Transcript Welcome to Class

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