Download Ecology

Ecology:
Ecological Succession and
Population Density
Population
Characteristics
1. Population Density:
•
The number of organisms
per unit area
2. Spatial Distribution:
•
•
Dispersion: The pattern of
spacing a population within
an area
3 main types of dispersion
•
•
•
•
Clumped
Uniform
Random
The primary cause of
dispersion is resource
availability
Communities
• Review:
• A community is a group of interacting
populations that occupy the same area at the
same time.
Communities
• Limiting Factors
• Any abiotic or biotic factor that restricts the
numbers, reproduction, or distribution of
organisms.
Ecological Succession
• Ecological Succession
• The change in an ecosystem that happens
when one community replaces another as a
result of changing biotic and abiotic factors
Ecological Succession
• Ecological Succession
• Consists of 2 types:
• Primary Succession
• Secondary Succession
Ecological Succession
• Ecological Succession: Primary
• The establishment of a community in an area
of exposed rock that does not have topsoil is
called Primary Succession.
• It occurs very slowly at first
Ecological Succession
• Ecological Succession: Primary
• The first organisms to arrive are usually lichens
or mosses, which are called pioneer species.
• They secrete acids that can break down rock
• Their dead, decaying organic materials,
along with bits of sediment from the rock
make up soil.
Community Ecology: Ecological Succession: Primary Succession
Ecological Succession
• Ecological Succession: Primary
• Small weedy plants and other organisms
become established.
• As these organisms die, NEW SOIL is created
Ecological Succession
• Ecological Succession: Primary
• Seeds brought in by animals, water and wind
begin to grow in the soil.
• Eventually enough soil is present for shrubs
and trees to grow.
Ecological Succession
• Ecological Succession: Primary
• The stable, mature community that eventually
develops from bare rock
is called a
climax community.
Ecological Succession
• Ecological Succession: Secondary
• Disturbances (fire, flood, windstorms) can
disrupt a community.
• After a disturbance,
new species of plants
and animals might
occupy the habitat.
Ecological Succession
• Ecological Succession: Secondary
• Pioneer species in secondary
succession are usually plants that
begin to grow in the disturbed
area.
• This is much faster
than primary
succession
Ecological Succession
• Ecological Succession: End point?
• Cannot be predicted
• Different rates of growth &
human involvement
make it impossible to
know if a true climax
community has been
reached.
Population Limiting Factors
3. Population growth rate
• How fast a given population grows
• Factors that influence this are:
• Birth Rate
• Mortality – Death Rate)
• Emigration (the number of individuals AWAY
FROM a population)
• Immigration (the number of individuals
MOVING TO a population)
Population Limiting Factors
• Density-independent factors
• Factors that limit population size, regardless of
population density.
• These are usually abiotic factors
• They include natural phenomena, such as
weather events
• Drought, flooding, extreme
heat or cold, tornadoes,
hurricanes, fires, etc.
Population Limiting Factors
• Density-dependent factors
• Any factor in the environment that depends on the
number of members in a population per unit area
• Usually biotic factors
• These include
• Predation
• Disease
• Parasites
• Competition
Population Limiting Factors
• Population growth models
• Limits to exponential growth
• Population Density (the number of individuals
per unit of land area or water volume)
increases as well
• Competition follows as nutrients and resources
are used up
• The limit to population size that a particular
environment can support is called carrying
capacity (k)
What population do you think this is?
So, what do you think is going to
happen to the human population?
• We will probably reach our carrying capacity.
• Our growth rate will start to look like most organisms, which is
the Logistic Growth Model
Carrying Capacity (k)
What letter does this curve
kind of look like?
Population Limiting Factors
• Occurs when a population’s growth slows or stops
following exponential growth.
• Growth stops at the populations carrying capacity
• Populations stop increasing when:
• Birth rate is less than death rate
(Birth rate < Death rate)
• Emigration exceeds Immigration
(Emigration > Immigration)
Biodiversity
• What is Biodiversity?
The variety of life in an area that is determined
by the number of different species in that area.
• There are 2 main types:
Genetic Diversity
Species Diversity
Biodiversity
Penicillin: Derived from
bread mold
Teosinte: A
distant relative
of corn
Domestic corn
plant
Madagascar Periwinkle: Used to
treat childhood forms of leukemia
Extinction Rates
• The gradual process of becoming extinct is known as
background extinction.
• Mass extinctions: When a large percentage of all living
species become extinct in a relatively short period of time.
• 250 MYA: Over
90% of species
died
Estimated number of Extinctions since 1600
Group
Mainland
Island
Ocean
Total
Approximate
Number of
Species
Percent of
Group
Extinct
Mammals
30
51
4
85
4000
2.1
Birds
21
92
0
113
9000
1.3
Reptiles
1
20
0
21
6300
0.3
Amphibians
2
0
0
2
4200
0.05
Fish
22
1
0
23
19,100
0.1
Invertebrates
49
48
1
98
1,000,000+
0.01
Flowering
Plants
245
139
0
384
250,000
0.2