Studying Populations 5 d using a visual model

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

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