POPULATION ECOLOGY Greta-the-Dog says: Fill out Anticipation Guide for your IN. THIS IS #9!!! WHAT IS A POPULATION? Look back at the Ecological Levels of Organization What is a population? A group of two or more organisms within the SAME SPECIES WE are a population of humans! WHAT IS POPULATION ECOLOGY? The field of biology that describes how groups of organisms (populations) grow over time. Much of population ecology is concerned with the trends different populations follow as they grow. WHAT IS POPULATION SIZE? The health of a population can often be monitored by tracking how the size changes. What would happen to the size of a population with good health? Poor health? Population size describes the number of individual organisms present in a given population at any given time. What is the population size of our classroom today? The population size changes each day! HOW DO SCIENTISTS DETERMINE POPULATION SIZE? Usually, populations are numerous and spread out! Sampling is necessary in these instances. Instead of counting every individual in a large area, ecologists count the number in a smaller sample area. For example: (# of students per table) X (# of tables in room)= estimated population size. WHAT IS POPULATION DENSITY? A populations density is a measure of how crowded it is. Its the number of individuals within a population per unit area. Example: students at a table High population densities can be good and bad. Good: protection, mates Bad: competition, disease MEASURING POPULATION DENSITY IN REAL-LIFE Counting trees all day is the best job! Ecologists use quadrats to take samples of population size and density! WHAT IS POPULATION DISTRIBUTION? It describes how organisms are arranged within an area. There are three distribution types: Random Distribution (No pattern; resources are plentiful) Uniform Distribution (Evenly spaced; rare; resources are scarce) Clumped Distribution (Around resources; most common) HOW IS THIS POPULATION DISTRIBUTED? CLUMPED HOW IS THIS POPULATION DISTRIBUTED? UNIFORM HOW IS THIS POPULATION DISTRIBUTED? RANDOM HOW IS THIS POPULATION DISTRIBUTED? UNIFORM AGE STRUCTURE AND SEX RATIOS Age structure describes the relative number of organisms of each age within a population. Helps to predict population growth. A sex ratio is the proportion of males to females in a population. What is the most ideal ratio? Why? AGE STRUCTURE: COPY DOWN, YO! POPULATION GROWTH Population growth is affected births, deaths, immigration, and emigration. IMMIGRATION AND EMIGRATION I mmigration : I NTO (arrival of individuals) E migration: E XITING (departure of individuals) Immigration and births ADD to population size Emigration and deaths REDUCE a population size Take out human population sheets! THERE ARE TWO MAIN TYPES OF POPULATION GROWTH: Exponential and Logistic! EXPONENTIAL GROWTH This is when a population increases by a fixed percentage each year. Will only occur in nature if population is small and environmental conditions are ideal. J-shaped curve Example: humans in the Industrial Revolution HUMAN POPULATION: EXPONENTIAL AT FIRST LOGISTIC GROWTH Exponential growth cannot continue forever. Most populations are evenly constrained by limiting factors. S-shaped curve Limiting factors determine a populations carrying capacity (K). Carrying capacity (K) is the largest population size a given environment can support. Example: students at a table LOGISTIC GROWTH: MEETING CARRYING CAPACITY (K)