Welcome to Class

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Transcript Welcome to Class

What kind of plants do we see in a
climax community?
Agenda for Thursday Oct 13th
1. Root word quiz
2. Go over HW
3. Communities notes
4. Review stuff
Quiz Tuesday! – cycles, biomes, succession,
• Def. – interacting populations in an area at the
same time
• Different organisms occupy different biomes
– Different adaptations
– Different communities around the world
• Limiting factors – any biotic or abiotic factor that
limits the number, reproduction, or distribution
of an organism
– Sunlight, food, temperature, acidity of soil
• Tolerance – ability of an organism to survive
when subjected to abiotic or biotic factors
– Upper and lower limit = range
What is a population?
Agenda for Monday Oct 17th
1. Population notes
2. Go over HW
Quiz tomorrow
Final root word quiz next Thursday
Ecology test Next Friday
• Populations – members of a single species that
live in once place at a single time
• Why study populations?
– Learn how organisms change over time, how many
individuals are born, how many die, and relationships
between organisms
Population Ranges
• Species might not expand due to abiotic or
biotic conditions
• Abiotic conditions
• Biotic conditions
Population Characteristics
• Population Density – # of organisms per area
• Dispersion – pattern of spacing of populations
– Based on available resources (food, sunlight),
predators, etc
– 3 types
• Uniform
• Clumped
• Random
Which one provides most protection?
Dispersion Pattern: Uniform
Dispersion Pattern: Clumped
Dispersion Pattern: Random
Population Growth Rate
How do we 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
Exponential Growth Rate
• Occurs when organisms have
ideal conditions
• More individuals = faster
• Rarely happens
– WHY?
– Limiting factors – food, space
Logistical Growth Rate
• Populations go through a
number of growth phases
– Lag Phase – slow growth, low
– Exponential growth – rapid
growth, few dying, many
– Population growth slows
– Steady state – population
levels, birth rate = death rate,
population stays the same
Carrying Capacity
• Logistical growth rate curve
• Maximum number of individuals that an
environment can support for the long term
– Limited by energy, water, oxygen, nutrients available
– Draw a line through steady state it will give you
carrying capacity
Density independent factors
Def. – any factor that does not depend on the
number of organisms in a population
• Abiotic
– Weather –flooding, temp., tornados, hurricanes
– Water
– Fire
– Sunlight
– Human alterations of landscape – dams, pollution
Density Dependent Factors
Def. – any factor that depends on the number of
• Biotic factors
– Predation, disease, parasites, competition, over
• More members of a population = more predators
• Outbreaks of disease tend to occur when
population size has increased
– Disease is transmitted faster
– True for humans as well as animals
• Parasites increase at higher densities
• When resources become limited animals
– Within a population or between 2 different species
– Lead to starvation – population can decrease
Reproductive strategies
R-strategy (rate strategists)
• Produce as many offspring as possible in a short
– 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
Agenda for Monday Oct 24th
1. Go over quiz
2. Sampling techniques
1. Labs
You are given the task to determine the number
of sunfish in Horseshoe Lake. Discuss with
your lab partner how would you accomplish
this task.
• A technique called sampling is sometimes used to
estimate population size.
• Organisms in a few small areas are counted and
projected to the entire area.
• Example: A biologist counts 10 squirrels living in a
200 square foot area, she could predict that there
are 100 squirrels living in a 2000 square foot area.
1. A biologist collected 1 gallon of pond water
and counted 50 paramecium. Based on the
sampling technique, how many paramecium
could be found in the pond if the pond were
1,000 gallons?
2. What are some problems with this
technique? What could affect its accuracy?
Mark and Recapture
• Capture animals alive and mark them
– Animals are returned unharmed to environment
• Animals with and without mark are caught
– formula is used to estimate population size
Population estimate = (total number captured) x (original # with mark)
(Total number captured with mark)
Mark and Recapture Concerns
Capturing could injure the animal or scientist
Disturb animal's normal behavior pattern
The marks may cause injury to the animals or get lost
Marked animals may be more/less attractive to predators
• Assumes all animals require the same effort to get caught
– might catch the weaker or younger animals more
• Some animals learn to fear the traps and avoid recapture
– or become trap-happy and attempt to get caught because
there is food
Formula for Mark and Recapture
• Ecologists marked 20 bears in an area. Over 5
years they captured 100 bears. Of those 100
captured 50 had a tag. What is the population
of the bears?
Population estimate = (total number captured) x (original # with mark)
(Total number captured with mark)
Determine how many oak trees are
in the forest using the random
sampling technique. Use the grid.
Agenda for Tuesday Oct 24th
1. Human Populations
Human Population Growth
Trends in Human Population
• 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
• Concerns about reaching/exceeding carrying
– resources being used
Describe what is happening to the
population in the graph below.
Agenda for Wednesday Jan 26th
1. Finish Notes
2. Human pop. graph