# Your “Do Now” 5/14 Fill out a pre-test from up front Try your best and pay attention! – This is the material we’ll be learning this week.

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Your “Do Now” 5/14 Fill out a pre-test from up front Try your best and pay attention! – This is the material we’ll be learning this week

Agenda5/13 Quizzes back – Retakes Wednesday Notes #3 on Populations Practice

Learning Target #35/13 3) I can explain how multiple factors affect population sizes

Population: all the members one species that live in the same place at the same time

Limiting factor: anything that can slow/limit the growth of a population Carrying capacity: the maximum population of a species that a habitat can support

The carrying capacity depends on the limiting factors so it can change Example: a habitat supports 10 mice while food is a limiting factor. Add more food and carrying capacity goes up

Types of limiting factors BioticAbiotic Food supply Competition # of mates Predators Space Climate Oxygen Water Light

Summarizing how biotic and abiotic factors can affect a population A change in one or both of these factors can affect a population

CFU Popcorn questions: – Look at your notes – Pick a person and ask them a question from the notes – If you get picked, pick the next person

Population density: the number of individuals in a certain area Less dense More dense

The resources available to support a population of organisms is mostly finite (there is a limited amount of them) As the number of individuals in a space increases, resources are limiting and the organisms compete

Density-independent: Factors that could affect any population, no matter how many individuals are in the area Example: Weather. A tornado could kill individuals in any population, no matter what size/density

Density-dependent: factors that affect populations differently depending on how many individuals are in the area

Example: Predator-Prey Relationships Predator and prey population sizes are often closely related

1.If there are too many prey in one area, the predators will reproduce more and eat more prey, making prey population go down 2. If there are too few prey in one area, the predators will starve, allowing the prey to reproduce and go up.

Factors that can increase the size of a population Birthrate: number of individuals produced in a population over time Immigration: new organisms moving into a population

Factors that can decrease the size of a population Mortality (death rate): number of individuals that die in a population that over a certain period of time Emigration: organisms leaving a population

Population Growth Rate of change: how fast/slow a population is changing at one point in time Zero population growth: time when a population’s size stays constant Note: This only happens when # births = # deaths

Phases of Population Growth 1.Lag phase: time when a population grows very slowly (small size) 2.Exponential phase: time when a population grows exponentially (very quickly) 3.Stabilization phase: time when a population grows slowly (close to carrying capacity)

J Curve Exponential growth Population does not reach carrying capacity

S Curve Population has all 3 phases Has reached carrying capacity

Measuring the size of a population Mark re-capture method (common with mammals): Catch some animals, mark/tag them, then catch more and see what percentage are marked

Quadrant sampling (common with large plants): Use a grid to count the number of plants in a certain area, then use that to predict how many are in a bigger area

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