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POPULATIONS
Kraj
What is a Population?
• All the members of a species living in the
same place at the same time.
• Examples: Palm trees on an island, a school of
specific fish, daisies in a field in Ohio.
Properties of Populations
• Population Density-the number of individuals
per unit area or volume
• Example: the number of small mouth bass per
cubic meter of water in a lake.
Properties of Populations
• Dispersion- the relative distribution or
arrangement of its individuals within a given
amount of space.
• Descriptions of dispersion•
Even
Random
Clumped
POPULATION DISPERSION
How Does a Population Grow?
• Growth Rate-the birth rate minus the death
rate of a population.
• Change in population size = Births - Deaths
How Fast Can a Population Grow?
• Biotic Potential:
• The fastest rate at which its potential
population can grow.
How Fast Can A Population Grow?
• Reproductive Potential:
• The maximum number of offspring that each
member of the population can produce.
Reproductive Potential
• If perfect conditions, it would take a pair of
elephants 750 years to produce 19 million
descendents.
Reproductive Potential-Exponential
• A bacteria cell could produce 19 million new
cells in a few days or weeks.
BACTERIA REPRODUCTIONGROWTH
LIMITS TO POPULATION
GROWTH
• Carrying Potential is the maximum population
that the ecosystem can support indefinitely.
RESOURCE LIMITS
• All organisms require resources to grow and
increase in population.
• Natural resources (water, food, shelter, etc.)
are limited.
• This helps determine the carrying capacity of
an ecosystem.
• Competitions within a population.
• Members of a species use the same resources.
RESOURCE LIMITS
• Each must compete with each other for those
resources.
• Some species have territories-areas that are
defended by one or more individuals against
others.
• Example: Leopards have a large area of land
they hunt. They will attack any other leopards
that hunt in that area.
• Honey Bees
TWO TYPES OF POPULATION
REGULATION
• DENSITY DEPENDENT REGULATION
• Deaths occur more quickly in a crowded
population than in a sparse population.
• Reasons for deaths1. Competition
2. Predation
3. Disease
TWO TYPES OF POPULATION
REGULATION
• Density Independent Regulation
• When certain portions of the population die
regardless of how dense the population is.
• Reasons for deaths:
1. Weather
2. Natural disasters
3. Human actions (deforestation, damming a river,
hunting, etc.)
HOW SPECIES INTERACT
• An Organism’s Niche
• Niche: the unique role of a
species in an ecosystem
• It includes the species’:
• Physical home
• Environmental factors needed for survival.
• All interactions with other organisms.
• Its functional role.
• An organism’s pattern of use of its habitat.
Example of a Niche
• KANGAROOS
• Kangaroos occupy Australia’s niche of large
grazing (feeding on grasses) herbivores
5 Major Ways Species Interact
• Competition
• Adaptation to competition
• Predation
• Symbiosis
• Coevolution
COMPETITION
• Different individuals or populations attempt to
use the same limited resources.
ADAPTATIONS TO COMPETITIONS
• Species have adapted to competition in their
ecosystems when niches overlap.
• Populations are lower
• If one species is removed, the one that
remains expands to fill the niche.
PREDATION
• Predator- an organism that feeds on another
organism
• Prey- an organism that is fed upon
• Some predators feed only on one species and
its population adjusts to that prey population.
• Others have adapted to eating many different
species, allows for a more stable population
due to varied resources.
SYMBIOSIS
• A close, long term association between 2 or
more species.
• There are 3 types:
1. Parasitism-organism feeds on a host organism.
They rarely kill their host-mosquitoes, lice, ticks.
2. Mutualism-All participating species benefit.
Lichens are examples-photosynthesis, nutrients
e.coli-in humans-bacteria helps digest, bacteria
secretes vitamin K
3. Commensalism-One species benefits and the
other is unaffected. Whales and barnacles
EXAMPLES OF SYMBIOSIS
COEVOLUTION
• Two or more species evolve in response to each other.
• Examples:
• Bees and Flowers1. Pollen in flowers are sticky
2. Attaches to bees and the bee travels to another flower
fertilizing it.
3. Bees can’t see red and most flowers that bees use for
pollination are blue and/or yellow.
*Madagascar Orchid and Hawk Moth