1. Populations Chapter 5

2. In Your Notebook Look at the picture on page 128 Identify and Explain three factors that could cause a change in the number of red crabs on Christmas Island.

3. Chapter Mystery Read the chapter mystery on page 129 Hypothesize why the rabbits turned into a plague in Australia.

4. How Populations Grow Hydrilla in Florida Used in home aquariums Farmer threw in canal Taking over native plants Costs $$$$ to control

5. Describing Populations Population – group of organisms of a single species that lives in a given area Studied using – Geographic Range – Density and Distribution – Growth Rate – Age Structure

6. Describing Populations Geographic Range – The area inhabited by a population – Can be large Cod in Western Atlantic ranges from Greenland to North Carolina – Can be small Bacteria on rotting pumpkin

7. Describing Populations Density – The number of individuals per unit area Distribution – page 131

8. Describing Populations Growth Rate – Determines if the size of the population increases, decreases or stays the same – If the number of species in a given area remains basically the same over a large amount of time the growth rate is zero – Hydrilla in Florida has high growth rate – Cod in Atlantic have negative growth rate

9. Describing Populations Age Structure – The number of males and females of each age a population contains – Important because: Must reach a certain age before you can reproduce Only females can reproduce

10. Population Growth Factors that affect population size: – Birthrate # born – Death rate # that die – Immigration rate Moving in – Emigration rate Moving out

11. Exponential Growth What happens when you provide a population with everything it needs? – Food, shelter, protection from predators Will the population increase, decrease or stay the same? – How? Population produces offspring and those offspring produce offspring, etc.

12. Exponential Growth The size of each generation is larger than the one before The larger a population gets, the faster it grows Under ideal conditions with unlimited resources, a population will grow exponentially.

13. Exponential Growth Read “Organisms That Reproduce Rapidly” on Page 133 How are these graphs the same/different?

14. In Your Notebook Read the Analyzing Data Box on Page 135 Calculate the number of rabbits/generation – Generation 1: 1 pair of rabbits = 6 offspring – Generation 2: 3 pair of rabbits = 18 offspring Construct a graph of your data Answer: What type of growth is the rabbit population going through after 5 years?

15. Logistic Growth Natural populations don’t grow exponentially forever What happens?

16. Logistic Growth Occurs when a population’s growth slows and then stops, following a period of exponential growth Reasons: – Birth rate decreases – Death rate increases – Immigration decreases – Emigration increases

17. Logistic Growth Populations eventually reach their carrying capacity – The maximum number of individuals of a particular species that a particular environment can support

18. In Your Notebook One Minute Response – How are exponential growth and logistic growth related?

19. 5.2 Limits To Growth A situation that causes the growth rate 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.

20. In Your Notebook Imagine a small island that has a population of five rabbits. How might each of the following factors affect the rabbit population? a. climate b. food supply c. predation

21. In Your Notebook Now imagine another small island that has a population of 500 rabbits. How would the same factors affect this population? – Climate, food supply, predation Which of the factors depend on population size? Which factors do not depend on population size?

22. Limiting Factors A factor that controls the growth of a population Determines the carrying capacity Some depend on population density, others do not

23. Density-Dependent Limiting Factors Affect populations when number of organisms per unit area reaches certain level Does not affect small, scattered populations Types – Competition – Predation – Herbivory – Parasitism – Disease – Stress from overcrowding

24. Density-Dependent Limiting Factors Competition – Fight for food, water, space, sunlight and other essentials – The more individuals in a given area – the faster the resources are used up – Can also occur among members of different species that attempt to use similar or overlapping resources

25. Density-Dependent Limiting Factors Predation, Herbivory and Human Predators

26. Density-Dependent Limiting Factors Parasitism and Disease – Parasites weaken or kill their host – If host population is large – parasites easily spread – CPV virus killed all but 13 wolves, only 3 were female so moose population skyrocketed. But, dense population of moose allowed winter ticks to run rampant so moose began to die

27. Density-Dependent Limiting Factors Stress from overcrowding – Fighting among themselves weakens ability to resist disease – Can cause females to abandon, kill or eat their own offspring

28. In Your Notebook Mystery Clue – What factors do you think could limit the size of a rabbit population?

29. Density-Independent Limiting Factors Affect all populations, no matter what size – Hurricanes, droughts, floods, wildfires, etc. Sometimes hard to tell difference – When moose population got large a snow storm covered their food source – Might not have had as big of an impact if population had been smaller

30. Controlling Introduced Species Hydrilla population controlled in natural environment – Plant-eating insects and fish might eat it – May be weakened by pests or diseases Those limiting factors aren’t present in US so population grows out of control – Have tried herbicides and mechanical removal – Grass carp introduced to eat it They must be sterile. Why?

31. In Your Notebook Make a T-Chart listing and describing limiting factors Density-Dependent FactorsDensity-Independent Factors