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Welcome to Class What does it mean if we have a lot of biodiversity? Agenda • Finish pond study wrap-up • Run-off/pollution readings Welcome to Class What are some water pollutants that come from our homes? Agenda • Populations – Random sampling lab Recall… • Populations – members of a single species that live in once place at a single time Population Characteristics • Population Density – # of organisms per area • Dispersion – pattern of spacing of a population within an area – Based on available resources (food) – 3 typed • Uniform • Clumped • Random Dispersion • Smaller animals usually clump – Larger animals usually independent – Fish Q: What advantage do smaller fish (animals) gain by forming schools (clumped groups)? Safety, confuses predators Q: Which type of population distribution allows you to predict more accurately how many individuals reside in a given area? Welcome to Class What are some things that can limit where a population can live? Agenda • Mark and Recapture lab • Population Notes Agenda • Population Notes Welcome to Class Describe what is happening to the population in the graph below. Population Ranges Limiting Factors • Abiotic conditions – Temperature – Humidity – Rainfall – Sunlight • Biotic conditions – Predators – Competitors – parasites Density independent factors Def. – any factor in an environment that does not depend on the number of members in a population in an area • Abiotic – Weather – drought, flooding, extreme heat/cold, tornados, hurricanes Density Dependent Factors Def. – any factor in the environment that depends on the number of members in a population in an area • Biotic factors – Predation, disease, parasites, competition Predation • More members of a population = more predators Disease/Parasites • Outbreaks of disease tend to occur when population size has increased – Disease in transmitted faster – True for humans as well as animals • Parasites increase at higher densities Competition • When resources become limited animals compete – Within a population or between 2 different species – Lead to starvation – population can decrease Population Growth Rate How to figure out population growth rate • Must know birthrate and mortality • Emigration – moving out of a pop. • Immigration – moving into a pop. – Immigration rate = emigration rate • Calculating growth rate =(population at end – population at beginning) Population at beginning Different Growth Rates Exponential Growth Rate • Starts slow – few organisms • Faster because all organisms are reproducing • Rarely happens – WHY? – Limiting factors – food, space Logistical Growth Rate • Logistic growth occurs when a population’s growth slows or stops following exponential growth – Carrying capacity Carrying Capacity • Maximum number of individuals in a species that an environment can support for the long term – Limited by energy, water, oxygen, nutrients available • Population grows until carrying capacity – Births outnumber deaths – Exceed carrying capacity then deaths outnumber births Reproductive strategies R-strategy (rate strategists) • Produce as many offspring as possible in a short time – Little energy in raising young K-strategists (carrying capacity strategy) • Few offspring that have a better chance of living – Expend a lot of energy raising young Welcome to Class Describe two different strategies of reproduction. Agenda • Quiz • Human Population Growth Human Population Growth Trends in Human Population Growth • Was slow and stable • Recent increase in growth – Technology – agriculture, medicine, shelters • Developing countries add more than developed countries More trends • Zero population growth – birth rate + immigration rate = death rate + emigration rate • Age structure – # of males and females in three age groups • Pre-reproductive (0-19), reproductive (20-44), and post –reproductive (45-80+) Human Carrying Capacity • Humans have a carrying capacity • Technology allows an increase in carrying capacity • Concerns about reaching/exceeding carrying capacity – resources being used