressed in graph form as well. J shaped curve

12 Exponential Growth Curve Trace the trend line for the exponential growth curve and label the x and y axes with appropriate terms and Add a title

13 Time vs. Number of Individuals

14 LogisticModel of Population Growth Exponential growth is not sustainable long term!!! Most populations will face limiting factors and thus show a logistic growth rate. Populations are limited by finite resources in the environment.

15 Logistic Population Growth The amount of resources in an environment dictates its carrying capacity. Definition of Carrying Capacity: The number of individuals the environment can support over a long period of time. Based on the amount of resources in that environment.

16 Logistic Growth Curve On your notes trace the trend line Label the x and y axis Add a title Label the phrases Birth rate increases Death rate increases Carrying capacity

17 Logistic Growth Curve On your notes trace the trend line Label the x and y axis Add a title Label the phrases Birth rate increases Death rate increases Carrying capacity

18 LOGISTIC Model of Population Growth When at carrying capacity, birth rate is equal to death rate As population reaches carrying capacity, death rate increases Stretched out S When population is small, birth rate is higher than death rate

19 Logistic Growth Curve According to the graph, how many individuals will this environment carry for the long term? 2.50 thousand

20 Negative Feedback Logistic growth is an example of negative feedback. Since resources are limited, there is competition for these resources, therefore death rates rise, causing the population to stabilize.

21 Negative Feedback Negative Feedback Loops can be expressed in graph form-the graph is shaped like the letter S (logistic).

22 Logistic Growth Curve Often the population Carrying Capacity oscillates up and down, but there is an overall equilibrium to the population. Draw in the carrying capacity line in your notes

23 Logistic Growth Curve The carrying capacity is around 1.5 million individuals

24 Negative Feedback Limiting factors cause negative feedback loops. There are 2 types of limiting factors: 1. Abiotic Examples of abiotic limiting factors temperature Space

25 Negative Feedback 2. Biotic factors Examples of biotic limiting factors Food Disease

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27 Population DENSITY Definition: Population DENSITY Number of individuals per unit of area Low density High density

28 Do the math In a 3 km 2 area there are 7 deer. What is the density of the deer population? Answer: 2.3 deer/km2

29 Population Size REGULATION 1. Density Independent Factors: factors that reduce population regardless of population size Examples: Weather Fires Floods

30 Population Size REGULATION 2. Density Dependent Factors: triggered by increasing population density Examples Food shortages Space limitations Waste accumulation

31 Example of Exponential Growth Phase (J-Shaped Curve) Ex. Human Population Human population increased relatively slowly until about It then doubled in the next two centuries It doubled again in the next 80 years. Our population is now over 7 billion. This increases by 80 million/year This in an increase of 214,000/day. It takes 3 years for the world population to add the population equivalent of another U.S. (which is around 300 million).

32 Example of Exponential Growth Phase (J-Shaped Curve)

33 Human Carrying Capacity How long will it be until we reach our carrying capacity? What will happen then? What factors increase our carrying capacity? Farming Medicines Better sanitation Resource choice

34 Human Carrying Capacity Resource Choice There are 3 resources choices 1. renewable resources 2. Non renewable resources 3. Consumption

35 Human Carrying Capacity Resource Choice Renewable resources Increase carrying capacity resources that come from things that can regenerate Fish, timber, wind

36 Human Carrying Capacity-Resource Choice What factors decrease our carrying capacity? 1.Nonrenewable Resources Resources that are finite Oil, Natural Gas, Coal

37 Human Carrying Capacity-Resource Choice 2. Rate of Consumption

38 Human Carrying Capacity What impact does this stretching our carrying capacity have on other species. Endangers them or completely wipes them out.

39 Human Carrying Capacity What are some consequences of human population growth? Global Warming Caused by the increasing burning of fossil fuels which lead to enhanced greenhouse effect. Pollution Acid Rain Pile up of Waste Ozone Depletion

40 The End!!