Transcript birth rate - AHS Science Resources

“The first law of ecology is that everything
is related to everything else.”
Barry Commoner
Holt Modern Biology
Chp 19
Quick summary of Populations
 defined as a group of organisms that belong to the same species and live in
a particular place at the same time
 population density measures how crowded a population is
 populations are dispersed in 3 basic patterns:
Scientists who study population dynamics – demographers
4 processes affect population dynamics:
birth rate - # births in a given period
death rate or mortality rate - # deaths in a given period
immigration – movement of individuals into a
emigration – movement of individuals out of a population
GROWTH RATE
=
BIRTH RATE – DEATH RATE
Sum of all
Earth’s
ecosystems
Includes both
biotic and
abiotic factors
in an area
group of individual
organisms of the
same species living
in a particular area
smallest unit
in ecology
All the
interacting
organisms
living within
an area
Key Abiotic Factors:
Emergent layer
Canopy
Understory
Forest floor
Temperature
- Most life lives within a fairly narrow range
of temperatures (~ 0 – 50 C)
- extremophiles are the exception
Severe Disturbances
- Major natural disturbances like fires,
hurricanes, tornadoes, volcanic eruption
effect organisms by its ability to adapt
quickly enough
Sunlight
– provides light and warmth
- the major energy source for almost ALL
ecosystems on Earth
Water
– essential to all life on Earth due to its
remarkable properties such as
 Ability to dissolve gases and solutes
allowing a balance in water loss and uptake
(homeostasis)
Soil
- the product of abiotic forces (ice, rain, wind)
and actions of living organisms (mirobes,
plants, earthworms) on the rocks and
minerals of Earth’s crust
- extremophiles are the exception
Wind
- affect the distribution and activities of
organisms through movement and by nutrient
cycling
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Each organism is adapted to function within
a specific range of environmental conditions
A graph of performance versus
environmental variable – tolerance curve
Ability of an organism to adjust its tolerance
to the abiotic factors in its environment

Control of internal conditions

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
Conformers – change as external conditions
change
Regulators – use energy to control internal
conditions
Escape from unsuitable conditions
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Dormancy (hibernation)
Migration – movement to another favorable
habitat

Each specie plays a role in its community, eat or
be eaten, live or let live
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
Spatial  habitat (where species live and
reproduce)
Ecoregions/biomes

Functional  niche (what its role is
both with abiotic and biotic factors)
 Fundamental: ideal conditions and
resources a specie can potentially use
 Realized: what species can actually use in
nature

Niche Differences
Generalists: species with broad niches
Specialists: species with narrow niches
Multiple niches in a lifetime