chapter 4. characteristics of populations geographic distribution density growth rate age...
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Chapter 4
Characteristics of Populations
Geographic distribution
Density
Growth Rate
Age structure
Population Density
Number of organisms you have in a certain area
Population Density
Compare population density of: Trees Shrubs Grasses
Different species in an ecosystem have different densities
Population Dispersal Populations are not equally dispersed
Population growth
Population sizes can change
Three factors effect population size: Births Deaths Individuals that enter or leave
Healthy populations increase and decrease at the same rate
Population trends
No matter the organism, we all follow the same population trend
Population Growth
Compare & contrast the following graphs:
Population Growth Linear Growth
Always increasing at the same rate (constant slope)
Exponential Growth Rate always
increasing (increasing slope)
Which one accurately represents population growth?
Exponential Population Growth Under ideal
conditions, a population would grow exponentially
Unlimited resources
No competition
Can a population increase forever? No- it eventually flattens out
What happened? As resources
become less available, growth of a population slows or stops
It has been limited by some factor
Carrying Capacity
Reached when the population starts to level off (birth = death)
All that an environment can support
Limiting Factors
Population Size
Competition
Natural Disasters
Disease
Predators
Human Involveme
nt
Which ones…?
Population Size
Competition
Natural Disasters
Disease
Predators
Human Involveme
nt
Limiting Factors
DENSITY DEPENDENT Depends on population size Usually biotic
Competition Predation Parasitism Disease
Limiting Factors
DENSITY INDEPENDENT (usually abiotic) Affect all populations in similar ways,
regardless of population size
Unusual weather Natural disasters Seasonal cycles Human involvement
Limiting Factors
Limiting factors are responsible for bringing an ecosystem to its carrying capacity
Why isn’t this a straight line?
Carrying Capacity
What would happen if a population exceeded it’s carrying capacity?
What would this look like on a graph?
Need to examine a population’s LIFE-HISTORY PATTERN
Life History Patterns
Depends on the organism
Bacteria reproduce fast E. coli takes 12 minutes!
Elephants reproduce slowly Almost 2 years! (22 months)
Life History Patterns
RAPID LIFE HISTORY SLOW LIFE HISTORY Small bodies
Short life spans
Many offspring in short time
Can handle readily changing environments
Large bodies
Long life spans
Reproduce less frequently
Live in more stable environment
Life History Patterns
RAPID LIFE HISTORY SLOW LIFE HISTORY
Chapter 5
Section 5.1
Biological Diversity
Consider a Rainforest
What will we find? A single rainforest reserve
in Peru is home to more species of birds than the entire United States
One single tree in Peru was found to harbor forty-three different species of ants - a total that approximates the entire ant species in the British Isles
One hectare has 400 species of plants.
Biological Diversity
BIODIVERSITY Measure of the
variety of species in a specific area
How can you tell when one area is more diverse than another?
Biodiversity
Which has more biodiversity?
A field with 300 corn plants?
A forest with 6 pine trees and 7 oak trees?
One of these has a higher SPECIES RICHNESS Number of species
BIODIVERISTY INDEX Calculates level of diversity in an areaBiodiversity Index =
total of each individual species total number of individuals in the areaΣ
2
Biodiversity Index The closer the B.I. to 1, the more
diverse
Where is biodiversity found?
E
V
E
R
Y
W
H
E
R
E BUT…
…Which location has more?
Biodiversity in nature
Biodiversity in nature
Living things are interdependent
Populations are adapted to live together in communities
Losing one species may result in the loss of another, and another, etc…
Compare the following
A potato field with one species of potato is attacked by pests.
Rainforest with many different species of plants is attacked by pests.
Which one will the pests affect more? Why?
Which will survive?
• Potato field– All the same species– All planted next to
each other– All the potatoes are
destroyed
• Rainforest– All different species– All randomly
dispersed – Only one species
destroyed
Biodiversity Brings Stability
The rainforest will more easily cope with the loss of one species
A diverse ecosystem remains stable
Importance to Humans
Did you get it?
How would the over-hunting of white-tail deer affect the community in
which it lives?
Did you get it?
Which of the following would be the ideal distribution of a population of
trees to prevent it from being destroyed by pests?
Did you get it?
Would it help or hinder the trees if they were separated by different species of
plants?
Loss of Biodiversity
What are some reasons we are losing biodiversity?
Loss of Biodiversity
It is natural for certain species to become extinct over time
It is not natural to lose one species every 20 minutes!
Human activities have increased the rate of species loss
Loss of Biodiversity
THREATENED-->(Close to becoming endangered)
ENDANGERED-->(Close to becoming extinct)
EXTINCT(Species has
disappeared)
Reasons for the Loss of Biodiversity
HABITAT LOSS
Clearing for farmland
Demolition to build houses
Increased water temps damage coral reefs
Reasons for the Loss of Biodiversity
HABITAT FRAGMENTATION
Separation of wilderness areas from other wilderness areas
Habitat Fragmentation Leads to:
Loss of species due to relocation
Increased extinction of local species
New opportunities for invasions by introduced or exotic species
Reasons for the Loss of Biodiversity
EDGE EFFECT- differing conditions along the boundaries of 2 ecosystems
Forest meets field; water meets land; road cuts through wooded area
Edge Effect Edges tend to have
more biodiversity Different habitats
with different species meet
When a new edge is made, some animals habitats may be exposed
Why might this be a problem?
Reasons for Loss of Biodiversity HABITAT
DEGREDATION- Damage to a
habitat by pollution
Habitat Degradation
ACID PRECIPITATION (RAIN) Factories release
sulfur dioxide and nitrogen oxides and they combine with water (become acidic)
Why might this be a problem?
Habitat Degradation
Water pollution Excess fertilizers
wash into water Increased
nutrients cause an algal bloom
Why might this be a problem?
Habitat Degradation
OZONE DEPLETION Ozone layer protects
us from ultraviolet rays
Holes in the ozone layer allow move UV to come through
Why might this be problem?
Habitat Degradation
Land Pollution Excess garbage Use of pesticides
A pesticides effects are magnified as it moves up a food chain
BIOLOGICAL MAGIFICATION
Your Footprint
What mark do your actions leave on our environment? Let’s find out!
http://www.myfootprint.org
Conservation of Biodiversity
Section 5.2
Today’s Goals
Describe the ways in which we keep plants, animals and their
environments safe and healthy
What is CONSERVATION BIOLOGY?
Why is it important?
Conservation Biology
CONSERVATION BIOLOGY study and
carrying out of ways to protect biodiversity
Conservation Biology
NATURAL RESOURCES Parts of the
environment needed by living organisms
Sun, water, air, etc
Conservation Biology
Not an easy task Sometimes a
complete reverse of major changes to an environment
Restoring a strip mine to a grassland
We work harder not to prevent loss rather than reverse it
Protecting Species and Habitats In the US, we have passed laws to
protect endangered and threatened species
Endangered Species Act of 1973
Protecting Species and Habitats Habitats must be preserved as well
Created national parks or reserves
Yellowstone National Park Crater Lake National Park
Conservation Biology
Remember HABITAT FRAGMENTATION?
How could we fix the problem?
HABITAT CORRIDORS Strips of land
connecting two fragmented areas
Allows organisms to move between
Conservation Biology
SUSTAINABLE USE Using the natural
resources in ways that benefit them yet still maintain the ecosystem
Conservation Biology
REINTRODUCTION PROGRAMS Take members of an
endangered species and breed and raise them in protected habitats
Black footed ferret
Conservation Biology
CAPTIVITY Organisms kept by
humans
Kept in captivity to increase numbers
Eventually returned to the wild