Ecology Day 2 - Mr. kapa's Digital Biology Classroom · Ecology Day 2: Populations and Human...
Transcript of Ecology Day 2 - Mr. kapa's Digital Biology Classroom · Ecology Day 2: Populations and Human...
Ecology Day 2:
Populations and Human Influence
Populations
• members of the same species that reside
in the same area
Characteristics of populations
a. Geographic
distribution:
Where do they live?
b. Density:
How many are
found in a given unit
of area
c. Growth rate:
How quickly do they
grow? Daisy population
Factors affecting population growth?
1. Birth rate:
number of offspring per time period
2. Death rate:
number of deaths per time period
3. Migration rate
movement in and out of populations in a period of time
• Immigration: in
• Emigration: out
Exponential growth
• Occurs when
individuals in a
population reproduce
at a constant rate
• Only under ideal
conditions
Logistic growth • Occurs when a population’s growth rate slows or
stops, following a period of exponential (geometric)
growth
• Carrying capacity:
largest number
that a given
environment
can support
Click image to play video.
Limiting factors • cause population growth to stop
• Density-dependent factors depend upon
population size:
– Competition
– Predation
– Parasitism
– Disease
Competition • Occurs when 2 species occupies the same
niche & habitat
• What are some things they compete for?
Competition
• Using this 1990
census map of
US population
densities, what
can one deduce
at resource
competition
between the
different parts of
the country? How can competition explain
population size in nonhuman
species?
Predation
• Predator: one that consumes or exploits a particular species for self gain
• Prey: one that is consumed or exploited
• What would you expect to happen to prey populations if the predator numbers increased or if predator numbers decreased?
Figure 5-7 Wolf and Moose Populations
on Isle Royale
60
50
40
30
20
10
0 1955 1960 1965 1970 1975 1980 1985 1990 1995
2000
1600
1200
800
400
0
2400
Moose Wolves
Describe the relationship between the wolf and
moose populations shown in the graph.
Predator-Prey relationships
Parasitism and Disease
• Both deplete the
host organism of
vital minerals and
nutrients to sustain
life.
• Death of the
organism results in
the decline of
population size. Heart worms (roundworms) as
exposed by a veterinarian
Density-independent factors
• Limiting factors on
population size,
regardless of the
number of individuals
in the population
– Weather
– Natural disaster
– Seasonal cycles
– Human activities (habitat
destruction) Corals that have died from weather
changes, leading to increased
water temperature and pollution.
Historical Human Population Growth
Agriculture begins
Plowing and irrigation
Bubonic plague
Industrial Revolution begins
It took 500,000 years to reach 1 billion
& less than 200 years to reach 5 billion.
What might be some reasons why?
What’s the carrying capacity for the human
population?
What if it’s right here? ---------------------------
But, what if it’s right here? ---------------------------
(We do know it lowers when pollution occurs)
Age structure diagrams (population profiles):
graphs showing numbers of people in
different age groups in the population
U.S. Population Rwandan Population Males Males Females Females
What conclusions can be drawn from these graphs?
Why do the population growth curves
look different between developing and
developed countries?
Demography
• Study of human population size, density
and distribution, movement, and its birth
and death rates
• Birth rate is the number of live births
per 1000 population in a given year.
• Death rate is the number of deaths per
1000 population in a given year.
Calculating how fast populations
grow
• Birthrate – Death rate = Population Growth
Rate (PGR)
• If PGR > 0, then the population is growing.
• If PGR < 0, then the population is
declining.
Human activities that affect the
biosphere
• Hunting& Gathering
• Agriculture
• Industry
• Urban development
Types of resources
Nonrenewable resources:
• unable to be replenished through natural means
– Ex: fossil fuels, natural gas
Renewable resources:
• able to be replenished but is not unlimited
– Ex: freshwater
Sustainable development
• A way to use natural
resources without
causing long term
environmental
problems
• This plan takes into
consideration
environmental,
economic, and
community demands
Problems land resources face
Desertification
• the process of overusing land
and drought leading to the
formation of arid, desert lands
that cannot sustain agriculture
Soil erosion
• loss of topsoil layer from over farming
(plowing) lands
Deforestation • The process of cutting down (logging) forests for lumber and land.
• Leads to severe erosion during heavy rains.
• Which can lead to permanent changes to local soils and microclimates.
Overfishing
• Harvesting fish faster than they can be
replaced by reproduction.
• What happens to aquatic food webs if
overfishing continues to occur?
Aquaculture • raising water animals
for human use
• Pictured to the right
are tilapia fish farms
in Australia that then
export the fish to
markets.
• “Farm raised”
Air pollution
• Combustion of carbon
fuels released nitrogen
and sulfur that
combine with water to
form acid rain.
• Pollutant:
• any harmful substance
that enters the
biosphere from land,
air, or water
Acid rain
Why should we preserve
biodiversity? Biodiversity:
• sum total of
genetically based
variety of all
organisms in the
biosphere
–Ecosystem diversity
–Species
diversity
Why should we preserve
biodiversity?
• Biodiversity is one of Earth’s greatest
natural resources.
• Species of many kinds have provided us
with foods, industrial products, and
medicines – including painkillers,
antibiotics, heart drugs, antidepressants
and anticancer drugs.
Threats to species biodiversity
• Human activity can reduce
biodiversity by altering habitats,
hunting species to extinction,
introducing toxic compounds into food
webs, and introducing foreign species
to new environments.
Threats to species biodiversity
• Endangered:
species that is
declining in
population size
• Extinction:
species that
disappears from
all or part of its
range Endangered status:
Ailuropoda melanoleuca
Dodo Bird
• The dodo has been
extinct since the mid-
to-late 17th century.
• Its extinction occurred
during recorded human
history and was directly
attributable to human
activity
Habitat fragmentation
• When land is developed through or around
ecosystems, the species residing within
are impacted in what way?
Central Park in New
York City is a perfect
example of habitat
fragmentation.
DDT
• First synthesized in 1874, DDT's insecticidal
properties were not discovered until 1939, and it
was used with great success in the second half
of World War II to control malaria and typhus
among civilians and troops.
• After the war, DDT was used as an agricultural
insecticide, and soon its production and use
skyrocketed
• DDT was banned in most countries in 1972
Biomagnification:
• Increasing the concentration of harmful
materials up the food chain
Introduced species • Humans transport animal and plant species from
one part of the world to another.
• Many of these species can become invasive (non-native to a specific location; an introduced species); and has a tendency to spread).
Nutrias are native
to South America
but have become
pests in coastal US
cities.
Water Hyacinth
Hydrilla
Kudzu
Fire Ants
Conserving Biodiversity
• To conserve biodiversity and multi faceted
approach is best:
• Protection of species
• Protection of habitat
• Protection of biodiversity
Conserving Biodiversity Challenges
• Balancing :
• Public need and economics
• Public policy
• Conservation
Charting a Course for the Future
• Researchers are gathering data to monitor and evaluate the effects of human activities on important systems in the biosphere.
• Issues:
• Ozone depletion
• CO2 emissions
• Global warming
• Alternative fuels
• Alternative food sources
Ozone depletion
• Ozone: layer of
concentrated gas that
protects the Earth
from harmful UV rays
• O3
• 1970s, scientists
found a gap in the
ozone layer near
Antarctica.
NASA image
Global warming
• Compounding the
ozone depletion was
the buildup of CFCs
(chlorofluorocarbons)
from aerosols and
AC units with Freon.
• CFCs trap heat,
leading to a rise in the
global temperature.