Populations Biology 2015-2016

http://www.worldometers.inf o/world-population/ Populations Objective: to understand the way that populations of different organisms grow and shrink, and what factors cause these changes in a population http://www.worldometers.inf o/world-population/

I. Describing a population Geographic Distribution: the area inhabited by a population Map shows the Geographic Distribution of the California Quail 1994-2003

2. Population density: number of individuals per unit area

few individuals in a unit area: example: trees High density: Population Density: b. Low density: few individuals in a unit area: example: trees High density: lots of individuals in one area: example grass

3. Growth rate: how quickly a population changes in size Example: Some bacteria can double their population in minutes!  45 Minutes

3. Growth rate: how quickly a population changes in size Example 2: Trees can not double their population in 45 minutes. Its takes years and years for a population of trees to double in size.  45 years

II. Factors affecting population growth Birth rate Death rate

Birth = Death  Stays the same 100 Born 100 Die

b. Birth > Death  Increases 150 Born 50 Die

Birth < Death  Decreases 50 Born 150 Die

3. Immigration: movement of individuals into an area Example: The Bison immigrates to a meadow full of grass because it provides a good source of food.

4. Emigration: movement of individuals out of an area Example: The Bison Emigrates away from a meadow without grass because it does not provide a good source of food.

5. You must emigrate from somewhere in order to immigrate to somewhere.  Emigrate from.. Immigrate to..

Exponential Growth: individuals reproduce at a constant rate III. Types of Growth Exponential Growth: individuals reproduce at a constant rate Conditions necessary for exponential growth Example: Shape of graph Graph 1. Unlimited Resources 2. Absence of disease and parasites Bacteria J

Exponential Graph

2. Logistic Growth: Population grows rapidly until some factor limits growth When does population growth slow or stop? Birthrate: 3. Death rate: Immigration: 4. Emigration: b. Example: c. Shape of Graph d. Graph Down Up Down Up Most animal populations in nature S

Logistic Graph

e. Carrying capacity: Maximum # of individuals that an area can support

IV. Limits to Growth Limiting Factor: Condition that controls population size ex: food, land Animals in a population may not have enough food to go around

IV. Limits to Growth example: Effect on evolution: 2. Competition: Two or more species attempt to use same resource example: Effect on evolution: Bird and squirrel both eat berry

b. Effect on evolution: both species under pressure to change in ways that decrease their competition Squirrel eat nuts Bird eat worm

3. Predation: one organism eats another a. example: Mouse and Snake b. predator: Hunter c. prey: Hunted

3. Predation: one organism eats another d. Effect on evolution: prey species evolve defenses against predators, predators evolve counter defenses Snake: forked tongue and heat vision Mouse: Camouflage

4. Parasitism: organisms live and feed inside/on a host organism examples: Fleas, ticks, leaches, tape worm

5. Random events: Unusual weather, human activities, natural disasters.