Studying Populations 5d using a visual model to track population changes in an ecosystem.

Vocabulary 1.Population Density-The number of individuals in a specific area. 2.Estimate-An approximation of a number based on reasonable assumptions. 3.Birth Rate-The number of births in a population in a certain amount of time. 4.Death Rate-The number of deaths in a population in a certain amount of time. 5.Immigration-Moving into a population. 6.Emigration-Leaving a population. 7.Limiting Factor-An environmental factor that prevents a population from increasing. 8.Carrying Capacity-The largest population that an area can support.

Population Density Population Density = Number of individuals/Unit Area Example: 50 monarch butterflies in a garden 10 square meters. What is the population density? 5 butterflies per square meter

Determining Population Size Direct Observation Indirect Observation Sampling Mark and Recapture Studies

Direct Observation Count members of population one by one. Can be difficult….

Or not so much….

Indirect Observation The members may be too small or difficult to find. To estimate the number of birds, one might count nests and multiply by the average number of birds per nest.

Sampling Counting the number of organisms in a small area and then multiplying to find the number in the larger area.

A problem If 8 maple trees occupies a 100 square meters in a forest, how many could be expected to occupy 10,000 square meters? 800 (if the population density were the same.)

Mark and Recapture Studies 1.Capture a random sample of a population. 2.Mark all and release them. 3.After a period of time capture from the same population. 4.The ones that have marks of those recaptured indicate the percentage that were marked in the beginning.

Changes in Population Size Populations can change in size when new members enter the population or when members leave the population.

Births and Deaths Birth Rate Example: 1000 snow geese produce 1,400 goslings in a year. The birth rate is 1,400 goslings per year. Death Rate Example: 1000 Geese die in a year. The death rate would be 1000 geese per year.

Population Equation If birth rate > death rate, population increases. If death rate > birth rate, population decreases.

Immigration and Emigration The size of the population can increase or decrease when members move into or leave a population. Example: If some antelope wander off in search of food and permanently become cut off from the herd.

Limiting Factors 1.Food 2.Space 3.Weather Conditions

Food Example: A giraffe eats 10 kg a day. The trees in the area can provide 100 kg a day. What is the carrying capacity the area can support? The carrying capacity is 10 giraffes.

Space Often space is a limiting factor for plants. The amount of space a plant has often determines how much water and sunlight it gets.

Weather Temperature and rainfall can limit population growth. Insects can die with early frost as can tomatoes. Floods can wash away nests and burrows.